Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: sluckey on February 13, 2019, 08:34:31 pm
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This is an idea I've been sitting on since I began putting LEDs in my tremolo oscillators. I finally took it to the bench and tested it today. It works much better than I had hoped. This produces a very strong, smooth tremolo without the hassles of power tube bias modulation or neon bulb optocoupler ticking. And only one triode!
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Steve, would your circuit be a good candidate to modulate the cathode bias of this V4A pre-PI 12AX7?
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This circuit is not meant to bias modulate anything. It simply ties into the signal path and shunts the signal to ground. If I were gonna put this circuit in your circuit I would connect Rx to the right side of C15. The PI would also need an input cap.
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ooooo cool!
Thanks very much for putting this up!
I almost want to swap this into the princeton deluxe thingy I made.
I like the sound of bias vary but it always seems to be a bit of a balancing act. Sometimes it gets weaker when it gets faster and can distort in an ugly way at higher volumes and intensity settings.
Does it insert where a standard fender optibug tremelo would insert and is it closer in sound to that tremelo
and can you explain the 'swamp' switch. Does that emulate the bias vary sound?
Now I have to build something to try this, and or dod a version on a tiny board and try hooking i into my princeton deluxe build to hear how it sounds.
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You could insert at the same point as an AB763, or at the volume pot, or you could insert at the junction of the two 220K mixing resistors and the PI input cap if you want tremolo on both channels. I think it has a much smoother and deeper sound than the neon roach used by Fender. The swamp switch just gives you a slower speed range.
I tried this in my supro amp. I just replaced the cathode resistor for the oscillator triode with the opto and connected the output to the #2 volume pot. This way I still had stock preamp bias tremolo on Channel 1 and new trem on Channel 2. Very easy to compare. Sounded very close but the new trem was capable of much more intensity.
http://sluckeyamps.com/supro/supro.pdf
You could do a similar test in your DR or PR. Only takes a few minutes to do a temporary mockup. And you would still have your original tremolo circuit. Compare the two simply by turning one intensity to zero. You could even run both trems at the same time!
Experiment by connecting the trem output to different places in the signal chain. The only caution is don't connect it to any place that has dc voltage present, such as tube plate or PI grid.
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Where do you get your Vactrol VTL 5C1 ?
I see antique electronics has it. I can't seem to find it on the Hoffman site.
What about 'Trem - U - Later'
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I bought some 10 years ago when I was working on my Sunn tremolo. I've already renamed it Tremo-Nator. Not really locked in on anything. This may just fade away.
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This may just fade away.
.. then come back.. you know.. then repeat cyclically. :laugh: :laugh:
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i bought the last vtl5c1 doug had in stock last week.sorry bout that.are the xvive not as good?
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what is th usable b+ range for this circuit?
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Wide range. I have nine amps with tube tremolo. The B+ for the oscillator ranges from 210V up to 440V.
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I bought some 10 years ago when I was working on my Sunn tremolo. I've already renamed it Tremo-Nator. Not really locked in on anything. This may just fade away.
tremotrol?
--pete
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What is the triode you are using?
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12AX7
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Not really locked in on anything. This may just fade away.
Attached is a different way to do the footswitch. It puts the photocell at maximum resistance when the tremolo is switched off. It also kills the LFO when switched off.
I don't think this idea is going to fade away as long as these photcell optocouplers are available.
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Does this dispense with the need for a bias voltage as per the previous modification?
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Yes it does. I like that idea. Have you tried it? Did the oscillator start quickly.
My dead was similar but without the 10K. The tube would be completely off. I was concerned that may be slow to start up though. I haven't had any time to tinker lately.
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I only built it by itself on the bench. I haven't tried it in an actual amp. The oscillator started immediately, but it took it a couple of seconds to stop completely. Doesn't seem to matter because the optocoupler cuts the signal immediately. I couldn't detect any transients, but you just never know until it is actually in an amp.
I have noticed that VTL5C1's have wildly different output performances. The only thing that is of concern to me is the minimum resistance, but that can be altered somewhat by changing the plate resistor.
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> Attached is a different way to do the footswitch.
I think with plate resistors as high as 470k, the cathode resistor may need to be more than 10k to get for-sure oscillator quit. (The trem of course will stop when the LED is cut out.)
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> Attached is a different way to do the footswitch.
I think with plate resistors as high as 470k, the cathode resistor may need to be more than 10k to get for-sure oscillator quit. (The trem of course will stop when the LED is cut out.)
Peters out pretty fast with 430V, 470K plate, and 10K cathode. The thing loses its motivation with a 4.7K cathode resistor when the bypass capacitor is removed, although it takes a lot longer. If other people are not getting satisfactory results, then by all means increase the cathode resistor.
You can also switch the speed pot off of ground with the same switch and take the middle 1M resistor off of the cathode and switch it off of ground, also. I did this with an LND150 design and it worked pretty good.
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I've read only now the thread and .... :thumbsup: :thumbsup: :thumbsup:
Beautiful idea
Franco
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> with a 4.7K cathode resistor ... it takes a lot longer.
The oscillator needs a gain of 27 to work. With 220k and 10k the no-LED gain is 22, minus other losses, so should fade quick. At 470k:10k the apparent gain is 47; won't be that high but if it comes to gain of say 25 the oscillation will fade slow.
I'm not sure that there is any "upper limit" on the "10k". 100k may idle fine and fade quick.
Obviously you know what you are looking at, but for benefit of others with less insight it might be interesting to know if the "10k" may be large and die more reliably/quickly.
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Actually it would be better to keep the oscillator running. The FS is gonna kill the LED immediately and if the osc remains running the LED will immediately start flashing when the FS is kicked on.
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> better to keep the oscillator running
Agreed, as long as leakage doesn't throw thumps when trem is off.
Thinking over many systems: sometimes the osc is left on for instant action, sometimes shut-down for for-sure no interference. While 5Hz is not going to go far, in a compact chassis with marginal filtering it can sneak around.
A side effect: osc left running the trem will start at "any" point on the wave. Osc stalled but self-kick-starting, it always comes up from the same point (zero), less and more predictable turn-on transient.
But I may be over-thinking because I don't want to go out and chip any more ice.......
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ICE! Sorry to hear that. My azaleas and daffodils and peach trees are in bloom. Bees are a buzzin.
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The oscillator needs a gain of 27 to work. With 220k and 10k the no-LED gain is 22, minus other losses, so should fade quick. At 470k:10k the apparent gain is 47; won't be that high but if it comes to gain of say 25 the oscillation will fade slow.
I'm not sure that there is any "upper limit" on the "10k". 100k may idle fine and fade quick.
Obviously you know what you are looking at, but for benefit of others with less insight it might be interesting to know if the "10k" may be large and die more reliably/quickly.
I must be calculating the gain for the 470K/10K combo wrong because I keep getting 30. I tried a couple of tubes in real life and observed a gain of 20.
I don't have any particular 10K fetish, it's just that it worked well in a source-follower design. I have noticed that the 10K shunts enough current to adversely increase the minimum VTL5C1 output resistance with wimpy VTL5C1's. A 47K cathode resistor seems to be acceptable as far as output resistance goes and it stops the oscillation quite rapidly when the LED is disconnected.
It has crossed my mind that the sudden change in current might cause a pop when the pedal is toggled on and off. If this is a legitimate concern, it would argue for the smallest cathode resistor feasible to keep the current difference as small as possible. I would have to install this in an actual amplifier to see if any problem really exists.
If you are really, really concerned about shutting down the oscillation, you could also switch out one or two of the RC phase shifters.
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Thanks Steve for sharing the Tremor-lator circuit. I finally got around to install it in my 7591A cathode biased 6G16 style amp and works great. Finally got rid of that thumping that was in the other circuit. Takes about a second and a half to start the trem once the Ft Sw is pressed, shuts off quick. I can live with that. :worthy1: Punky
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Look at some of the simple mods 2deaf offered. Should give a fast startup.
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trees are in bloom
rub it in, still artic blast here, but yours is coming, when my trees bloom, you'll be sweating you azaleas off :icon_biggrin:
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Hey it's been cold down here the last couple days. I may have to fire up the pool heater! :laugh:
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again with full disclosure, I spent 90days enjoying every second of "your" southern weather, I just came back early enough that I could whine about the 20days I've had to endure the cold :icon_biggrin:
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June, July, and August are tough. High 90s, temp and humidity! We have to turn the pool heater off during the day! :l2:
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I've found I "acclimate" within a day to large swings, but can't seem to regulate with small swings :dontknow:, 40's by the weekend, PRR by Wed. :laugh:
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going to be in the 70's here tomorrow :icon_biggrin: it got down to 28deg. last night. we'll get about 2 weeks of spring and then it'll be hot and humid with continued hot and humid for 6 months.
--pete
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Did 2deaf`s mod#2 with the 10k cathode resistor and moved the foot switch location. Trem works flawlessly. Instant start and stop. Thanks Guys.
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That's good to hear. Thanks
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Added the original, highly acclaimed, "patented" TREMOR-LATOR to a Martin 112/ 5E3 build. Very happy, Thanks Mr. Sluckey. :icon_biggrin:
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Do you think a MOSFET can be used instead of a triode?
I have seen LND150 used in place of a triode. If you could get the LND150 to work in this circuit, it would be smaller and there would be a lot less heat. It shouldn't affect the tone since the signal is being shunted to ground and the MOSFET is not in the signal path.
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I think it would work. If I had a breadboard I'd try it.
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Do you think a MOSFET can be used instead of a triode?
I'm not sure I can get that LND150 to oscillate with a bias that cold. Could put the VTL5C1 in the drain circuit and I bet it would work. I put the VTL5C1 into a source follower circuit where I could control the current and it worked.
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I think it would work. If I had a breadboard I'd try it.
It never occurred to me to try it in your configuration. If I can free up some time this afternoon, I will play with it a little.
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How critical is the VTL5C1 to the design? They're pretty scarce=expensive. There are Chinese made ones on eBay but would they work the same in this circuit or are they junk?
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Hey Steve, 2deaf. Does the 220K resistor in series with the VTL5C1 resistance provide the proper load for V4A, and also act as a mixing resistor for the "Tremor-lator" and the ac signal at the plate of V4A? Would this be the proper implementation of the "Tremor-lator" in the circuit? Thanks
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Try and see.
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This is how the BF DR mixes. This must work, huh?
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Where did R37 come from?
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Hey Steve, R37 is one of the feedback resistors, along with R38. I was adding a selectable FB range, or no feedback, to the LTPPI. Is that bad?
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Hey Steve, 2deaf. Does the 220K resistor in series with the VTL5C1 resistance provide the proper load for V4A, and also act as a mixing resistor for the "Tremor-lator" and the ac signal at the plate of V4A? Would this be the proper implementation of the "Tremor-lator" in the circuit? Thanks
The Fender roach tremolo works by varying the load on the output of a 12AX7. The varying load causes the gain to vary. The gain only changes a little if the load is from 470K to 100K and a tremolo working in that range would be too light. The gain changes a whole lot if the load is from 50K to 5K and a tremolo working in that range would be heavy. Another one of those exponential things. You wouldn't want a 220K resistor in series with the 50K pot because that would put you in a load range that isn't conducive to tremolo.
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2deaf, the VTL5C1 resistor varies from 50M (dark resistance -OFF) to 20k with 1mA through the LED, to 600 ohms with 10mA through the LED, and 200 ohms with 40 mA through the LED. If the Tremor-lator resistor is connected as a varying load for the output 12AX7(past the plate CC), would the swing from 50M down to 600 ohms provide the wobble needed for good tremolo? Or assuming that the tube is drawing 1mA, would the variation from 20k to 600 ohms be enough for good tremolo without loading the 12AX7?
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Hey Steve, R37 is one of the feedback resistors, along with R38. I was adding a selectable FB range, or no feedback, to the LTPPI. Is that bad?
Say what! I'm asking about the schematic you posted in this thread.
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Sorry Steve, the 100K load for V4A? Isn't that how the BF DR is wired?
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There is no 100K parallel to the INT pot as you've drawn.
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Steve, how are these?
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Sorry, pre amp section
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2deaf, the VTL5C1 resistor varies from 50M (dark resistance -OFF) to 20k with 1mA through the LED, to 600 ohms with 10mA through the LED, and 200 ohms with 40 mA through the LED. If the Tremor-lator resistor is connected as a varying load for the output 12AX7(past the plate CC), would the swing from 50M down to 600 ohms provide the wobble needed for good tremolo? Or assuming that the tube is drawing 1mA, would the variation from 20k to 600 ohms be enough for good tremolo without loading the 12AX7?
The LDR output resistance is connected in parallel with the 50K Intensity pot, so the total resistive load on the 12AX7 output cannot exceed 50K. As an example, I connected a 47K resistor in parallel with the LDR output with the LFO running at 4.6Hz. The total output resistance wobbled from 11K to 44K. One of my Twins wobbled from 5.3K to 41.4K at 5.1Hz.
With 1mA through the LED, I got an output resistance from 2.5K to 44K with a sample size of 21 pieces. The average was 17.7K, so I used the two that measured 17K for my tests. In order to get the dark resistance, you have to take lunch then come back and measure it. Under LFO conditions, the high resistance of the photocell is something under 1M.
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Do you think a MOSFET can be used instead of a triode?
I have seen LND150 used in place of a triode. If you could get the LND150 to work in this circuit, it would be smaller and there would be a lot less heat. It shouldn't affect the tone since the signal is being shunted to ground and the MOSFET is not in the signal path.
I fooled with it a little and posted my findings under Solid State.
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Good stuff guys, but a bit over my head....
My "TREMOVERB" http://el34world.com/Forum/index.php?topic=23554.50
The trem is good but I'm keen the give the tremor-lator a go.
In my circuit it uses the two triodes to do the work.
I either drop one triode or could the 6S4-A work.
OR any suggestions for the spare triode otherwise.
(https://i.imgur.com/44xqNgX.jpg)
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Tim, I would connect the trem output directly to the output jack.
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> ...could the 6S4-A work.
No.
This type oscillator needs gain over 27. 6S4 is Mu of 16, likely gain in-circuit maybe 12, much too low.
6AV6 is the obvious trem-tube, and was once super-common as radio 1st audio.
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Thanks PRR, The 6AV6 is always a first choice for a single triode valve.
Just didn't want to change the 9 pin socket or have an unused triode.
:icon_biggrin:
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Guys the trem works well.
I did not rewire the oscillator as per sluckey's circuit, I left it as I originally had it.
A few things...
I did not need the " maybe" resistor.
The intensity pot only worked at the last part of the rotation. Smaller K pot?
Speed had good range.
Interacted well with the reverb.
Some static from the LDR.
Note...
I made the "roach" myself.
3mm waterclear red led 1.8VF
LDR Cadmium sulphide similar to Philips ORP12 (these were used in most local vintage amps)
Found this http://www.valvewizard.co.uk/trempcb.html
A use for the spare triode....
(https://i.imgur.com/TYT69od.jpg)
Using the 2nd channel of the Belton I think should work great.
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I was recently gifted a '67 Band Master amp. The amp had a custom Hoffman style board with the 6G16 bias vary tremolo circuit. It also had several issues. I got all the issues resolved and then set about tweaking the bias vary tremolo. After several hours of applying every tweak I knew I had a good sounding tremolo but I also had that annoying pumping sound at higher speeds. It finally occurred to me that this was no collectors amp so it was a good candidate for the Trem-O-Nator circuit. A bit later I had it installed. Wow! What an improvement over the 6G16 bias vary trem. Very smooth with tons of intensity if you want and a very good speed range. Instant on and off. What more could you want from a tremolo circuit. I used 2deaf's mod 2 version. I'm convinced that if Leo had a VTL5C1 we would have never seen that choppy neon opto roach.
If you are thinking about juicing up your tremolo or just adding tremolo to an amp give this circuit some consideration. And go buy some VTL5C1s before the price skyrockets!
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Here's the before and after shot...
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sluckey, no Swamp switch? How is the tremolo speed?
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It's in permanent swamp mode. Speed is 2.5Hz to 8Hz. I'm not gonna drill the chassis. Want to keep this amp lookin' like a '67.
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PSM! (permanent swamp mode) :thumbsup:
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Wow! What an improvement over the 6G16 bias vary trem. Very smooth with tons of intensity if you want and a very good speed range.
I'd love to hear sound clip of this if someone has the means to post one. :thumbsup:
I'm looking for a tremolo that sounds like this one (my old Dano came close to this) :
with respect, Tubenit
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I believe this circuit will do that.
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I have 2 questions.
1. Can you still use an LED for the cathode, to show the trem speed with this circuit?
2. Do you think it would sound good/better in the Warbler than how it is now?
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No indicator LED. The Warbler circuit doesn't need a super strong LFO signal. It has plenty of intensity as is.
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Sluckey,
Think this schematic might work regarding the Tremolo? Don't know IF I will do this OR IF the small tweed style chassis even has room to make this work, but I am curious whether this would be heading it in the right direction?
Not sure where the signal path and the tremolo should hook up? It would be converting an existing TBM amp that does work well.
With respect, Tubenit
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That will work. May need to use a 250K INT pot so you don't load down the signal path too much. Or you may want to try it at the top side of your trim pot. I would just use a gator clip lead to connect the INT pot to different points in the signal chain. Don't try to go farther into the PI input like you have it now. And don't clip it to any DC point such as directly to a tube plate. Have fun.
BTW, I think 2deaf has worked up a circuit for a MOSFET if that interest you.
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Thanks! I've got to work on this a while to see IF I can get this into the chassis using the current layout board and maybe a terminal strip? IF I put this in the amp, I will definitely post the results and make a sound clip.
UPDATE: well it's a no-go on this amp unfortunately. Not nearly enough room on the layout board NOR enough room in the chassis. This is a Tweed BluezMeister with clean and overdrive and reverb and 3 relay channel switching crammed into a
18.5" x 2.5" x 7" chassis.
I'd have to rip out the layout board from perfectly great sounding amp and put another board in.
Maybe another build another time. :dontknow:
With respect, Jeff
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No indicator LED. The Warbler circuit doesn't need a super strong LFO signal. It has plenty of intensity as is.
Ok, thanks Sluckey. :icon_biggrin:
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I'm going to swap this circuit into one of my builds, either my vibrolux or my stereo deluxe.
I enjoy the bias vary but something a little less finicky and prone to thump would be better.
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I'm going to try the tremor later in my blackface vibrolux build today.I'm tired of the ugly distortion on the tremelo at higher volumes.
I'm going to implement it like S. Luckey did in his bandmaster.
Anybody have a good idea for using the unused triode ?
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Okay I have this installed in my single channel blackface vibrolux reverb build and working. I was wondering if there was a way to get a bit more depth out of the tremelo. Maybe use a 100K intensity pot?
As it's a one channel amp (with the 220K resistor and a 280 resistor to ground where the channels would normally mix) does it matter which side of the 220 'mixing resistor ' I insert the tremelo ?
Currently I have it before the 220k resistor
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Totally remove both resistors.
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Isn't that just going to give me uber preamp gain going into the PI ?
Does using a larger (say 100K) intensity pot help at all?
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I don't know what you are talking about with the "280 resistor to ground". I can only assume you mean a 270K to ground. A 270K would simulate the load of the second channel 220K mixing resistor plus the 50K int pot. Adds up to 270K.
But you don't need that now that you are using this trem circuit. The 50K pot will prevent this uber gain. And since you only have one channel, you don't need any 220K mixing resistors.
So, instead of questioning, just take 2 minutes and remove the resistors. Then you'll know for sure how the circuit will react. If you don't like it, put them back in.
I'm surprised you don't have enough intensity. I've tested this circuit in my Supro, a BandMaster, and another AB763 build. 2deaf has tested in more than one amp. Platefire put it in his Fender Pro Reverb. And several others have used this circuit in other amps. You are the only one that says you need more depth. Maybe you have an error in the circuit? This circuit should give you way more trem than you will likely ever use, unless you play Crimson and Clover, over and over. :icon_biggrin:
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Well I'm usually good for a certain amount of unintentionally annoying questions
It's good to know I haven't lost my touch
Undoubtedly you are right
I usually learn things by doing them but also by asking questions when I am unsure.
I really do appreciate your more extensive response though
Yes I meant 270..not sure why I wrote 280 but there you have it.
I will try removing the resistors, and check the circuit as well.
To be sure of my assessment I was comparing it to the bias trem on my stereo deluxe reverb build
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Circuit right.
Tried taking out the resistors etc, moved things around as necessary,things are getting a bit messy
Amp is louder , trem much the same.
I'm not complaining or being unreasonable
I just asked if there's a way to make it have more tremelo. It's not as deep as the bias vary on an AB763 deluxe.
Is there or way or is it actually offensive to ask?
It sounds like I am offending you
I seem to be missing something here.
These forums are tricky things.
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Isn't that just going to give me uber preamp gain going into the PI ?
Does using a larger (say 100K) intensity pot help at all?
It sounds like you have a 220K : 280K voltage divider in parallel with the 50K Intensity pot. If so, the voltage divider has ten times the resistance of the Intensity pot so that the total resistance of the circuit is essentially 50K for practical purposes. You can make that voltage divider larger or tap into it at different points and it really won't change things so that you would notice.
The Fender tremolo works by varying the load on the mixer triode of the Vibrato channel. The difference in gain between a 100K load and a 50K load is 1.9dB. The difference in gain between a 50K load and a 5K load is 14.2dB. Running that thing in the 50K to 5K range is obviously going to give the deepest tremolo and running it from 100K to 5K isn't going to change things much. But it does start affecting the Normal channel more when the range is from 100K to 5K as compared to 50K to 5K. Of course, this is of no concern to you when you only have one channel, but you will be hard pressed to tell the difference between a 100K pot and a 50K pot.
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Thanks. I appreciate the explanation.
My circuit is right, I have 255V on the plate and 2.9V on the cathode, It's probably working reasonably well
Maybe my Silonex VTL 5C1is not so hot
I was just curious if the circuit could be tweaked to provide a bit more. I haven't tried the amp at higher volume since the mod so I guess I'll find out.
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Is there or way or is it actually offensive to ask?
It sounds like I am offending you
I seem to be missing something here.
No offense taken. Maybe a bit annoyed that you didn't just take the 2 minutes to try it. My directness is not always understood. That's OK.
My circuit is right, I have 255V on the plate and 2.9V on the cathode, It's probably working reasonably wellMaybe my Silonex VTL 5C1is not so hot
That may just be the problem. That 2.9V is the voltage drop across the LED inside your VTL5C1. My Vactec Vactrol VTL 5C1 has a voltage drop of only 1.6V. A few years back before I came up with this circuit, I was experimenting with different LEDs to replace the cathode R||C. Different colored LEDs have a different voltage drop. IE, reds and yellows typically have a 1.7V drop. Greens, blues, and whites typically had a 2.5 to 3.5V drop. The higher voltage LEDs produced a weaker tremolo signal and narrower frequency range before drop-out. That's why I always specified a red LED for a stronger trem.
Probably if you use a 5C1 with a lower LED voltage your trem will be stronger. AES sells the Vactec Vactrol that I used...
https://www.tubesandmore.com/products/optocoupler-vactec-channel-switching (https://www.tubesandmore.com/products/optocoupler-vactec-channel-switching)
Here's the datasheet...
https://www.tubesandmore.com/sites/default/files/associated_files/r-vtl5c1.pdf (https://www.tubesandmore.com/sites/default/files/associated_files/r-vtl5c1.pdf)
I still recommend omitting the 270K to ground since you now have a 50K-RA pot just like the original AB763 circuit. The bias vary tremolo circuit uses a 250K pot. You did change to a 50K pot, right? I do think you will be pleased with this circuit once the cathode voltage is brought down. Hang in there. It's worth it. My Band Master had a bias vary trem installed when I got it. The trem effect was weak since I was using 6L6s. This circuit took the Band Master to an over the top trem. I think it will do the same for you since our circuits are the same.
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I think the circuit is a very cool thing and I'm very appreciative.
I wasn't knocking it at all.
Especially on the vibrolux to have a tremelo that isn't going to start introducing distortion at higher volumes or have differing amounts of tremelo depending on the speed it's set on, not to mention the whop whop through the JBL and watching the cones of the speaker going in and out dramatically (gives me the willies)
So I like this idea a lot.
I have another VTL 5C1 from the same maker. I might try swapping that in and see if there's a difference.
However I'm pretty sure I bought the exact ones you are referencing and from Antique Electronics supply.
I did have a 50k pot in but it was audio and only was effective right at the top of it's range which was annoying. I found a 100k RA and put it in and it makes a lot more sense with perhaps a shade more tremelo.
So I have a question and I'm just looking for clarification.
Initially my understanding was that you were suggesting I removed the 220K (mixing) resistor and the 270k one to ground.
I did that but mostly maybe gained a bit of volume.
Were you actually suggesting just removing the 270 k to ground and leaving the 220K in?
Anyway off to rehearsal now. breaking in a new singer!
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I have 255V on the plate and 2.9V on the cathode...
That sounds suspiciously like the expected voltages with a 10K cathode resistor. Do you have a footswitch and, if so, is it closed?
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Initially my understanding was that you were suggesting I removed the 220K (mixing) resistor and the 270k one to ground.
Were you actually suggesting just removing the 270 k to ground and leaving the 220K in?
My first response was "Totally remove both resistors." I still stand by that statement. But if you want to remove the 270K and keep the 220K, that's OK. Be sure to connect the INT pot to the preamp side of the 220K mixing resistor. Otherwise, if you connect your 100K INT pot to the PI side of the 220K you will create a voltage divider that will only allow 1/3 of the guitar signal to reach the PI.
2deaf makes a good point about your high cathode voltage. Recheck that voltage with the tremolo running. Is it still 2.9V? If so, put your other VTL5C1 in the circuit and recheck.
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I was checking the voltage with the tremelo switched off because the voltages were fluctuating with the tremelo.
However I slowed the speed down and check them again and they're pretty well bang on your numbers
Plate - 164 V and Cathode- 1.57V
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I've got 170 plate voltage & 1.58 cathode voltage but I have PLENTY of Tremolo using the AES vactrol.
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Maybe I'm just greedy! :icon_biggrin:
I'm going to try it out at higher volumes tonight and reassess
It's undoubtedly a cool circuit and much appreciated.
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Well I tried it tonight back to back with my deluxe with bias vary tremelo and thedeluxe's tremelo was waaaay deeper. I'd say the vibrolux's tremelo '10' was the deluxe's 5
So maybe half as much
I must have something amiss
i have the intensity pot feeding into the PI right before the 220K resistor. The 270K load resistor to ground has been removed. I've gone over the ciruit a few times. It's elegantly simple so not too hard to check. It seems like it's right.
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i have the intensity pot feeding into the PI right before the 220K resistor.
It's not clear to me where the pot is connected. It needs to be connected to the preamp side of that 220K, not the PI side.
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Sorry about that. I should really post a schematic. Yes it is connected as you describe to the Preamp side of the 220k resistor.
One thing I had different from the circuit was that I had a 5meg linear pot for the speed control (The local electronic store had them much cheaper than any online 3meg RA pots.)
Somehow I don't think that would affect the circuit other than offering more range of speed.
I put the 3 meg pot in as I had a couple I bought with the Vactrols.
Next I'll try swapping in the other vactrol, as I've read (on the infallible internet haha) that there's often a fair amount of variation between them
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Next I'll try swapping in the other vactrol, as I've read (on the infallible internet haha) that there's often a fair amount of variation between them
That's what 2deaf said too. There is truth in his words. I've done this in 3 different amps with 3 VTL5C1s. All three produced VERRRRY strong tremolo. I only have one more Vactrol for a spare. Not gonna test it since I'm pleased with my trem. I think it's worth your time to swap in another one though.
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Next I'll try swapping in the other vactrol, as I've read (on the infallible internet haha) that there's often a fair amount of variation between them
I can replicate your results using a "cold" VTL5C1. Doesn't prove that you have a particularly cold VTL5C1, but it does raise the possibility. If that is the problem, hopefully the other one is more middle-of-the-road.
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It seems to me that an LDR with radically higher impedances would be better suited for a high impedance circuit rather than with the 50K in the AB763 circuit. One of my LDR's wobbled between 60K and 4.5M at 6.2Hz with a 470K plate resistor on the LFO. So I designed a voltage divider that would take advantage of that range using the largest readily available reverse audio pot (AES). This one works by varying a voltage divider instead of varying the load on the mixer stage. You can still load down the mixer stage with a 47K resistor if so inclined.
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Interesting. Your voltage divider is the 500k pot and the 330K resistor? (he said , sadly displacing his ignorance)
I tried the other vactrol with identical results and I even swapped out a couple of the caps just to make sure.
(I have a couple boxes of NOS sprague ceramic caps that I use for non-critical audio applications so not a big deal)
I wouldn't say that the tremelo was weak. there's a fair bit of it. I was wanting to know if there's anything to tweak to get it a bit deeper. It is completely usable.
I sometimes like to use tremelo chords as accents in arrangements when recording. In that application you want LOT's of tremelo
As I said before it's great to have a straight up working tremelo that doesn't have the blocking distortion,whop whop etc etc.
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Interesting. Your voltage divider is the 500k pot and the 330K resistor?
Correct. With the Intensity at zero, the signal at the junction of the 330K resistor and the 500K pot (the output) is 0.6 times the signal going into the 330K resistor (the input). The LDR varies from 60K to 4.5M. When the Intensity pot is at ten, this 60K to 4.5M is in parallel with the 500K pot. This makes the output vary from 0.14 times the input to 0.58 times the input.
This setup only works for LDR's that have an unusually high resistance when the LFO is at its minimum current. A more typical LDR might have a range from 10K to 900K. This makes the output vary from 0.03 times the input to 0.49 times the input. A real good wobble, but the maximum output is 0.49x and the off output is 0.6x. This means that you will get a volume drop when you engage the tremolo with the tremolo set at higher settings.
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When my 74 Pro Reverb Head Trem was weak on Intensity(speed ok) and had the thumping sound, sluckey advised me to try this, so I did. Very pleased. Perfectly quiet and effective tremolo. Thanks for sharing sluckey! Platefire
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I finally got around to trying this. Love it! Tonight my 73 Jacked up Super Reverb is getting it.
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I was hoping you would get around to trying this. Glad you like it.
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Well, you know me. Added now to my Super Reverb, 73 model, which is Madly Modded and now is a 2 10 and tubed her up with some Philips 6L6 WGB (in fresh boxes, fans how does he do it.
Installed a cathode bias switch while I was in there, you know. It sounds almost as good as the damn Hampeg you have. Ever since I saw George Benson, he was young and I was very young. He played a Twin with the tremolo intensity very little. Appeard to be about 2 on the knob and speed was over 8. Makes a very unique sustaining tone when the hollow body is just on the edge of feeding back.
Once I actually heard this, then I began to hear how many songs the guitar has tremolo on it. Prior to that day, I really didn't care for AM.
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I bet it's not as ugly as my Hampeg! I may have to give that to you one of these days.
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I'm looking to implement 2deaf's LND150 version into my amp; http://el34world.com/Forum/index.php?topic=24472.0
I have a Hoffman single channel AB763 Deluxe Reverb. Instead of the 47K to ground after V3B I have a master volume pot. Unfortunately, this is where the tremolo should be. Anyone have any tips about how I should go about implementing this tremolo into my amp?
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Instead of the 47K to ground after V3B I have a master volume pot.
What size is the master volume?
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1Meg. Too large I know. I've been planning on reducing it to around 100k. Incorporating this Trem into the amp will give me the perfect opportunity.
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Just modded my Vibrochamp Reverb with the vactrol tremolo. Trem works great! Does not cause added distortion at higher intensity levels as the original VC preamp bias trem did. My amp is not a Deluxe Reverb like Joel's but has the fender Reverb. I could not resist using the freed-up triode for an extra gainstage like the CeeJay11 has. I'm still tweaking that to eliminate blocking distortion. Thanks for a great trem circuit!
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1Meg. Too large I know. I've been planning on reducing it to around 100k. Incorporating this Trem into the amp will give me the perfect opportunity.
If I understand it correctly, leave the 1M master volume in and put the 50K reverse audio intensity pot in parallel with it.
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That would mean that both controls would be highly interactive wouldn't it?
Sluckey's original description says, "Intensity pot value depends on which part of the signal path you tap into. If you connect to a volume pot, then use the same value as that volume pot."
How exactly are we connecting to the volume pot?
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How exactly are we connecting to the volume pot?
Like this.
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Thanks mate. I appreciate it. Now I need to find the time to try it out.
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I have to try 2deafs mod for a weak bug in rehearsal context, because I was trying the circuit as is in my vibrolux at rehearsal and one song has a very that's just tremelo chords with the trem set to the songs temp and I couldn't hear it very well and I have a fair amount of experience with tremelo from various amps.. Still a cool circuit but there must be something amiss with my vactrols.
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2deaf your insert variant seems to do the trick for the vactrol I'm using. Seems to be much more tremelo depth now.
I'll try it in rehearsal when my bass player returns in October.
Thanks!
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Has anyone applied this in Vibro champ type tremolo?
https://el34world.com/charts/Schematics/files/Fender/Fender_vibrochamp_aa764_schematic.pdf (https://el34world.com/charts/Schematics/files/Fender/Fender_vibrochamp_aa764_schematic.pdf)
/Leevi
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I bet it's not as ugly as my Hampeg! I may have to give that to you one of these days.
Sorry, been away! You do know I need another amp! And that amp looks perfect. Think of playing behind a fence in a roadhouse and it fits right in. :laugh:
Seriously, I wouldn't change it especially the white and black. That is a country amp, well Country from like 1995 and older. Jason Aldeen's guitar players both use MESA Dual Rectifiers and PRS guitars and i guess he is what is considered Country now. It was so easy for me to hear Roy Nichols tone plugged straight in with that tele I had.
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I'm sure you've been watching Ken Burn's "Country Music" documentary on PBS? I've really been enjoying it. Tonight they get into Merle Haggard.
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I'm sure you've been watching Ken Burn's "Country Music" documentary on PBS? I've really been enjoying it. Tonight they get into Merle Haggard.
I have been. Of course, my preference is the Jimmy Rogers over the Carter Family. Plus, Ole Jimmy Rogers just took his guitar and himself and recorded in Brisol, leaving behind those who told him timing was bad.
I am not quite sure, but I am very partial to blue notes. I will miss tonight and it is a 2 hour show so I cannot watch one whole show. You can stream it from PBS.org and watch. I just finished with Lefty Frizell/Hank Williams.
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I added this tremolo to Princeton reverb AA1164 by using the following setup (see the pic).
I also changed some cap values in the oscillator that are not visible in the picture.
I agree with other members that the concept is excellent.
Thanks Sluckey for sharing it.
/Leevi
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Glad someone has finally tried this in the Princeton. Did you experiment with different value Intensity pots? Now you're the goto guy for Princeton Trem-O-Nator. Thanks for sharing.
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I tried 250K pot without voltage divider (i.e. without grounding the pot) but the result was too weak (volume drop) on full intensity.
I also noticed that the tremolo effect was much weaker if you connect it before the 3.3M resistor.
/Leevi
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I added this tremolo to Princeton reverb AA1164 by using the following setup (see the pic).
I also changed some cap values in the oscillator that are not visible in the picture.
I agree with other members that the concept is excellent.
Thanks Sluckey for sharing it.
/Leevi
Do you have a schematic for the cap changes you implemented?
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No but I changed the 0.02 to 0.047 and the 0.01 (on the grid) to 0.02.
Together those will slow down the tremolo. Already the first change might be enough.
/Leevi
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How critical is the VTL5C1 to the design? They're pretty scarce=expensive. There are Chinese made ones on eBay but would they work the same in this circuit or are they junk?
I tested the following replacement and didn't find any difference.
https://www.banzaimusic.com/xvive-vtl5c1.html (https://www.banzaimusic.com/xvive-vtl5c1.html)
/Leevi
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After fighting for weeks trying to add bias wiggle trem to my Valve Jr style creation, I stumbled upon this thread and WOW- what an utterly simple, brilliant idea! :worthy1: I "borrowed" a photo-resistor from my son's snap circuits kit, stuck it and a yellow LED inside a short piece of black plastic tubing and taped the ends shut with electrical tape to seal out the light. It works like magic-- smooth, rich wobblulations!
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I'd like to see this thread moved to the Archives of Favorite Topics section
Franco
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I put this in a 5E3 and JTM 45 this weekend. Then I built, yes I actually built a pedal. A tremolo on a marshall is very cool. I took the thing to a place called Musicians Workshop in Asheville and didn't think I was ever going to get it back.
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I also used this circuit in my DR style build before the master volume. No more thump! It really helped me out!
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I'm getting close to building a 6V6 Plexi with the VTL5C1 tremolo and variation of the one tube reverb. Hoping to tremulate only one channel but verb on both. I would appreciate ideas or input on any part of the schematic but especially on the tremolo insertion point and value on the intensity pot. Schematic voltages are guesses. Thanks in advance.--Craig
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the tremolo insertion point and value on the intensity pot.
Try it as drawn but be prepared to experiment with int pot value. May even need a resistor between the int pot and the vol pot. And be prepared to move it to the MV pot.
Here's an adaptation into a Dumble ODS last week. Forget about the components in the tube side and just look at the INT pot interface.
(https://ampgarage.com/forum/download/file.php?id=56644&mode=view)
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What would be the best way to place the tremolo after the reverb?
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I would connect to point "R2".
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Thanks Sluckey. I 'm stubborn enough to try inserting as originally posted in an effort to keep the other channel trem-free. If that doesn't work I'll use R2 as a fall back plan. Gotta have my tremolo.
I am curious to know how the circuit was used in the ODS amp. That link won't work in Firefox.Craig
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Follow this link to the discussion on TAG. Start on page 12 and read to the end. The final circuit and a nice sound clip are there. You may have to sign up but that's quick and easy.
https://ampgarage.com/forum/viewtopic.php?f=4&t=16833&start=165
And here's the final schematic just for easy access...
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Does this look correct? Sort of a crude "cut & paste" version. I was trying to use Sluckey's layout as a starting place for someone to build a layout board with this design.
With respect, Tubenit
EDIT: I added another layout board section that may be easier to read & indicates 5 rows of turrets to build.
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Yes, that's correct. Keep in mind that dbishopbliss originally designed the layout for Hoffman's bias vary trem. I adapted that layout for the Trem-o-nator circuit. If I had designed this trem circuit on a fresh board the layout would most likely be a bit different.
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Thanks again. Looks like the ODS version would use the same layout as the original Treminator so I can start cutting and drilling my board and use either set of component values when I build.
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How much voltage would a vtl5C1 or other need at least? Like 0.8V, if you replaced a marshal 18W tremolo 820R resistor with a diode? Maybe 0.5V?
And thanks for posting all this by the way, Jens.
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How much voltage
read the post(s) on pg2, just skimmed seen, #'s, reasons, trials..... :dontknow:
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The Trem-O-Nator looks like a great mod, I have two AB763's and a Princeton. I also have a little time to start doing some amp work.
I just ordered some 50K RA pots, can I get verification that I am ordering the correct Vactrol VTL5C1's?
They are about $10 on ebay
https://www.ebay.com/itm/331860686515 (https://www.ebay.com/itm/331860686515)
Thank you all ahead of time, I'm sure I'll have a few questions after I study the changes on the two Hoffman boards.
BV
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The one from eBay is made by Xvive, not Vactrol, but it should work fine.
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The one from eBay is made by Xvive, not Vactrol, but it should work fine.
I'll start a new thread for the Hoffman AB763 as well as the Princeton when the parts come in and I have my layout edited.
Thanks
BV
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I am still pondering how to shoehorn a tremolo in one of my 3 amps. So, I have a question.
Rearranging my layout board, I can exchange active FX for reverb. And IF I drop one of the 4 gain stages, I can have a triode to do this Vactrol tremolo idea.
However, I don't really have enough room on the board to install everything (without gutting almost all the layout board and starting over which I'm not gonna do).
I've been thinking about IF I make a small layout board for just the Vactrol and then mount it vertically (as opposed to the horizontal layout board) that this may work? While it would not be under the heater wiring, it would be somewhat close to it.
As I understand it, the tremolo doesn't carry a signal but does alter the signal (& volume) to make tremolo? So, I am thinking that the tremolo section would be less prone to having oscillation and noise problems as opposed to a regular gain stage? Would this be correct in my thinking?
I'm presuming the tremolo section would not add noise within it's own system but perhaps could induce noise into gain stages next to it?
I have to experiment with changing the gain structure of the amp 1st to see if this is a reasonable thing to do.
Thoughts? Thanks and with respect, Tubenit
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That should work. Depending on how far the INT pot is from the Optocoupler and the injection point, you may need to shield those two wires. I'd try without shield first.
BTW, tremolo is a signal, just not an audio signal. It's a very clean sine wave that can be measured and observed with an oscilloscope just like any other signal. But it is only about 5Hz, so you can't hear it.
Also, 2deaf developed a MOSFET version of this. I think the schematic is in this thread.
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Ciao Steve
Don't remember if I've asked this previously
Will your Enanched Tremolo function in a circuit like the Ampeg Gemini 15 ?
(http://i.imgur.com/wmnXESq.jpg)
Thanks
Franco
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Yes, but the insertion point could not be points X and Y like the Ampeg.
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Yes, but the insertion point could not be points X and Y like the Ampeg.
So the reply is NO (probably I didn't ask in the correct way), I was meaning for a connection to points X & Y
Thanks Steve
Franco
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I probably should have explained. In the Ampeg, the LDR part of the optocoupler is connected in ***SERIES*** with the guitar path. And the tremolo circuit is designed such that the neon bulb part of the optocoupler is illuminated when the footswitch is turned off. The continuous light shines on the LDR and it's resistance is a constant low value. This allows the guitar signal to pass through points X and Y with very little attenuation.
My circuit is designed to shunt the guitar path to ground. In my circuit when the footswitch is off, the LED is also off (no light), so the LDR has a very high resistance. If you used my circuit connected to points X and Y, when you turned the footswitch off your guitar signal would be choked off, just like turning off a water valve.
My circuit would be very effective if it was simply connected to V3 pin 7.
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OK, Understand
But what if we don't consider the Foot Switch and we connect the photoresistor of the photocoupler to the X & Y instead of to the wiper & ground ?
Franco
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That should work. Depending on how far the INT pot is from the Optocoupler and the injection point, you may need to shield those two wires. I'd try without shield first. Also, 2deaf developed a MOSFET version of this. I think the schematic is in this thread.
Thanks Steve! Always grateful for your generous help! I should know in a day or two whether this is a reasonable thing to try.
With respect, Tubenit