More tremolo?

[Swampertech]

Sorry Steve, the 100K load for V4A? Isn't that how the BF DR is wired?

[sluckey]

There is no 100K parallel to the INT pot as you've drawn.

[Swampertech]

Steve, how are these?

[Swampertech]

Sorry, pre amp section

[2deaf]

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.   

[2deaf]

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.

[TIMBO]

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.

[sluckey]

Tim, I would connect the trem output directly to the output jack.

[PRR]

> ...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.

[TIMBO]

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.
 

[TIMBO]

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....

Using the 2nd channel of the Belton I think should work great.

[sluckey]

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!

[sluckey]

Here's the before and after shot...

[Swampertech]

sluckey, no Swamp switch? How is the tremolo speed?

[sluckey]

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.

[Backwoods Joe]

PSM! (permanent swamp mode)

[tubenit]

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.   

I'm looking for a tremolo that sounds like this one (my old Dano came close to this) :

with respect, Tubenit

[sluckey]

I believe this circuit will do that.

[Willabe]

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?   

[sluckey]

No indicator LED. The Warbler circuit doesn't need a super strong LFO signal. It has plenty of intensity as is.

[tubenit]

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

[sluckey]

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.

[tubenit]

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. 

With respect, Jeff

[Willabe]

No indicator LED. The Warbler circuit doesn't need a super strong LFO signal. It has plenty of intensity as is.

Ok, thanks Sluckey.   

[Toxophilite]

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.

[Toxophilite]

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 ?

[Toxophilite]

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

[sluckey]

Totally remove both resistors.

[Toxophilite]

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?

[sluckey]

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. 

[Toxophilite]

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

[Toxophilite]

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.

[2deaf]

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. 

[Toxophilite]

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.

[sluckey]

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


Here's the datasheet...


     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.

[Toxophilite]

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!

[2deaf]

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? 

[sluckey]

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.

[Toxophilite]

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

[Backwoods Joe]

I've got 170 plate voltage & 1.58 cathode voltage but I have PLENTY of Tremolo using the AES vactrol.

[Toxophilite]

Maybe I'm just greedy!
I'm going to try it out at higher volumes tonight and reassess
It's undoubtedly a cool circuit and much appreciated.

[Toxophilite]

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.

[sluckey]

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.

[Toxophilite]

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

[sluckey]

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.

[2deaf]

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.

[2deaf]

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. 

[Toxophilite]

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.

[2deaf]

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.   

[Platefire]

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