Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on July 14, 2018, 12:55:59 am
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Hi guys, Anyone have success with using these with a tube circuit???
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Yes. I use the brick like a reverb tank, sandwiching it between 2 halves of a triode, that way you get that wet/dry mix going. IMO it sounds really nice. Not as lush as real spring, but pretty nice. I like either medium or long decay.
I have so far, always had to use either a separate winding, or small 6V tranny to power the 5 volt supply for it, NOT tap into the heater supply. Otherwise, it injects lots of noise into the circuit. It is possible of course that I'm just too simple to do it right. ;)
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John can you show us a Picture of one you have done with the brick?
Cheers~
Silat
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I've never used one but I've read several success stories, probably here on the forum. Search for belton reverb and see what turns up.
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Hi Silat, here is the schematic. I didn't come up with this reverb circuit on my own, I stole it :icon_biggrin: off the innerwebs. IIRC, I tinkered with the resistors coming off of, and going into the A side of the valve, and of course the "mixer" resistor (commonly a 3.3M in Fender reverb amps)
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here is one thread on the subject:
https://el34world.com/Forum/index.php?topic=6760.0 (https://el34world.com/Forum/index.php?topic=6760.0)
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John, your da man.
Wanting to adept to this.
(https://i.imgur.com/ngEJBb6.jpg)
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I suppose it would work just fine after the tone stack. I don't recognize those tubes in your preamp, but I would think the values should be close anyway. And hey, parts is cheep. :icon_biggrin:
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John,
I am VERY intrigued by your "one tube Belton brick" !
Can you help us out and add some more detail to your schematic, please?
Can you draw where the hook ups are from the tubes to the brick & then please repost the drawing for us to look at?
I appreciate your help with this question.
I have so far, always had to use either a separate winding, or small 6V tranny to power the 5 volt supply for it, NOT tap into the heater supply. Otherwise, it injects lots of noise into the circuit. It is possible of course that I'm just too simple to do it right.
IF I am understanding this correctly, …….. it looks like the Belton Brick still needs a 5v power supply even with the tubes? Is that correct? And if so, can you show us what you did for a power supply, please?
I am wondering IF one could use the Relay power supply that Hoffman sells to power this? It certainly is quite in my amps regarding the relay switching?
With respect, Tubenit
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I like the long decay only. I will warn you the brick is not forgiving which makes it great in stiffer amps. Plainly stated, Fender spring verb will make the amp feel open and almost seems to simply continue on all the time and I really notice the attack soften. The brick does not do this. The brick responds to signal changes without any ambient verb hanging around.
The decay can be shortened, but I have found setting up the amp control pots long decay is fine and preferred.
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Attached is a reverse schematic on the brick, i use this to determine how and where to insert.
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IF I am thinking thru this correctly …………………….
Belton Brick $13 + Hoffman's 5v relay power supply (all parts) $12 = $25
vs.
Reverb pan $33 + reverb transformer $17.50 = $50.50
This assumes the 5v relay power supply idea would work and be quiet? Could be some savings in cost and size?
With respect, Tubenit
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IF I am thinking thru this correctly …………………….
Belton Brick $13 + Hoffman's 5v relay power supply (all parts) $12 = $25
vs.
Reverb pan $33 + reverb transformer $17.50 = $50.50
This assumes the 5v relay power supply idea would work and be quiet? Could be some savings in cost and size?
With respect, Tubenit
Also the extra tube stage(s), socket, wiring, etc... To have reverb with all the space savings and not have the nasty spring noises when moved or bumped... Lots of win wins here....
Boys: need to see the footswitch control also???
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Attached is a reverse schematic on the brick, i use this to determine how and where to insert.
Ed, those look more like PT2399s than Belton bricks???
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Q1) I am wondering IF one could use the Relay power supply that Hoffman sells to power this?
Q2) In reply #8: Does that attachment/drawing/photo on hooking up the tubes, 5v DC power supply and Belton brick look correct?
With respect, Tubenit
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The Hoffman 5V relay power supply is fine. However, use a separate 6.3VAC source. Don't use the existing filament string. The Belton brick negative terminal (pin 5) should connect to chassis ground since guitar signals will be passing through it.
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The Hoffman 5V relay power supply is fine. However, use a separate 6.3VAC source. Don't use the existing filament string. The Belton brick negative terminal (pin 5) should connect to chassis ground since guitar signals will be passing through it.
Thanks Steve! I always appreciate your help!
Respectfully, Tubenit
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I just looked at the spec sheet for that brick. Pin 3 also needs to connect to chassis ground.
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Thanks guys, lots of good info.
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Hopefully, one last question ……………………….. ON the relay power supply rectifier, it was not truly chassis grounded in the relay system but was sort of a floated pseudo ground to help with the relay switching.
Using that relay power supply rectifier with this Belton brick, ……….. would the rectifier be "chassis" grounded in this instance?
With respect, Tubenit
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Yes, the power supply "Grnd" terminal needs to connect to chassis. I just realized that pin 3 and 5 are internally connected, so only need to connect pin 5 to chassis ground. Here's some more info...
http://www.accutronicsreverb.com/main/?skin=sub01_05.html
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Sorry it took me a while... So, here's the schematic of the 5V supply, and how I laid it out the first time I tried it, using the H1 brick.The H2 is much smaller.
Ed, I haven't really noticed it being "stiff". It seems to linger a while if I have the level turned up pretty good. Then again, the way I play it don't really matter much. ;)
Sluckey, thanks for the info about the power supply. Now I feel better!
Tubenit, I've though about making a dogbox for the brick and supply on the outside of the chassis to save space inside, but haven't ever tried it yet. Maybe it would be quieter? Maybe not. I know that the quietness of the tube used for the "buffer" matters. I think lead dress is every bit as important using the Brick as it is for the spring.
Hope this helps!
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Steve and John,
Thank you both for helping with this and giving some clarity to it. I did add information from this thread AND referenced the thread in ARCHIVES (3rd page reply #119) under "one tube reverb" Belton Brick.
John, I appreciate your taking the time to show the schematic and layout.
I am understanding that the 6SL7 has a mu = 70. So, I'm thinking a 5751 (12A_7 type) might work well also?
with respect, Tubenit
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Checked the Belton site. They specify a 5V regulated supply.
Signal input is 1.5VAC max. So 12ax7 cathode drive looks fine. Mu should not matter.
Guess thing sou ds OK??? Seem to be 3 versions re duration of decay: Short, Medium, Long. Any suggestions.
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See Reply #9 on this thread
Ed Chambley prefers the long decay I like the long decay only.
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This has been passed on to me from the supplier of the brick.
(https://i.imgur.com/UYFMTjT.jpg)
I don't think it is an approved circuit from Belton but was given to the supplier as a reference from Belton.
:dontknow:
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Timbo,
There is a PDF file for that schematic and a photo of that "reverb" amp built on this thread in reply #24. One of our forum members, Leevi built this.
https://el34world.com/Forum/index.php?topic=6760.msg94327#msg94327
With respect, Tubenit
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Hi T, I'm going to finish the amp first then fit the reverb to it as I have left some options in the layout.
I'll bread board it first.
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Attached is a reverse schematic on the brick, i use this to determine how and where to insert.
Ed, those look more like PT2399s than Belton bricks???
Sorry Joe, it is.
This is what I meant to post.
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Revising my post above: Looks like the BDTR-3 now has adjustable decay. Also, schematics show that tube drive can be either plate or cathode. This is useful for phase when the wet is recombined with the dry signal. (in case the Brick doesn't like polarity reversal of it's ground & output terminals)
OTOH, SS drive and recovery is probably OK under the circumstances -- kinda like a guitar pedal circuit inside the amp.
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This has been passed on to me from the supplier of the brick.
I don't think it is an approved circuit from Belton but was given to the supplier as a reference from Belton.
Probably just an old-school thing, but I don't like shorting the output of SS devices. How about a grid-stopper resistor on V1B with the footswitch connected to the grid? Maybe even a grid-leak resistor so that you aren't depending on the SS device for the V1B ground reference.
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> tube drive can be either plate or cathode.
Note details. The plate-drive form has IIRC 220K in series with a low-Z input, so maybe 22:1 reduction. Against tube gain of 50, it's not-quite unity gain (more, but not >>more).
> I don't like shorting the output of SS devices
It's sometimes safe and fine. It is not usually done. And in this case it does nothing about the hiss of the following tube stage. We might try to short-out reverb after the tube. Or at least throw 1K between chip and switch.
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(https://i.imgur.com/5BuXR8c.jpg)
Guys, I'm going to do a pedal as a type of breadboard and once working I should be able to graft it into the parallel SE amp.
The trem is just a thought at the moment. :think1:
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I believe tapping off the heaters of the 12ax7 for your 5V supply will inject lots of hum.
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Thanks John, I'll give this a try first and add another transformer if there is a problem.
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Heck yeah, even if it hums it'll let you hear how it sounds. And adding a little 6V tran is no biggie. I had my one amp totally built when I added mine. :icon_biggrin:
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I just stumbled across this thread. Over on diyaudio I have a thread going along similar lines - wanting to add, basically, the inners of a reverb pedal to an amp. Thought it would be worth sharing what I've come up with. Schematic attached.
Briefly:
- A solid-state loop (to save space & current) using LND150s for buffer and recovery
- Lots of input on how to bias the LND150s and set attenuation / gain for unity across the loop
- Reverb circuit added after the return input, using the newer Belton BTDR-3, borrowed from the Rub-a-dub deluxe
- Reverb bypass switch
- Power supply taken from 6.3V or 5V taps, doubled then regulated
I hope to make a small PCB (or two) with all this on. For the reverb I'd ideally like to use trimpots for all but the reverb mix which would go on the front panel - to keep things simple. The effects send pot would be on the rear panel along with the bypass switch.
The schematic may be overly complex and, yes, I could buy ready-made boards but where's the fun in that?
I'd appreciate any further input / warnings etc!
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Guys, we have success.
I think it needs a bit of tweaking by using a 12DW7 as the 12AX7 drives it a bit hard.
I tried a 12AU7 and there is a much better boing, so using the AU7 side for the driver and the AX7 side for the recovery should work well.
Rewired the half wave rectifier on the 6.3v side as the output volts only reached 4.5v and there was some distortion in the decaying notes.
(https://i.imgur.com/2o4mpks.jpg)
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Hi guys, The TREMOVERB is born.
(https://i.imgur.com/OxGSl3O.jpg)
(https://i.imgur.com/SVRzEgk.jpg)
(https://i.imgur.com/tWsNGca.jpg)
I cut the ground wire with the thought of adding a GROUND switch, but had another think and it's probably not a good idea :BangHead:
Doug described the spring reverb as "vintage splash and drip"
The brick is more like a crash and linger, with a bit of bite when you dig in.
Sounds great :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup:
The tremolo also sounds great, so I'll leave it at that. :thumbsup: :thumbsup: :thumbsup: :thumbsup:
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Good stuff!!
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What happens when you turn the Reverb knob all the way down? Looks like all signal is lost.
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Hey PRR, reverb stops but dry signal still passes.
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Hey PRR, reverb stops but dry signal still passes.
Really? According to that schematic the output jack would be grounded. Nothing goes out.
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I'll check :w2:
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I'm interested in how this turns out. I hadn't heard of a reverb brick until recently. I wonder if a tremolo brick is a future plan?
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Sorry it took me a while... So, here's the schematic of the 5V supply, and how I laid it out the first time I tried it, using the H1 brick.The H2 is much smaller.
Ed, I haven't really noticed it being "stiff". It seems to linger a while if I have the level turned up pretty good. Then again, the way I play it don't really matter much. ;)
Sluckey, thanks for the info about the power supply. Now I feel better!
Tubenit, I've though about making a dogbox for the brick and supply on the outside of the chassis to save space inside, but haven't ever tried it yet. Maybe it would be quieter? Maybe not. I know that the quietness of the tube used for the "buffer" matters. I think lead dress is every bit as important using the Brick as it is for the spring.
Hope this helps!
John,
I did not say the verb itself was stiff. I guess I was not very clear. So, let me clear it up. On a Dumble type, or any amp deriving the most of its tone from the preamp, generally the outout section is tight and not forgiving. FUCHS made a Overdrive Dumble clone and I had a 50 watt version at my house for a little while. The amp is super responsive and nice soundinfg too. Andy Fuchs used a brick in this amp. When playing the reverb is present, but quickly dampen the strings and the Reverb will immediately stop.
I couldn't get it to act like a spring reverb until Brick 3. You know, you bump a fender and hear reverb and the speakers over the tank would have to wiggle the spring some. I am just saying it is a little different is all. Good sounding reverb and probably better for recording.
I still prefer plate reverb. I made one of these, https://hackaday.com/2018/03/23/building-a-plate-reverb-on-the-cheap/
Since I did not have room for a full size plate, I made one of these but covered. Works really well.
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When playing the reverb is present, but quickly dampen the strings and the Reverb will immediately stop.
Ah hah, now I know what you mean!
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Hey John, going to fit a brick to the parallel Se amp this weekend.
Trying the BTDR 1 long delay, I'm keen to hear it.
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Sluckey/PRR, are right, the signal is lost when the "reverb" is turned to "0"
Another observation is the trem strength is weak when the "reverb" pot is on 1-2 one the reverb dial, so it's a bit of tweaking of the dials to get enough trem without getting heaps of reverb.
I might try connecting the trem to V1a cathode?
Just had a thought of a 220k resistor off the wiper of the reverb pot as a mixer, will that let the signal pass?
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I've never seen a tremolo signal applied only to the reverb signal. Applying the trem to V1A should be much better. However, I've never seen tremolo applied prior to the reverb circuit either. Curious to hear how you like that.
Adding another mix resistor should fix the "no signal" issue. Like this...
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Thanks mate, I'll give'em a bash.
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Hi guys, I have had some success....
Adding the 220k mix resistor has added another problem.
It lets the dry signal pass with the reverb pot turned to zero, but it also lets a full strength dry signal through to the amp input.
So it acts like an overdrive pedal, which is not a bad thing.
I connected the 220k to the wiper of the trim pot, this has helped to reduce the dry signal but it also looses signal it the trim is turned to 0.
Inturn if V1b does not have the reverb pot turned up enough the tremolo won't work and then if the reverb pot is turned up there is too much reverb.
Side note, connecting the trem to V1a cathode sounds crap.
I might try putting the reverb pot between the brick and V1b.
:think1:
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Watching this with great interest! Thanks for sharing your build and schematic. Looking forward to seeing what you come up with that you're
most favorable towards.
With respect, Tubenit
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> acts like an overdrive pedal
There's much too much gain to be a straight-through signal path.
Try a 50K resistor on the output jack.
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Thanks PRR, Just not sure what you are asking.
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Hi guys, I think this one is sorted.
Retried some of the suggested tweaks and there is now a good mix between the trem and verb.
(https://i.imgur.com/xRiLfVP.jpg)
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Hi guys, Put the finishing touches on this one.
With some great info from sluckey and a bit from http://www.valvewizard.co.uk/trempcb.html
The trem works great.
(https://i.imgur.com/1uSXP9R.jpg)
(https://i.imgur.com/peZHK2k.jpg)
(https://i.imgur.com/KGSeTVD.jpg)
(https://i.imgur.com/3vRT0zO.jpg)
(https://i.imgur.com/r3EoErF.jpg)
(https://i.imgur.com/NHQCWOa.jpg)
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I recently built a reverb pedal with the Belton brick. I actually prefer it over the real spring reverb.
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Hi guys, With the valve circuit working well with these bricks...
Could the IRF820 type mosfet be used to replace the valve???
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Could the IRF820 type mosfet be used to replace the valve???
Don't see why not. I used a TL072 as input buffer and make-up (just like a pedal) and it seems to work well. No need for high voltages. I used LND150s for my loop (following MOSFET Follies, normal B+ voltages) with the reverb hardwired in the return section. Very happy with it so far.
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Thanks mate, I was looking to modify this
(https://i.imgur.com/fbW2eV3.jpg)
In a way I could remove the transformer and connect the brick input to Q1
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connect the brick input to Q1
I would think the bottom of C1 1st, if there isn't enough drive then maybe you'd need Q1 to drive the brick :dontknow:
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> connect the brick input to Q1
No. Q1 outputs a hundred volts signal. The Brick needs like one volt signal. If it worked it would blow up the brick. However it won't do anything without some DC feed to Q1, a transformer or resistor.
Do the opamp plan in #59.
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Thanks PRR, That's all I need to know. :thumbsup:
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Thanks, tristanc :thumbsup:
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Thanks, tristanc :thumbsup:
If you want I could send you one of my reverb PCBs I had made up? £5 + shipping. Might save you some time.
Let me know.
Am very pleased with the resulting sound and there's scope for adding more controls (length of reverb and tone) to the front / rear panel if desired.
Tristan
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Tristanc,
Are the two back to back zeners for protection or to limit possible distortion to the inputs of the LND's?
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Are the two back to back zeners for protection or to limit possible distortion to the inputs of the LND's?
They're to protect the LND150s if they get heavily overdriven.
Here's the thread where I went through development:
https://www.diyaudio.com/forums/instruments-and-amps/325029-adding-belton-reverb-module-pedal-amp.html
And the specific post on the zeners: https://www.diyaudio.com/forums/instruments-and-amps/325029-adding-belton-reverb-module-pedal-amp-post5492663.html