All-Star Reverb

Stompboxes circuits published in magazines, books or on DIY electronics websites.

Re: All-Star Reverb

Postby induction » 26 Nov 2013, 17:04

Does the distortion occur on the bypassed signal? What about on the dry signal with the effect engaged but the reverb knob turned all the way down?
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Re: All-Star Reverb

Postby ilearn » 27 Nov 2013, 01:19

induction wrote:Does the distortion occur on the bypassed signal? What about on the dry signal with the effect engaged but the reverb knob turned all the way down?


Only from the wet signal.
with the reverb knob all the way down, I don't get that gainy sound.
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Re: All-Star Reverb

Postby induction » 27 Nov 2013, 17:02

That sounds like it could be a bad solder joint, but really could be any number of other things. If you post some pictures of your board I'll see if I can spot any problems. If you could post an audio sample of the problem, that would help too.
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Re: All-Star Reverb

Postby brwifrbo » 28 Nov 2013, 03:31

I disconnected vref from the switch but still had the same problem. I've got it wired for true bypass. Tested it minus led but she still pops. I was searching around on the net and the general consensus seems to be the discharge and recharge of the input and output caps is what generally causes the pops. It'll usually make my other pedals in the chain pop also, and I have it before a delay and after an overdrive. Maybe component related? It's got me beat :hmmm:
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Re: All-Star Reverb

Postby ilearn » 07 Dec 2013, 06:29

induction wrote:Does the distortion occur on the bypassed signal? What about on the dry signal with the effect engaged but the reverb knob turned all the way down?


I think I found the reason. I put 3 resistors back for 1x wet and the problem went away.
Somehow wetter mod was not for me. I still miss the wetter mod, though.
Can someone come up with the right resistor values for 1.5x wetter mod? :lol:
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Re: All-Star Reverb

Postby induction » 09 Dec 2013, 23:00

brwifrbo wrote:I disconnected vref from the switch but still had the same problem. I've got it wired for true bypass. Tested it minus led but she still pops. I was searching around on the net and the general consensus seems to be the discharge and recharge of the input and output caps is what generally causes the pops. It'll usually make my other pedals in the chain pop also, and I have it before a delay and after an overdrive. Maybe component related? It's got me beat :hmmm:


Sorry I forgot to respond to this.

If you wired it up for true bypass, there shouldn't have been Vref on the switch in the first place. I'm wondering if it's popping because it's wired wrong. Post some pictures of your build and I'll see if I can spot anything.
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Re: All-Star Reverb

Postby induction » 11 Dec 2013, 17:26

ilearn wrote:
induction wrote:Does the distortion occur on the bypassed signal? What about on the dry signal with the effect engaged but the reverb knob turned all the way down?


I think I found the reason. I put 3 resistors back for 1x wet and the problem went away.
Somehow wetter mod was not for me. I still miss the wetter mod, though.
Can someone come up with the right resistor values for 1.5x wetter mod? :lol:


These resistors control the gain of the last opamp. The gains are calculated as follows:
Dry gain = ((R8+R9)*R11)/((R10+R11)*R8)
Wet gain = R9/R8

These calculations ignore a few things, but they should get you in the ballpark.

The trick is to choose a wet gain and use that to set R8 and R9. Then choose a dry gain and use that to set R10 and R11.

BTW I think that the dry gain in the original and in the wetter mod is slightly above unity. This doesn't matter if you use buffered bypass, but if you use true bypass, you can drop R11 to reduce the dry gain. (FWIW you can also increase R11 to give a clean boost.) Setting R11 at 39k should get you to unity, but you may have to experiment.

Anyway, for more reverb than the original, but less than the wetter mod, you can do something like:
R8 = 10k
R9 = 15k
R10 = 56k
R11 = 47k
This should give the same dry gain and 1.5x the wet gain of the original (wetter mod is 2.2x). Or you can always experiment to find your own values now that you know the formula.

But to be honest, I'm very surprised that the wet signal would overdrive that op-amp if the dry signal doesn't. Nobody else has reported this problem, and the reverb signal should have a lower amplitude than the direct signal, even with the reverb pot dimed. I still suspect that something else was going on, but I may be wrong. Did the distortion continue as the wet signal decayed?

Hope this helps.
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Re: All-Star Reverb

Postby ilearn » 12 Dec 2013, 06:47

Induction,

Many thanks for writing up long reply for me.
I have tried to capture what the wet signal does to the sound, but I was not able to do that.
My friend's practice room doesn't have a recording system. I tried to record with my iPhone, but didn't capture the wet signal well.

I should describe the sound of the wet signal again. Sorry English is not my primary language, so my word of choices and explanation was poor.
The sound I got from the wet signal is more like the small thunder sound. I believe everyone knows who owns combo amp with reverb tank. You kick/hit the amp or the reverb tank and you hear crashing, kind of thuner sound. Whenever I hit the notes, few mil seconds later I hear that thunderish noise. That's what I was trying to explain. I get usual reverb sound plus tiny thunderish sound. That was my problem and that was gone by changing back to 1x wet value.

I'll try your values of 1.5 x and report later.

Again, Many Thanks to you!
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Re: All-Star Reverb

Postby WannabeGeek » 21 Dec 2013, 00:36

Hi Induction,

Thanks for posting this. I have a couple of novice questions for you. I’m more of a guitar player than an electronics expert. I have the basic box of hall circuit working on my breadboard using the BTDR-2H (medium) without the dwell and it already sounds pretty good. I’ve been reading other posts in my search for a way to add tails and also trying to find the right dwell circuit. I think your version looks like the best one for me. Also I’ve been waiting for a 3PDT stomp switch to come in the mail, which was preventing me wiring it up and mounting it into my 1590BB enclosure. I was hoping to get it done in time for my gig on New Year’s Eve. I do have a 2PDT switch on hand, so that’s another problem your circuit solves for me. I don’t need or even want true bypass. For the reverb pot, I’m using a very old 25k pot that has a bad slider and creates noise when turning. I have a new one, but it’s only 20k. Is that a suitable substitute? How will that affect the circuit? Is there a minimum resistance there that has to be met? What would a 50k do? Also, the schematic that I have doesn’t include the 1N4001 diode although it is listed in my parts list. What exactly does that diode do for the circuit? I was thinking it’s some sort of reverse voltage protection, but I’m just guessing there. I’m also a little confused as to the difference between signal ground and power ground. My signal grounds and power grounds are connected together and it seems to work just fine. Should the ground signals be separated? Sorry if my questions seem obvious to you, but I like to understand the circuits I build. It’s a learning experience for me. Thanks in advance for your time.
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Re: All-Star Reverb

Postby induction » 22 Dec 2013, 17:41

WannabeGeek wrote:For the reverb pot, I’m using a very old 25k pot that has a bad slider and creates noise when turning. I have a new one, but it’s only 20k. Is that a suitable substitute? How will that affect the circuit? Is there a minimum resistance there that has to be met? What would a 50k do?

Either of those should work just fine. I'd go with the 20k, but it shouldn't matter very much.

Also, the schematic that I have doesn’t include the 1N4001 diode although it is listed in my parts list. What exactly does that diode do for the circuit? I was thinking it’s some sort of reverse voltage protection, but I’m just guessing there.

You're right, it's just polarity protection. It's in the top right corner of the schematic on the first page of the thread.

I’m also a little confused as to the difference between signal ground and power ground. My signal grounds and power grounds are connected together and it seems to work just fine. Should the ground signals be separated?

I think that people usually like to keep the signal ground separated from the power ground in circuits with digital components because digital circuits can add noise to the power line. I haven't found this to be the case with PT2399's or with Belton bricks. In fact, to the best of my knowledge, the two grounds are connected inside the brick with something like a 10k resistor anyway. If it sounds ok, leave them connected. I think keeping them separate is more important in higher gain circuits.

Sorry if my questions seem obvious to you, but I like to understand the circuits I build. It’s a learning experience for me. Thanks in advance for your time.

No problem. I learned this stuff the same way, and continue to learn by reading this site. I'm glad when I can help anyone else do the same.

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Re: All-Star Reverb

Postby WannabeGeek » 23 Dec 2013, 05:28

Hi Induction,

Thanks for the help. I now have the All Star Reverb circuit on my breadboard. I swapped the old 25k pot with a new 20k and everything seemed to work fine. The dwell is nice and the damp does more than it did with the box of hall version. Before I started soldering, I wanted to hook up the switch to test the tails. I’m using an identical foot switch to yours wired up as indicated. When switched on and LED lit, it performs as usual but when I switch off, I’m getting a slight reverb sound instead of the expected clean, dry sound. That is to say, aside from the tail of the last thing I played, if I keep playing, the dry sound still has a little reverb on it. I put the old 25k pot back in the circuit to make sure that wasn’t the problem. I even tested it with a 50k pot. I also separated the signal and power grounds. The slight reverb sound gets a bit louder when I turn the damp pot to full treble and the reverb and dwell pots to maximum wet sound. This is with the switch in the off position. I wired the circuit back the way it was without the switch and I’m still getting a slight reverb sound with the reverb pot at minimum and the rest at maximum. With all pots at minimum (reverb off, damp off, dwell off) the sound is clean and dry but if I leave the reverb pot at minimum and turn the damp and dwell up, the reverb can be heard enough that it affects my clean sound. Just for fun, I swapped the reverb pot with a 100k pot. Now with reverb at minimum, the sound is truly dry with the other pots at maximum; however, the point at which the signal starts to get wet has now shifted toward the high end of the reverb pot. I can live with this but I’m thinking there must be a simpler way to correct this problem without losing the range I had before. Have you noticed any residual reverb on your build with the reverb pot at minimum and the rest at maximum? Do you have any idea how I might solve this problem? I’ve also noticed that there’s quite a pitch modulation in the echo if I play something that has a short duration and just listen to the echo afterward. I’m thinking it’s just the way the BTDR-2 sounds, but if you have any way to tweak that, I’d appreciate the help.
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Re: All-Star Reverb

Postby induction » 26 Dec 2013, 19:08

With the effect bypassed, there should be no reverb at all no matter what pot you use, since there is no signal path to the brick input. If you are hearing reverb in bypass, then you likely have a mistake in your build, or stray wire or solder bridge somewhere. Another user reported something similar, but when he rebuilt the circuit, the problem went away. You shouldn't have to tweak any values to get rid of the problem.

The modulation is inherent to both the BTDR-1 and the BTDR-2. You can minimize it with darker settings on the damp control, but I don't think you can design it away.

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Re: All-Star Reverb

Postby WannabeGeek » 27 Dec 2013, 02:58

Hi Induction,

At the time of my last post, my All-Star Reverb was still on the breadboard. When I transferred it to vero, I noticed the 1M resistor left over that I didn't remove when testing the switch. I swapped the reverb pot to a smaller value and the dry signal works as advertised. You were right! I'm now in the process of getting the whole thing into my enclosure. It looks like I'll have to go buy a new 7mm drill bit, because the aluminum is tougher than I thought. My old bit must be pretty dull. Anyway, thanks again. 3 more days 'til Happy New Year! :thumbsup
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Re: All-Star Reverb

Postby biliousfrog » 19 Jan 2014, 22:46

I've been trying to figure out the best way to add a preset switch/pots to this layout.

Would I be correct in assuming that I'd split the signals from the board to two sets of pots and the return wires would be switched on the way back in? A TPDT switch would allow for two full sets of controls but no way of adding an LED...I'd need four poles for that.

Does this sound do-able or have I missed something? I'd use the buffered bypass.
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Re: All-Star Reverb

Postby biliousfrog » 20 Jan 2014, 20:51

I've attached a diagram to show how I was thinking of wiring up a second set of controls with a 4PDT switch and LED indicator.

I play a mixture of upbeat rhythm and lush ambient guitar so was hoping to get a dual purpose reverb that can have a short, spring-like, sound and a very wet, plate-like, sound.

Would this work or am I hoping for too much and should have two reverb pedals?
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Re: All-Star Reverb

Postby induction » 20 Jan 2014, 21:52

I haven't tried it, so I can't say for sure, but you're wiring idea will probably make the two sets of pots interactive. The main areas of concern for me are the second lugs of all of the pots, each of which is connected to its counterparts at all times.

For example, look at the dwell knob on the schematic. When one of the pots is set to minimum, the second lug of the other one is grounded no matter what its setting, which will likely kill off the the dwell signal. At other settings, the bottom halve of the voltage divider depends on both pots, making them interactive.

Looking at the damp pot, connecting the second lug of both damp knobs together will create an additional path to ground, which will change the impedance and may attenuate the signal.

Like the dwell pots, having the second lugs of the reverb pots connected to each other will give parallel resistance in the bottom part of the voltage divider. Its response will change when the unused reverb pot is adjusted.

I say it's worth a try on the breadboard, but I'd test it very thoroughly at a lots of settings to see how interactive the two sets of controls are. See if you can get everything you want from it before you build it.

I suspect you'd get a much better result with two separate pedals.
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Re: All-Star Reverb

Postby biliousfrog » 21 Jan 2014, 10:09

induction wrote:I haven't tried it, so I can't say for sure, but you're wiring idea will probably make the two sets of pots interactive. The main areas of concern for me are the second lugs of all of the pots, each of which is connected to its counterparts at all times.

For example, look at the dwell knob on the schematic. When one of the pots is set to minimum, the second lug of the other one is grounded no matter what its setting, which will likely kill off the the dwell signal. At other settings, the bottom halve of the voltage divider depends on both pots, making them interactive.

Looking at the damp pot, connecting the second lug of both damp knobs together will create an additional path to ground, which will change the impedance and may attenuate the signal.

Like the dwell pots, having the second lugs of the reverb pots connected to each other will give parallel resistance in the bottom part of the voltage divider. Its response will change when the unused reverb pot is adjusted.

I say it's worth a try on the breadboard, but I'd test it very thoroughly at a lots of settings to see how interactive the two sets of controls are. See if you can get everything you want from it before you build it.

I suspect you'd get a much better result with two separate pedals.


Thanks for that :thumbsup

I guess it would hit the same problem if the scheme was reversed and the signal flowed from the switch and into the pots?

I'm just trying to get away without building two complete pedals - although it seems that it might be easier.

I guess I could use a single damp control, lose the LEDs, and have the four remaining pots switch in/out completely?...it would be nice to have an indicator though. Perhaps it's time to look into relays.
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Re: All-Star Reverb

Postby induction » 21 Jan 2014, 19:33

Really, you don't have to switch out the damp and reverb pots separately. Doing them together makes sense since the only other component between pin 6 of the brick and lug 2 of the reverb pot is the 33nF to ground. If you use the existing Reverb 2 connection on the board for one damp pot, and point-to-point a second 33nF cap from lug 2 of the second damp pot to ground, you can do both of those pots with two poles of a double-throw switch.

Two more poles will switch out the dwell pot completely.

So a 4PDT will get you everything but the led.

I can't swear it won't pop when you switch it, though. Some well-placed pulldowns might be necessary.
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Re: All-Star Reverb

Postby biliousfrog » 21 Jan 2014, 19:42

induction wrote:
I can't swear it won't pop when you switch it, though. Some well-placed pulldowns might be necessary.


I wouldn't change it mid-song so it wouldn't be too much of an issue - I just like the convenience of an all-in-one-all-star-reverb :D

Thanks for your help, I'll look into it in more depth in a few days :thumbsup
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Re: All-Star Reverb

Postby biliousfrog » 29 Jan 2014, 22:50

I've had a chance to build this, purely as the veto with wetter mod and tails.

I'm getting a signal through, almost the same as bypass, but the reverb control changes the tone slightly. My Belton module has been kicking around my bits box for a while so I wonder if it's that cause of the problem...but how can I check it?
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