TripleWrek Clone volume

[m37a]

Hi I recently completed my triple wreck clone based on this layout at tagboard effects. http://tagboardeffects.blogspot.com/2012/10/wampler-triple-wreck.html

Pedal seems to work however with the volume maxed it is still a little below unity. I measured voltages at each pin of both ICs and the voltages appear correct. I traced the signal path with an audio probe and the volume seems good until the last 10k resister in the circuit (R23). I have verified my layout against the online board and checked for shorts/cold solder joints but everything seems okay. Some others have reported similar issues, but others have reported it's plenty loud. I tried shorting the last resister and the volume is closer to unity. Curious if I should just remove the 10k resister?

Voltages:
TL074
1: 4,2v   14: 4.2v
2: 4.2v   13: 4.2v
3: 4.0v   12: 4.2v
4: 8.8v   11: 0v
5: 4.0v   10: 4.2v
6: 4.2v     9: 4.2v
7: 4.2v     8: 4.2v

TL072
1: 4.2v   8: 8.8v
2: 4.2v   7: 4.2v
3: 4.0v   6: 4.2v
4: 0v      5: 4.2v

Thanks!

[antonis]

10k resistor (R23) serves dual purpose..

It limits IC2B output current and also forms a LPF with C25 (4n7)

If you delete it, you may have current limiting via Volume pot (although NOT on full CW setting) but NO current limiting when Tremble Boost switch (S1) is closed..
You will actually ground your signal (zero output) and IC2B out (via C24 & C25) when you activate S1.. 

P.S.
Is your R23 value 10K..??

[nickbungus]

I had the same issue

http://www.diystompboxes.com/smfforum/index.php?topic=112559.msg1039115#msg1039115

[Elijah-Baley]

It seems to be a recurrent issue, though I have (still out of the box) a well working tagboard's layout ot the TW. Without the bypass switch is difficult to say how much works the volume pot, I guees it works fine in my case, but I think, as well as the original pedal, you can't use the volume pot under the half setting because you get a volume drop.

[m37a]

I had the same issue

http://www.diystompboxes.com/smfforum/index.php?topic=112559.msg1039115#msg1039115

I read through your thread before posting. Did modifying the value of R16 fix your issue?

[nickbungus]

Yes it did. Can't remember what I put in there at the end but all is good and  I now use mine on my gig rig.

[m37a]

okay, I will try some different values and see what results I get. Wish I had discovered this before I put it in the enclosure 

[antonis]

Let's make some definitions..

Signal coming from Bass/Treble tonestack is divided by 2 (R16=R17, ignoring c16) and goes to IC2A pin 3 (non-inverting input) which op-amp has a gain of 2 [1+(R18/R19)].
So, signal voltage level at IC2A out is (or should be..) identical to the one coming from R14/P2..
(IMHO, the reason for such a circuit design apparently "baloney" has to do with tonestack output impedance, R17 bias resistor and succeeding independent (not cross-reacting) MIDs tonestack impedance, but let it be for the moment..)

Lowering R16 value results in raising signal voltage at IC2A pin 3 and consequently at the OUT (Volume pot).

So, R16 value should be a good starting point ONLY in case of your following statement doesn't aplly: 
<I traced the signal path with an audio probe and the volume seems good until the last 10k resister in the circuit (R23).>

[m37a]

Let's make some definitions..

Signal coming from Bass/Treble tonestack is divided by 2 (R16=R17, ignoring c16) and goes to IC2A pin 3 (non-inverting input) which op-amp has a gain of 2 [1+(R18/R19)].
So, signal voltage level at IC2A out is (or should be..) identical to the one coming from R14/P2..
(IMHO, the reason for such a circuit design apparently "baloney" has to do with tonestack output impedance, R17 bias resistor and succeeding independent (not cross-reacting) MIDs tonestack impedance, but let it be for the moment..)

Lowering R16 value results in raising signal voltage at IC2A pin 3 and consequently at the OUT (Volume pot).

So, R16 value should be a good starting point ONLY in case of your following statement doesn't aplly: 
<I traced the signal path with an audio probe and the volume seems good until the last 10k resister in the circuit (R23).>

I measured the voltage at R14 and at IC2A Pin 1. The voltage is 4.2 volts at both locations.  Should the voltage after R23 be in the millivolts range?  The voltage it 4.2 going into C24.

I think something may be wrong around R23 or C24 but I will need to remove the circuit from then enclosure to be able to test it.

Thank you for the help!

[duck_arse]

m37a - can we see photos of what you've built, please? if you have a wrong cap value at C25 (like 47nF instead of 4n7), you might see a large sig loss. or R23, obvs.

as for your voltages, all after C24 will be 0V DC, thereabouts

[antonis]

Now I get it...
(Stephen got it in advance..) 

You're dealing with DC measurements (bias voltage actually) BUT can't get the way you used audio probe and found your signal volume OK till R23.. 

Anyway, if that's true, something happens around R23/C25..

Did you try it with S1 open..??

[m37a]

Here are some pictures https://imgur.com/a/R8Lk1. I can't really get to the bottom of the board until I take everything out. I tried to get some close ups of the components in question.

[m37a]

Now I get it...
(Stephen got it in advance..) 

You're dealing with DC measurements (bias voltage actually) BUT can't get the way you used audio probe and found your signal volume OK till R23.. 

Anyway, if that's true, something happens around R23/C25..

Did you try it with S1 open..??

Yes with s1 open/closed same result.

[Elijah-Baley]

I need the schematic to follow your explanation.

[duck_arse]

some things I can (tell myself I) see in your photos -

* it looks like some hanging copper visible through your emphatic track cuts. this could mean shorts where you don't want them, even tho you've drilled right thru the board,
* your 47R resistor is showing signs it has been heat stressed. this usually indicates excessive current flow, often caused by shorts, where you don't want them,
* some of your lead dress is a bit "funky". much as I don't like stretched component layouts, the components still need to be fitted as neatly as if they was on correct spacings, otherwise, wander-y leads may cause shorts, where they are not wanted.


and antonis - did I? I missed the effect of the open switch on the cap value, until later.