Cattle Driver Volume pot operating issue

C

c.est.baastien

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Hi
My Cattle Driver build don't operate as expected

c.est.baastien said:
Whatever gain / treble / bass dialed in.
The overall volume that goes out sounds like this sketch.
IMG_20241019_171529.jpg
Click to expand...

I don't get what's wrong, I swapped IC1 and the circuit still behaves the same.

Power supply 9,46V
Vcc 8,59V
Vref 4,27V

IC1 TL072
pin 1 4,28V
pin 2 4,28V
pin 3 2,14V
pin 4 0V
pin 5 2,14V
pin 6 4,28V
pin 7 4,28V
pin 8 8,57V

IC2 LM301AN
pin 1 1,37V
pin 2 4,27V
pin 3 2,13V
pin 4 0V
pin 5 1,28V
pin 6 4,27V
pin 7 8,57V
pin 8 3,65V

IMG_20241019_170603.jpg

Edit : according to first answer, less words, more sketch
 
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What is exactly is the issue? A100 pot for volume sounds like it's behaving correctly..... are you using the gain knob as well? if you have the gain turned down all the way it would possible react in a low volume manner..
 
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I had trouble finding this thread by @MattG , reporting voltages measured by others and @music6000 on circuits vs. mine in first post.

I may need to first look around IC1 TL072 pins #3 and #5.
Do you have some clue ?

MattG said:
@steelplayer - Thank you! That is indeed very helpful. Here they are typed out for easier readability:

Supply voltage: 9.34

TL072:
pin 1: 4.20
pin 2: 4.20
pin 3: 3.81
pin 4: 0
pin 5: 3.82
pin 6: 4.20
pin 7: 4.20
pin 8: 8.40

LM301:
pin 1: 1.39
pin 2: 4.11
pin 3: 3.74
pin 4: 0
pin 5: 1.31
pin 6: 4.11
pin 7: 8.40
pin 8: 3.52

Below are my voltages, and below that, music6000's from his TD-X.

I would say we are all in agreement on the TL072. Likewise, I would also we all agree on the LM301 voltages except for pins 1 and 5. For those two pins, steelplayer and I agree. Is there a chance something in the TD-X circuit was missed by PedalPCB?
Click to expand...

music6000 said:
Here is my Original Buffalo TDX readings, Supply Voltage 9.09v
TL072:
pin 1: 4.15
pin 2: 4.14
pin 3: 3.73
pin 4: 0
pin 5: 3.73
pin 6: 4.15
pin 7: 4.15
pin 8: 8.27

LM301:
pin 1: 7.63 - Did you read yours wrong, I rechecked 3 times?
pin 2: 4.13
pin 3: 3.72
pin 4: 0
pin 5: NEARLY 0. , DMM fluctuating.
pin 6: 4.12
pin 7: 8.26
pin 8: 4.20
Click to expand...
 
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So if I understand correctly, it looks like the volume is essentially constant, regardless of how the other three knobs are set? With a very slight step-function bump in volume near the end of the volume pot’s sweep?

Putting the volume issue aside - do the other pots seem to work?

The volume (aka level) control is essentially the very end of the circuit, so if all the other controls appear to work, and the tone is more or less correct, then my guess is a wrong component value near the level pot, or following it to the end of the circuit. Or possibly a solder bridge near the tail end of the circuit.

Can we see a good pic of the back of your board?
 
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Hi Matt, I've read that you've got experience in building this circuit, I appreciate your help ! 🙏🏼

I've checked and organised my bench while soldering in order to minimize risks of mistake.
I am now triple checking and comparing resistors colours rings, capa values etc with photos of other builds including yours.

MattG said:
So if I understand correctly, it looks like the volume is essentially constant, regardless of how the other three knobs are set? With a very slight step-function bump in volume near the end of the volume pot’s sweep?
Click to expand...
Yes exactly
 
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MattG said:
Putting the volume issue aside - do the other pots seem to work?
Click to expand...
Tricky to answer, essentially because I am not very accustomed with baxandall EQ.
But it sounds ok to me and that EQ pots are effective. Gain pot definitively is.

MattG said:
The volume (aka level) control is essentially the very end of the circuit, so if all the other controls appear to work, and the tone is more or less correct, then my guess is a wrong component value near the level pot, or following it to the end of the circuit. Or possibly a solder bridge near the tail end of the circuit.

Can we see a good pic of the back of your board?
Click to expand...

For now "level" pot is still on the board. From lugs, pot resistance goes gradually from 107k to 0 kOhm (not to say "linearly").
So I think level potentiometer is ok
 

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Did you get this working? I took a look at the schematic, and that A100K level pot is quite literally the last thing in the circuit. So assuming the rest of the build is working correctly, I think either the pot is wired wrong or you might have a bad pot. Just for the sake of testing: can you instead solder the level pot directly to the PCB (instead of using wires)? Or at least use super-short wires between PCB and pot so as to reduce the chance of a wiring mistake as much as possible. And if that doesn't fix it, do you have a spare A100k pot to try?
 
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Thank you for your interest with my problem !

To be honest, what is puzzling me is that commun measurement on TL072 are
pin 3: ~3.8
pin 5: ~3.8
While I get ~2,1
So on LM301 pin 3.

I should probably look at R16 because my build acts like there are two dividers from 8,5V to 2,1V.

Pots are correctly oriented, no mistakes in their wiring. I've measured each pot resistance evolution while turning variable resistance and they behaves normally.
 
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Hi
Here's my follow-up in my journey to fix this up, at least for recording.

So first off, the kit I've got is true to the BOM. Included A pots.

Then secondly, I am aware of the risks of misorientation because using wires to connect all 4 pots to the board. I've checked multiple times. Connections are correct.
What's the incidence of the length of added wire ? Little resistance added in the circuit. More or less than cumulating every components tolerances ?
Extra wires pots incidence is negligible.



Then, the better starting point of investigation : Why are my measures on each 3 op amp non inverted inputs ~2,13V while other people's reports ~3,74V ?

I measured Vcc @8,57V and Vref @4,27V. Nothing more than 1meg R between Vref and op amp non-inverted inputs.

I've temporary removed capa in order to isolate op amps.
Removed C5. Measures.
Removed C4. Measures.
Nothing conclusive.
 
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