SOLVED Cattle Driver - low output volume

MattG

Well-known member
I just built the Cattle Driver. It works, except the output volume seems way too low to me. Unity gain is just past 3:00 on the level control (i.e. a little past 75%). I'm thinking it's probably not supposed to be like that. I think it's working as-expected otherwise, though I can't be 100% sure, since I'm just going off online videos of the Cattle Driver and the Buffalo TD-X (of which the CD is supposed to be a clone). Other than the volume issue, there's no other obvious problems.

Does anyone else happen to have a Cattle Driver that's willing to take voltage readings for me to compare with, particularly around the op-amps? Otherwise, what's the most likely culprit to start with for debugging this?

Thanks!
 
Last edited:
Here are the voltages now:

Supply voltage: 9.36

TL072:
pin 1: 4.23
pin 2: 4.23
pin 3: 3.84
pin 4: 0
pin 5: 3.84
pin 6: 4.22
pin 7: 4.22
pin 8: 8.43

LM301:
pin 1: 1.45
pin 2: 4.12
pin 3: 3.77
pin 4: 0
pin 5: 1.35
pin 6: 4.12
pin 7: 8.43
pin 8: 3.52

Essentially the same as before.

For the LM301, either my build has another bug, or maybe that opamp naturally puts some voltage on pin5?
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
 
Still doesn’t explain voltage on pin 5!
I'm surprised it works at all!
When you stray from the BOM, this sort of thing tends to happen, You know this too well.
As long as it looks Cool , why stick with the correct parts is not the way to build a pedal!
This is why some of the long term Members just don't participate in these situations.
I just happen to see the voltages, Own a genuine pedal & gave the voltages
My 2 cents.
 
Maybe the 47pF's needs to be bought down to 50V values to bring the voltages back!

Honest question, why should that matter? You always choose capacitors with a higher voltage rating that what you're working with, for some safety margin. I've heard 50-100% margin is the typical rule of thumb for electrolytics. I know some multilayer ceramic types have dramatic voltage versus capacitance curves, so people often get those with voltage ratings as high as budget/footprint will allow. I've never heard a technical reason as to why you shouldn't go too high on a capacitor's voltage rating. But I am just a hobbyist, learning from forums and such, so there are definitely gaps in my knowledge! I'd definitely like to know if there are some reasons beyond cost/size why capacitor voltage ratings shouldn't be too high.


I'm surprised it works at all!
When you stray from the BOM, this sort of thing tends to happen, You know this too well.
As long as it looks Cool , why stick with the correct parts is not the way to build a pedal!
This is why some of the long term Members just don't participate in these situations.
I just happen to see the voltages, Own a genuine pedal & gave the voltages
My 2 cents.

The Cattle Driver BOM doesn't call out capacitor chemistry, nor voltage ratings.

Electrolytics are shown on the schematic (and implied by the BOM footprints). I only deviated from that in four cases: C11, C16, C17, C19. C11 appears to simply be a coupling capacitor, film is very common for that role; here I assumed electrolytic was specified simply for cost/size reasons (as film above 1uF tends to get expensive). C16 and C17 I believe are just frequency filters, and I've seen every kind of cap used in this kind of role. Again, my assumption was electrolytic was chosen for cost reasons, and the chemistry shouldn't matter. I'm not exactly sure what C19's role is, though.

I would definitely like to learn how using film instead of electrolytics could affect the functioning of the circuit, so I can be smarter about this in the future!

I do have some 47pF ceramic caps that I could use to replace C12, C13. But C13 is a frequency filter cap, so I'd really be curious how a 1kV film cap could be a problem here. C12 is the LM301's compensation cap, ceramic does indeed seem more common for that role. I might go ahead and swap that out?

Here is my Original Buffalo TDX readings, Supply Voltage 9.09v

LM301:
pin 1: 7.63 - Did you read yours wrong, I rechecked 3 times?
pin 5: NEARLY 0. , DMM fluctuating.

I just re-checked, indeed mine is 1.46 on pin1 and 1.36 on pin5.

What kind of caps is your TD-X using for C12 and C13 (chemistry and voltage)?
 
I have some 50v 47pF ceramic disc caps on hand (C0G). I replaced C12 (the LM301's compensation cap), took measurements: no change.

Then I replaced C13 as well. Also no change in measured voltages. But, unfortunately, when removing the old cap, I didn't do a good enough job de-soldering the old cap leads, and pulled off the plating of one of the cap's holes. I tried to fill the hole with solder, but something is definitely not right now - the drive pot no longer has any effect, and it sorta sounds like the drive pot is maxed out (or at least on a very high setting), also with some noise. Taking a break for now, I don't feel like debugging it.

I'd really like to see someone else with a Cattle Driver post their voltages. If someone else has a CD with voltages like music6000's TDX, then that suggests I have other problems as well. In which case, I'd probably just scrap it and start fresh.
 
Here are test points to find where you damaged trace., just jumper the the broken trace with resistor leads.
steelplayer has just finished his, Check Build reports :

Cattle Driver Trace.jpg
 
@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?

Supply voltage: 9.36

TL072:
pin 1: 4.23
pin 2: 4.23
pin 3: 3.84
pin 4: 0
pin 5: 3.84
pin 6: 4.22
pin 7: 4.22
pin 8: 8.43

LM301:
pin 1: 1.45
pin 2: 4.12
pin 3: 3.77
pin 4: 0
pin 5: 1.35
pin 6: 4.12
pin 7: 8.43
pin 8: 3.52


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
 
Here are test points to find where you damaged trace., just jumper the the broken trace with resistor leads.
steelplayer has just finished his, Check Build reports :

View attachment 5327

Still struggling with this. Using my DMM, I have continuity between all the points of the same color. What I wrote above was wrong, the pulled trace is actually the red through-hole plating on the 47p (I mistakenly said cyan above). I don't think I actually pulled any traces (other than the hole plating), but I'm not 100% sure.

Basically the pedal sounds as though the drive pot has been turned all the way up; rotating the pot has no effect. To me, this suggests the pot is essentially out of the circuit (and therefore forcing all the signal to go through the clipping diodes). Assuming my understanding of the circuit is correct, of course! :)
 
@music6000 - thank you! It was the connection from the "red" side of the 47p to the pot. I patched that up, now it's working as expected. (Kicking myself for not knowing to check that myself, it's plain as day on the schematic. :oops:)
 
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