Durham - Crazy Horse [goop-alarm]  [traced]

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Barcode
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Post by Barcode »

Barcode wrote:Here's a layout I whipped up. A few comments:

1) This specific layout is meant to replace the board I nearly ruined, so I relies on utilizing the same pot and switch placement Durham used. I don't like it, but it's purpose-built.

2) I will make a cleaner, more reasonable looking layout in the coming days. Again, this one is meant to restore functionality to a broken unit, since Durham has a shitbag 2 year warranty and doesn't stand behind is stuff after that. Hopefully this will help those who have repair problems at least build their own replacement.

3) I know, jumpers. I don't like them either.

4) This isn't verified yet, but I should know in the next few hours if it is solid. It does check out on Express PCB's node checker.

5) I left out D5 and D6 all together, since D6 is unconnected, which also kind of renders D5 useless. It seems to me though that the way it is wired, D5 isn't going to conduct anyhow due to polarity, so to match sound it may need C5 omitted as well. As it is configured in the schem, I don't see how it does anything at all.

Let me know if you see any glaring errors, otherwise I'll report back when I build it up.
Actually, I just found a glaring error on my own! 15 and 16 are not connected. The unconnected end of R15 should go to the intersection of C6 and Q3, and the unconnected end og R16 should go to ground. I'll update th layout shortly. If you have already downloaded this one, it's nothing two wires can't fix.

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Post by Barcode »

I also just noticed that I posted the schematic with part numbers but no values. I'll update, but for questions refer to Phibes' schematic, the part numbers on mine match the values on his.

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Post by Greg »

phibes wrote:
Greg_G wrote:
phibes wrote:So this goop can busted after all. I found a good method that takes it off rather easy and doesn't fuck the board and stuff up.
:hmmm:

I don't mean to be smart, and I think you did well to get this traced..
but to me that does look a little fucked up, and like it will take quite a bit to have it working and tidy again.
Well if you weren't meaning to be a smart ass then why did you open your statement apologizing for being one!?
:scratch: I didn't apologize... I just asked that you didn't take the comment the wrong way.
I was making an observation.
:blackeye

Has anyone ever tried this: http://www.esslinger.com/attack.aspx
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Post by Barcode »

I haven't, but it is certainly worth a try on the sex drive.

I just built my layout and I've got an issue somewhere. I'm thinking it's that whole mess in the feedback loop of Q2. Any ideas from looking at my layout peeps?

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Post by Barcode »

Okay! Just had a little wiring issue, the layout (v2) I posted above is 100% verified. I used mpsa18 for Q3 and Q4 and used plain old 2n2222A in a t0-92 package instead of the tin can ones. Sounds exactly like the videos. Consider this thing traced and the layout verified.

By the way, I left C5 in, but I'm pretty sure it will work fine without it.

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Post by Greg »

Barcode wrote:I haven't, but it is certainly worth a try on the sex drive.
Unfortunately I can't try it as it's only available in the US and says it can't be shipped OS.
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Post by Barcode »

Pics of the new board in action:
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Post by Barcode »

Greg_G wrote:
Barcode wrote:I haven't, but it is certainly worth a try on the sex drive.
Unfortunately I can't try it as it's only available in the US and says it can't be shipped OS.
Well, you could ship your pedal to Phibes or me and we could try it. If it doesn't work, we could just ship it back.

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Post by phibes »

Yeah, if your're going to take the diodes out of the first FF, C5 can be taken out as well. All it's doing is preventing the diodes from throwing the bias off. And since there not hooked up, it really doesn't play any purpose. Nice looking board barcode! Definitely a way better use of space in the enclosure!

Greg that stuff looks promising. I might have to pick it up just to have around. That would sure as hell beat the whole fucking around with a heat gun and blade.
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Post by Greg »

phibes wrote: Greg that stuff looks promising. I might have to pick it up just to have around. That would sure as hell beat the whole fucking around with a heat gun and blade.
Yeah it'd be worth a try.
There's actually a fair amount of info on the 'net about using chemicals on epoxy.. but most are nasty, and not terribly effective it seems.
This stuff claims it doesn't damage most surrounding parts.
I doubt the markings on components would survive though.

Even if it can soften the lump it should make life easier.

Again guys, I wasn't trying to be critical of anyone.. you did a stellar job of getting this done.
It's not easy, and it requires someone willing to put in the time.. and also to risk their pedal.
My input is merely observation and discussion on methods we can try in order to refine what we're doing.

If you're prepared to make a new board, like Barcode is doing.. then it gets a bit easier, but I feel like I've been defeated if I have to do that.
Obviously if it's vero or perf it's a lot easier to make a new one.
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Post by greenskull »

First of all many thanks to all involved!! I've been curious about this pedal for a long time.
Second: Would it make sense to have the loose cathode end of D5 connected to D6's anode? Would that make C5 functional?
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Post by MoonWatcher »

Greg_G wrote:
phibes wrote:Again guys...you did a stellar job of getting this done. It's not easy, and it requires someone willing to put in the time...and also to risk their pedal.
I agree - stellar job, especially in light of the way these things are gooped, and how long it's taken to get to this point. Most grateful for the efforts.

Sexdrive should be interesting to see how it was executed, and why Durham decided to go with buffered bypass. From what I hear, the switch pops on the early TBP ones can be legendary in loudness.

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Post by Barcode »

greenskull wrote:First of all many thanks to all involved!! I've been curious about this pedal for a long time.
Second: Would it make sense to have the loose cathode end of D5 connected to D6's anode? Would that make C5 functional?
Yes it would, but given how much the fuzz breaks up already, it could potentially sound very bad. Give it a shot, let us know how it sounds!

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Post by jonasx26 »

I've been curious about this pedal for a long time as well and I really appreciate the effort put in to tracing it. Great job Phibes and Barcode! THANK YOU.

I have been simulating and breadboarding the circuit and have been making some changes.
First of all, I removed IC1-B as it seems completely redundant.
The only function I can imagine it having is to increase the current drive capability, enabling the opamp-section to drive the rest of the circuit (and heavy capacitive 22µ load) even with the opamp supplyvoltage starved.
But it seems to me that IC-A will be able to drive the circuit just fine on its own and the circuit will act exactly the same without IC-B.
Any thoughts on this?

The 'Big Muff'-style clippingdiodes D5 and D6 look odd to me. With D5 unconnected, D6 does nothing due to polarity, as Barcode said.
Connecting both diodes (as in a Big Muff) will however change the sound (to the better IMO)
Not a huge difference due to the massive gain in cascaded stages but easily discernible.
So, is it a mistake in tracing or is the Durham-guy clueless?
Considering the overall circuit design my guess is clueless designer

/ Jonas

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Post by Barcode »

jonasx26 wrote:I've been curious about this pedal for a long time as well and I really appreciate the effort put in to tracing it. Great job Phibes and Barcode! THANK YOU.

I have been simulating and breadboarding the circuit and have been making some changes.
First of all, I removed IC1-B as it seems completely redundant.
The only function I can imagine it having is to increase the current drive capability, enabling the opamp-section to drive the rest of the circuit (and heavy capacitive 22µ load) even with the opamp supplyvoltage starved.
But it seems to me that IC-A will be able to drive the circuit just fine on its own and the circuit will act exactly the same without IC-B.
Any thoughts on this?

The 'Big Muff'-style clippingdiodes D5 and D6 look odd to me. With D5 unconnected, D6 does nothing due to polarity, as Barcode said.
Connecting both diodes (as in a Big Muff) will however change the sound (to the better IMO)
Not a huge difference due to the massive gain in cascaded stages but easily discernible.
So, is it a mistake in tracing or is the Durham-guy clueless?
Considering the overall circuit design my guess is clueless designer


/ Jonas
I'm going to have to disagree with you on that one. Durham has a good ear. His construction methods are questionable, but the circuit, while nothing revolutionary, is also pretty good sounding and isn't something offered by any other company. Just because the building blocks are common, that doesn't mean it's clueless design. You can build myriad different houses with the same bricks.

The second opamp is set up as a buffer with slightly more than unity gain, and I think it's completely necessary. It isolates the fuzz face-esque stages from the op-amp drive stage. As you may recall, fuzz face variants are typically quite sensitive to input impedance. I could be way off base here though, any more seasoned geeks please jump in!

I might revise the board to have the two diodes that are not currently functioning on a switch for two different sounds. It could have been a mistake, or it could be, given Durham's incessant use of resistor leads as traces on the bottom of the PCB, that he initially intended two versions of the circuit, one with the lead of the diode bent over to connect properly, and one without. He could have just populated all the boards in the same way and just added the jumper depending on which version he was building. Just a theory, if a shaky one :)

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Post by phibes »

jonasx26 wrote:The 'Big Muff'-style clippingdiodes D5 and D6 look odd to me. With D5 unconnected, D6 does nothing due to polarity, as Barcode said.
Connecting both diodes (as in a Big Muff) will however change the sound (to the better IMO)
Not a huge difference due to the massive gain in cascaded stages but easily discernible.
So, is it a mistake in tracing or is the Durham-guy clueless?
Considering the overall circuit design my guess is clueless designer

/ Jonas
I think it's just the design. Barcode mentioned it to me before I got to degoop. He checked all the pads on his unit for continuity and it didn't connect to anything. I checked the unit I got before taking it apart and I couldn't find anything either. I'll triple check the diodes polarity again tonight as their still on the board I got. I just drew the schematic out to as how it was. I wish I had a better answer...

The polarities for the electrolytic cap's on the silk screen are wrong too.
Greg_G wrote:This stuff claims it doesn't damage most surrounding parts.
I doubt the markings on components would survive though.
Yeah that would be my concern too. I would also be worried about it eating into the film around capacitors. Especially on the greenies. It doesn't take much to break the outer film. We could always test the stuff out on components before putting it on the board.
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Post by Barcode »

Yeah Phibes, you should have plenty of still gooped caps you removed! :)

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Post by phibes »

Yeah, I was gonna make a pretty necklace with them! 8)

Barcode's theory above would be better than any answer I could give.
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Post by jonasx26 »

I'm going to have to disagree with you on that one. Durham has a good ear. His construction methods are questionable, but the circuit, while nothing revolutionary, is also pretty good sounding and isn't something offered by any other company. Just because the building blocks are common, that doesn't mean it's clueless design. You can build myriad different houses with the same bricks.
I agree. No use reinventing the wheel, right? A good ear can certainly be enough.

But this forum is called -Circuit Analysis- and what I'm criticizing is the overall 'parts-swap'-feel I get from the design.
For example, why use a 22µ cap after the opamps if 10µ is sufficient?
Maybe to reduce the number of different values and keep costs down? (as there already is two 22µ caps in the circuit)
Assuming that's the reason he made that choice, WHY did he use a 1µ input cap instead of a 100n? (Again, to reduce the number of different values.)

Maybe because Durham don't keep his calculator nearby when he designs his stuff?
The second opamp is set up as a buffer with slightly more than unity gain, and I think it's completely necessary.
Explain to me how that is.
This would be true if the opamp was set up as an inverting amplifier.
It isolates the fuzz face-esque stages from the op-amp drive stage. As you may recall, fuzz face variants are typically quite sensitive to input impedance.
Yes, the low input impedance presents a heavy load to the opamps and the feedbackelements of IC1-A will change IC1-A's output impedance.

Simulation tells me the output impedance of the opamp-section is 250µ.
Without IC1-B the output impedance is 306µ.
Impedance-increase from very low to still very low..

I'm guessing this doesn't matter at all. And I KNOW I'm nitpicking :)
I could be way off base here though, any more seasoned geeks please jump in!
+1

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Post by phibes »

The circuit reminds me the way ZVex put his stuff together.

I doubt I'll ever put one of these together but I do dig the volts control. Before I dug into the circuit I figured it was going to be a simple voltage divider that would sag the whole power supply as you see in so many other pedals. Cutting current to the V+ and the bias reference while feeding the rest of the pedal full power was cool to see. I might just put an opamp overdrive together with the gain fixed and implement the volts pot to get different shades of sound. Would make a fun little one knob box. To you guys who put this together, how dramatic is the volts control?
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