Pigtronix Philosopher's Tone Germanium Gold LTD  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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mysticwhiskey
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Post by mysticwhiskey »

I've got a VTL5C2 and other parts coming in the mail so I'll tackle this one again soon. I've got a couple of things in mind to try with the grit circuit (from your suggestions coldcraft) so I'll post an update in the near future.

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okgb
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Post by okgb »

I liked the demo's i heard of it , not quite your typical compressor ,
usually when something breaks the 50-60.00 mark i consider building it
[ if it's close to the parts / time cost I'm happy to buy it ] but i don't see these
for less than 100.00 . Looking forward to making one gold or normal thanks for the effort
so far .
hey mysticwhiskey i tried to thank you as well but get some page error , thanks

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mysticwhiskey
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Post by mysticwhiskey »

Work's been crazy busy recently so I haven't been too motivated to do much on this, but I've got some much-needed vacation time coming up soon. I just ordered a Philosopher's Tone pedal to play with, so I'll be able to fill in the missing parts to the schematic in the next couple of weeks.

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jstbrowsin
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Post by jstbrowsin »

That is good news 8)

thanks button not working . . . so thanks :D

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mysticwhiskey
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Post by mysticwhiskey »

The pedal arrived yesterday and I corrected the problem areas on the schematic and PCB trace. I've also listed the component values as well. The pedal I got is the non-germanium version so there may be slight differences between component values. Will breadboard this in the next few days to see how it goes.
PigtronixPhilosophersToneSchematicDraft_0.9_20111129.png
PCB Trace With Component Names V0.9 20111129 1911.png

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mysticwhiskey
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Post by mysticwhiskey »

coldcraft wrote:i don't have this circuit, but just from a fresh perspective, R15 and D1-6 just looks wrong IMO.

If I had to guess, I'd say R15 should go to Pin 5 of U3B, and NOT pin 6, as U3B is set up as a non, inverting amplifier.

My next guess would be that D4, 5 & 6 should parallel D1, 2 & 3 completely, to Pin 6 of U3B, although, I haven't seen anything like this before.

Just my 2 cents.
You were pretty much spot-on here :thumbsup

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coldcraft
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Post by coldcraft »

cool! I just checked in on this yesterday. Thanks for taking the time to trace it down!
Black Dynamite wrote:you need to shut the fuck up when grown folks is talkin.

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Post by guycapuano »

yeah thanks, the "thanks" button is not working

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coldcraft
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Post by coldcraft »

in soviet russian, the thanks button clicks you.
Black Dynamite wrote:you need to shut the fuck up when grown folks is talkin.

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Post by mysticwhiskey »

I breadboarded this tonight and it seems to be working fine (one mistake on the latest schematic is R20 should be 56K, not 5K6). Only thing I found though is that the LDR/LED combination I'm using doesn't seem to be quite fast enough in its response, so a heavy attack is very briefly distorted before the LDR kicks in to reduce the gain of U1B. I'm ordering a VTL5C6 to see if this fixes it. Which reminds me - the vactrol on the unit is marked "VTL5C6-A" - does anyone know if there's any significance to the 'A' suffix?

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Post by daverdave »

Not sure, doesn't mention any suffixes in the catalogue.

Just out of curiosity, what's driving the follower / rectifier? I can't see a signal applied, just +9V to the non-inverting input of the buffer, am I missing something?

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Post by mysticwhiskey »

From what I can work out (and it's entirely possible I've got this wrong):

* The LDR is acting as a variable negative-feedback mechanism for U1B. At higher resistance, less feedback is applied (thus more gain). At lower resistance, more feedback is applied (thus less gain).
* The 741 is acting as a buffered 9V supply
* The signal from U1B is biased to 9V dc

The buffered 9V supply is there so that only the AC signal from U1B is charging the capacitor, and not any DC.

Then when we have a large signal from the output of U1B as a result of the guitarist digging in, this charges C14 via the output of U1B by the rectifier made up of diodes D13 to D16. If the signal's large enough such that we have enough voltage in C14 to overcome the forward voltage of the LED, the LED then starts to conduct, and as a result there's a reduction in gain due to the decreasing resistance of the LDR (applying more negative feedback to U1B).

Then as the signal strength decreases, less current flows through the LED, increasing the gain as the LDR's resistance increases. Eventually once the signal is low enough, the LED switches off completely and we're back to maximum gain.

I hope I've got this at least half-way right!

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Post by daverdave »

Ahhh, I completely missed that connection to cap 14 from the output of U1b. Thanks for clearing that up, it's a pretty sweet circuit.

Just quickly redrew it to get my head around it. The output of U1b is fed into your traditional fullwave rectifier, which is grounded to 'virtual earth' or +9V, provided through the buffer for impedance seperation I think (and to provide a decent output current). I'm guessing C10 is a decoupling cap for the +9V virtual earth supply, and the 47R series resistor is to limit the current slightly.

Then C14 is just yout typical reservior cap found in rectifiers, seems a massive value for a guitar signal, guess there's a good reason for that, compressors aren't something I'm too hot on.

Then the optocoupler is decreasing gain with the full guitar signal and increasing as it drops in amplitude. Sweet, think that's right, although I could have totally missed something and be wronger than wrong.

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Post by okgb »

Hey Mystic , let us know when you're happy with the circuit [ and maybe repost the schemo
so we know it's the lastest rev . ]
It sounds like it would be a good comp to use like a rangemaster , that is into a half dirty
[ up loud ]

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kato
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Post by kato »

Hey, I'm a latecomer to this thread. Just wanna say Bravo Mystic Whiskey for tracing this. :applause: The pigtronix is the only new boutique design that really piques my interest.

As a fellow colorblind motherfucker, I will share a perhaps obvious trick: use a multimeter. I don't even try to read the color stripes anymore. I was getting them wrong about 50/50. Purple, blue, and green all look the same to me. But with a multimeter, I know for sure every time.

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mysticwhiskey
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Post by mysticwhiskey »

okgb wrote:Hey Mystic , let us know when you're happy with the circuit [ and maybe repost the schemo
so we know it's the lastest rev . ]
It sounds like it would be a good comp to use like a rangemaster , that is into a half dirty
[ up loud ]
I'm placing an order today for a VTL5C6 to see if that addresses the response issue. That should get here either late this week or early next week. If that fixes things, then I'll post the final schematic (with the R20 fix).

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mysticwhiskey
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Post by mysticwhiskey »

The VTL5C6 came in today and it all sounds good. I reckon we're good to go now. Here's the latest schematic (version 1.0), consider this schematic pretty much verified.
PigtronixPhilosophersToneSchematic_1.0_20111214.png

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Post by rasta_maleek »

which layout did you use mystic? One made it your own?

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Post by mysticwhiskey »

It's only breadboarded at this stage, I haven't made a layout. I have the PCB trace layout but that's a double sided board and I haven't made one of those before.

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Post by lukatosh »

When you say that the schematic is pretty much verified. what is missing? have you build it?...how it sounds?

Thank you!

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