Same old parentheses fuzz octave issue.

[jcrews]

I dug thorugh some older threads but most are for the older board. I used 1N34A diodes across the board in D1 D2 and D8 and D9.

It seems like I have the same issue. (no octave effect and turning up the octave knob cuts volume)

I just didn't see where we landed because I'm not using old school russian stuff. I grabbed what was sold as GE 1N34A, but they look just like my silicon diodes. Pic attached.

My first guess is to swap those around. I'm assuming if they are marked backwards from what the circuit calls for, it wouldn't matter in the clippin section because all that matters is they be installed in opposite directions?

I'm going to try that first and report back. If there's any other reason for the the whole "octave knob kills the output" issue everyone seems to have.... I'm all ears

Thanks,

p.s. everything else works and sounds flawless. Love the rat and the boost. Really wanna hear the octave as that's the only "new" thing for me on this one.

 

[jcrews]

Final update:

It sings now. That octave is cool. It's more than an octave. It's nasty.

So I
a.) messed up the boost and octave pots (and boy are those ZERO fun to remove)
b.) misread my bands and put a 4.7k resistor in a 47k spot (r6 to be specific)


I am the noobest of noobs again

Thanks to all. Now i can finally get this one out of the "broken" pile. Down to just one left

 

[Chuck D. Bones]

Which diodes did you end up using?

 

[jcrews]

The leaky russians (de9's i believe) I know I know...... the bat 41's sounded fine. A little more defined actually..... But i spent like 15 bucks on ten of the damn things, so after I fixed my resistor issue i popped em back in to see if they were ever the problem...... they weren't, and they have a rattier charecter than the bat's. I wish i had socketed them the first round. I have never before pulled more things out of a finished pedal than this one (4 diodes, 2 pots and a resistor, 2 ribbon cables).

Since they are socketed I'll keep playing around with it. With my luck the cheapies i had in in first (non socketed) will probably sound the best. It's a fitting punishment honestly.

 

[Chuck D. Bones]

Save the D9x's for something that will make good use of them. Anything with a hard clipper is a candidate. I put 3 in a Chrystal drive in place of the Schottkys and they sounded good (check my Build Report). They'll also work well in a Klon or a Tone Machine.

 

[fig]

Save the D9x's for something that will make good use of them. Anything with a hard clipper is a candidate. I put 3 in a Chrystal drive in place of the Schottkys and they sounded good (check my Build Report). They'll also work well in a Klon or a Tone Machine.

In your opinion, what would be a solid auditioning circuit for clipping diodes (side-by-side audible & scope)?

 

[jcrews]

sounds good. I'll hang on to em.

 

[Chuck D. Bones]

In your opinion, what would be a solid auditioning circuit for clipping diodes (side-by-side audible & scope)?

If I'm considering Germanium, first thing I do is analyze whether the circuit will tolerate the high leakage. If the answer is "no," then it's down to silicon or LEDs. I use a purely subjective approach. I build a breadboard, play guitar thru it, try different diodes, usually with a toggle switch, and see if I have a preference. I get recommendations from folks here and I get ideas from other pedal designs. It's all very ad-hoc.

A while back, I tried Ge diodes in a BMP, with poor results. The gain was very low. That's because Ge diodes behave like they have a resistor in parallel. They never really turn all the way off. The more leakage, the lower the parallel resistor. In low-impedance circuits, like hard clippers, that's usually ok, but in a high-impedance circuit I might just as well install a 10K resistor where the diodes would go.

Recently, I started testing Ge diodes in a single-stage of the BMP circuit. The clipping diodes are in the feedback loop, in parallel with a 470K resistor. I measure the gain with the diodes out of the circuit, then measure the gain with the diodes in-circuit. I keep the signal level low enough so that the diodes do not distort the signal. What I'm measuring is the change in gain caused by the diode leakage. From that I can calculate the effective leakage resistance of the diodes.

I also tried a similar circuit, using an opamp instead of a transistor, with diodes in the feedback loop. The results were similar. None of the Germanium diodes I have are suitable for use in a BMP because their leakage resistance is significantly lower that the 470K resistor in the feedback loop.

Once I'm satisfied that I have collected meaningful diode leakage data, I'll share it here.

 

[fig]

Once I'm satisfied that I have collected meaningful diode leakage data, I'll share it here.

Fantastic!

 

[mnemonic]

New germanium diode pedal name - the leaky Russian