Greer Green Giant

[rocket88]

Surgeon I'm the dumbass not you. I'll correct that mistake so no one else does it. I must have miscounted the rows when I designed it.

Also, beaker I haven't tried the d310's but I'm planning on it. And I what markings are on the Motorola 2n2222's? I have some old military ones that are awesome in fuzzes, but I. And find them as easily.

[rocket88]

pnp layouts have been fixed. also, still working on choosing the diodes i want. to be honest i feel like every Ge i've tried sounds great, and has a slightly different flavor to it. i feel like whatever diodes you choose you will get a great od/distortion/boost.

[rocket88]

finally settled on the diodes. i went with the D9D's. i find them to have a warm and fat sound, and smooth distortion when clipping, and add a deeper growl that i feel in love with. the other D9's i tried, including D9E, D9K, D9J, D9V, and D9B's as well as the 1D507A's have a little more treble to them, and since i want to use this more with my bass i prefer the fatness the D9D's add. i also tried aa143, OA-7, 1n34a (Ge and schottky workalikes), 1n270's, sfd-112, as well as LED's,and various common Si diodes. they all definitely have their own flavor.

the sfd-112's, D9K, D9J, D9E, and D9V's i think are the most transparent and have more clarity to them, which could explain why i hear them as having a little more treble. all great choices. the D9V's breakup a little earlier then the D9E, and have a little more punch. the D9J's are a little sweet, the D9K's are smooth and do add some growl. the D9E has the most treble to my ears, and clip later, to the point where it can be hard to make them clip, even if you play hard.

the 1n34a schottky workalikes seem to have the warmest tone to my ears and are SUPER fat and thick.

the D9B, OA-7's, aa143, and the 1D507A's were somewhere between having a fat sound and having more treble to them. the 1D507a's fully engaged are magic, and throughout the entire clean controls sweep there's amazing tone.

the only diodes i wasn't crazy about were LED's, they just didn't do it for me. i was hoping they would be "tube-like," but they just sounded harsh to me.

the 1n270 and 1n34a Ge diodes were just ok, IMHO, not bad, but nothing to right home about.

i tried to get the D310's into the socket, but could only get 1 lead into the socket, so i have to do some modifications to get them in and try.

also, depending on the diode you choose to use, the overall output when the diodes are 100% engaged can be drastically altered to the point where you need the output to be fully CW to be just above the bypassed volume. which makes me want to look at this circuit and figure out how to get more output so when you do have the clean pot fully pegged CCW you still get a boost. preferable without having to add a gain recovery stage after clipping.

[Silver Blues]

rocket88 wrote

also, depending on the diode you choose to use, the overall output when the diodes are 100% engaged can be drastically altered to the point where you need the output to be fully CW to be just above the bypassed volume. which makes me want to look at this circuit and figure out how to get more output so when you do have the clean pot fully pegged CCW you still get a boost. preferable without having to add a gain recovery stage after clipping.

I've been thinking the exact same thing since I began following this thread, and really the simplest way to do it would actually be to set up a simple recovery stage after the transistor/diodes, and then replace the saturation pot with a dual of the same value where the second half controls the gain of the recovery stage. Then you only have to tune the gain sweep of the stage so that the volume remains constant as you turn the saturation up. The second half of the dual pot would be either the feedback loop resistor of a non-inverting op-amp setup or the source/emitter resistor of a FET/BJT stage with the wiper connected to a booster cap. At it's worst it's 6 extra parts (op-amp, the other gain-setting resistor, a cap for the low-pass, an input resistor and then two resistors for the voltage divider for Vref) and at best it's three to five (transistor, drain/collector resistor, booster cap, possibly a coupling cap, and an input resistor).

[rocket88]

you lost me at the op-amp, did you mean the transistor? also, this brings me back to something you and i were working on a year or so ago with the Ge/JFET booster concept, like the phat phuk b. but that concept had the Ge as the second stage, as opposed to having it as the first stage in this design, that is if a gain recovery stage is added at the end, as was JFET based.


which by the way, i started doing more investigating on the phat phuk b, and it seems even simpler then i had thought. it's not 2 boosters, one pushing the other, but a JFET buffer that has a pot to control its output into the germanium booster section. not sure why i didn't think about doing something like that.  so now, it's time to hit the breadboard again for some designing.....

[Silver Blues]

Yeah sorry, meant the transistor. The op-amp I refer to would be possibly part of a theoretical addition to the circuit before the volume pot, as I outline later. Edited.

I kind of remember that, but can't recall exactly what the circuit was. Try out your Phuk idea (...) and see how it works, you never know.

This is what I meant with my last post.

[Surgeon]

Hey guys, I'm wondering if anybody has verified Rocket's PNP layout (without the diode switching).
I built it last night but only get a very very faint output. Tried a few different transistors (1t308, gt313, even a Si BC560), all with the same result. Tried to increase the trimmers value to up to 50 to no different result as well.

Just wondering...

thanks!

[rocket88]

I haven't had a chance to build the PNP version, but I'll take a look at it and see if there's something a miss. Out of curiosity, what are your voltages on the transistor? I'm wondering if I screwed up the charge pump, cause if I did that's going to be the issue.....

[Surgeon]

Thanks for the reply, I'll try to measure the voltages tonight.

I'm not implying that you made a mistake, I'm actually trying to prove that I, once again, did something bad or can't trust those damn germs...

[rocket88]

Lol. I know you're not implying that, nor would I take offense. Well I would if you started cursing me out and saying I fucked up or something like that, lol, but I have a strong feeling that could be the issue. Aside from one other pedal that I designed with the charge pump this really is the first that I made the layout 100% with one, so it's a strong possiblity. And if there is an issue that I didn't catch I'm glad someone would catch it so it can be fixed and we all get some mileage out of this effect.

[Surgeon]

I get weird voltagesbat the transistor... basically 7.6ish at all points....

[rocket88]

That's really not right. What happens if you turn the trimmer, does the voltages change at all?. I'm going to look over the layout and see if I fucked something up with the inverter. Check to see if you have any bridges by the transistor or if you the legs are touching. If I find something wrong with the layout I'll post a new one. Hopefully I'll have some time to make the layout and test it too.

[Surgeon]

Ok, I rechecked the voltages and I don't know what was wrong earlier but here they are now: (left is fully ccw, right is fully cw)
C: -9.23 to -9.18
B: -2.3 to -0.19
E: -4.72 to zero

note that this is with a 50k trimmer. I changed from 5 to 50 since I noticed that the only very faint signal I got was when the trimmer was fully cw, I thought it was worth trying...

[rocket88]

hmmm, i like the collector current, but the bass and emitter not so much. stupid question, cause i forget if you said this or not, the layout you used, it had a SWTC, right? cause if so, i'm thinking it's sucking all the output.......

also, i'm looking at how i made the layout with the charge pump on board, and i think i fucked that part up, cause i still have the diodes to actual ground, as opposed to -9V, since this circuit is now PNP not NPN, so i have to go back and fix that. what you could do is remove the charge pump from the board, and build a separate one and connect it like it should be (-9V to where ground should be, and ground to where +9V should be) and see if that fixes it. i'm 99% sure that's the cause of the problem.

Edit: i also caught an error in the PNP layout I posted with the tone control. the 2M2 resistor is in the wrong place, as is the link to the left of it, they should both be on row 2, NOT row 1. check your board and see if the 2M2 resistor and corresponding link is like that, if so i'm certain that's the problem. i'm also including an updated PNP Layout, without Tone Control. i think this is good to go now.

[Surgeon]

Thanks a lot Rocket!

I'll check these out tonight and post ASAP afterwards... forgive my ignorance but I'm not the best with abbreviations: SWTC? If you mean the diode switch, I used your PNP without it and included it the same way I suggested: from the holes of the actual diodes.

Cheers!

[rocket88]

Stupid wonderful tone control (SWTC). It was the name given by Jack Orman for a design of a passive tone stack that can be added to any circuit. So if you made the layout with the tone pot, that layout has the error. Also, the tone stack because it's passive is going to suck some of the output, so it would need a booster at the end, because there isn't enough output from the effect when the diodes are fully engaged. I'm working on another layout that will have a gain recovery stage after the tone stack to compensate.

Link to SWTC: http://www.muzique.com/lab/swtc.htm

[Surgeon]

rocket88 wrote

Stupid wonderful tone control (SWTC). It was the name given by Jack Orman for a design of a passive tone stack that can be added to any circuit. So if you made the layout with the tone pot, that layout has the error. Also, the tone stack because it's passive is going to suck some of the output, so it would need a booster at the end, because there isn't enough output from the effect when the diodes are fully engaged. I'm working on another layout that will have a gain recovery stage after the tone stack to compensate.

Link to SWTC: http://www.muzique.com/lab/swtc.htm

Oh ok, now I see. Yep, it had the tone control... but I would need more than a booster to get anything useable from the circuit at this point. To hear anything, my 1w head needs to be set on 10, while any normal pedal is easily heard on 1  or 2...

I'll try the circuit without the SWTC and see. Thanks for all the work!

[rocket88]

No problem. I'm going to remove the ones with the tone control, because until one of us tried it we have no way of know how much output you'ld loose. I should have another layout that has a gain recovery stage after the tone control. Also, the diodes you choose will determine the final output when they are fully engaged. With the D9D Ge diodes is just a hair above bypass volume when they are fully engaged. As I back off the diodes and get more clean in my signal the output goes through the roof.

i also fixed the error on the PNP version with SWTC. I still think it needs a booster at the end to regain the lost output, or you could wait till i make a version with a built in gain recovery stage to help raise the output.

[Silver Blues]

I'm going to resurrect this old thread because the itch to build one has struck me now that I own some germanium. I'd just like to know what everyone's favorite combination of transistor/diodes are?

I'm a very go-with-my-first-instinct kind of person and I was thinking 2SA49 and D9D might be cool. This'll be the next thing I try once my breadboard is clear once again.

[rocket88]

I've got an MP38a with D9D's or I may have changed them to D9B's I'll have to check the diodes again, I don't remember as it's been forever since I opened the back up.