Harmonic Percolator - make one!

[pinkjimiphoton]

i did years ago, dino, a couple versions, including alll npn. they all sounded about the same to my ears, but i don't really remember what i did, its been at least 6 or 7 years since the last one.
when i get done with the latest order i'll see if i can mess with it on the breadboard some.
i found this circuit to be REALLY weird and almost ANYTHING will fuzz in it pretty nicely in almost any combination, ge, si,npn and pnp. they don't necessarily have to be npn/pnp with ge as i recall. a lot comes down to leakage and gain.

wish i was more help. making popcorn.

ps... merry christmas to you and deb bro! hope all is great!

[digi2t]

wish i was more help. making popcorn.

ps... merry christmas to you and deb bro! hope all is great!

No worries bro. It's just been a while since I futz'd with this circuit, so I was just looking for someone to validate what I'm hearing.

And a very merry Christmas to you and yours, and of course, happy holidays to all here as well. Quiet on all fronts here, just like we like it. 

[duck_arse]

Dino - if you have a P416b lying about, plug that in for the pnp. when I built my coffee pot, I was trying to tune for "the sub octave", and the P146b didn't suit in that version - but it sounded ..... well, it grabbed me as the best of the russians I cycled thru the bb. couldn't hurt to listen, could it?

are you getting subs on yours now?

[digi2t]

Dino - if you have a P416b lying about, plug that in for the pnp. when I built my coffee pot, I was trying to tune for "the sub octave", and the P146b didn't suit in that version - but it sounded ..... well, it grabbed me as the best of the russians I cycled thru the bb. couldn't hurt to listen, could it?

are you getting subs on yours now?

I do believe that I do have 416's, from the Wow Signal build if I'm not mistaken. I'll check tonight and give it a whirl. No, no subs, but I'm not tuning for them either. Just wanting to kill the fizz on the decay, which I seem to have done with the germ NPN. It sounds quite woolly. I took the breadboard into the studio yesterday, and tried it at volume, and it was quite pleasing indeed. It made cycling the guitar volume very effective.

I'll check my stash and report back.

[pinkjimiphoton]

found this, can't seem to find all the graphics tho

https://www.diystompboxes.com/smfforum/index.php?topic=99596.msg887302;topicseen#msg887302

[pinkjimiphoton]

https://www.youtube.com/watch?v=NlUf9ZMt0h4

the germonic perc from days of yore

"harmonic percolator, but all germanium, no silicon.
2x 1n34a diodes, one 2n2273 ge hfe 87 one ac176 ge hfe 80"

[digi2t]

Yup, that's what I'm talking about. Much more organic, though I've stayed down in the gain range.

I've tried the following in Q1 tonight;
- MP42B - gain 78 - leak 0.0
- MP16B - gain 52 - leak 0.0
- P416A (sorry duck, no Bees) - gain 41 - leak 0.0
- 1T308B - gain 67 - leak 0.0

Q2 keeps the GT404B, with a gain of 62, leakage at 0.1mA.

My favorite combo to date is the 308/404. I also reduced the 220K feedback resistor on Q1 to 205K (strange value, I know, but I had I had some really cool glass resistors on hand, so I'm going for maximum Spaceman mojo here). This edged back the fuzz a tiny bit. Finally, I found that tweaking the collector resistors so I get 1v on Q1C (10.8K), and 2v on Q2C (74.7K) is really the sweet spot. By "sweet spot" I mean when you strike an open chord and let it ring, you get shimmering harmonic notes that cascade through the mix as the chord decays. Also, the clean up is beautiful. There's still so much gain on tap that you can easily just run the Harmonics pot at 50%. Plenty of bark just loafing. Crank the Harmonics pot and it just gets nasty quick, in a good way though. There's a crispiness to it, but not fizzy. It'll probably work really well on a darker amp, which I plan to test on tomorrow. Traynor YBA-3 Custom Special > 2 x 12" Texas Heats. I also have a Univox 1051 on standby as well. It'll be Doomsville around here tomorrow morning as soon as Deb steps out the door.

The fact that the two transistors are close gain-wise might have an impact, though I'm really not sure. All I know is that using transistors in the Q1 spot that were higher/lower didn't tickle my ears like the 308 did.

That's it... calling it a night.

[MaxPower]

Finally tried this. The jerculator(sp?) version anyway. If anyone wants to make an audio oscillator just disconnect the 22uf cap. Frequency range is limited as is but can be adjusted by the input pot and/or your guitar volume/tone controls. The waveform sounds more sawtoothy than square to me, if anyone cares and can be bothered to check it with a scope. Similar to those relaxation oscillator circuits I guess.

And no, playing the guitar has no effect.

[digi2t]

Follow up on my previous report....

As is the norm, a 15w transistor practice amp, feeding a pair of Bose headphones might sound glorious, but real world conditions didn't bear quite the same results.

Not that I had to make wholesale changes mind you. Simply tweaking the emitter voltages on both transistors seemed to work fine. I ended up with about 1.8v on Q1, and 2.4v on Q2. I was still getting a tiny bit of fizz at 1v and 2v, but the tweak cleared it up. What that amounts to resistance-wise I can't say at the moment, the paper is at home. I'll add that in later today. Of course, there's also the "breadboard vs. boxed" factor. It might be just me, but I've had a few fuzz circuits on the breadboard that react one way, only to sound really different boarded and boxed. We'll see.

Overall, quite respectable. Like I said, lots of bark and bite at half throttle, with adequate flexibility via the guitar volume. The clean up wasn't what I was hearing through the 15 watter. In my best Hippynese - through the YBA, it gave a bit more grit to the stringiness when you rolled off the guitar volume, but cool nonetheless.

I guess I'm at the point where I'm willing to box this. Now... if only the boards would get here.

UPDATE:

Resistances for the Q1 and Q2 collectors are 16K and 98K respectively. That gives me 1.219v and 1.898v on the respective collectors. You can also push Q1 collector resistance alone up to 26K, which ups the voltages to 1.815v and 2.440v respectively. This pumps up the roar up a bit more, but the roll off is dirtier. It's a trade off. Still gives excellent performance though.

[rankot]

I'm having trouble with hfe measurement of my Ge trannies: if I measure with my DMM, they're from 80-120, if I measure with my GM328 component tester, they all appear with hfe=60-62. Whom to believe???

[digi2t]

I'm having trouble with hfe measurement of my Ge trannies: if I measure with my DMM, they're from 80-120, if I measure with my GM328 component tester, they all appear with hfe=60-62. Who to believe???

I should specify, I test all my transistors with a Peak Atlas DCA55. Other than that, I would use R.G. Keen's method of testing germanium devices.

[digi2t]

FINALLY! Committed to a board, and ready to box. Only took.... how many years? 

[amz-fx]

I'm having trouble with hfe measurement of my Ge trannies: if I measure with my DMM, they're from 80-120, if I measure with my GM328 component tester, they all appear with hfe=60-62. Who to believe???

Transistors can yield different hfe values if tested at different currents. Higher current usually equates to higher gain measurements.

http://www.muzique.com/news/transistors-and-hfe/

regards, Jack

[rankot]

I've just finished one with the following values:
Q1 AC152, hfe=41, Vc=2.55V
Q2 2N2369, hfe=55, Vc=6.77V
B100k instead of A100k for Harmonics pot, gives more control, at least to my ears.
Diodes 1N34x2 + BAT46+1N4148 (switchable)
R1 220k
R2 20k
R3 750k
R4 18k
R5 4k7

Sound is interesting, not sure if it is 100% original HP since I tested it on bass amp, but sounds quite good to me. I tried with trim pot in place of R4 and finally settled with this really low value, but it gives me the most volume. I don't know, maybe that's wrong, but sounds good to me. Maybe I could first set Q1 Vc, but I soldered R2 first and, since it is squeezed between other parts, it was very complicated to remove it and put a trim pot instead, so I settled with Q1 Vc at 2.55V.

[rankot]

Just finished another one for my late friend's little son - those are the values. It seems to be singing even nicer than the first one, which was closer to Albini specs. This one is almost classic HP. I used two pots to find sweet spots for collector resistors:
Q1 MP20, hfe 52, Vc=4.67V, Vce=0.22V
Q2 2N6517, hfe 140, Vc=5.84V, Vce=1.07V

Resistor values, following schematic above:
R1 750k
R2 220k
R3 39k
R4 56k
R5 2k2
D1, C5 and C7 not installed, C3 is 1u.

[Rob Strand]

Q1 MP20, hfe 52, Vc=4.67V
Q2 2N6517, hfe 140, Vc=5.84V

Given the emitter voltage must somewhere in between those collector voltages  (not necessarily midway) ,
the collector emitter voltages are quite low, close to 0.6V.


EDIT:
After looking at digits's schematic, I remembered when he did that work he come-up with different voltages.  In particular the voltage at the collector of Q1 had a higher Vce that I'd seen in the past.   (On the schem he's quoting Vc which is measured to ground not Vce measured between c and e.)

[rankot]

I have also measured to ground - so those are Vc,gnd voltages, not Vce. I used pots for this and set them where I liked sound the most and I suggest that everyone do it that way, so no need to chase a voltage at all - chase the sound.

[Rob Strand]

I have also measured to ground - so those are Vc,gnd voltages, not Vce. I used pots for this and set them where I liked sound the most and I suggest that everyone do it that way, so no need to chase a voltage at all - chase the sound.

Yep, I realized that.   Since from you two Vc measurement we can guess the Ve is in between the two Vc say around 5.3V.   Since your Vc1 4.67V we can guess your Vce1 = 5.3V - 4.67V = 0.63V.    Digit's Vc1 on the other hand is about 1V much lower than your Vc1 of 4.67V, so that makes me think his Vce1 is somewhat larger than your 0.63V.

[Trying a bit harder with the numbers I got Ve = 4.89V, Vce1 = 0.22V and Vce2 = 0.95V, as expected both quite low.]




Late EDIT:

It's still possible for digit's circuit to get a low VCE across Q1.  What happens is the voltage between the emitters can drop down toward the voltage set on Q1's collector.

[iainpunk]

some ou you might already have read my recent posts and schematics, but i havent seen this thread before, and it seems a good place to post the schematic and name explain:


the 39k resistors are just place holders, if you decide on building it, i recommend experimenting on breadboard beforehand to find the resistors that match your transistors and diodes best.
the 4n7 was initially selected becaus its the value i have most of, about 60% of all my caps are 4n7, but in lots of diffetent materials and packages, i tried smaller and larger caps, but i keep coming back to the 4n7, it just sounds the best to my ears.
i have also put my NPN transistor in reverse Beta, that gives a really nasty, nasal, noisy tone

i called it the Harmonic Instant Coffee

Code Select Expand


percolator coffee is nice, high quality, fine tuned by the masters of coffee making and soft in aroma's.
instant coffee is mediocre at best, poor quality, the cheapest beans are used and can be really harsh tasting.
Harmonic Percolator is nice, high quality, fine tuned by the masters of pedal building and is soft in tone.
Harmonic Instant coffee is NOT NICE, simplistic, cheapest parts are great for it, and can be really harsh sounding.


cheers, Iain

cheers, Iain

[Rob Strand]

the 39k resistors are just place holders, if you decide on building it, i recommend experimenting on breadboard beforehand to find the resistors that match your transistors and diodes best.

It's an interesting idea since it forces the collector-emitters voltages  to be low.  Probably sounds a little different to no diodes and stuffing around trying to get the bias right.    Maybe a comprimise is to only use one of the diodes then adjust the collector resistor of the transistor without the diode.

If we unravel the series connection of the Percolator it becomes something like Howies Metal Simplex.  Funny thing is the Metal Simplex sounds like a fairly low gain pedal.  Maybe the size of the CB resistors does that.

https://www.hgamps.com/2n3904-metal-simplex-fuzz/