Interfax - Harmonic Percolator  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...

Re: Interfax - Harmonic Percolator

Postby bockduse » 29 Aug 2012, 21:57

Hi everybody,

i bought a used Interfax Harmonic Percolator on ebay quite a while ago and after using it, it seems to be broken.
I think it' s one of the reissues but i don't know exactly.
Here are some pics of the pedal and hopefully someone can tell me what version I have.
The problem with the pedal is:
When the Harmonics lever is up, i get the full fuzz/distortion but only when the balance lever is NOT down.
The balance lever seems to function as volume. So when the balance is down, no sound comes out of the box
and when you push it to the top, it just makes the distorted signal louder, but doesn't change the balance between the clear
and the distorted signal. i don't hear a clear signal at all, cause when the harmonics are down, you don't get a sound out of the pedal,
no matter at what position the balance is.
so, can anyone help me with my problem?
thanks in advance
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Re: Interfax - Harmonic Percolator

Postby bockduse » 29 Aug 2012, 22:00

and another one from the backside
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Re: Interfax - Harmonic Percolator

Postby John Lyons » 30 Aug 2012, 03:31

The Balance slider is a Level control.
Controls the balance of Level between bypassed and "on". :D
Just a little confusing but the order convention was to call it "balance"
It should not mix clean and distorted signals while the pedal is engaged.
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Re: Interfax - Harmonic Percolator

Postby bockduse » 30 Aug 2012, 08:27

Oh, ok!
But still, when the pedal is on and the harmonics lever is down, there's still no sound coming out of the pedal,
even when balance is all up.
And pushing up the harmonics just makes the signal louder, but there's no change in the amount of the distortion.
It's always fully distorted and you just can control the volume with the harmonics lever.
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Re: Interfax - Harmonic Percolator

Postby cortezthekiller » 01 Dec 2012, 19:11

Recently built a few percolators, and wanted to show this build. I used Ivlark's tagboard layout and modified it to the Albini specs. I tried both the "stock" version and the "albini" version a few times and I think that the albini one sounds the best. It is smoother and more harmonically rich with less fuzzy splattery weirdness than the stock. In this build I used old RCA silicon can diodes which gives it plenty of volume and drive. Also, for the transistor I used a black can RCA PNP germanium with leakage around 150 and hFE of 70. Very awesome sound and thanks to Ivlark for the excellent layout!
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Re: Interfax - Harmonic Percolator

Postby norim_13 » 11 Apr 2013, 23:59

Hi!

I've searched in many places, but still can't get an answer to my question these days... :P

I'm building a percolator for a friend. Is it ok to use 2N404 instead of 2N404A?

Thanks and best regards
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Re: Interfax - Harmonic Percolator

Postby LucifersTrip » 13 Apr 2013, 00:03

norim_13 wrote:Hi!

I've searched in many places, but still can't get an answer to my question these days... :P

I'm building a percolator for a friend. Is it ok to use 2N404 instead of 2N404A?

Thanks and best regards


the model # means nothing. you just need to find something with the right hfe & leakage that works for you.
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Re: Interfax - Harmonic Percolator

Postby astrobass » 23 Jul 2013, 14:28

Bumping this thread because I just put one of these together and I love it.

Don't have any > 1M resistors laying around, so I built the 750K version with the resistor from the Ge transistor's collector to ground at 20K. Sounds awesome, but when the order of resistors I'm waiting on shows up, I'll try the other version.

Used a P416B that I measured (with leakage accounted for) in the mid 40s, and I think a 2N3904, but whatever it was, the silicon has an Hfe of like 260 something. So, close to Mr. Bill's specs on that front.

Tried the pre-gain control, found it to be as useless as most are, removed it. Tried an input blend cap, and saw something interesting:
With the blend cap using a 1 uF and 1 nF cap and a B100K, the bottom range cleaned up substantially. Didn't really sound good that way though. So I swapped the 1 nF for the schematic indicated 47 nF and kept the 1 uF, and this is really decent. The bottom end still distorts effectively and rolling it to the 1 uF brings in more bottom and makes the distortion more intense at the same time.

So, it seems that a lot of the clipping comes from overdriving the ge transistor. This meshes with the previous findings that silicon only variants don't sound right. Maybe that conclusion is based on a misinterpretation of the circuit's functioning, I won't claim to have a great grasp of the theory side yet, but at any rate, an input blend cap is a useful mod here.

I also bumped up the output cap substantially, though. I think it's a 1 uF cap right now. That may play a factor in the value of using the input blend cap.

Anyhow, using a Godin active bass into an Eden Nemesis 4x10 combo, gear that bears no resemblance to that used by Bob Weston, I got > 90% of the way to the End of Radio bass sound without even trying. And I love that sound. So, quite pleased.
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Re: Interfax - Harmonic Percolator

Postby astrobass » 23 Jul 2013, 20:36

Alex Frias wrote:The excitement makes me a fool with one more mistake, C3 IS 2.2uF on the Jonathan's Pussy Fuzz, no double values on it.
A better draw:

pussyfuzzClone.JPG


So, Mr moderator, if you can erase the wrong schematic...


So, I tried changing R1 to 3M9, R4 to 91K and R2 to 51K and got nothin' usable.

To be fair my values were 4M7, 100K and 47K, but those are 1% metal film and Mr. Bill measured his "3M9" at 4M4, so I figure I'm in the ballpark where things should sound mostly right, but no dice.

R1 at 750K, R4 at 20K and R2 at 220K sounds amazing though. So go figure.

Anyhow, I've got a pedal that sounds the way I wanted it to, even if I don't understand why my results are so different. Maybe it's the transistors. My Si is a 2N2222A and the Ge is a P416B. I measured both and they're very close to what Mr. Bill had for his, though.

But anyhow. Skip the pregain and add a blend cap. That's my advice. I also used a 100K for my balance/level pot, the 50K seemed quiet. Didn't A/B the change, so maybe it didn't change much. Sounds perfectly good with a B100K there though, if you don't stock B50Ks.
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Re: Interfax - Harmonic Percolator

Postby astrobass » 29 Jul 2013, 14:57

I tried one more mod with this thing, adding a switch to swap between the 1N60s I've been using and a pair of 1N914s in the same config with the series resistor.

I purposefully clicked the switch an unknown number of times before boxing it up, with no indicator light for which set of diodes was in use.

The difference was barely noticeable at first. At lower volumes and with the input blend towards the thin end, there's almost no difference. At higher settings and on bass guitar particularly, one of the modes sounded substantially less good, more buzzy/synthetic sounding. That was the 1N914 side, determined by opening the box up and checking the switch position using my DMM.

So my take away is, the diodes are of minor importance but you probably do want to use germanium rather than silicon there. I can't imagine being blown away by the difference between 1N60s and 1N34As or any other Ge diode. Going to remove the switch and just use the 1N60s.

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Re: Interfax - Harmonic Percolator

Postby astrobass » 27 Sep 2013, 15:11

Built this unit to Sardonic Albinator specs for my buddy's birthday. Skipped the pre-gain. I did up a PCB too, I'll post it later if anyone is interested.
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Re: Interfax - Harmonic Percolator

Postby pinkjimiphoton » 06 Oct 2013, 17:05

check out my photonic juergulator. 4 knob variant. it's kinda cool.


Link


viewtopic.php?f=28&t=23031
"When the power of love overcomes the love of power the world will know peace."
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Re: Interfax - Harmonic Percolator

Postby joegore » 15 May 2014, 18:28

Hi folks! I haven't posted for a while, but I wanted to share a link to an article on my (non-commercial) site that includes demo video of four Harmonic Percolator variants. (Sadly, I have no original, but I rounded up all the original parts, thanks to Christian Magee from Tube Depot, who sent me a couple of 2N404As for evaluation.)

Not to spoil the punchline, but ... the exact parts don't matter much. It's all about the topology, man. 8)

http://tonefiend.com/guitar/museum-lost ... ercolator/

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Re: Interfax - Harmonic Percolator

Postby disorder » 12 Oct 2015, 00:10

On the Collins clone that uses two 1uF capacitors, is the silver mica 100pF or 390pF? what about on the version that uses two 100nF caps... what is the value of the silver mica there?
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Re: Interfax - Harmonic Percolator

Postby PEPPER! » 14 Oct 2015, 19:07

somebody just sold one on Reverb for TWO F*CKING GRAND. for a Percolator.

http://reverb.com/item/1197481-vintage- ... eve-albini

the ad had a decent gut shot:
Image
I know the originals vary a bit so I thought this may be of interest as well as comedy/tragedy value. dude says he bought it from Harry Belafonte (?)

disorder wrote:On the Collins clone that uses two 1uF capacitors, is the silver mica 100pF or 390pF? what about on the version that uses two 100nF caps... what is the value of the silver mica there?

its 390pf on the 1uF guy, not sure about the other as I can't find a schematic with 2 100nF caps. there's a layout on turretboard.org - don't know if it's from the Collins version - with 47nF in and 100nF out that has a 100pF cap.

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Re: Interfax - Harmonic Percolator

Postby disorder » 15 Oct 2015, 16:58

http://i324.photobucket.com/albums/k349 ... rsion2.gif

That seems to be the other "accepted" NPN/PNP version of the percolator I think. Two 1uF electros or two 0.1uF (100nF) ceramics.
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Re: Interfax - Harmonic Percolator

Postby astrobass » 12 Dec 2015, 05:43

Aishabag23 asked for my PCB layout, but I lost it a while ago. It was kind of trash tho. So I've done up a brand new one, and it is WAY better. 2" x 1.5", board mounted pots, ground pour with a 50 mil isolation and 86 mil traces. 300 DPI un-mirrored negative is attached.

Sardonic Albinator Home Etch Layout.png


Sardonic Albinator Home Etch Layout.png
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Re: Interfax - Harmonic Percolator

Postby astrobass » 12 Dec 2015, 05:44

Oh that tiny little break between the right side of the ground pour and the ground side of C1, that can be bridged. It would be if I didn't have thermals on.
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Re: Interfax - Harmonic Percolator

Postby astrobass » 12 Dec 2015, 05:47

Ugh one last note: I specced the MPSA18 there. I don't know that it's a particularly good choice for this, I just left the label there so that in the future folks will be able to look up the datasheet to know which pinout the board uses for Q2.
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Re: Interfax - Harmonic Percolator

Postby aishabag23 » 12 Dec 2015, 17:16

astrobass wrote:Aishabag23 asked for my PCB layout, but I lost it a while ago. It was kind of trash tho. So I've done up a brand new one, and it is WAY better. 2" x 1.5", board mounted pots, ground pour with a 50 mil isolation and 86 mil traces. 300 DPI un-mirrored negative is attached.

Sardonic Albinator Home Etch Layout.png


Sardonic Albinator Home Etch Layout.png


Thanks a bunch! And happy holidays to you.
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