Interfax - Harmonic Percolator  [schematic]

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

skumberg wrote:I just breadborded this thing using the sardonic albinator schem. I'm using 2n404 and 2n3565(hfe 260) but AA119 diodes(Vf around 0.3). It's got a healthy output but I don't get any crazy fuzziness like on this one . More of a smooth distortion. It's similar to the YT sound clips I've heard from fredriceffects so I guess it's correct. I found good use of the bass control on my g&l legacy strat. I think a similar filter in place of the harmonics control would be better as I control the input with the guitar anyways. The filter consist of a 2.2nf in parallell with a 1M pot just before the 250k volume control. So just a hipass filter. This way it would work better with humbucker guitars.
the HP in that video isn't biased properly at all, it sounds horrendous. :lol:

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phibes
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Post by phibes »

I agree with Alex on his noise gate idea. I did the same thing with a NS-2 and had very pleasing results. You can get a really nice decay die off with the clipping and you can keep it on balls to the wall without having to worry about the squealing. I know Steve Albini uses a MXR is his pedal chain and my guess is it's there to work with the Perc. The last time I seen Shellac was almost ten years ago so I can't remember when he stomped it on and off. The 'Prayer To God' tone is easier to achieve with a Noise Gate.

One improvement I think would work really well would be to incorporate a blend control instead of the input gain control. I like doing the faux effect with a 4 input amp using the perc between the channels and controlling how much the signal comes in through the channel volume. I think the Perc sounds best with everything all the way up so I rather control how much crazy clipping I want to bring behind the dry signal rather then just control how crazy the box can get.
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mr.stahl
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Post by mr.stahl »

the HP in that video isn't biased properly at all, it sounds horrendous. :lol:[/quote]

Dear bottle,
many thanks for your comment on my HP. I think it's a waste to post a comment like this!
The HP you see in this video is just perfect. It does excatly what it should do and it sounds like the original does!
When you talk about biasing the trannys you should better understand the circuit first!

Steffen

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bootle
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Post by bootle »

hi steffen,
my apologies, no offence meant!
I noticed afterwards you had another video with another HP (or the same one?) along with a collins clone and it sounded very good.
maybe the audio quality of the first video doesn't do it justice, but it didn't sound too good to me and I didn't want that guy (skumberg) thinking that's how it should sound if he was building one.
if I am mistaken, I apologise.

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skumberg
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Post by skumberg »

mr.stahl I also saw your other video and it sounds very good. You also have a cool sound with the HP bypassed.
I guess you are using the 220k 750k 20k bias resistors. I measured 10 2n404(bought from minifux) and they are all high gain, all above 160hfe using geofex method. I tried a 2n404 which had the same voltage(hfe+leakage=2.61V) on the geofex tester as the 2n3565(2.61V) and changed the bias resistors to what you got and now I have enough gain from the thing, noise increased as well. I'll have to get some lower hfe 2n404 and 1n695 and try the mr.bill values again.

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mr.stahl
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Post by mr.stahl »

Hi bottle,

I accept your apologies. It was the first thing I read with my morning coffee today - so I was a bit upset.
The HP from the first video was a preliminary tryout version with the same parts as the other. I hope you recognized that the one with the decals is my self made.

To skumberg
The 2N404 is a switching transistor - this is very important to notice.
You'll need a very low hfe 2N404.

Steffen

By the way: I still have some HP's lying around...

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Post by ringworm »

Does anyone have voltages to compare for the two circulating versions, the Collins and the original/Mr Bill's?

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bootle
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Post by bootle »

these were taken from a collins clone (not by me).
don't know what the supply voltage was.

PNP 2N404A:

E 1.61 v
B 1.46 v
C 1.46 v

NPN 2N3565:

E 1.62 v
B 1.93 v
C 2.49 v

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bootle
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Post by bootle »

jeez they were on page 2 :roll:

mr bill's voltages weren't from a stock unit, they were from a modifed unit, from what I've gathered.
the collins clone is traced from original stock units.
fwiw I've had best results using the collins schem.

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Post by ringworm »

Thanks, I should have checked. I can't find any reference to voltages from an original unit in the thread to compare. Did Mr Bill take any?

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Post by westarttodrift »

Is it at all possible to make a decent all Si Percolator?

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Post by phibes »

westarttodrift wrote:Is it at all possible to make a decent all Si Percolator?
http://www.home-wrecker.com/harmonic.html

I built the Jerk years back before when info on the HP-1 was still pretty hit and miss. It's a really great sounding silicone unit. Add the clipping diodes on the end you'll sound pretty close.
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Post by rune-hammer »

If you guys and girls are having trouble finding the fancy transistors in the posted schematics I can recommend trying a combination of AC128 and BC108A. The A in BC108A was very important for the sound of the circuit, the other BC108s and 2N2222s will have too much gain and will not sound right, at least the didn't for me. The AC128 is of course a germanium transistor, but should be fairly easy to find.

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mr.stahl
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Post by mr.stahl »

does anybody remeber the early dual NPN HP's?
Here is my clone...
IMG_3025copy.jpg

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Alex Frias
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Post by Alex Frias »

Pretty awesome looking!

I built a couple of this version HP's a long time ago and they sounded really bad, how does sound your one?

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mr.stahl
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Post by mr.stahl »

Hi Alex,
this version sounds really really good. It doesn't have the germanium gnaaarrrll.
I really like the blend between the distorted and undistorted sound.
I just need a blue 2.2uF tantalum to let it also look perfect!
Steffen

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Alex Frias
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Post by Alex Frias »

Glad to know that!!!

Could you post the exact values of components and the exact circuit?

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mr.stahl
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Post by mr.stahl »

here it is - good luck!
HP1-dualNPN.jpg

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Kregg
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Post by Kregg »

I have one of Chuck's HP's and I want to make a few alterations, including housing it in a different box.
I figured before I tear apart a perfectly good device I'd ask the experts for guidance first.
1/ Add a true bypass.
2/ Add an LED indicator light.
3/ Either add a battery on off, or a DC jack.

Pros/Cons/Diagrams/Links to all of the above are welcomed. Thanks
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Post by timhulio »

I've a few suggestions, one of which I'll PM you due to board etiquette.

1) This pedal is already true bypass.
2) You can do this using a 3pdt switch instead of the dpdt in there. Unless you want to get into Millenium bypass etc
3) Drill a hole and mount a 2.1mm DC jack. Remember it's center negative.

All these can be performed on the original enclosure, but because of the board shape/size, you won't save too much space removing it and putting it in a standard BB enclosure.

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