Harmonic Perculator

[mattpocket]

Which clone is closest to the original, and do we have schem's/layouts lying around anywhere?

I have searched, and watched a couple of albini vids.

I think we are looking at:

A. TimE's Harmonic Jerkulator
B. Doug Hammonds Harmonic Speculator
C. The Brick

Matt

[tcobretti]

This is possibly the schem for it.  I say possibly because there has been speculation that it is not correct.

[mattpocket]

I have read that those schems have errors in and are not the same as the original. Something to do with the trannies being NPN or PNP. In the above i think they are both NPN, and a lot of people say there is one NPN and one PNP?

Matt

[Stompin Tom]

I suspect that the original mad scientist (as albini likes to think of him) who created the Percolator and chuck collins (http://pages.prodigy.net/chuckcollins/percolator.html - my friend has one and it sounds excellent, BTW) fine tune each circuit to taste... of course I could be wrong. I made Tim's jerkulator and modded the crap out of it to try to get it close to the percolator's sound... never really got there, but I liked the end result anyways. I never tried the brick or speculator... although I always meant to.

Oh, and yes, one npn and one pnp... one Si and one Ge...

[mac]

I posted about Hermida´s schem V2.

http://www.diystompboxes.com/smfforum/index.php?topic=49035.0

I used several trnasistors, including a all Ge version that sound the best.
The trick is to use trimpots for r5 and r7. If I remember well the npn should be a Si or a Ge almost no leakage, <50uA. If the npn is leaky maybe trimpots for r1 and r4.
Once you find the G point it sounds amazing.

mac

[RLBJR65]

Gut shots, revised schematic, layout, etc.
http://www.diystompboxes.com/smfforum/index.php?topic=36110.40
It's Percolator BTW

[Steben]

Seen it before. It looks very much like a cascode amplifier (common emitter + common base amp), with a complicated feedback.

[mattpocket]

RLBJR65: I couldnt find one schem or layout that worked in there. According to that thread link you posted MartyB?? put one in his gallery, but theres none there now.

Anyone have anything?

[slacker]

I have read that those schems have errors in and are not the same as the original. Something to do with the trannies being NPN or PNP. In the above i think they are both NPN, and a lot of people say there is one NPN and one PNP?

Matt

In those 2 schematics Q1 is PNP Q2 is NPN. If you look at the arrows on the emitters Q1s points towards the base so it's a PNP. Q2's points away from the base so it's NPN.

[mattpocket]

Those schems are correct then?

If so, has anyone built one from this schem? I want to know that they are good?

Matt

[LP Hovercraft]

Use the input of version 1, but follow version 2 from the 1st tranny back (including the 220K between the base and collector).  I made one a long time ago and it sounds very Big Black-esque.  I never got it to work with the 1n34 at the front. 

[RLBJR65]

Sorry, I was not aware MartyB took his stuff down

I believe DanN used this schematic for his PCB layout http://users.rio.com/senorris/junk/Percolatorplay.gif

You did a nice job with your LoFoMoFo layout give the Percolator a try. Have you tried bancika's DIY layout creator yet?
IMO it makes the job much easier. http://www.storm-software.co.yu/diy/index.php?project=software

[johngreene]

Sorry, I was not aware MartyB took his stuff down

I believe DanN used this schematic for his PCB layout http://users.rio.com/senorris/junk/Percolatorplay.gif

That bottom schematic is only correct if you change the Q1 transistor to an NPN. It would appear that some of the harmonic percolartors were made with 2 transistors that were the same (NPN and Si?) and there were others made with Q1 being a PNP Ge transistor which is basically the same schematic as the top one only with the input Diode to ground removed. R6 is something like a 4.7K too.

--john

[RLBJR65]

That bottom schematic is only correct if you change the Q1 transistor to an NPN. It would appear that some of the harmonic percolartors were made with 2 transistors that were the same (NPN and Si?) and there were others made with Q1 being a PNP Ge transistor which is basically the same schematic as the top one only with the input Diode to ground removed. R6 is something like a 4.7K too.

? Dan posted in that thread that he used a 2SB77 GE for Q1 that's a PNP. http://www.datasheets.org.uk/datasheet.php?article=357683

[johngreene]

That bottom schematic is only correct if you change the Q1 transistor to an NPN. It would appear that some of the harmonic percolartors were made with 2 transistors that were the same (NPN and Si?) and there were others made with Q1 being a PNP Ge transistor which is basically the same schematic as the top one only with the input Diode to ground removed. R6 is something like a 4.7K too.

? Dan posted in that thread that he used a 2SB77 GE for Q1 that's a PNP. http://www.datasheets.org.uk/datasheet.php?article=357683

I would be surprised if he did and it worked. From the pics on the web that Dan's bottom schematic corresponds to, you can see that the 2 transistors are very much the same in size and shape and are wired in a cascode type arrangement. If you look at the picture of the harmonic percolator that Chuck Collins has on his website, you can see that Q1 is different in size and shape and you can definitely tell that the emitter tab is connected to the second transistor. You can also see that the traces under the board match the ones from the harmony central thread except the holes are drilled differently to support the 220K resistor connecting to the other side of the transistor. Amongst several other things.

I'm pretty sure that the schematic that is shown on Barge Concepts webpage is correct for the Harmony Central thread's pictures.

--john

[Dan N]

Surprise surprise! I did and it did!

Ha! It's been so long...

I can't find the one I built before so I just made another. I used a BC549C for Q2.

For Q1 it worked best with a silicon NPN with E to the 1K/20K/(I used 1uf film) junction.

For laughs, I threw a PNP 2SB187 into Q1 with C to that 1K/20K/1uf  junction. Not quite as much growl, but it worked fine. The tranny was just a handy pull knocking around a part drawer.

I'm with John on what was in the photos, and the 2 NPN is what I would run with if I was going to put this in a box. I like fuzz and weird stuff, so this thing does not make the cut for me.

[johngreene]

Surprise surprise! I did and it did!

Ha! It's been so long...

I can't find the one I built before so I just made another. I used a BC549C for Q2.

For Q1 it worked best with a silicon NPN with E to the 1K/20K/(I used 1uf film) junction.

For laughs, I threw a PNP 2SB187 into Q1 with C to that 1K/20K/1uf  junction. Not quite as much growl, but it worked fine. The tranny was just a handy pull knocking around a part drawer.

I'm with John on what was in the photos, and the 2 NPN is what I would run with if I was going to put this in a box. I like fuzz and weird stuff, so this thing does not make the cut for me.

Heh, I guess I should retract the "I would be surprised if it worked" especially after the discussions of using transistors 'upside down'. It was just a wrong thing to say. But the fact that it didn't have as much 'growl' falls in line with what is expected when you use a transistor with emitter and collector swapped.

--john

[mattpocket]

I am really confused now. Just to clarify.

Both of those schematics posted above are correct? Which on should I use.

What tranny setup am I going for? NPN/NPN? PNP/NPN? What trannies (part numbers) do you suggest?

Thanks guys,

Matt

[RLBJR65]

Thanks John I had not seen that schematic. Could be like 4 versions if all the schematics are correct

Matt, I'm sure I have MartyB's layout around here someware. Pretty busy this weekend (family comming to my place) but If you want it I'll see if I can dig it up for you.

Thanks Dan does yours sound like the clips at HC?

Q1 low gain?? NPN??
Q2 med to high gain NPN 2N3904, BC549, 2N5088, etc.

I planned on building MartyB's or Dan's version but never got around to it. I have built both the Jerkulator (with clipping diodes added) and the Speculator AKA The Brick. Unfortunately I don't have either anymore, one of them I gave away and the other I tore apart. Both sounded okay but I don't recall either of them sounding like the clips at HC.

Richard

[johngreene]

I am really confused now. Just to clarify.

Both of those schematics posted above are correct? Which on should I use.

What tranny setup am I going for? NPN/NPN? PNP/NPN? What trannies (part numbers) do you suggest?

Thanks guys,

Matt

I think version 2 is the one you want, but without the input diode. The input cap to ground is 100pF and the input coupling cap is .05uF. 90K should be 82K (or 91K). R6 should be something like 4.7K.

I think the schematic on Barge Concepts is how it was originally designed. Only because the original description of the Percolator describes it as being very low currenthttp://pages.prodigy.net/chuckcollins/harmonic.jpg. So a common method of reducing current consumption but have 2 transistor stages is to stack them so they share the same bias current. Make the junction between them AC ground and you have an input emitter follower and a output buffer with gain. Many VCOs are constructed this way. The bottom transistor is a colpitts VCO and the top transistor is a buffer with gain. The stack uses the same amount of current as just one device. The designer probably thought the original design was lacking in gain so he changed the bottom transistor to a gain stage but did it in such a way that he could use the same PCB artwork. Just had to drill a couple of holes differently.

Compare the traces (visible through the PCB) of this photo:
http://pages.prodigy.net/chuckcollins/oldpercolator.jpg

And this one:
http://i14.photobucket.com/albums/a333/mbet/CIMG3329.jpg

You can see the traces under the board are the same but the components around Q1 are different.

--john