Walco Effects - Schematics for the fuzz generator and others inside...

[zachomega]

http://www.evillovekills.com/zachomega/reviews/effects/walco.html

I wrote this review a while back when I got all of those effects.  I have since disassembled each of the 8 and drawn the schematics.  Unfortunately, I only took the time to draw two of them on my computer.

The chord and note sustainer is pretty terrible.  The stock footswitches are garbage and the detector circuit is so overly sensitive, it actually functions more like a reverse swell sort of thing.  The 3sk30 is the noisiest transistor I have ever heard.  It actually sounds like staticy hiss from an untuned tv station.  Anyway, replacing the 3sk30 with a 2n5457 still functions identical and reduces the noise to nearly nothing.  The detector circuit is still worthless, but oh well.  I have about 25 of these unit broken (having never been used) due to faulty footswitches.  Anybody interested? 

The fuzz is a cool sounding circuit.  As I mentioned in the japanese round fuzz thread, the decay is kind of short and it sputters a bit. 

The treble/boost effect is nothing special.  The treble boost is noisey (could just be the transistor they chose and the fact that it is emphasizing high end) and the bass feature wasn't as good as I first thought when I just recently used it. 

If you have any questions, I'll be happy to answer them or disassemble the units to give a better answer. 

Enjoy!

-Zach Omega

[Harry]

Thanks! Wish I had a printer set-up so, I could print it off and read it on the john.

[zachomega]

I just noticed I referred to the boxes as aluminum...They are actually ferrous...some low grade steel.

-Zach Omega

[Harry]

Hmmm, interesting. Unfortunately I am holding my breath for the sound clip.

By the way if you haven't seen:

[zachomega]

Actually, I hadn't seen it and drew my own schematic for it...and I could be wrong, but shouldn't the 1uf input cap be facing the other way?  My unit has the same thing going on...Mine also has a 4.7k resistor on the collector of the first transistor in the oscillator circuit instead of the 2.7k.  Otherwise it appears to match my schematic. 

-Zach Omega

Hmmm, interesting. Unfortunately I am holding my breath for the sound clip.

By the way if you haven't seen:

[tcobretti]

First, thanks Zach and Harry for the schems!

Second, what is the Walco Sound Go Round?

[zachomega]

It is a really choppy tremolo.  Basically the signal is shunted to ground pretty abruptly when the shunting transistor is turned on by the oscillator. 

It is one of those love it or hate it sort of effects.  Definitely not subtle. 

When I first saw the name sound go round, I was hoping it was going to be some sort of Leslie simulator. 

-Zach Omega

First, thanks Zach and Harry for the schems!

Second, what is the Walco Sound Go Round?

[Dan N]

 The SGR was my first trace. I just pulled it from a box and that cap is backwards . The other values seem to be the same as on the schematic.

Thanks for the fuzz schematic! I bought the fuzzless 7 pack. Looks like another Fuzzrite family fuzz.

[zachomega]

What is funny about that is that the cap is actually installed backwards in mine...so I drew it in backwards on my schematic with a big question mark above it.  To be honest, I never even plugged it in to see if it'd work. 

And you are dead on about the fuzz.  The fuzz and Signal Booster are my two favorites of the Walco family.

-Zach Omega

The SGR was my first trace. I just pulled it from a box and that cap is backwards . The other values seem to be the same as on the schematic.

Thanks for the fuzz schematic! I bought the fuzzless 7 pack. Looks like another Fuzzrite family fuzz.

[Meanderthal]

 Hey, thanks for the schematics... I don't have the fuzz or tremolo(but I have all the others) so those 2 sort of complete the ...collection. Actually, I kinda like the bass & treble booster and the feedback eliminator which is a niose gate. The level control is a limiter, might also be useful someday. The tuner is useless unless you need a sound source for debugging and such. And of course the sustainer- WTF were they thinking? I'm gonna hafta try that mod- the noise is absolutely horrible, to the piont where it's completely unusable as is!

[Doug_H]

My take on the chord & note sustainer:

http://www.diystompboxes.com/smfforum/index.php?topic=48977.msg367410#msg367410

I breadboarded the sound go round. Nice effect but the LFO was too noisy. I'm going to try the vox repeat percussion instead.

[markm]

zachomega,
any chance that you could verify the schem that is posted?
I've built it twice and it won't function 
Any chance....Please!!

[Paul Perry (Frostwave)]

When I first saw the name sound go round, I was hoping it was going to be some sort of Leslie simulator. 

The designer probably hoped that too! 
Not a bad idea, but sometimes cheapness just doesn't quite pay off.... but if you want to invest $10 or so, you could use the flip flop collectors to drive a couple of vactrols (led/ldr pairs) and clean it up!
edited to say, I mean you would then have the basis for a ping-pong device.. needs extra circuitry for the 2nd output, of course.

[zachomega]

The 2n5457 works really nice and I've heard the J201 works nice.  Watch out though as the 3sk30 has 4 connections.  You just ignore the grounded 2nd gate. 

Also, the tuner is a good source for the 2sc828 if you need just one.  From screwing around with the Walco signal booster, I've found that these are low gain transistors (hfe < 200).  I don't know if this is true of all of the pedal line, but the Signal booster is definitely not at the 300+ hfe of all modern 2sc828 replacement parts. 

-Zach Omega

Hey, thanks for the schematics... I don't have the fuzz or tremolo(but I have all the others) so those 2 sort of complete the ...collection. Actually, I kinda like the bass & treble booster and the feedback eliminator which is a niose gate. The level control is a limiter, might also be useful someday. The tuner is useless unless you need a sound source for debugging and such. And of course the sustainer- WTF were they thinking? I'm gonna hafta try that mod- the noise is absolutely horrible, to the piont where it's completely unusable as is!

[zachomega]

I read that entire thread.  Interesting.  I originally thought a lot of the same things about the noise coming from the 644.  It is all in the 3sk30.  I scoped it and the static alone with no input signal was like 1 volt peak to peak.  Then I shorted the output to that first stage and measured the noise and it was negligable. 

Also, these effects hail from 1974.  Apparently a large cache of these and other Walco effects were found in a Warehouse in New Jersey.  They weren't stored in the best conditions.  I had an opportunity to buy around 2500 Walco units, but the price wasn't right. 

Modifying the time constant would be simple if there was room on the board for additional parts or room in the box for a pot.  I also thought about using a FET to instead of the 644 rather than the bipolar which seems overly sensitive.  And due to the poor recovery, if you hit the thing hard enough, you lose all output for 2 seconds or so. 

I wonder if this effect would be more useable if the volume on the guitar were turned way down.  Most guitars in the 70's didn't have the same kind of output that modern guitars have now.  On top of that, most Japanese guitars have very low outputs.  Think Teisco Del Ray. 

Anyway, replacing the fet does wonders for the noise, but doesn't make the effect any more practical.  One thing I did notice though, is that perhaps if you replace the fet and turn the volume way down, you might be able to get something and if the signal loading overly darkens your sound, there is a drilled hole on the board of one of the gain stages to fit a small value capacitor as an emitter bypass which could be used to compensate for the high end loss. 

I think it is quite obvious that I've spent a bit too much time with these units. 

-Zach Omega

My take on the chord & note sustainer:

http://www.diystompboxes.com/smfforum/index.php?topic=48977.msg367410#msg367410

I breadboarded the sound go round. Nice effect but the LFO was too noisy. I'm going to try the vox repeat percussion instead.

[zachomega]

I took apart multiple units and the schematic is definitely correct.  The diodes are germanium and otherwise unmarked.  Also, don't forget to put 2.2M resistors on the input and output to prevent the input and output capacitors from popping and to serve as a grid resistor for some tube amps...This thing wouldn't work with this Univox amp I had until I did that. 

-Zach Omega

zachomega,
any chance that you could verify the schem that is posted?
I've built it twice and it won't function 
Any chance....Please!!

[markm]

Thanks for the info Zach,
About the other trannies, I used 2N5088's previously.....any better sugesstion?

[zachomega]

I'd imagine the 2n5088 is too high a gain.  I'd try the BC547 or 2sc1815.  I never measures the actual gain of the transistors inside.  Give me a couple of minutes and I'll snip them out of one of my spare units and give you exact numbers to look for in gain. 

-Zach Omega

Thanks for the info Zach,
About the other trannies, I used 2N5088's previously.....any better sugesstion?

[Barcode80]

maybe a 2n2222 or a 2n4041....

[zachomega]

I just snipped out the two 2sc871's and they measured an hfe of 595 and 640.  I was way wrong.  The 2n5088 should work. 

-Zach Omega