# 'SRV Special' effects pedal....questions



## greco (Jul 15, 2007)

A friend (and forum member) has asked me to work together with him to build this effects pedal.

I'm posting a few questions as I have very limited experience building pedals. However, I do have a lot of electronics test/measure equipment, components, soldering station, wire, tools, etc just waiting to be put to more use. I have some knowledge of electronics theory and reasonbaly decent soldering skills. 

Does anyone know of a kit for this pedal?

Does the following schematic seem to be a reasonable build project for relative beginners?

Are the components fairly standard (mainly the op-amps and transistor) OR easily substituted?

http://www.lynx.bc.ca/~jc/SRVspecialSchematic.gif

Thanks for you help.

Cheers


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## mhammer (Nov 30, 2007)

JC Maillet has a good ear for tone, knows a good shortcut when he sees one, and has even spent an afternoon at my home trying out pedals and amps.

What he does not do, however, is provide kits. So I'm afraid you're on your own for this one. The components involved are pretty standard. The 2N5210 is simply there as his preferred choice for low noise tranny, but can be replaced with any of a variety of other units. Tradition would indicate a 2SC1815, but a 2N5088/89 will do fine.

Tradition also calls for tantalum caps for the .22uf units shown, but given so much else is NOT according to "tradition" here, feel free to use the cap type of your choosing.

The biggest point of departure from a standard TS9 is the use of a 2meg gain pot (500k in the original), and the direct coupling between the input transistor-buffer stage and the op-amp. The direct coupling may get you back a wee bit of bass, but not that much. No big deal either way, but if it saves you the nuisance of scoring a non-polarized 1uf cap, so much the better. The 2meg pot may be awkward to come by, but is not needed unless yo want to use the pedal as a true distortion, rather than merely an overdrive. A stock TS9 has a maximum gain of 118x, and this one, with a 2meg pot, will have a max gain of 426x, putting it more in the category of something that produces serious distortion on its own, even with the cleanest of amps. Like I say, if you want that, fine, but if SRV is what you aim for, then 1meg will do you just fine to cover the clean-through-angry spectrum.

As for chips, my advice is to use a socket, and try out whatever you like in it. People have widely varying opinions about what sounds "best". Given that the design, as shown, goes way beyond classic SRV sounds, I can't see why the chip would HAVE to be a JRC4558D from 1982. But like I say, different chips sound good and bad to different ears, so leave yourself the option to experiment. If you're buying your parts from somewhere that has decent selection and prices, pick up a TL072, a 4558, an LM833 (or NE5532), and an OP-275 if you feel experimental. Try 'em all out and see what sounds best to your ears.


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## greco (Jul 15, 2007)

Many thanks for all the detailed info Mark !...I was hoping that you might see this.

I will likely have more questions ...but this is a great start.

Cheers


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## 360+ (Mar 13, 2011)

mhammer said:


> JC Maillet has a good ear for tone, knows a good shortcut when he sees one, and has even spent an afternoon at my home trying out pedals and amps ... The biggest point of departure from a standard TS9 is the use of a 2meg gain pot (500k in the original), and the direct coupling between the input transistor-buffer stage and the op-amp. The direct coupling may get you back a wee bit of bass, but not that much.


thanks for the kind words Mark ... yeah, the removal of signal caps is really the main thing here, as it's meant to provide a better transient response rather than give a fuller low end // the low-end tweak is not covered in that schematic ... 

the high gain range is a secondary thing really as many players prefer to use the pedal at lower gain settings // in this case a 100k Gain pot gives them more desirable spread in the control ... it's a personal thing really

as for low-end extensions are concerned I might add some suggestions here later on ... also, the tone control range should also be tweaked versus the original as the removal of muddying caps affects the Presence aspects of the circuit 

I also perform a "selection trick" on the clipping diodes to give the circuit a sharper edge/squeal on the pick attack ... that's the part that I like best about this circuit

combine these mods with the removal of the sucky jFET switching and the end result gives a pedal that doesn't sound so cardboard-ish as the original pedals did


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## mhammer (Nov 30, 2007)

The biggest difference for me in the usability of a TS circuit has actually come from the guitar. I've told the tale before, but it bears repeating. Some years back, my main guitar at the time had a preamp built in. Not especially "hi gain" (only about 3-4x) but it was enough to goose the signal past the point where the TS behaves optimally. Made myself a TS to 808 specs and just *hated* it. For the life of me, could not see what all the fuss was about. It sounded like a 3rd rate distortion.

Then, I got another guitar with weaker pickups and no preamp. All of a sudden, the TS came alive and sounded exactly like what you'd want and expect to hear.

So, as much as tweaks to the circuit will most assuredly improve and tailor the tone to what you want, the basic starting place, for me anyway, is to feed it the sort of signal that brings out its best. Avoid using it with hot humbuckers, or with any sort of booster ahead of it.....at least if you want to be able to hear what people love about it.


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## 360+ (Mar 13, 2011)

Paul's, Strat's, Tele's ... don't matter with this circuit, you can dial in a terrific sound always // never sounds like mudd ... the attack has a nice sharp edge and presence that the original didn't have // that's what I mean by "better" transient response ... like I said, freq response is secondary and can be tailored for player's musical penchant and style

case in point, I recently had an ex-NY producer dude show up to A/B/C mine against his collection of originals (Ampeg A3, TS-808, voodoo OD) where mine stood right out in terms of clarity of response and ability to hear original tone of guitar ... not that the others were bad or anything // well, the TS with its magical JRC chip was actually

Any player who would like to get into better OD transient response realms may wanna try this approach ... 
a hand-tweaked version of the SRV Special can be ordered from me directly http://www.viva-analog.com


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## 360+ (Mar 13, 2011)

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