Sansamp Classic PCB encased in plastic?

[Samnunn92]

Hi all,

I'm trying to repair a Sansamp Classic and so far it's going okay (managed to get power to the boards and signal to pass while in bypass mode.) However no signal passes when the effect is active so I figured something must be wrong with the actual effects board, but it seems like its been encased in plastic and I can't figure out how to get into the thing without breaking it! Anyone had any experience with these?

Thanks a lot

Sam

[J0K3RX]

Yes, I have and all I have to say is good luck! Does yours look like a square with a white sheet on the top and on the bottom with black epoxy sandwiched in between? The pots are the only thing accessible and they are sticking directly into the sides of the white sheets. Yes?

[J0K3RX]

Look familiar? That is not plastic by the way... more like porcelain with bullet proof epoxy in between.

[Goodrat]

Check that the foot switch is operating properly with an ohm meter. I had that go bad on mine.

[joegagan]

supergoop'd

WOW

[J0K3RX]

My brother had the classic and one of the small (and I mean small) leads coming out top of the epoxy sandwich broke off right where it disappears into the goop. I could see it but there wasn't enough to solder to so I tried to dig around it with an exacto knife. It was like a rock, I got a dremel with a small diamond type tip and tried to grind around it and it actually threw sparks! That's the same stuff they use in DieBold ATM machines on the circuit boards and in other protected circuits like cash dispensers etc... If you flip that wafer over you will see the dip switch coming through the top of the wafer on the other side. Just impossible to get into!!  They were never intended to be serviced... or copied!  

Do what you can and check the switch like Goodrat said...

[R.G.]

Epoxy with silicon carbide grit in it.  Some banks have vaults made with concrete filled with carbide grit.

But remember - never a horse that couldn't be rode, never a rider that couldn't be throw'ed.

[Samnunn92]

JOK3RX that's exactly the same as I've got! And very irritating it is too. I contacted the Tech21 guys and apparently a replacement board will be about $85 + shipping, which I would rather have avoided but doesn't look like I have much choice.

Goodrat I think the footswitch is still operating correctly as the LED lights when it's pressed, just all the sound cuts out? Will check it again later anyway and resolder if necessary.

That's insane that it's the same stuff used in bank vaults! I understand they don't want their circuits copied but jeez...

Cheers

[deadastronaut]

it should have tiny armed guards around it ...

there is this..

http://www.tonepad.com/project.asp?id=22

[Dirk_Hendrik]

Epoxy with silicon carbide grit in it. 

Nope, worse
Ceramic board. Start tampering and it breaks. Quite uncommon for audio but seen a little more often in the regions where the DIY HF guys perform their shortwave experiments.  The Sansamp Classic is one of the 11 effects I ever had (so far) on my bench for repair where I had to say sorry to the owner.  Other cases mainly consist of burned out ASIC's.

[wavley]

Epoxy with silicon carbide grit in it. 

Nope, worse
Ceramic board. Start tampering and it breaks. Quite uncommon for audio but seen a little more often in the regions where the DIY HF guys perform their shortwave experiments.  The Sansamp Classic is one of the 11 effects I ever had (so far) on my bench for repair where I had to say sorry to the owner.  Other cases mainly consist of burned out ASIC's.

You mean Alumina http://www.coorstek.com/resources/8510-1164ThinFilm.pdf?  Seems like overkill/over-expensive for audio.  That stuff is a pain in the a$$.  I've never seen it encased on both sides, it's usually just a substrate with a ground plane on the down side and traces on the up side.  Not much reason to use the stuff unless your design calls for it's dielectric constant or you're building room temperature microwave stuff, we've switched to CuFlon soft substrates for all of our cryogenic amps, much less troublesome.

[J0K3RX]

JOK3RX that's exactly the same as I've got! And very irritating it is too. I contacted the Tech21 guys and apparently a replacement board will be about $85 + shipping, which I would rather have avoided but doesn't look like I have much choice.

Goodrat I think the footswitch is still operating correctly as the LED lights when it's pressed, just all the sound cuts out? Will check it again later anyway and resolder if necessary.

That's insane that it's the same stuff used in bank vaults! I understand they don't want their circuits copied but jeez...

Cheers

$85.00 isn't as bad as when I was quoted like $180.00 to have the pedal replaced, which I did not do and ended up junking it! These have been around for a long time.. Wasn't really anything like it when it came out and to this very day it is one of the most realistic modeling sound alike boxes around..! I have a PSA-1 and it doesn't even have the tone, characteristics or sound that the Classic has... The GT2 sounds real good but still doesn't sound anything like the Classic. Not long ago it was going $350.00.. Whatever Andrew Barta has entombed in that epoxy is magical and I don't blame him for keeping it secret and he has very well for all this time. I have not heard anybody successfully clone it yet... and there is a SansAmp Classic clone with the dip switches and everything still not even close..

[joegagan]

i may have told this story before, but there is no time like the president.

a friend of mine used to work on 48th st in NY. he talks about andrew coming in with paper grocery bags full of the very early sansamp pedals. he had a deal with salesmen, if you sold X number of the pedals, he would slip you a free pedal or two.

here is a cool read from 96:

http://www.soundonsound.com/sos/1996_articles/jun96/andrewbarta.html

[Earthscum]

...  Not much reason to use the stuff unless your design calls for it's dielectric constant or you're building room temperature microwave stuff, we've switched to CuFlon soft substrates for all of our cryogenic amps, much less troublesome.

From the article Joe just linked:

The production SansAmps use some form of hybrid circuit design, but I guess your prototypes relied on traditional, hand-built circuitry?

"Yes, and there was a lot of circuitry which didn't fit comfortably into the box -- so I was looking for a way to miniaturise the circuit. I was fortunate to hook up with a company which was prepared to work on a much smaller scale at the beginning. Back then, there was no surface-mount PCB technology; only the hybrid technology which uses a ceramic substrate. Metal is evaporated onto this, and then the resistors are formed by laser cutting. It is a very involved and expensive technology, but it was all that was available at the time, and we still use it. It took four or five attempts before the hybrid performed properly, mainly due to layout problems. We could change it now to surface-mount, but you know how people are -- they would say it doesn't sound quite the same. We've decided to stick with what we have, because that's what people want, and the same circuit is at the heart of all our products."

Yeah, IMHO, that's pretty badazz. So... Wavely, apparently you were stepping on the right track and didn't know it, in a sense. Kinda like large scale IC die in this context, right?

[joegagan]

well, this was 96, i am pretty sure he succumbed to more normal const methods in the meantime. funny, a lot of guys i know from new york think very highly of the tech 21 stuff. local pride.
i recall being at a blues jam in around 95 , a guy had a sansamp, it sounded really good into 'regular' amps.

[Ronan]

"...and the same circuit is at the heart of all our products."

hmmm. Interesting statement.

[Earthscum]

I liked what he was saying about their combo amp. It's basically a mosfet powered loudspeaker with modeling circuitry inside. This is the way I've always suspected my Peavey TNT 115BW (halfway) worked. When I was trying to look up info on it (I want to mellow out the chorus), I found the Black Widows listed as sound reinforcement speakers, as well as it seems my amp uses a compression in the power stage. I haven't had it open in a couple years, but I suspect it's D-Class power stage from all I've been reading. A couple articles I've read on D-Class seem to point it towards programmable compression and every other way this amp seems different from a TKO or other older amps. That leaves almost all the shaping to be done in the pre. The first time I took a Bazz Fuss on a ride through it without my phaser in between, I thought I broke something... pure BF fuzz, like you hear plugging it straight into a mixer. Now I kind of rely on the always-in tone of my phaser to mellow out my distortions, and the amp just won't distort on it's own (at least not until the coil starts popping).

That article was actually REALLY informative... I think he gave away alot more clues to finding an SS "tube" sound than he intended, but it seemed like he was fairly protective of certain ideas. Really decent interview.

[Dirk_Hendrik]

. Back then, there was no surface-mount PCB technology;

Which, since the article is from 1996, is absolute bollocks....

[teemuk]

. Back then, there was no surface-mount PCB technology;

Which, since the article is from 1996, is absolute bollocks....

Kinda like many things he says. My personal favourite is the claim of spending decades to develop a 100% analog F.E.T. hybrid circuitry when it really meant just using generic SMT mounted rail-to-rail opamps and concealing them with goop. His hype about the innovations he made in the field of power amp emulations are kinda intriguing too since the power amps in trademark combos are pretty much just a standard LM3876 -based circuits and the sansamp "cores" are nothing but generic overdriven opamps or diode clipping circuits coupled to some well-thought out filters.

Anyway, it's a recipe that works. But a very generic recipe still.

But these days realizing that people talk absolute bollocks to hype up their products shouldn't be anything new.

[Earthscum]

I understand "talking it up" and all that, but from the article, it sounded like he was doing all this in the mid 80's.

I just checked Tech21, founded in 1989.

Wiki says: Surface-mount technology was developed in the 1960s and became widely used in the late 1980s.

So I really don't think he's talking up too much hype. Didn't seem like he tried to claim he invented the inter... I mean, Surface Mount technology.  Just seems like another Mike Fuller type, ya know?