Varistor Characteristics for Magnatone Vibrato Circuits

[dinkotom]

To get most warble and less thump, the varistors should be matched. I've bought few sets of original varistors from Gary Croteau (couldn't help myself ) for Magnatone 260 builds and the matched sets sound perfect, no thump at all. Here is the sound I was hoping to get, I'm close but no cigar: https://www.youtube.com/watch?v=qIhiucfOEWQ

[tubeswell]

To get most warble and less thump, the varistors should be matched. I've bought few sets of original varistors from Gary Croteau (couldn't help myself ) for Magnatone 260 builds and the matched sets sound perfect, no thump at all.

Soundbytes or it didn't happen

[dinkotom]

Haha, could you post your favorite if there is any?

[dinkotom]

Ah, sorry Pete if this sentence somehow turned out wrong. I'm at a web cafe right now, so I can't hear any youtube videos, I meant if you can post any of our songs that you like.

[tubeswell]

Can I detect it on your guitar in Last Ride in Zagreb?

https://www.youtube.com/watch?v=CJKr-Btq8zI

Or Point of no Return?

https://www.youtube.com/watch?v=8Mc6Xxg9fsg

http://youtu.be/8Mc6Xxg9fsg

[dinkotom]

Yes, those two are Maggie show offs But, compared to Robert Ward, hmm... I guess his band wasn't named Ohio Untouchables for nothing!

[andyfromdenver]

Hi guys.
This thread is really spectacular and pertinent right now. I'm about to make a Magnatone 210/410 mini-chassis head from scratch and paint a nice and custom-y chassis.

http://www.magnatoneamps.com/210.html

I had a chance to play a 210 at my friends repair shop and loved it. I took pics of the 210 schematic which was miraculously still present with the amp. I'd be happy to share those pics as even the Magnatone homage site doesn't have it, but a slightly incorrect hand drawing (470k input resistors instead of 47k) *I sent them the pics today*.

Sorry to ramble, but!! I'm on the varistor chase and truly appreciate the thread. I'd love to try one of the aforementioned new Russian substitutes; I thought that soundclip came handgrenade close/ was pleasing of it's own merit.

[Smokebreak]

Hey Andy, I'd be happy to send you a pair for testing. Right now they are en route to Martin's place for testing and matching. Shoot me a PM and we'll keep in touch.
These are the 100V Silicone Carbide, maybe we can find another source, or even try out some of the different voltages still up on Ebay. I'm trying to wrap my head around how 2 50V in series would act vs. a single 100V...

[andyfromdenver]

Tyvm Smokebreak! Pm'd

Thanks Martin Manning for starting the thread.

Gonna get crackin' on the layout.
It's going in a cool 9.5 x 6 box from Watts.
I'd be happy to share the layout and a few pics when it's done.
May be over a month or so, unless I get a wild hair

[Smokebreak]

Looking forward to your build Andy! I'll be curious to hear how varistors sound in that circuit as it's quite different.

[andyfromdenver]

Hi peeps.
I bought the little treasured NOS varistors.
Gotta get the true sound
I really hope Martin M or another can come up with an awesome solution!
I've got all the parts for my little single ended Magnatone 210/410.
I drew up a layout just for everything roughly after the Preamp and tone stack which is all PTP near the front end.
I hate dropping such expensive parts in an untested layout,
But this is like my 13th or 14th project and I'll just make sure to heat sink them.
I was chatting with a friend on some of the strange design choices in the stock amp, but having heard the stock and liking it, I'm gonna stay true, mostly, for now.

I'm thinking in such a bare bones circuit, I'd be willing to guinea pig any varistor substitute designs and share.
I'll build this thing next after a current project.

[martin manning]

No good solutions for a replacement yet. I did test the Russian parts and they are definitely usable, but there aren't any more on offer AFAIK. Who is selling the NOS Workman parts?

[Smokebreak]

Andy, don't know if you have it but here is the original layout : http://ampgarage.com/forum/download/file.php?id=32851

I wouldn't worry too much about damaging the varistors. IIRC the core of the amp works fine without them, so you could get it up and running then plop them in.

[andyfromdenver]

No good solutions for a replacement yet. I did test the Russian parts and they are definitely usable, but there aren't any more on offer AFAIK. Who is selling the NOS Workman parts?

Hi Martin,
I believe it's the general chap who has amassed many and is slowly doling them out on eBay. I made a best offer for two and he accepted.
Says he has more, I can pm the seller id if you'd like.

[andyfromdenver]

Andy, don't know if you have it but here is the original layout : http://ampgarage.com/forum/download/file.php?id=32851

I wouldn't worry too much about damaging the varistors. IIRC the core of the amp works fine without them, so you could get it up and running then plop them in.

Oh cool, I hadn't seen that, thank you! Yeah, I have an alternate, more PTP
layout with the 12DW7 closer to the controls, but the drawing shown is like V3.2 and I think it "flows" well, we'll see though...
I know it's a bit tricky and some interaction issues may have to be sussed out in the testing.