Magnatone varistors

[Leevi]

Does anyone know what is the type of the varistors in the Magnatone Tonemaster circuit
and can they be replaced by some other components?

For more information see the Magnatone Tonemaster schematic below:

http://www.tdpri.com/forum/attachments/amp-central-station/53528d1278865473-building-magnatone-tonemaster-214-titano-custom-314-schematic-same-magnatone-213-jpg

/Leevi

[kagliostro]

Ciao Leevi

Unfortunately the matter isn't so simple

http://www.el34world.com/Forum/index.php?topic=14650.0

K

[plexi50]

I have dreams of finding a big box of them. No luck so far

[kagliostro]

Instead of search with the term varistor I've done a search with the term Carbide Varistor (which are those we are looking for)

here the result

http://www.ebay.com/sch/sis.html?_nkw=Vintage%20Russian%20Silicon%20Carbide%20Varistor%20100V%201W%20Oty%208&_itemId=190632044975

K

[darryl]

I have experimented with the Russian varistors - they do not behave quite the same as the "genuine" Magnatone ones.

http://www.guitargear.net.au/discussion/index.php/topic,31524.0.html

[Leevi]

It seems to be very challenging to find them.

Maybe ask here:
http://www.vibroworld.com/magnatone/index.html

I also found these pages:


/Leevi

[kagliostro]

Albert sometime ago told

Everyone knows something is impossible, until comes an inexperienced who does not know and invents

so I'm hoping arrive someone that reinvents an old varistor with new components 

K

[smackoj]

a rusky tube is one thing, but a rusky varistator is a diff. animal fo sho!  what exactly does a varistor do, make the tremolo work?   

[jazbo8]

Albert sometime ago told

Everyone knows something is impossible, until comes an inexperienced who does not know and invents

so I'm hoping arrive someone that reinvents an old varistor with new components 

K

A bunch of 3.9V Zeners paralleled with 2M2 to 10M resistor get pretty close, but still not quite. See Mr. Robbins' report -> http://dalmura.com.au/projects/Vibrato%20effect%20measurements.pdf

Jaz

[SoundmasterG]

In the link kaligstro posted, I attached some pictures of the two types used in the Magnatones and a word document in the last current post that lists the specs for those particular varistors and others. Hopefully that info can help you locate something that will work.

Zack doesn't run Vibroworld anymore as a business where you can buy products, and he doesn't have any of those varistors anymore.

Greg

[kagliostro]

Very interesting pdf Greg

Thanks for sharing

K

[SoundmasterG]

You're welcome Kagliostro. Hopefully it is useful to people looking to make the Magnatone vibrato circuit.

Greg

[Steve_P]

Check the magnatone/valco yahoo group. you can buy NOS from a guy on Ebay, or you can buy new production from England, but you'll pay for it...

[Leevi]

A bunch of 3.9V Zeners paralleled with 2M2 to 10M resistor get pretty close, but still not quite. See Mr. Robbins' report -> http://dalmura.com.au/projects/Vibrato%20effect%20measurements.pdf

The curve seems to be pretty close to the original.
Do you have any wiring scheme for it. Is it just the zeners in serial. How should the resistors be connected? One per each zener or one  per chain?

/Leevi

[jazbo8]

I have not tried this myself, but I think it's just a single resistor parallel with all the zeners connected in series. A lot of zeners!

Jaz

[kagliostro]

A lot of zener mean we require a lot of space

about price $ 10.00 I think is enough to have it

K

[Leevi]

A lot of zener mean we require a lot of space

Low wattage zeners are quite small but still... I agree with you.
Another question is the number of zeners, 37?
I suppose it has a relation to the used voltage. 37 x 3.9V =144,3V,
could it be less?
/Leevi

[jeff]

I finally took a hard look at that circuit in my search to understand phase shifters.
It's a pretty ingenious and eloquent design.
I'd really love to play with that circuit, If you do wind up getting the parts and building it, try a little experiment. Come up with a way to add back some of the dry singal to the vibrato signal and see how it sounds.
Vibrato singal + original signal = phase shifter.