Varistor Characteristics for Magnatone Vibrato Circuits

[johnnyreece]

Thanks for sharing, Andy! I've got my own 410 project started, but I'm working on a layout still. Kinda making me crazy, actually. My tube layout is different than yours, or I might totally steal that idea...I'm thinking of adding a footswitch, too. I've got a thread going here somewhere of a PTP layout. I'll probably post my progress on that eventually.

[andyfromdenver]

Thanks for sharing, Andy! I've got my own 410 project started, but I'm working on a layout still. Kinda making me crazy, actually. My tube layout is different than yours, or I might totally steal that idea...I'm thinking of adding a footswitch, too. I've got a thread going here somewhere of a PTP layout. I'll probably post my progress on that eventually.

Hi Johnnyreece,
I just logged in and see your thread there now too.
I'm going to put the bright switch on a pull pot for discretion. Otherwise we'll have similar amps. I'm expecting a B+ around 350, and am keeping all the quirks of the preamp biasing voltage et al. I wouldn't be surprised if I go 30-40mfd on the power supply filtering, also my input network is more proper hi lo.

If the half board half ptp layout is a success, I'll letcha know and maybe start a new thread (sorry Martin M!).
I'm pretty giddy about wiring the inputs and preamp and tone stack all ptp, feels like the 50's!

Now I'm motivated to work on it today, thanks!

[martin manning]

Let's keep this thread about varistors and substitutes. Start a new thread in the Tech section for amp projects. Any comparative listening tests of substitute varistors will of course be welcome.

Here's a picture of the breadboarded parts for the two tripple-MOV "units" tested above. Resistors are 1/2W for size reference.

[ubxf]

It looks good, did you get a chance to listen to your circuit

[martin manning]

It looks good, did you get a chance to listen to your circuit

Not yet... Smokebreak will put a couple of these in his Maggie clone and record a clip or two (I hope). I've been mulling over configurations for soldering the parts together... pix later today. I'll get them in the mail in a day or two.

[ubxf]

Thanks Martin

[martin manning]

These parts are now on their way to Tejas.

[ubxf]

Did you end up changing the parts that you had in your schematic on page 6.

[martin manning]

The only difference is the 1M47 is 1M5, and these are the same parts shown on the breadboard above and traced on page 7.

[Kagliostro]

SiC_Varistor_Sub.jpg

They looks so nice

Many Many thanks for your effort on finding an alternative

I high appreciate your research job

[img:48:33]http://el34world.com/Forum/Smileys/defa ... ppy096.gif[/img] [img:48:33]http://el34world.com/Forum/Smileys/defa ... ppy096.gif[/img] [img:48:33]http://el34world.com/Forum/Smileys/defa ... ppy096.gif[/img]

K

[martin manning]

Thanks, but hold on... We need to see if these are quiet and sound like the real thing!

[ubxf]

Ok i'll wait to see what Smokebreak says but may be i'll try it anyway

[Kagliostro]

I know that are work on progress and not a defined solution

but guy YOU ARE GREAT only for the reason you are trying to

solve this age-old problem

Many thanks !

K

[martin manning]

Ok i'll wait to see what Smokebreak says but may be i'll try it anyway :)

He should have the parts in a couple of days, but it would be nice to get more than one opinion on what I'm hoping will be a subtle difference in the vibrato sound ;^)

[Kagliostro]

I'm wondering if the new varistors or your engeenered version can be used

as to experiment the expression control (find in some organ amps) on a guitar amp ?

What do you think about ?

[img650]http://i217.photobucket.com/albums/cc29 ... a25de4.jpg[/img]

And too, what do you think about organ circuits as a source for old varistors to be used in Magnatone like vibrato ?

Many Thanks

Franco