Selmer Zodiac Twin - Weird Science?

[Fresh_Start]

Vintage Guitar magazine recently wrote up this amp Zodiac Twin 50. (look at second page - it's much more readable)  As usual, parts of their circuit description made no sense so I pulled up the schematic.  They were right about this circuit being original!

First off, I don't understand the way the switches for the "tone stack" in Channel 2 are drawn.  There is a series of buttons across the control panel if that helps.  Also, there's an unidentified inductor (choke?) there.  Can somebody point me to an explanation of this set of tone selectors?

Second, the tremolo circuit looks like it jiggles the B+ for the EF86. Is that correct? NO - jiggles EF86 screen grid

Third, is the EM84 tube the "glowing tremolo indicator"?

Last, VG said something about this amp having a very unusual phase inverter.  Looks like a fairly normal cathodyne PI to me, except that it has a form of fixed bias.  Am I missing something?  YES, it's just a normal cathodyne drawn funny.

Cheers,

Chip

[kagliostro]

I think that the Twin 30 has near the same tone control

Kagliostro

[Fresh_Start]

Thanks very much!  Those schematics are much easier to read.  Even the way the tone buttons were wired, although I still don't quite "get" how the switching works.

I'd never thought of diddling/jiggling a preamp pentode's screen grid voltage to generate tremolo.  Wonder what that sounds like!

I was wrong about the PI.  There isn't anything odd about the PI except the way it was drawn.  Despite that fact, this isn't a typical Fender or Marshall circuit by a long shot!  Just thought you all might enjoy noodling through it.

Cheers,

Chip

[terminalgs]

First off, I don't understand the way the switches  for the "tone stack" in Channel 2 are drawn.

FWIW, the typewriter style  buttons on the front of a old Radio  (the buttons that might select
FM AM PHONO SHORTWAVE, etc)   were often drawn like that in schematics (esp.  european
models).

Third, is the EM84 tube the "glowing tremolo indicator"?

"magic eye" type tube.   usually used as tuning indicators to show the strength of a signal on FM/AM radios.   

[carausius]

Some various pictures of Selmer Zodiacs

[carausius]

That switch bank looks like a 1176 FET compressor  !!! Also check out the earlier version Selmer Selectortone which seems to be a rotary switch version? Later Selectortones had the switchbanks

These amps sound really great, Vox meets a JTM45 Marshall, second hand they are becoming very expensive & hard to find, I'm assuming a Matchless Clubman is similar to the Zodiac?

Any clones out there?  

http://www.vintagehofner.co.uk/britamps/selmer/schematic/rselpre.jpeg

[DummyLoad]

I think that the Twin 30 has near the same tone control

Kagliostro

those schematics where drawn by one of our forum members - katie 77. he likes odd-ball stuff, but then again, he's a lovable odd-ball.

it is an unusual and intriguing circuit... hmmm...

 

--DL