Seeking for suggestions (for a small SE stereo Guitar amp)

[kagliostro]

Hi Friends

Recently I recovered (from an old Graetz tube radio) a PT, 2 x EL84 tubes and 2 x SE OT

I'm seeking for ideas about a stereo SE amp that I think It will be nice with two different preamp circuit

Please if you have a schematic or ideas about how to arrange this thing, share It

Many Thanks

Franco

[66Strat]

VOX AC4 - EF86 pre-amp with tremolo => EL84 output

VOX AC4TV - ECC83 (12AX7) pre-amp => EL84 output

[kagliostro]

Many Thanks for the suggestion 👍

Franco

[kagliostro]

Looking in my archive I've found some documentation

But NO Layout for the AC4TV

Please someone has one to share or know where I can find it ?

AC4TV (pre ecc83)

Till now I didn't foud a layout for the AC4TV

AC4 (pre ef86)




Other Layout


AC4 (pre ef86) with Mods




AC30pre -  AC4PowerSection




Many Thanks

Franco

[kagliostro]

OK, seems that isn't so simple to find one (layout for the AC4TV)

I think I'll draw one by myself starting from a 5F2a (as It Is very similar)

So now I'm looking for an improved (on the filtering) version of the 5F2a (or similar) to plagiarize

I'll search by myself, but if you know a version with good performances in ripple control I'll be glad if you share

Many Thanks

Franco

[sluckey]

So now I'm looking for an improved (on the filtering) version of the 5F2a (or similar) to plagiarize

Maybe this...

[dwinstonwood]

Here's a PSUD2 model of sluckey's recommendation.

[kagliostro]

Many Thanks Sluckey & Dwinstonwood

A choke wasn't exactly what I was thinking but I'll look in my stock if I've something usable

I was thinking to add one or two RC filters, this because the OT of the donor radio has an intake for B+ one for Plate and one (not UltraLinear) for G2, something that acts as a "filter" for G2


B+ is connected to the rt/ws wire - G2 is connected (via the 2.5K resistor) to the rt wire

connection point 38




Be patient I forgot to say that 

Franco

[kagliostro]

I decided to use, for this project, the original AC4 ef86 version and the AC4TV ecc83 version

a more articulated future project will use the AC30/AC4 for one channel and this SE Dumble style

http://el34world.com/Forum/index.php?topic=9149.0



The following question is about the standard AC4 (ef86) and the AC4TV (ecc83)

I put the question as to learn something more than a real intention to apply the mod (if possible) also if the responses are positive may be I'll use it

The AC4 has a Vibrato Oscillator (OK Tremolo), the AC4TV don't has an oscillator ... is possible to use the circuit of the AC3 Vibrato and connect it (alternatively) to the AC4TV circuit

I looked to the AC4 oscillator but I'm not really able to find how I can connect it to the AC4TV, to how to connect the tremolo to an SE amp we had a long discussion with lot of examples
https://el34world.com/Forum/index.php?topic=20727.msg218834#msg218834
but is the oscillator circuit connected to the ef86 tube in the AC4 that is confusing me

Many Thanks

Franco

[kagliostro]

I've find the solution (AC4 ef86 vibrato on AC4TV ecc83)

Keep It simple, no vibrato on the AC4TV channel

Franco

[dwinstonwood]

Hi Franco, in this thread I used the Vibrochamp vibrato with my EF86 AC4. It adds the Intensity (Depth) control, in addition to the Speed control. My files are in my last posts in that thread.

https://el34world.com/Forum/index.php?topic=27253.0

[kagliostro]

Many Thanks

I've read previously your thread

But my question was if It was possible to use the oscillator of the AC4 channel on the AC4TV channel, not if It was possible to add an oscillator to the AC4TV circuit

(Just to complicate a bit life)

So I arrived to the solution, keep It simple, both channel will be as on original, only in a single chassis/case

Franco

[kagliostro]

Lot of other things to do so despite the time that is passed I didn't did really much about this project

(to have a 1924 class father that requires attentions isn't a so simple thing)

However a bit of work was done

This is the idea for the Layout, to keep both preamps at the higher distance from the PT I mirrored the VOX AC4TV Layout

that way I can put the PT at the centre of the chassis and each amp (AC4TV & AC4) has the Power Tube faced to the PT and the preamp tubes at the far possible distance from it



And this is a first attempt to the PS that will feed the existing PS of each amp, to be furtherly developed



Any consideration / council will be greatly appreciated

Thanks

Franco

[Williamblake]

So would you connect to the chassis at the rectifier as you cannot connect both inputs to the chassis?

[sluckey]

Could we see the schematic this layout is based on?

[kagliostro]

Thanks Friends

About the input I still didn't decided if I'll use a single input and an ON-ON-ON switch to have the input connected to the AC4 or the AC4TV or Both Joined or two input (one for each circuit) and a Switch to perform the sames alternatives (AC4 or AC4TV or Both Joined)

GROUND is a BIG DOUBT, I'm not practical with Stereo Amps, I'm thinking to refer all to a single point for each circuit, then use two of this (without the lift switch) to connect this two points to the Chassis



what led me to think not to ground the amplifier input is this (note, insulated connector)



Steve, this are the schematics which refers the Layouts

This is the VOX AC4TV (you know it because you kindly draw the Layout for me)



And this is The VOX AC4 (Dwinstonwood modified version)



I apologize, I forgot to specify that wasn't the standard AC4 (the old EF86 version), Dwinstonwood developed it, you can see the thread here https://el34world.com/Forum/index.php?topic=27253.0

Franco