Vox AC 30 top boost sans tremolo

[xtian]

Got a prospective client who wants a Top Boost Vox, '63-ish, like something Mike Campbell would play. Doesn't want the tremolo channel, which is fine, because that simplifies the build by three tubes and a circuit board.

The vintage Vox schematics aren't helping, because they all have the trem circuit. Maybe Ceriatone Dizzy 30?

Would really like to avoid drilling my own chassis, and pre-made faceplates would be nice, too.

Where should I look?

[Ondrej]

Hi,

I am building an ac30 Weber Clone without the tremolo circuit. The schematic is here https://taweber.powweb.com/store/6v30_schem.jpg.

All you need to do is cut the connection between c9 and VR4 pot and just ground the c9. Then drop the rest of the circuit. Of course you drop the c40 and r36 in the power supply dropping string.

I believe doing this raises the B+ a bit, but my voltages are within the original values.

The Dizzy 30 chassis can be used too, although it uses an extra EF86 tube. You can just leave an empty hole if you want to implement the ac30 normal channel.

The amp is great!

[LeftyStrat]

Or you can just build a Trainwreck Rocket, which is essentially the same thing. I think rjguitars might sell the Rocket chassis.

[super100]

A few options.

http://www.el34world.com/Hoffman/images/AC30Old.gif

http://www.el34world.com/Hoffman/images/AC30New.gif

http://www.el34world.com/Hoffman/AC30parts.htm

RJ Guitars

http://www.rjguitars.net/Medium.html

[xtian]

Or you can just build a Trainwreck Rocket, which is essentially the same thing. I think rjguitars might sell the Rocket chassis.

Yes! Rocket ahoy! I just looked carefully at the schems. Nearly identical circuits, except that the coupling caps between PI and power tubes differ: 0.1uF on AC30, and 0.047uF on Rocket. Effect?

Thanks for the heads up on RJ's page. That's perfect.

-a

[Reeltarded]

The difference in the couplers is almost nothing. Make a Rocket with .1s. Nobody would know. It would kick about .053 more ass.

[LeftyStrat]

Or you can just build a Trainwreck Rocket, which is essentially the same thing. I think rjguitars might sell the Rocket chassis.

Yes! Rocket ahoy! I just looked carefully at the schems. Nearly identical circuits, except that the coupling caps between PI and power tubes differ: 0.1uF on AC30, and 0.047uF on Rocket. Effect?

Thanks for the heads up on RJ's page. That's perfect.

-a

Season to taste.

[renshen1957]

Or you can just build a Trainwreck Rocket, which is essentially the same thing. I think rjguitars might sell the Rocket chassis.

Yes! Rocket ahoy! I just looked carefully at the schems. Nearly identical circuits, except that the coupling caps between PI and power tubes differ: 0.1uF on AC30, and 0.047uF on Rocket. Effect?

-a

Hi,

The early 1960's Vox AC30 came in three versions, Treble, Normal, and Bass. I recall the Treble had 0.047 coupling caps between PI and the Tubes. the Normal and Bass had 0.15 originally, later one might find 0.1 as JMI scrambled to keep up with the demand.

The other caps in the preamp were different in each version; the treble version was for a short time called "Top Boost" in Vox's advertisements, until the term was recycled to described the extra tube added as an aftermarket mod, before being incorporated into production. The was an opinion in the UK that the Mod retrofitted to an existing amp sounded better than the production Top Boost.

The Top Boost Mod was based on a Gibson schematic, which incidentally had an error in the schematic, which Vox incorporated into its Amps.

Best Regards,
Steve

[Ondrej]

Good discussion on coupling cap values is here:

http://vintageamps.com/plexiboard/viewt ... t=tweaking