Carvin Belair/Nomad/VT50 circuit design question?

[sjturbo]

I have a Carvin VT50 and since it is an EL84 based tube amp I wondered if the circuit is related to any other EL84 amps and if so which one's? Thanks!

[Jazz P Bass]

Check it out for yourself.
Here is the schematic: Vintage50 REV-E.zip

[Enzo]

Based on? AMps are amp, and they all tend to be very similar inside.

[sjturbo]

Got it. Thanks much.

[Jazz P Bass]

Yup.
Nothing new under the Sun.

[Mike Sulzer]

Based on? AMps are amp, and they all tend to be very similar inside.

To make a gross oversimplification, I would say there is a linear progression of different kinds of EL84 amps. At one end is the M. 18 watt (and clones) type, which use a pair of EL84s, run cathode bias, do not push things too hard, and have a medium amount of gain, or maybe these days you would call that low gain. At the other end there are the high gain (more 12Ax7s), higher power kind such as this Carvin that uses four EL84s, push pull parallel, grid bias, and approaches 50 watts (but those EL84s better be very well matched since there are no individual bias controls). Also you have a high and a low gain channel operating from the same input (with relay type switching), and an "effects loop".

The 18 watt and clones often have 68K grid stopper resistors (on the input), which make them somewhat noisy (hiss). This Carvin uses no grid stopper resistor, but rather a ferrite bead and, presumably, very careful layout and good shielding. It should approach the noise level of a single 12AX7 which is a lot better than a 68K resistor.


The high gain channel on the Carvin uses diode clipping after two stages. Not my favorite thing, but that is just me.

[Chuck H]

I think the OP was asking the question from a guitarists perspective rather than an engineering perspective. And I think Mike hedged to that. Is it more like a Vox ac30, a Marshall 18W, a matchless, a Peavey, etc.

To which I would answer 'all and none'. The circuits aren't different from what has been used in other amps, though not in the combinations I see in the Carvin schematic. Making it it's own animal that is pretty much just a tube guitar amp not unlike any other, but not a clone of anything and not pegging any specific design as a jumping board.

[Richard]

Looks like a Baxendall tone stack, most of the amps that I'm aware of do not have that.

[überfuzz]

Looks like a Baxendall tone stack, most of the amps that I'm aware of do not have that.

I had a similar carvin amp. The clean channel sounds really good, imho. I never did care for the 'soak' channel. It had some wonky diode circuitry for imposing distortion (breakup).

[sjturbo]

Thanks to Mike, Chuck and Richard for being a bit more concise! I was actually looking for engineering comparisons as well as tonal!