Model 3 - amped

[av]

Late in his life, Harold Beveridge worked on a smaller tube amplifier, the one we now nickname the "half-amp" for the Model 7. It was basically a half voltage Model 2/2sw amp, with only 2 tubes providing the half voltage required by that half-spaced electrode (compared to the Model 2/2sw electrode). It drove a Model 6, renamed Model 7 with the included amps.

To the best of my knowledge, only a couple or so were made, one of which now happily resides in, and drives, a Model 3 speaker.

The schematics for this amp exist and I wonder how many Model 3 owners might be interested in driving their speakers this way. It means direct drive with an OTL amp, discarding the step-up trafo and polarizing network. It surely must render a big improvement in the sound reproduction of the system.

I'm also toying with the idea of a possible solid state amp to drive these half-spaced electrodes. The c.2000V requirement is certainly at the limit of current devices - but not impossible. Someone even suggested halving that voltage - solid state devices can certainly achieve that now - and using a 2:1 step-up trafo only to double voltage. Such a low ratio may well be welcome in place of the current high ratio trafo employed, but it would be nice to dispense with them altogether.

What say you?

[Sergio Zori]

That could be an excellent upgrade to the Model 3's.

The sound of good tube OTL amps would make the Model 3's sing for sure.

Separate amps would be needed for the electrostatic element and the two 10" woofers.

In fact, the best performance might be to drive the electrostatic element with OTL amp and use separate digital amps for the woofers.

Also, optimal performance might be achieved by using digital corrective crossover to replace either the built in cross over or an analog outboard crossover. Something like one of the DEQX units would bring performance to a new level.

DEQX High Definition Audio

Of course the mechanical construction of the original Model 3's should also be enhanced where possible.

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[av]

The half amp was designed to go into the base of the Model 3, replacing the current electronics (step-up, xover, polarizing network, etc). The xover is envisaged to be incorporated, just as in the Model 2sw. Same for a separate woofers solid state amp. There is no point in placing the tube amp externally, the high voltage connecting cord is not a safe thing. The kind of woofers solid state amp is open to discussion, many will have their own preferred topology/technology, but either way it isn't rocket science.

The surrounding gap around the Model 3 base can use as ventilation for the tubes. Rick and I also thought of the possibility of placing those tubes outside, behind the base - that works really a treat with Model 3-G where the whole electronics is placed inside a metal, removable draw (see photos of that model which I placed on Beveridge site).