I haven't built a power amp for some time, the demand for custom preamps remains high and I really think a good preamp provides the most bang for buck.
Of all the power amps I have built over the years, the compact and lovely sounding Malbec EL34 monobloc was one of my favorites.
With same size chassis as the preamp you could have a reasonably compact 4 box system (preamp and power supply and the two monobloc power amps) that looks and sounds a million dollars.
I have a horn system that has a >100dB bass horn and I wanted an amp that was dead quiet without using DC heaters (they radiate a lot of heat with power tubes)
As my preamps all have true balanced outputs I decided to utilise the perfect balance these provide and build a XLR input power amp with balanced inputs. Balanced inputs means the power amp doesn't need an internal phase splitter and you could say, that despite the driver stage being a little more complex, it is a "purer" system.
Its certainly quite with no noise detected with ears in bass horn. Measured noise is less than 1mV.
The driver stage is very powerful and consists of a 6SL7 input driver with 6SN7 White Cathode Follower driver stage( for each phase) for the 6N3C, 6L6GC, EL34 or KT66 power tubes.
Bias is automatic, and no adjustment is ever needed.
I wanted this amp to be super reliable and last for ever, and of course to sound very good.
It puts out a very clean 40 watt at very low distortion, and because of its formidable driver stage continues to put out good sounding power with a clean wave form well beyond 40 watts.
It has very big Hammond transformers that have high bandwidth , so good in fact that I decided to use zero feedback in this amp.
A very nice amp , beautiful sounding, powerful enough for just about any situation , very reliable and easy to live with, just plug it in and it will play for years.
Someone heard it and it was sold immediately, but I was so pleased with the way it came out I'm putting it into production.
$US4000 per pair.
