Sorry for the late reply! There is no parts list, they are made from leftover 5mm aluminium sheet and kwila decking that I had in my shed - slightly bigger than Stephe suggested. And the paint was an aerosol low-sheen black over an etching primer - I can't remember the brands. Sorry I can't give more specifics 😉

With a preamp or DAC with volume control or similar before the KT120's

Cheers

Thank you!

I am trialling a couple of USB fans which seem to be helping - they are silent, and I guess extra airflow over the tubes and tranformers can't do any harm. I'm up to 95ma with no apparent overheating.

In order to replace the KT120's with EL34's or 6550's (leftovers from my Willsenton R8 days), do I need to do anything other than change the bias to the appropriate setting? And how much influence on the sound do the driver and rectifier tubes have? Is it worth trying alternatives?

Cheers, Stephen

I honestly haven't tried EL34 tubes yet in mine, I would just caluculate the cathode current/voltage to stay under their 25W limit and go for it :)

Hi @Skunkie - I finally got around to trying some EL34's and 6550C's in my monoblocks. The EL34's sound even better than the KT120's to my ear..slightly more differentiation between instruments and more precise soundstage. The 6550C's were less pleasing..slightly flatter, less holographic. Both had plenty of grunt for my 95db open-baffles (supplemented as they are with a pair of active subs).

Oh what fun! Thanks for the inspiration :) Edit: I take it back - I just went back to the KT120's and bumped the bias to 95ma, and they sound the best of the 3 options I have tried. They definitely measure best on the Analog Discovery 3 - much better THD + noise, and more than twice the power output of the EL34's - and sound best too. I'll keep an eye on the heating, and if there are no problems I'll bump the bias up a bit more 😉. Edit: Just bumped the bias to 100ma - no overheating issues after 1 hour of playing music at fairly loud level. and sounding good!

Thanks Stephe - would it be ok to use a 470k 1w bleeder resistor, and a 10R 1w 5% test point resistor just until the correct ones arrive?

The resistor will have 0.6W across it so should be OK at 1W for temp use but for long term reliability 2W would be safer. And 5% resistors are OK, I would just try to get them as close to 10ohms as possible.