Bigger amp desired

[Acorn to Oak]

Ok I’ve got 3 options to view by Friday.
2 are through advice given and one is from the gut.
TBC

 

[Acorn to Oak]

I have the BTA400s fraternal twin the Small Block 427. They have the same power amp section but a totally different preamp. The 427 is the loudest tube amp I have ever played and I own multiple big tube amps.

IMHO if you find a BTA400 for £1K that sounds like a price that is too good to be true.

I have the BTA400s fraternal twin the Small Block 427. They have the same power amp section but a totally different preamp. The 427 is the loudest tube amp I have ever played and I own multiple big tube amps.

IMHO if you find a BTA400 for £1K that sounds like a price that is too good to be true.

Got one. It’s a minter, sounds awesome and £950 delivered with an equally mint Ashdown 810 cab.

 

[Wasnex]

Got one. It’s a minter, sounds awesome and £950 delivered with an equally mint Ashdown 810 cab.
View attachment 3769869

Sounds like you stole it! I hope you will post a complete review once you get a chance to fully explore the preamp.

FYI there is a factory update to the output section you might want to have your tech look into. This is from the amp's designer:

Halfway through production something changed and the KT88 started to oscillate when the tube count went over 6 . I eventually traced this to a small change in the internal structure of the KT88 . Other makes were tested but non delivered the power or lasted more than a few hours. Only the JJ would stand the full 800V .

The solution was to add 220R resistors right up close to the tube socket on the screens.

This cures the problem without affecting the final output power, this is because the amplifier is ULTRA LINEAR and the screens are driven from the output transformer.

The final HT should be 675V off load and the quiescent current for each tube should be 28mA ( this current requirement is set by the wind of the output transformer to some degree) and the whole output operates in a LOW LOADING condition.
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When I first got my 427 it was popping KT88s because the plate voltage was set too high. My tech reconfigured the plate supply to lower the voltage to the proper range, and added 220 ohm 5W Xicon flameless resistors on the tube sockets inline with the screen circuit as directed by the amp's designer. It's been rock solid every since and it is easily the most powerful tube amp in my collection.