Trevor Wilson wrote:

I have one of the above-mentioned amps on the bench. Pretty
straightforward - 3 X EL84 output valves have air inside the valve. The
plate on one valve appears to have suffered somewhat, but I don't expect
any serious problems apart from that. However, my main questions a

* Should I match the output valves (more accurately, buy a matched quad
from Evatco)? Cost = AUS$100.00/set. Tung-Sol, Genalex (I have an
aversion to Chinese valves, even though they are cheaper),
Electro-Harmonix, JJ, etc.
* My other supplier has no matched sets (and I don't want to buy a
crap-load so I can match them), but sells two brands: Sovtek $13.75 each
or Electro-Harmonix $17.05.

Although cost is not an over-riding concern, the time to ship the Evatco
valves could be. My other supplier can ship today.

Thoughts appreciated. Particularly from PA.


** Finding reliably good EL84s is a PITA - there are many duds being sold, with low current output and long warm up times, like over 5 minutes.

Your safest bet is probably JJ or else EH brand.

Matching is best done by YOU with the valves in the actual amp.

At least try to get the idle current the same on each half of the OT as many of them are intolerant of any unbalanced DC component resulting in severe distortion at low frequencies.


..... Phil