On 13/01/2016 3:46 PM, Phil Allison wrote:
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.


**Thanks for the tips. The guys at Musiclink were quite helpful,
suggesting that the original valves were crap and anything would be an
improvement. In fact, they responded to my email with good advice AND a
full schematic, board layout and parts list (which I did not request).
Great service.


--
Trevor Wilson
www.rageaudio.com.au

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