2. amps-preamps
  3. 985801464

Tube biasing for ARC and fender equipmen

Hi,

FENDER QUESTION:

In my fender hot-rod delux amp, I recently swapped the stock sovtek 5881 6l6 tubes for some svetlana 6l6gc's. I checked the bias, and it was at 80mv instead of the 60mv it should have been at. I next put the old tubes in, and noticed they were at the prescribed 60mv. I put back the new tubes, and lowered the bias so they too were at 60mv. I guess i learned to turn the bias DOWN before putting new tubes in. Should these tubes be run at 60mv as the old tubes were ?

ARC QUESTION:

1) Is it safe to put a set of Svetlana kt88's in my vt100m2 amp? It currently uses Svetlana 6550C's with bias point of 130mv. According to everything I have read, it is a safe swap.
2) Also, should I set the bias point the same with these tubes, and is there anything else I should do to the amp ?
john_l

Showing 1 response by frap

frap
213 posts
 
John, The 6L6/ 5881 tube In one of my ARC amps I set for .65ma. I have had no problems at this heater setting. Of course even better sound is attainable at higher ma. settings, but MELTDOWN will occur inside the tube.
The KT-88 tube is generally more lush sounding than the 6550. Some swear the 6550C is the most accurate though.
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