KT120's are built to withstand even higher voltages (600+ VDC) than is found in the VTA ST-120. KT120's should be a more durable tube than a KT88 in the VTA ST-120.
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Scott,pscottlowe wrote:Cool,And Thank you Bob, Do you have advice on the best place to get them ? Thank you for the information
pscottlowe wrote:HI AGAIN , I was running my VTA ST-120 for several hours yesterday and my variac blew a fuse and so the st-120 went silent . I found the variac problem and when i started the st-120 I still had no sound but I do have bias and all tubes lit . I guess I will have to take it back to the shop again .I was not running it loud because it was late and I don't need to run it loud .ANY IDEAS ? thx Scott
Bob Latino wrote:Hi Scott,
You are off a decimal point on your bias setting. Whether it is a KT88 or a KT120, the recommended bias setting is .550 VDC per each output tube (550 millivolts). This will correspond to 55 milliamps of bias current per each output tube.