I have a Rogue Cronus Magnum integrated with the KT120 tubes. I wanted to try the EL34 sound in my system so I purchased 4 Shuguang EL34B tubes which were graded and matched from Upscale Audio. I checked with Rogue and was told to set the bias at 30ma. I received the tubes today, installed them and let them warm up for 30 minutes. The sound was a little ragged and distorted and try as I may, I couldn't get a reading on the bias meter.
Thinking I wrecked the amp, I reinstalled the KT120 tubes (thank God I marked which socket they came out of) fired the amp up and the sound is again full with no distortion. I checked the bias on the KT120's after 30 minutes and the bias on one tube was off a little.
Why did the EL34 tubes sound distorted and why couldn't I bias them? What did I do wrong? Do you think these tubes are all toast now?
Joe - From thetubestore.com's page for the Tung-Sol EL34B - "When driven into distortion it starts off a bit crunchy like a 6L6 but as you push it, the sound blooms into that singing EL34 tone with great sustain and modest compression." From the manufacturer: "The Tungsol EL34-B is a higher impedance EL34 tube design with increased touch responsiveness and a unique clipping characteristic with a hint of the 6L6 sound." Hope this helps!
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.