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Hiwatt DR504 bias

5/23/2000 5:55 PM
Hiwatt DR504 bias
Anyone have experiance with Hiwatt biasing. I set the bias to -36v as per the schematic. The cathode current measures 58milliamps. Is this value to high? the El34's don't glow and the amp sound fine. I've read that 55-58milliamps is ok for el34's and have seen here that 35-36milliamps is best for el34's.  
5/26/2000 8:40 AM
Mark Cameron

With some Hiwatts (& sound citys) you have to make a voltage doubler to get the right -bias voltage. .Theres a schematic of this in the groove tubes book.Also make sure to use real good tubes(NO chinese tubes for Hiwatts).  
5/26/2000 3:47 PM

It does sound a bit high to me. What is the plate voltage on your amp? Also, what tubes are you using? My DR103 vapourises the insides of a lot of tubes pretty quickly at tht sort of current.  

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