Hey all-
I recently swapped the stock 6l6's in my HRDV for a pair of Groove Tubes 6l6ge's with a rating of "1". They sound incredible, but after playing awhile the amp gets hot and smells funny. I checked the bias at the bias test point and it was at 60mV, which I thought it was supposed to be. I adjusted the bias to 45mV and the heat and smell have gone away. How can I calculate the best bias voltage for this amp/tube setup? Thanks.
Hot Rod Deville Bias Question
Moderators: pompeiisneaks, Colossal
Re: Hot Rod Deville Bias Question
Since no one has chimed in on this. You need to know your VDC at the power tube plate. I just had one in and it was 495VDC. A 6l6 is considered a 25w tube. so 25/495 = .050. That converts to milliamps current. Taking the standard 70% rule 50 x .70 = 35ma. per tube.
That is almost always a sweet spot for a fixed biased 6l6. but they can and do sound pretty good at 25ma per tube. or anywhere in between. Burning smells can be new paint, dust bunnys or anything getting hot for the first time or last.
IF you had only one tube running due to a burnt screen resistor on the other and you measured 60millvolts at the test point , you were too hot for one tube,it would have sounded bad as well. you need to measure both tubes individually for solid performance. If one was running 12 and the other 48 it would add up to 60. But one is way too hot and the other way too cold (arc).
That is almost always a sweet spot for a fixed biased 6l6. but they can and do sound pretty good at 25ma per tube. or anywhere in between. Burning smells can be new paint, dust bunnys or anything getting hot for the first time or last.
IF you had only one tube running due to a burnt screen resistor on the other and you measured 60millvolts at the test point , you were too hot for one tube,it would have sounded bad as well. you need to measure both tubes individually for solid performance. If one was running 12 and the other 48 it would add up to 60. But one is way too hot and the other way too cold (arc).