I received my bias probe today in the mail and finally biased my Rev properly with the JJ6L6GC Tubes.
Typically you want to bias the tubes at 70% of their Max Rated Power (this get's the tubes running at above the crossover distortion area and not too hot as to cause them damage). In the JJ6L6GC case they are rated at 30W so they should be biased around 21W (70% of 30W). I originally had them biased at around 33.3mA at 526V = 17.5W. I had used 25W as the Max Rated Power giving me 70% of 25 being 17.5W and therefore:
70% X 25W/526V = 33.3mA 17.5W which wasn't correct
When I measured the Plate Voltage today I had around 548V (average of the 4 tubes) and not 526 as I had about 10 months ago (measured with a different voltmeter at a different place). So:
70% X 30W/548V = 38.3mA 21W which is typically correct.
I biased the tubes with an average of around 38mA.
I made a QUICK test recording before the biasing and after the biasing with the same amp settings, mic placement etc... I should have spent more time getting a better Before sound but I was in a hurry to do the bias. I have included the RAW tracks before and after the bias and a basic mix with just 90-12kHz hi/low and a small cut at 5.7k and tamed the low end. The low end from the Hellraiser is huge and this was recorded with the mic over an inch away and the Bass on 5 (out of 10) on the amp and it still has too much low end. After I did the bias and listened back to the Before sample it was too late to redo a new sample so I was stuck with it and used the same settings for the After sample. Anyway, the difference is not night and day, just a little more refined with a little less fizz..................maybe
.
Check it out:
http://www.esnips.com/doc/b66bd4a3-f3fe-438f-8e91-01016b0cd1ea/Bias-samples
EDIT: The Master Vol on the amp was only on 2 (out of 10), I am expecting to notice more of a difference when I raise the Volume. If anyone is interested, I will record a sample (just an After sample obviously) with some more Master Volume.
Typically you want to bias the tubes at 70% of their Max Rated Power (this get's the tubes running at above the crossover distortion area and not too hot as to cause them damage). In the JJ6L6GC case they are rated at 30W so they should be biased around 21W (70% of 30W). I originally had them biased at around 33.3mA at 526V = 17.5W. I had used 25W as the Max Rated Power giving me 70% of 25 being 17.5W and therefore:
70% X 25W/526V = 33.3mA 17.5W which wasn't correct
When I measured the Plate Voltage today I had around 548V (average of the 4 tubes) and not 526 as I had about 10 months ago (measured with a different voltmeter at a different place). So:
70% X 30W/548V = 38.3mA 21W which is typically correct.
I biased the tubes with an average of around 38mA.
I made a QUICK test recording before the biasing and after the biasing with the same amp settings, mic placement etc... I should have spent more time getting a better Before sound but I was in a hurry to do the bias. I have included the RAW tracks before and after the bias and a basic mix with just 90-12kHz hi/low and a small cut at 5.7k and tamed the low end. The low end from the Hellraiser is huge and this was recorded with the mic over an inch away and the Bass on 5 (out of 10) on the amp and it still has too much low end. After I did the bias and listened back to the Before sample it was too late to redo a new sample so I was stuck with it and used the same settings for the After sample. Anyway, the difference is not night and day, just a little more refined with a little less fizz..................maybe
.Check it out:
http://www.esnips.com/doc/b66bd4a3-f3fe-438f-8e91-01016b0cd1ea/Bias-samples
EDIT: The Master Vol on the amp was only on 2 (out of 10), I am expecting to notice more of a difference when I raise the Volume. If anyone is interested, I will record a sample (just an After sample obviously) with some more Master Volume.
