Egnater Tweaker 40 tube bias question?

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jimmyt

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Awesome amp! I like it better than the Rebel 20 & Tweaker 15.
Here's my tube bias issue:
I have put in new power tubes - SED winged "C" 6L6GC rated @ 30watts
My TW 40 Plate voltage measured @ 446vDC. Tube bias formula: (W x .7) / Plate voltage = I (mA)
The formula comes up with: (30watts x .7) / 446 = 46mA @ 70%
I put my bias probe under one tube, hooked up a speaker load, and let the amp warm up and I set the bias to read 45mA. Then I checked the mvDC accross the test points Tp1 - Tp2. This reading was 92mvDC - which is much higher than the factory recommended setting of 65mvDC.
My question to Ian or Bruce: Is this setting too high and will this setting harm the amp?
 
That is high. It won't harm the amp but it will wear your power tubes out much faster. The test points are the sum of both tubes so the reading will be twice that of the external bias probe for one tube.
 
jimmyt":3ntiid3c said:
Awesome amp! I like it better than the Rebel 20 & Tweaker 15.
Here's my tube bias issue:
I have put in new power tubes - SED winged "C" 6L6GC rated @ 30watts
My TW 40 Plate voltage measured @ 446vDC. Tube bias formula: (W x .7) / Plate voltage = I (mA)
The formula comes up with: (30watts x .7) / 446 = 46mA @ 70%
I put my bias probe under one tube, hooked up a speaker load, and let the amp warm up and I set the bias to read 45mA. Then I checked the mvDC accross the test points Tp1 - Tp2. This reading was 92mvDC - which is much higher than the factory recommended setting of 65mvDC.
My question to Ian or Bruce: Is this setting too high and will this setting harm the amp?
Click to expand...


How do the Winged C 6L6 sound? I put a pair of Tung Sol 5881 in mine as soon as I got it, thinking of switching it back.
 
the winged "C" tubes sound really good. I liked the 6v6's better in my tweaker15. For a sweeter clean depth the winged "C"'s are the best. I finally setted with a 62mvDC bias setting.
 
That's 62mvDC across the test points with both tubes in. So, it would be about 31mvDC per tube.
 
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