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65 Bandmaster Bias


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I have set my bias to 30 mA and have all JJ tubes.


It sounds great, but I'm wondering what some of you Bandmaster owners have yours set on.

 

I assume you mean JJ 6L6GC's, what is your plate voltage?

 

The 30 MA looks low to me if you are using 30 watt 6L6GC tubes, your plate voltage should be around 440 VDC so your bias should be closer to 45 MA if you wanted to bias at 65%

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bandmasters only pump out about 40 max watts regardless of what tubes are in them, so they need to be biased accordingly. any much hotter will just muck up the sound, since you won't really be pushing the tube to its limits with the bandmaster's low plate voltage, just over-saturating the teeny tiny OT.

 

this is one reason those amps LOVE tubes like philips 6L6WGB, which are a lower-powered 6L6. with those, the amp puts out about 35 watts and you can actually get the tubes running nice and warm while staying in the sweet-spot of the OT.

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I assume you mean JJ 6L6GC's, what is your plate voltage?


The 30 MA looks low to me if you are using 30 watt 6L6GC tubes, your plate voltage should be around 440 VDC so your bias should be closer to 45 MA if you wanted to bias at 65%

 

I think my plate voltage is around 470.

 

I'm going to try 38 mA and see if I get more punch.

 

That is what it says on Weber VST.

 

http://www.webervst.com/tubes/calcbias.htm

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with those, the amp puts out about 35 watts and you can actually get the tubes running nice and warm while staying in the sweet-spot of the OT.

 

That bandmaster is running 440+ volts on the Plates, that is not exactly what I would call "Low"

 

Actually the Jan Phillips are just a 6L6GC in a smaller bottle to meet military specs. (a leftover Sylvania design) It is a 30 watt tube, but the Tung-Sol 5881/6L6WGB is a 23 watt power tube, most 6L6GBs are 23 to 26 watts.

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I swapped my speaker to a Jensen 12K and adjusted the bias to about 42 mA.

 

It is now an extremely loud amp with tight bass. It starts to break up around 5 with my Gibson SG Standard. By that time your ears begin to hurt if you are in a small room.

 

This amp was originally a head that was made into a 1/12 combo.

 

It takes pedals VERY well.

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I have set my bias to 30 mA and have all JJ tubes.


It sounds great, but I'm wondering what some of you Bandmaster owners have yours set on.

 

is the Bias circuitry modified because that amps circuitry is really a bias balance. not a bias adjust as in todays amps.

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is the Bias circuitry modified because that amps circuitry is really a bias balance. not a bias adjust as in todays amps.

 

 

A 1965 Bandmaster would not have bias balance, which did not come into use until the CBS years.

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A 1965 Bandmaster would not have bias balance, which did not come into use until the CBS years.

 

I stand corrected. I have a 64 Bandmaster that I rebuilt over twenty years ago and I thought I had modified that circuitry, but checking it did have a bias control.

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