What value do you bias your amp at?

[Quencho092]

I was just curious about the average bias settings for each respective power tube "species". Anyone here plays 6l6's, KT66's, EL34's, and bias their own amps? If so at what values.

[TwilightOdyssey]

Re: What value do you bias your amp at?

I let my tech do all that stuff!

[mrid]

Re: What value do you bias your amp at?

It Depends On Plate Voltage!!!! There Is Not A "magic Value"!!!!

[Quencho092]

Re: What value do you bias your amp at?

hmmm....plate voltage, don't know?

[Quencho092]

Re: What value do you bias your amp at?

how do i check the ...plate voltage

[mrid]

Re: What value do you bias your amp at?

how do i check the ...plate voltage

Very carefully! You're dealing with several hundred volts of DC. With a multimeter, you probe pin 3 of a power tube socket.

[Quencho092]

Re: What value do you bias your amp at?

so what's your bias/plate voltage

[mrid]

Re: What value do you bias your amp at?

so what's your bias/plate voltage

In my Bogner it's ~460VDC and in my friends JCM 800 it's ~480VDC. When you plug that info into this form (http://www.ionpool.net/arcade/tech/W...alculator.html), you'll get the correct bias.

[STRATDELUXER97]

Re: What value do you bias your amp at?

Very carefully! You're dealing with several hundred volts of DC. With a multimeter, you probe pin 8 of a power tube socket.

Pin 8 is the cathode....You want pin 3...Be very careful or you will never forget the shocking experience!

The safeset way to bias your amp is to put a 1% 2 watt or better resistor across pin 8(The cathode to ground)...The resistor is placed in series between pin 8 and ground..You then measure your current in millivolts...The resistor converts milliamps to millivolts...That's how I bias all of my amps..

Plate voltage is found at pin 3
Pin 5..Gives you your - bias voltage
Pin 8 is your cathode...This is for the EL34,6L6,6550,5881 tubes...

John

[mrid]

Re: What value do you bias your amp at?

Pin 8 is the cathode....You want pin 3...Be very careful or you will never forget the shocking experience!

My bad...I forget these things.

[STRATDELUXER97]

Re: What value do you bias your amp at?

My bad...I forget these things.

I got your back buddy....

[aleclee]

Re: What value do you bias your amp at?

70% of max plate dissipation unless Lord Valve (my tube pusher) suggests something different.

[Gearjoneser]

Re: What value do you bias your amp at?

Thanks for that bias calculator link MRID. I use a mA bias tool I got off Ebay for $15.
I strum the guitar while turning the minipot, also watching the number on my amp meter. That way, I know when my amp sounds the best, and I also see that the mA value is close to what it usually is....36-38mA for EL-34's and 31-34mA for 6L6's, depending on the amp and tubes.

[Quencho092]

Re: What value do you bias your amp at?

what about the groove tubes bias thing, looks cool...does it work. I think you just probe the pins, plug in the tube and watch the meters, but yet again, theres gotta be a catch

[aleclee]

Re: What value do you bias your amp at?

I use the Weber Bias Rite. Plug it into the tube socket(s) and check current. Mine has the V/I option so I can also check the plate voltage. The hardest part of biasing my amps is pulling the chassis to get access to the trimmer pots.