Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mresistor on January 26, 2018, 02:50:03 pm

Title: power level during operation
Post by: mresistor on January 26, 2018, 02:50:03 pm

I retubed an early BF Deluxe and set the bias up at 8.2w per tube. Plugged in my guitar and turned it up to 5 on the Vib channel and was watching the Plate V and I and during some hard strummed chords it was getting up to around 11.5 watts per tube and spiking higher at times.  Is this normal?  I tend to think it is, but wanted to check for sure. I usually don't watch the meters after I've set quiescent current.

Title: Re: power level during operation
Post by: shooter on January 26, 2018, 04:32:28 pm

Quote

Is this normal?

I believe in a PP configuration you can swing 2X the Idle plate volts.  For that reason n others I believe that's why bias is typically set ~70%.  As long as you're not red-plating when you're picking HARD, you're probably ok

Title: Re: power level during operation
Post by: mresistor on January 26, 2018, 04:34:22 pm

Thanks shooter - I'm going to wait till the sun goes down and check the 6v6s for redplating to make sure. Appreciate the response.


Cheers   :occasion14:

Title: Re: power level during operation
Post by: PRR on January 26, 2018, 06:13:08 pm

> up to around 11.5 watts per tube

11.5W dissipation would be plenty safe.

You measured, not dissipation but power IN to the tube. Was there power coming OUT to the speaker? (That's the whole idea.) Deduct that from the plate input, that's the plate dissipation.

Measuring live guitar power is not easy. But assume 23W in and average 10W out (20W amp clipped half the time). The actual dissipation has *fallen* to 6W per tube.