Tube Amp Archive

i've built a simple SE amp using hammond 125ESE OT and have parallel cathode biased output tubes each with their own MV for blending different tubes at different volumes. i would like to use 1 6V6 and 1 6L6 but am not sure how to determine which output tap to use for the correct speaker load. i assu...

does anyone out there use a compu-bias with a JTM45?

thanks

what would the lower HT do? i am under the impression that a lower voltage will make the amp sound better

got any pics bob?

is the 50k pot sensitive/precise enough?

thanks drew

Wayne wrote:The bias wire would be hooked to the 100k, then the 100k and the 27k values juggled to give the proper voltage (100k would wind up much smaller).

Is there a formula to use to calculate?
Original voltage is 340 bias tap is 50

i accidentally bought a mercury PT with a bias wire for my blackface princeton build.
FBFPP-M Blackface -- 50V bias tap -- lower B+ -- 325-0-325

i'm adding a bias adjust pot, but don't know how to integrate the bias wire from the PT into the build. what does that diode do on the bias board?

i use my SF vibro champ through a marshall 4x12 and it kicks much harder than i ever expected. have you considered just using a huge 8ohm cab with 12s or 15s?

i built a BF princeton (no reverb AA964), but split the tube that is shared by the vibrato and PI. i added another tube socket and rewired the heaters at both sets of pins 9 & 4/5. now i have one 12AX7 with connections on pins 1, 2, & 3, but NOT on pins 6, 7, & 8 - they are untouched. And the same t...

does anyone have any visio drawings of BF fender chassis and boards?

I recently purchased one of these and i love it. it's fast, easy, and small.

must i re-bias my twin 6V6's when i change the speaker outs from 8 ohms to 4 ohms to use a different cab? i'd like to be able to change setups rapidly in a studio environment.

even if it's not necessary, should i re-bias?

OT is 4/8/16 and amp has exterior bias probe outlets and bias pot.

thanks

Phil_S - thanks, your lamp suggestion seemed to be the solution i was overlooking. i took the lamp completely and rewired the PT from scratch paying very very close attention to solder joints etc. i powered up and measured ~6.3VAC on the heaters. popped in tubes, saw glow from all tubes, although th...

Phil_S - thanks, your lamp suggestion seemed to be the solution i was overlooking. i took the lamp completely and rewired the PT from scratch paying very very close attention to solder joints etc. i powered up and measured ~6.3VAC on the heaters. popped in tubes, saw glow from all tubes, although th...