S
SalsaNChips
Guest
I am interested in replacing the tubes in my late 80’s-era ADA T100S tube head. It still has the original Siemens tubes (EL34 and 12AX7) which are 20-something years old. They are working fine except the DC hum out of the amp when I take it off standby has grown louder as of late. I’m thinking it would quiet down and perhaps sound better with new tubes and a proper biasing. Which brings me to the point of my post.
To bias tubes, my understanding is you have to put a sine wave input into the amp and measure the peak to peak amplitude and signal quality pre/post gain on each tube, adjusting the input voltage to the tube (anode/cathode?) to get it as clean and accurate as possible. That requires an oscilloscope and a sine wave generator, both of which I don’t have (closest I have 40 year old Techtronix scope that doesn’t work). Please correct me if I am wrong on this or over simplifying.
I wanted to see if anybody here can provide insights into a quick and dirty (but reasonably effective) method of biasing, or if biasing is even really necessary (suspect it is).
Thanks for any info.
To bias tubes, my understanding is you have to put a sine wave input into the amp and measure the peak to peak amplitude and signal quality pre/post gain on each tube, adjusting the input voltage to the tube (anode/cathode?) to get it as clean and accurate as possible. That requires an oscilloscope and a sine wave generator, both of which I don’t have (closest I have 40 year old Techtronix scope that doesn’t work). Please correct me if I am wrong on this or over simplifying.
I wanted to see if anybody here can provide insights into a quick and dirty (but reasonably effective) method of biasing, or if biasing is even really necessary (suspect it is).
Thanks for any info.