Hlt,
"How can I tell if my tubes need to be replaced? "
If you hear excessive hiss, hum or microphony, replace the tubes.
Also, if there is a noticeable channel imbalance, you should consider replacing the tubes.
To 100% sure, swap the tubes between channels. If the noise or imbalance follows the tube, Bingo.
There is another reason for changing tubes: lack of dynamics and less bass punch, a sign of weak tubes. Unfortunately the only way to find out is by swapping in a new pair of tubes (NOS or new production) that are matched and measure very close to 100%.
I agree with the above NOS recommendations and would like to add the king of the hill (IMO): Amperex USN-CEP gold pin 7308, a super-quiet and matched-section 6922 developed for Sonar applications.
The equivalent european tube is Philips Netherlands E188cc, I believe developed for the professional Studer reel-to-reel recorders.
Have fun!
"How can I tell if my tubes need to be replaced? "
If you hear excessive hiss, hum or microphony, replace the tubes.
Also, if there is a noticeable channel imbalance, you should consider replacing the tubes.
To 100% sure, swap the tubes between channels. If the noise or imbalance follows the tube, Bingo.
There is another reason for changing tubes: lack of dynamics and less bass punch, a sign of weak tubes. Unfortunately the only way to find out is by swapping in a new pair of tubes (NOS or new production) that are matched and measure very close to 100%.
I agree with the above NOS recommendations and would like to add the king of the hill (IMO): Amperex USN-CEP gold pin 7308, a super-quiet and matched-section 6922 developed for Sonar applications.
The equivalent european tube is Philips Netherlands E188cc, I believe developed for the professional Studer reel-to-reel recorders.
Have fun!