I just took my first step into the world of valve amplification, and
have some questions regarding tubes:

How important is vacuum tube matching? If one out of a pair of, say ECC
82 tubes need replacing, do I then also discard the working one and find
a new pair of matched tubes, or do I find a replacement that matches the
one that is still working?

In any case, what are the obvious outcomes of using unmatched tubes?

I'm using a Soundstage Class A Hybrid Stereo Booster integrated amp.
Sounds like a mouthful, but that's what it is called.

In article ,
razak & william wrote:
I just took my first step into the world of valve amplification, and
have some questions regarding tubes:

How important is vacuum tube matching?

Depends on the use. Some power amps with push-pull output did not allow
for adjusting bias on each output separately, and it was a good idea to
choose matched tubes so that the tubes draw the same current with zero
input. Some designs work better if the tubes have the same AC gain
(most?).

Matching tubes was fairly easy with a decent tube tester; at current prices
it might be cheaper to buy a tube tester and match them yourself.

I fondly remember the red glow of the 4 EL34's in my Eico HF-89 (Eico rated
them at 50 watts per channel driving a pair of Altec 605-A's, which required
running them over spec) and the blue glow from the 8 6550A's in my 4 Dyna
MKIII's driving 4 KLH Nines (ca 1975). The NAD 2140 driving the pair of
University 315-C's doesn't glow at all, but it doesn't require constantly
finding new 6550A's either. The HF-89 allowed bias on each tube to be set
separately, but the MKIII's didn't. This was due in part of Eico's cheapness,
since they didn't want to have to ship matched pairs of tubes.

Mike Squires
--

Mike Squires (mikes at cs.indiana.edu) 317 233 9456 (w) 812 333 6564 (h)
mikes at siralan.org 546 N Park Ridge Rd., Bloomington, IN 47408

the only place tubes need to be matched is the output pair in either output
channel. as they are usually working in a push/pull configuration both anode
currents pass through the output transformer. so to minimise the hum, &
possibly distortion, a par of matched tubes with the same transfer
characteristics i.e. same anode currents for grid voltage should be used.
John D

"razak & william" wrote in message
...
I just took my first step into the world of valve amplification, and
have some questions regarding tubes:

How important is vacuum tube matching? If one out of a pair of, say ECC
82 tubes need replacing, do I then also discard the working one and find
a new pair of matched tubes, or do I find a replacement that matches the
one that is still working?

In any case, what are the obvious outcomes of using unmatched tubes?

I'm using a Soundstage Class A Hybrid Stereo Booster integrated amp.
Sounds like a mouthful, but that's what it is called.

Matching tubes help in biasing. Conrad-Johnson tube amps have a real easy
method to bias the tubes so match tubes are not needed.