Just wondering; when it is said that a pair (or quad) of tubes are
matched, what does that imply? If I set up my AVO MK. IV to a certain
tube, plug it in and it flows a certain amount of current than plug in
another of the same type and it reads pretty much the same, can these
be said to be matched? Or are more operating point matches needed?

"David Ginsberg"

Just wondering; when it is said that a pair (or quad) of tubes are
matched, what does that imply?


** You have to make enquires of the party that used the term - it means
whatever they mean.

In the case of " Groove Tubes " it means they have a similar "tone"
.......... -(



If I set up my AVO MK. IV to a certain
tube, plug it in and it flows a certain amount of current than plug in
another of the same type and it reads pretty much the same, can these
be said to be matched?


** If that is ****your **** matching criterion - then yes.


Or are more operating point matches needed?


** A good start is to compare tubes of the same make, type number and
vintage.

Then, the application determines what electrical parameters need to
be matched - if any.

A push pull pair may need to be very close over the whole operating
range - while a quad may consists of two close pairs split across each
de - for example.




......... Phil

David Ginsberg wrote:

Just wondering; when it is said that a pair (or quad) of tubes are
matched, what does that imply? If I set up my AVO MK. IV to a certain
tube, plug it in and it flows a certain amount of current than plug in
another of the same type and it reads pretty much the same, can these
be said to be matched? Or are more operating point matches needed?

Matching should mean the tubes will have similar Gm
and when a certain value of grid bias is applied to each,
a similar bias current flows.

New Sensor sell matched quads of tubes,
and sometimes you can score a matched octet
amounsgst a bunch of say 50 pcs, where I asked for
50 x EH6550, with 12 matched quads.
I did, last year.

Patrick Turner

You've got questions, Duncan's got answers :-)
http://www.duncanamps.com/technical/valvematch.html

According to the US distributor (and owner) of Sovtek, the basic matching
spec is the DC plate current for a specified (standardized) grid and plate
voltage. When I talked with them they did not specify the value of voltages
they use.

Essentially this is a crude measure of transconductance. A tube with high
transconductance will have a lower plate current for a given value of
negative grid voltage than a tube with a lower transconductance. A tube
with high transconductance will have a much narrower range of grid voltage
between saturation and cutoff than a low-transconductance tube. Therefore,
the high transconductance tube will clip and saturate much more 'quickly'
making it desirable for musicians who play heavy metal and overdrive guitar.
A low transconductance tube will have a broader grid curve, with a wider
range of input signal swing before clipping or saturation occurs, making it
more desirable for a blues or jazz player who plays 'clean'. Using this
principle, generally a tube with a lower matching number (lower plate
current) will distort more easily than one with a higher number.

Output tubes should be 'matched' in a typical push-pull amplifier to ensure
that both the positive and negative alternation of signal are amplified
equally to prevent undesired distortion. An amp with 4 output tubes may use
two matched pairs having slightly different ratings, but we try to keep the
pairs within about 10% of each other.

When we test output tubes we use a dynamic transconductance tube tester and
try to match their transconductance readings.


Neil Preston
npreston at swbell dot net
prestcomusic dot com

"David Ginsberg" wrote in message
...
Just wondering; when it is said that a pair (or quad) of tubes are
matched, what does that imply? If I set up my AVO MK. IV to a certain
tube, plug it in and it flows a certain amount of current than plug in
another of the same type and it reads pretty much the same, can these
be said to be matched? Or are more operating point matches needed?

Output tubes should be 'matched' in a typical push-pull amplifier to
ensure
that both the positive and negative alternation of signal are amplified
equally to prevent undesired distortion. An amp with 4 output tubes may
use
two matched pairs having slightly different ratings, but we try to keep
the
pairs within about 10% of each other.

Not necessarily.

see R. G. Keen's explanation on the Net, on why a tube amp sounds nicer with
it's output tubes slightly *unmatched*