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7591A Tube List
Tube matching is required when 2 or
more tubes are operated in push-pull in an output circuit. This
is especially important when the circuit is a fixed bias circuit and
the tubes are operated at or even a little beyond their maximum
ratings. This is typical in audio amplifiers as
manufacturers would try to squeeze every watt of power out of the
amplifier. If you don't use reasonably matched tubes in such a
circuit, you run the risk of destroying one or both tubes as you could
never properly bias the circuit for both tubes. They don't
usually have to be EXACTLY matched; just within a few percentage points
of one another. Also, if you have a stereo amplifier which run
the tubes in 2 pairs, IT IS NOT NECESSARY TO BUY A MATCHED QUAD!
2 matched pairs will be fine. Tube tester matching is NOT
normally effective matching because most tube testers operate the tube
far below the normal operating parameters used in the amplifier.
Tubes that match at typical tube tester voltages will NOT usually be
matched in the amplifier. I use different types of test equipment
to match tubes. I normally operate the tubes at typical amplifier
voltages and measure plate current. Transconductance is NOT
important when matching this way.
Matching is available when I have
enough tubes on hand to select from. Plate
current matching where available will add an additional $5 per tube.
Please inquire about matching for NOS and used tubes. Matching is
usually available on currently produced tubes like Russian tubes.
|7591 Original Westinghouse. NEW (NOS) Westinghouse was the
originator of this tube. Could be different brand names like
Philco, RCA, etc. which were made in the Westinghouse Factory. RCA DID NOT Manufacture any 7591's. They
bought them from Westinghouse and Sylvania (more common). Very
few available at any give time.
||As above but USED TESTED GOOD. May be other OEM brand
names like Eico, Heath, Scott, etc. which were made by
|7591 Syl / GE Full
/ 7591A Sylvania or GE NEW (NOS) May be other OEM brand
names like Eico, Heath, Scott, etc. which were made by Sylvania.
These have the full bases as opposed to the thin coin style base listed
|7591 Syl/GE Full
/ 7591A Sylvania or GE As above
but USED TESTED GOOD. May be other
OEM brand names like Eico, Heath, Scott, etc. which were made by
|7591A Syl/GE Coin
|| 7591A Sylvania or GE NEW (NOS) These have the thin
coin type base which was used in later production tubes. This
ISN'T BAD. Thin bases allow better heat dissipation so the the
tube will operate cooler and last longer.
|7591A Syl/GE Coin
|| 7591A Sylvania or GE As
above but USED TESTED GOOD.