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2A3 45
10 71A
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50 801
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7027A 7591
7868 6550/KT88
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7591A Tube List


Matching Tubes

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.

Type Description Price 
7591

Westinghouse

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.  $85 ea
7591 Westinghouse As above but USED TESTED GOOD.  May be other OEM brand names like Eico, Heath, Scott, etc. which were made by Westinghouse.  $45 ea
7591 Syl / GE Full Base 7591 / 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 below.  $75 ea
7591 Syl/GE Full Base 7591 / 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 Sylvania. $35 ea
7591A Syl/GE Coin Base 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.  $75 ea
7591A Syl/GE Coin Base 7591A Sylvania or GE As above but USED TESTED GOOD. $35 ea