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7591 Output Tubes
Tubes are tested  using a Calibrated Hickok
6000 Mutual Conductance Tube Tester
Sylvania USA 7591 Matched Quartet
These also came from McIntosh Labs. They
are a fully matched Quartet and test at 5150
in reference to the 5100 standard of the
Hickok 6000 tester.

Avid Audio
McIntosh 7591 Vacuum Tubes
McIntosh Matched Quartet 7591 Tubes


Mcintosh 7591 Vacuum tubes westinghouse
McIntosh Matched Quartet 7591 Tubes
This is a full set of matched Westinghouse
7591's. They tested at 4800 using the 5100
reference on the Hickok 6000.  Other than a
few marks on the bakelite bases as shown,
they are in excellent shape.

rca westinghouse 7591 output tubes
RCA USA 7591 Matched Quartet Tubes
These came from McIntosh Labs many
years ago. Westinghouse manufactured
these for RCA.  The RCA 7591's are NIB.

westinghouse rca coin base 7591 output tubes
RCA USA 7591 Matched Quartet Tubes
All four have the coin base like this one.
Removed for  picture and testing.

sylvania mcintosh 7591 output tubes new
philips 7591 output tubes
Philips USA Matched Quartet 7591 Tubes
These are NOS tubes from Philips USA. The
writing is smeared somewhat but they are
new and tested at 5150 on the Hickok 6000