Tung-Sol Factory Platinum Matched QUAD 7591A 7591

Description

New Platinum matched quad (set of four) Tung-Sol 7591A tube.  These are found in Ampeg, McIntosh and Fisher amplifiers (among others).  Some of these designs using the 7591 are considered the best tube amplifier designs ever.
The Tung-Sol 7591A is considered by many to be the finest 7591 ever made.
Why settle for NOS tubes of unknown quality when you can have these tubes that are burned in for 24 hours and then bias matched for plate current.
Application note
:
There occasionally have been cases where new production 7591A tubes have had trouble in circuits using a very high value grid resistor, such as Scott and Fisher (others too). If you find this to be the case, the best solution is changing the grid resistors to something in the range 200K-220K from the original value, since often the factory spec resistors exceeded the maximum recommendations.  For example, Fisher often used 330K carbon resistors that would often drift to 350K or more over time.
The factory matches at real world voltages and then the test results are labelled on each tube box.
They are all recent date codes.
The factory matches these tubes at 400V Plate, 250V Screen and -20.52 V bias.
Insist on factory platinum matched tubes for best performance.
All tubes carry the 90 day factory warranty against defects from date of purchase.
I have been selling tubes of all types for more than ten years.  Buy with confidence.
On Nov-06-19 at 06:20:39 PST, seller added the following information:
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