Rca 7591A Tubes

[jim3860]

I seen 4 RCA 7591A TUBES for sale and this is what they tested at according to the seller.

Four RCA 7591A tubes. All date coded BK for Feb., 1967.

Tested on my Hickok 600A where new tube is 6300 Gm. These tested better than new at 9000, 8500, 9000, 8000 Gm.

No shorts or emissions. Tubes are in excellent condition.

Now my question is do I need or want all four tubes to match exactly or are these close enough to use in a scott 233 amp?

Please excuse my ignorance in this matter but I am truly a dumbass when it comes to all thing tube at this point.



REGARDS JIM

[Kegger]

Those should probably work, put the (2) 9000 guy's together and then the other pair.

If you put a small resistor in the cathode of each output tube 1-10 ohms (if it's fixed)
then you can measure the current in each tube to see for yourself, I'd never trust that
a matched quad is all that matched anyway and would want to know on my own amp.

[jim3860]

Thanks Kegger.



REGARDS JIM

[FalconEddy]

I seen 4 RCA 7591A TUBES for sale and this is what they tested at according to the seller.

Four RCA 7591A tubes. All date coded BK for Feb., 1967.

Tested on my Hickok 600A where new tube is 6300 Gm. These tested better than new at 9000, 8500, 9000, 8000 Gm.

No shorts or emissions. Tubes are in excellent condition.

Now my question is do I need or want all four tubes to match exactly or are these close enough to use in a scott 233 amp?

Please excuse my ignorance in this matter but I am truly a dumbass when it comes to all thing tube at this point.



REGARDS JIM

I saw those the other day, but thought perhaps his tester wasn't working properly. 143% of brand new (9000) is quite a jump. But, under the right conditions, I guess it could be possible. Tubes from the early 60's will most likely have had more air leaking into them than tubes from the late 60's/early 70's. Those tubes did appear to be real nice, and if the readings listed are accurate; that clinches it.

. . Falcon

[hammr7]

Those numbers seem high if the sellers baseline for "new" is accurate. You might want to check his other tubes to see if they all seem equal to or better than new.

I would think those kinds of numbers would come from a certain adjustment knob being one notch too high, which might also imply the tester hadn't been calibrated in a while. Sure, those numbers might happen, but if all his reading seem high then something is wrong.

Trying to find tubes that will match in a specific piece of gear is always a crapshoot. But all other things considered, tubes that test within a few percent of each other is the best you can hope for from an unknown source. So check the seller's feedback to see if others have been happy with their tube purchases. And understand that there is quite a lot of room between a claimed tube performance on a tester and how they will perform for you.

[jim3860]

Thanks Guys I will run through his feedback also.



REGARDS JIM