Difference between 7189 and 7189A

[Andrew Huculak]

Is there any?

I'm restoring an old Scott 222C integrated amp, and have been advised
to use the original 7189's vs. 6BQ5's. I've found a local supplier who
has 7189A's at a great price, and am wondering what the "A" signifies,
if anything.

Regards,
Andrew Huculak

[CBusetti]

The letter suffix always indicates some kind of improvement in the basic
design. I think the rule is that the A, B, C, etc. must be interchangeable
with earlier versions. The improvement may not be relevant to your
application-- for instance, 6SN7GTB improves performance for series
-string operation in TV sets, but not necessarily for audio applications,
although Sylvania's ads claim tighter manufacturing limits for their
tubes.
Dan B

[Dave Cigna]

I thought that I posted this before, but evidently I sent it by private
email by accident. It might be of interest to others:

>I'm restoring an old Scott 222C integrated amp, and have been advised
>to use the original 7189's vs. 6BQ5's. I've found a local supplier who
>has 7189A's at a great price, and am wondering what the "A" signifies,
>if anything.

Maximum ratings according to the orange GE book:

7189-A 7189 6BQ5/EL84
---------------------------------------------
Plate volts 440 400 300
Screen volts 400 300 300
Plate watts 13.2 12 12
screen watts 2.2 2 2

Additionally, the 7189-A is supposed to have both pins 1 and 2 connected
to the control grid, while on the 7189 and 6BQ5 pin 1 is "internally
connected". However, many 6BQ5's that I have seen have pin 1 connected
to the grid along with pin 2, like a 7189-A.

-- Dave Cigna

[Eric Erickson]

Does anyone know where about the Sovtek EL-34M fits into this
category? I run these tubes at 390 volts on the plates, about 380
volts on the screens and they respond gracefully. However, I have no
idea what their rated output power is. They sound really nice, at any
rate!

Regards,
Eric