6973EH tubes for little Valco amps

[ken]

I just finished putting a pair of matched 6973EH power tubes in a small Valco guitar amplifier.

I was expecting them to work, after all tubes the same number designation are the same tubes... right?

Wrong.

The 'factory original' 6973's used a single 270 ohm 10 watt bias resistor for both tubes, but the new 6973EH tubes redplated in a couple of minutes using the original resistor.

I experimented with resistor values, and found that the 6973EH's sounded best with a 470 ohm 10 watt bias resistor.

Adding a 25uf 100volt bypass capacitor actually made the amp sound dirtier for some reason, so I went with the unbypassed resistor.

just sayin'...

ken

[EFK]

They really don't seem to be the same as the old RCA 6973. I do through a lot of Valcos and while the EH tubes are useful for replacement without having to rewire the sockets, they definitely do not sound very similar to me. As I understand it, the RCA 6973 was a very high-quality audio tube and you can certainly hear it when you can manage to find old stock tubes at a reasonable price.

[Jazz P Bass]

I prefer to rewire (and label) the sockets for a 6BQ5/EL84 tube.
The new EH tubes sound like ass.
And NOS, or even used, 6973 prices are stupid.

[ken]

I know what you mean, I have a Sansui tube home stereo in my office from the '60s that just got retubed with NOS - ouch!

The 6973EH's actually didn't sound so bad in a 15 watt amp with a 10" speaker, but I do think they would sound bad in a bigger amp.
I think the 6973's sold nowadays only have the pinout of a 'real' one, and I wonder what these tubes really are. I think they are some weirdo Russian
servo amp tube or something that got relabeled. However, they 'is what they is'. Maybe somebody at Sovtek got a deal on millions of these, and when they are finally gone we can get something closer to a 'real deal' tube.

ken