Positron Tubes?

[DaveP]

Just got a quad of Sylvania STR387 6L6's and 5 Positrion 12AX7's. Never ran across the Positron
tube before and there isn't that much info on them. Is it true they are relabeled RFT's?

 

[domct203]

Not too sure about the Positrons. Post some good clear pics, and I'm sure we can ID them.

I have a couple of NOS Tesla (not JJ) labeled RFT 12AX7's that I absoluty love, but I think a full boat of them will make the amp too loose and mushy sounding.

They are a fantastic tube in the right gain stages. Right now I'm running a NOS Mullard in V1 and one of the RFT's in V3 of my MKV and I'm loving the results in Ch3, all modes. I'm thinking of throwing a Matsushita 12AX7 in the PI, and I have a GE 12AX7 longplate that I will try in V2 or V5 eventually.

I also have some Seimens 12AX7 shortplates, Sylvania 12AX7 short and long (grey and black) plates, RCA 12AX7A's and Mullard CV4024's (12AT7) that will make their way in there down the road. I like to make one change at a time and play the amp for a few weeks before I mess with it again.

Tube rolling is half the fun of these great amps. Playing them is the other half!

Dom

 

[DaveP]

Thanks for the reply Dom,

Here is a couple of pics:

 

[212Mavguy]

That one is a no brainer, the Positron label is on a TUNGSRAM tube. They are no longer made, they deliver a particularly nice clean tone, the dirty reminds me of a Mullard shortplate kind of tone.

 

[212Mavguy]

Thick, fat, smooth, tons of mids, slightly rolled off top in comparison to similarly built Amperex ecc83. The Tungsram will have more top end/presence compared to the Mullard. In my amps Tungsrams exhibit a tad less sustain for a given amount of overdrive gain than the Mullard. The Clean tone is superior though due to the delicate, sweet, high end that the shortplate Mullard tends to lack. Much nicer to the ears than modern production tubes.

 

[DaveP]

Great info. Thanks.