7355 for HK Award A300 integrated amp outputs?

[GordonW]

Hey... could anyone verify, to reasonable certainty, that the 7355 is a valid replacement output tube for the HK Award A300 integrated amp? The original is an HK-branded tube with a proprietary number... I've found one schematic, that claims the 7355 to be the same thing- but I want to make sure. I've found a pair of NOS 7355s... before I plug them in, I wanna make sure I'm not gonna get a fireworks show or anything...

I've also heard that 6L6GT or 6V6GT (can't remember which) can be used, but may require a circuit mod... anyone know what the deal is here?

Regards,
Gordon.

[Tom Bavis]

I don't know this amp so this is generic. I know HK made amps with 6V6 (7408) as well as 7355.

7355 didn't last long because the 7591 (with higher gain) pretty much replaced it. Since the remaning circuitry could be simplified (7591 didn't need as much drive), it was cheaper overall to use 7591.

Look for a ground connection on pin 5 (maybe a low-value resistor - if it's there, it's wired for 7355 or 7591. Most other power tubes have the cathode on pin 8.

7591 can be plugged in and it will work - but will need rebiasing. The 7591XYZ from Sovtek is a perfect replacement as it's a rebased 6L6. In either case, make sure that pin 4 isn't used as a tie point on the socket.

[Thatch_Ear]

Look at one of the tubes that came with it and see if there is a number 4 pin. If it is there then it will be a 6V6. 7355s have no number 4 pin.
For what it is worth a reciever that was a 3000 used 7408/6V6s. Sounded very good too.
If you need a quad of 6V6s let me know, I'll make you a good deal.

[GordonW]

OK, THAT was the missing piece of info... that the HK 7408 (which, IIRC, is what is IN the amp now) is a 6V6GT. Someone had mentioned that they thought the amp used 6V6GTs... but then I found this other schematic, that indicated 7355s.

As for the quad of 6V6s... thanks Thatch, but I think I'm gonna be able to scarf me as many 6V6s as I will need, from the huge batch of tubes I'm helping catalog (see the RCA 2A3 thread nearby for details)... it's a good deal, I do the grunt work counting them, I get to spirit off some of them for myself... :D

Regards,
Gordon.

[Thatch_Ear]

Get the old RCAs, mine, just in case have all been tested and I could match up a quad. If you access to a good tester take all you can get of something good like old RCAs test them all and take the 4 that test the closest. A quad of equal strength of a good tube is always the way to go.

[GordonW]

Testing should be no problem. Got three tube testers (a RCA "depertment-store" tester, a HickokTV-7A, and a MightyMite 5) available to me; matching stuff should be a breeze.

I think there should, in this batch, probably be at least 4 of the same type of 6V6GT in there somewhere. All US or western European made, so they should work well. At first, even if I can only find two of them, I should be OK... two of the original 7408s work fine. I can use them in one channel, with the new 6V6s in the other, to test the amp... make sure it's working properly after I retrofit caps and the volume pot...

Regards,
Gordon.