Tube selection for HK A300

[dumptruckz36]

I've had a Harman Kardon A300 for the last 7-8 years. It's been recapped by a friend of mine, and I've bought new matched power tubes for it a few times. I don't use it much, maybe a few hours a week. It seems like I lose a power tube about once a year. I've been running Tung-sol 6v6GTs since the original tubes started failing and I'm getting annoyed with their failure rate. I just bought a new quad of Electro-Harmonix 6v6GTs. What do people think of the different available types of compatible power tubes?

 

[Dswankey]

I've had a Harman Kardon A300 for the last 7-8 years. ...I've bought new matched power tubes for it a few times. I don't use it much, maybe a few hours a week. It seems like I lose a power tube about once a year. I

I could be wrong but it sounds like you should be more concerned about why and what's causing the tubes to fail as opposed to buying new ones.

My guess is there is something in the amp that's causing this, I would start there before plunking down anymore money of new tubes

 

[mcheinstein]

Dswankey is onto something. I run my HKa300 pretty hard (in my childs room and plays ocean sounds for 8-10 hours a night) and I haven't lost a power tube in years. Not the best use of a tube amp, and has worried me, but it's been working okay for a while. I just got a HK ss amp that I'm going to replace it with.

 

[cademan]

I believe that the original tubes are 7408's which are more heavy duty tubes than the 6V6GT's. Unless your bias is way out of whack or the tubes are being driven hard, those things should last for years. I haven't retubed any of my tube amps in 20 or so years. Still playing strong on a daily basis.

 

[TriodeLuvr]

The 7408 has the same dissipation and voltage specs as the 6V6GT. However, it exhibits less of a kink in the zero-bias plots. It is designed specifically for hi-fi, where the 6V6GT is general purpose.

 

[buickguy62]

I've owned and restored a large number of A300's over the years. My experience is that the A300 is easy on tubes. Many (most) A300's I have bought still have their original power tubes and almost all test strong and work well after 60 some years. I would believe that your A300 has some internal issues.