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teaching VTA M-125 to sing

I've used the Sovtek KT88s (my favorite - used to be easy to get) now I use Gold Lions. I also use Sovtek 6550's. I haven't noticed any difference with any that I've tried but those Sovteks have lasted quite a while.

I think when my M125s are finished - I'll likely just run two output tubes per amp in order to extend tube life.
 
Well I can say these svetlana 6550c tubes sound great and were cheap. I don’t know how long they will last. They were from eBay. I think sound better than the new production Tung sols I had but that’s from memory so take it with a grain of salt.
 

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KT88Lvr said:
I've used the Sovtek KT88s (my favorite - used to be easy to get) now I use Gold Lions. I also use Sovtek 6550's. I haven't noticed any difference with any that I've tried but those Sovteks have lasted quite a while.

I think when my M125s are finished - I'll likely just run two output tubes per amp in order to extend tube life.
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The OPTs are designed for PP/P operation, four tubes per channel.
 
I’ve run 6550, KT88, and KT120. Never noticed much difference, the KT120 marginally edging out the others I’d say. Driver tubes another story.
 
Pio1980 said:
The OPTs are designed for PP/P operation, four tubes per channel.
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You can run the M125s with two tubes per channel and bias each tube individually vs in pairs. I've had good luck with that setup - and it is for sure easier on the rectifier setting the bias at half the value. In all I think it is an overkill amp running at two tubes. I've had all my issues when running at the limit and with four tubes.

Thanks.

Edit: But the author of this thread seems to advise against it - I'm not sure why as I'm a laymen when it comes to tube amp architecture (but I've run literally years with only two tubes.)
 
Legrace said:
I’ve run 6550, KT88, and KT120. Never noticed much difference, the KT120 marginally edging out the others I’d say. Driver tubes another story.
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Great to know as I've always wanted to try some KT120's - but man I've got a full stock of KT88s and 6550s.
 
Lavane said:
6550's are one tube I haven't had any experience with. I would like to try them, but two quads will cost a lot.
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I must like the 6550; everything I own uses lots of them:)

Audio Research VS110 (8), Audio Research D70 MKII (5), Audio Research D76A (5), Dynaco MKIII x4 (8 total), McIntosh MC-275 MKI (4), Ampeg SVT (6).

The VS110 arrived with eight new KT120s installed and also included a full set of eight spares. Pulled those and installed a set of NOS Mesa-branded (chinese) coke bottle STR 418 6550-A's. I like them better than the KT120's. :dunno:
 
After listening to the super bowl tonight I will say that midrange sounds a bit more hollow / sucked out with the svetlana 6550 after coming from the old stock Tung sol 6550 (three hole grey plates). You never know if that’s from the recording or what.
 
pjrengineer said:
After listening to the super bowl tonight I will say that midrange sounds a bit more hollow / sucked out with the svetlana 6550 after coming from the old stock Tung sol 6550 (three hole grey plates). You never know if that’s from the recording or what.
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Some recordings can throw you off making you think something is wrong. I was listening to a new CD sometime back and was hearing some noise and intermittent hum along with some distortion in the midrange. I thought something was wrong with my amplifier or preamp. But it turned out to just be a really dirty recording. If I had been the artist and heard the final mix I wouldn't have been happy.
 
Received my Auto-bias pcb the other day from Erhard Audio. Very nice looking PCB and will be installing soon into my VTA-120. I will post back when it's installed and up and running.

Looking to pick up some Tung-Sol 6550 and give them a try since the Gold Lion KT88's are going up in price now. My Gold Lions have about 300-350 hours on them since I switch between SS and the tube amps between seasons.
 
Things are coming together with my two high end amps. Auto-Bias for my VTA-120 and just ordered a Soft Start unit for my Edge M8 amp (No more crazy inrush current draw).
 
Lavane said:
it's stated on the Tube4hifi site that two tubes can be used per amp instead of four if you wish.
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do they tell you to use different taps? I'd figure 8 ohm load on the 4 ohm tap for that config in order to keep the loading proper on a pair vs a quad.
 
No, Just to re-bias the tubes if only using two. If I was going to just run two tubes, I would have bought MK lll kits. But I guess if I loose a tube I can run two until I get it replaced. The 16 ohm tap is used for the feedback circuit in these amps also.
 
Well, now i am reluctant to order assembled M-125s now, can anyone recommend a tech to assemble the kits and execute Ians corrections? Really a bummer that T4Hifi has no capacity for negative feedback. (see what i did there?)
 
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