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In Reply to: RE: OTL amps rule! posted by Mike Mount on June 26, 2014 at 18:07:18
Nice pic of your amp! The MA-1s are sweet I'm sure. Given the heat any moderate or larger OTL generates though, I think a more apt description is that OTL amps are (both metaphorically and physically) hot! :-) :-)
I'm working on (bringing back into service) a older pair of Joule-Electra VZN-220s (Rite of Passage 220W OTL) right now for a customer. Jeez, just got one of the amps going so far and boy do they pump out some heat (last thing my listening room probably needs in the middle of summer) when it is running, but boy do they sound good.
Happy Listening,
Rich Brkich
Retailer & Audio Asylum Industry Liaison
Follow Ups:
I converted my old Atma-sphere MA240s to run four 7241s per monoblock, instead of six 6C33Cs per monoblock. Since the 7241 can handle even more current than a 6C33C, there is no loss of power, but I expected the amps to run no less hot, because the 7241s also suck up filament current. Yet, surprisingly, the modified output stage runs notably cooler.
That Joule monoblock would be intolerable in most rooms during a hot month in the DC area, where I live. I can only imagine the heat of 24 6C33Cs in any normal size room, assuming the amp in your photo is one of a stereo pair.
HOT is correct...I'm running sixteen 6C33's ;-)
Vbr,
Sam
NO THANKS!! I listened the 80 watt Joule for a month in February in Central Florida and the heat generated was just unbelievable with 8 of those 6c33s I can't even imagine 24! The price to pay for such a glorious musical presentation I suppose.
They had 4 x 6C33C per monoblock and they made the room swelter after only a couple of hours playing! Finally couldn't deal with that anymore.
Funny enough, the Class A SETs I have now run notably cooler than those Class AB OTLs. That 6C33C is one hell of a current hog.
My NYAL OTL3's use 6 6LF6's per side to generate 80 to 100 watts or so. They have a fan, to prolong the life of the tubes, but don't generate much heat overall. So I'm not convinced that brute force and massive heat are necessary for a successful OTL design.
A lot of the heat comes from the class of operation.
In the case of the 6C33s a lot also comes from the filaments.
I guess your new Novacron is a real cooker as well?
Yes, the heat is an unavoidable fact of 6C33s. That is why the Novacron has a reflective panel behind the tubes- people think its there for looks, which is fine, but it also serves to keep the temperature down in the power supply.
Mr.Karsten
To solder conducting wires on that extra hot 6c33c-b sockets pins which type of solder wire yours company use ? , some standard 60/40 , 60/38/2 or some other type of solder wire ? , since that`s particular 6c33c tube socket solder points need to withstand good electrical contacts for years ( decades )ahead running under pretty hot environment ,
and did you ever consider to use cooling chimneys for 6c33c tubes in combination with some small & quiet cooling fan placed under(inside) the Novacron chassis ?
Best Regards !
__
Enlightened Evolution-Astral Projection
The area of heat that is the biggest problem are the filament connections.
We built a heatsink of sorts into the assembly to help out with the heat. So far it seems to be working fine.
Mr.KarstenThanks for you response !
BTW , I never understand why Russian manufacturer was build so powerful tube with so tiny tube pins ( except anode pin ) ! , with only 1,45 mm in diameter and only 10,5 mm long ,
maybe that was something intentionally with main design target to minimize temperature difference between joints of tube glass envelope ( bulb ) and metal pins just to avoid hard glass micro cracks( porosity ) and resulting vacuum loose , who knows ...
__
Enlightened Evolution-Astral Projection
Edits: 08/07/14
The reason it was done that way was because they were using an American tube socket design which was built for the 3C33, an American dual power triode. They doubled the plate area and made it into one tube instead a dual.
I have the Einsteins that use 4 of those 6c33 tubes each and it feels like having 2 little hibachi grills in that end of the listening room. I have visions of my electric meter spinning madly. But the sound!
Tom Collins
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