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Zero Feedback: Atmasphere vs. BAT

Do Atmasphere and BAT have similar sound because they both use low or zero feedback tube designs?

I am considering these amps for my 8 ohm 89db Spendor S8e's.

I am looking for smoothness, Transparency and sound on the warm side. I am leaning toward a BAT VK75, it can be upgraded and it runs AB instead of the hot class A. You can also upgrade to VK 150. From what I can gather the 140 watt MA1 is superior in the area of dynamics, that would be the main reason to go Atmasphere to the best of my knowledge as OTL is super fast and more of a rock out style.

I am looking for used gear that can be supported over the long term by a good company.
128x128scottlanterman
mcfarland
356 posts
 
Atma-Sphere support is nothing short of excellant. They are readily available by e-mail or phone and help with troubleshooting, upgrade suggestions, and whatever your questions might be. They give practical advise that I find has been downright superb. The sound is accurate, detailed, and with excellant bass extension, definition, and control not often found in tubed gear. BIG sound stage, too. Highly recommended.
kijanki's avatar
kijanki
4,413 posts
 

Scottlanterman - I read very positive review of Atmasphere (MA-1) but what makes them hot is amount of current that tube heaters consume. Each tube is about 6.3V 2.5A and there is 28 of them total. That equals to 441W dissipated power just for the heaters. Total power dissipated might be in order of 1kW.
marakanetz's avatar
marakanetz
5,473 posts
 
Zero feedback OTLs ???
scottlanterman's avatar
scottlanterman OP
24 posts
 
Hello Marakanetz,

If you look at the Atmasphere website they espouse very low to zero feedback and they claim to have achieved it. These guys often get very high praise by audio clubs that are not part of any audio magazine. I emailed them, and they do respond really well and are helpful even when dealing with someone looking to buy used gear. I think BAT is also very good from reputation and review. I wonder how they compare sound wise since one is AB the other is A?

Scott
marakanetz's avatar
marakanetz
5,473 posts
 
I know VK as an engineer. No doubt about him. They use differential driving stages(balanced circuits) and classic push-pull output design that really doesn't need deep negative feedback just like most of the tube amps.

I also know that to achieve transformer-less low tube output impedance, you need deep negative feedback.

I'm not looking to buy Atmasphere equipment since it's not only within my budget, but it also too much heat, too much tubes to roll(upkeep) and lots of idle power consumption.
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