2. amps-preamps
  3. 1447363377

Advice re the use of OTL amps vs others

In my recent transition from solid state to vacuum tube amplification I'm learning a little about the various types of circuitry designs available. I'm currently using the Cary Rocket 88R amp mostly in Triode mode, and Peachtree Audio Nova as a preamp. The warmth I gained is extremely satisfying but I'm not sure if this is attributable specifically to the Rocket or simply as a result of transitioning to this setup vs solid state Peachtree to Martin Logan ESL's.

I'm impressed with what I hear about the Atmasphere amps and would like to consider them but have some concerns. What I've read is that the OTL amplifiers supposedly present the best of both worlds between a solid state and valve amp sound. In one way of thinking, using the Peachtree pre and the Rocket amp, I have somewhat the same thing now. I know it's not that simple but that's why this thread. I'm not concerned about overall sound quality with the right OTL but am that I might loose some of the warmth or "roundness?" I've found with the Cary.

Therein lies the question. I have no way that I know of to locally (33064) audition the Atmasphere S30 which is the one I'm leaning toward based on my research so far. The speakers which I'm now using and intend to keep are the original Reference 3A MMC Serie having an efficiency rating of approx 85dB and 8 ohms impedance.
broadstone
tubegroover
2,320 posts
 
Thanks Al for your comments. With regard to the autoformer and the Transcendent amplifier you very well may be right, different topologies and tubes used. Interestingly enough, the gentleman I sold the autoformer to was using an Art Audio tube amplifier with 6c33 outputs. It too was recommended to him because of power issues. Never did find out out it worked out in his application. I really wanted to like it as I spent some time making several purpleheart cases for the autoformer for myself and another autoformer owner and invested in some nice edison price posts to easily change the turns settings. The things sat around for years before I finally sold them as the cases were so pretty.
almarg's avatar
almarg
9,670 posts
 
Spencer, my impression is that Ralph generally doesn't post on weekends, so while we await his response I'll mention the following, regarding your second question specifically:

First, the S30 which Broadstone is asking about, at least in its most recent version, is spec'd at a considerably higher power rating into 16 ohms (45 watts) than into 8 ohms (30 watts). Using the 2X tap of a Zero would, of course, result in the amp seeing a nominal load of 16 ohms with his nominally 8 ohm speakers.

Second, the output impedance of the S30 is spec'd at a rather high 7 ohms, which when used in conjunction with a nominally 8 ohm speaker without a Zero would probably have significant and somewhat arbitrary effects on tonal balance due to the interaction of the 7 ohms with how the speaker's impedance varies as a function of frequency.

If Zeros are not used, the M60s' considerably higher 8 ohm power capability (60W) and lower output impedance (4.1 ohms) figures to provide much better results with Broadstone's speaker than the S30, as I see it.

Best regards,
-- Al
unsound
7,375 posts
 
Al, I disagree with the 2nd sentence to the last paragraph:
..."It is a great disfunction {sic} to music loving audiophiles for speaker manufacturers to be making 4 Ohm speakers with 3 or 2 Ohm impedance dips, and then expect amplifiers and speaker cables to be able to transfer music into a load approaching a dead short."...
Some of the popular and most accurate audiophile loudspeakers ever made have such impedance plots, and many, many amplifiers and most speaker cables work quite well with them.
mapman's avatar
mapman
22,997 posts
 
4 ohm not a big deal for many amps 2 ohm or less separates the men from the boys.

It takes an amp and speakers to make good sound. Does not matter really which one carries a bigger load as long as the two can work together well as designed.

Granted an easy load makes choice of amp easier. But it isn't the end of the world if it is less than perfect which most all speaker designs are in some way regardless.
almarg's avatar
almarg
9,670 posts
 
Hi Unsound,

Yes, I for one would agree with your disagreement with that statement. While my own preferences have evolved such that I favor tube amplification and speakers having benign impedance characteristics, it seems abundantly clear that many audiophiles have assembled very fine systems with opposite approaches.

As is usual in audio, a multitude of different approaches can each provide good results, bad results, or results at various points in between, depending on many factors.

Best regards,
-- Al
More to discover