OTL or not? (Follow-on from the review of the Atma-Sphere S-30 review in Hi-Fi World)

[Martin213]

Well,i'm PMSL at this,as i'm sure BR would be,if he read this

On the Atma-Sphere website,the S-30 is quoted as 30 wpc,yet with 'normal' loadspeakers,just 9 watts at 3% distortion was achieved

Paul Speltz,a long time owner of Atma-Sphere amplifiers,has a solution:

http://www.audioasylum.com/audio/tub...es/108243.html

So,in the real world,do Atma-Sphere amplifiers qualify as OTL's?????

[NickG]

McIntosh use a autoformer on the output of some of their SS amps in the same way.

[Martin213]

Am i the only person with an opinion on this?

[Rob042]

Martin
I have read through the thread on the audio aslyum can am left questioning why do it.
on a std amp you all ready have output txs with a mass of wingings ,why add more. for th the cost wouldnt it be better to buy better matched std tx's.
on otls - doesnt adding a tx defeat the object?

Rob

[Martin213]

My point exactly Rob,A-S spout on about power figures too,but at the end of the day,BR is correct. I have realised,this thread is in the wrong place,hopefully someone will notice and move it

[Rob042]

Martin
am wondering if these AS amp are all they are cracked up to be .I know there was someone on the old board that had the amp based on the el84, but I believe he was using sensitive speakers.
maybe thats the way to go with otl amps.
It is shame as the idea of having an amp with the min parts in the signal path and no tx's has got to be the goal.
Rob

[Martin213]

I doubt it was EL84's Rob. Have you heard an OTL? Dave-The-Vinyl-Junkie runs a pair of BR's T16's,they sound awesome!

[Dave_The_Vinyl_Junkie]

I take it you liked them then, Martin! I suppose I ought to comment...

Autoformer 'solution' looks interesting, if I understand the principle correctly, it provides a way for your amp to see a more sympathetic load impedance, leading to better performance which outweighs the effect of having an extra device in the signal path.

Personally, I think if this device actually gives you an improvement, it indicates a pretty fundamental mismatch in your system. I would rather ensure the amp and speakers match properly. It might have provided a way for my T16's to drive Colin's electrostats at Eggfest though....

WRT Atma-Sphere amps, they are certainly very well thought of by the audio press. I haven't heard one so I cannot comment on how they sound compared to my T16's - which are the only OTL's I've heard! They seem to have higher heat rejection and are less efficient than the Transcendents - so higher electric bills and impossible to use in the summer!

Croft make transformer-less power amps as well, though they are still capacitor-coupled to the loudspeaker, as is the Transcendent single-ended OTL (it has to be). The T16 has the speaker directly connected to the output valve array.

[petercom]

Originally Posted by Rob042

Martin
am wondering if these AS amp are all they are cracked up to be .I know there was someone on the old board that had the amp based on the el84, but I believe he was using sensitive speakers.
maybe thats the way to go with otl amps.
It is shame as the idea of having an amp with the min parts in the signal path and no tx's has got to be the goal.
Rob

Hi Guys, moved this thread as requested.

On the note above I think we tend to get too hung up on the min parts in the signal path objective. Sometimes parts are a good thing if they solve a problem, using a valve for gain for example! Seriously it is the output transformer in a valve amp that is responsible for its good performance. The transformer provides an efficient match to the loudspeaker and, to a certain extent, acts as a buffer between the reflected impedance and back EMF of the speaker and the output stage (it helps if the level of loop back feedback is low if it is taken from the secondary).

Most of the reasons given for getting rid of transformers are because of their distortions. IMO it is perfectly possible to design transformers which have lower distortion than most gain devices and, if you do so, the subjective performance is enhanced. Hence the concept of the transformer preamplifier. Transformers are a 'good thing' in audio.

[Martin213]

Thanks for moving us Pete Have you heard a Transcendent Sound OTL? Dave's T16's were a revelation to me.