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Theta Prometheus Monoblock vs Bryston 7BSST2

I was all set to buy the Bryston 7B-SST2 amps to mate to a KEF Blade (or Blade2). However, the recent review of the Theta Prometheus on Stereophile has me intrigued. I like the benefits mentioned for the class D amps over AB or A. Less power consumption, run cool, small footprint.

I heard these amps at THE NEWPORT SHOW this year and they sounded very good but I cannot really tell in a show (unless it is really bad sound). I know how the Bryston sounds and like the fact that I would have a great RELIABLE amp if I went with Bryston. My pre-amp in the SS BAT VK-42SE. I will have a 2 channel computer based system, with the PS Audio DS DAC.

Anybody using these new Theta amps care to provide feedback on your experience. I would prefer to hide any new amps in a closed audio rack because of potential damage (spills etc..)
yyzsantabarbara
guidocorona
4,298 posts
 
Hi Santabarbara, I have not heard the Theta Prometheus yet, but I own and love the Rowland M925 NCore NC1200 monoblocks ($56K/pair), and have reviewed the lovely Merrill Veritas NCore NC1200 monos ($12K/pair) for Positive Feedback:

http://positive-feedback.com/Issue68/merrill_audio.htm

With the premise that I love the underlying NCore sound, for the very reasons of balanced musicality, power resolution, and lack of grain and distortion discussed in the Greenhill article, I suspect that Prometheus are probably capable of making wonderful music.

Prometheus appears to be different from other NCore NC1200 implementation targeting the $12K pricepoint in at least 2 major aspects...

Merrill Veritas utilize the Hypex NCore NC1200/700 switch mode power supply (SMPS). Conversely, David Reich at Theta has designed a custom linear power supply for Prometheus... Which one is "better"? I will make no assumption that a linear power supply is ineherently better than an SMPS, or viceversa. Thus... I have no idea, but they are likely to yield subtly different results from each other.

Furthermore, Merrill Veritas declare a power of 400W/8 and 800W/4, while Prometheus declares 250W/8 and 500W/4. This difference might reflect some internal design peculiarity, or perhaps simply a more conservative power rating philosophy by Theta.

Either way, if you have the opportunity, it might be worth while to evaluate both amps in your system. Merrill might be able to arrange an in home audition... Buzz him at (415) 562-4434. Perhaps Theta or one of its dealers can do a similar thing for the intriguing Prometheus.

Regards, Guido
bill_k
916 posts
 
If you have the opportunity I would suggest checking out the new Bel Canto REF600M mono amps. They also use the nCore output stage with a custom designed input circuit and list for $2,495 each. Rated at 300wpc into 8 ohms and 600wpc into 4. There are some big claims being made for the sound quality of these amps by the manufacturer as their best sounding amps yet. Could be worth an audition!
guidocorona
4,298 posts
 
I concur with Bill, Bel Canto has a superb track record with class D amps. Their older REF1000 Mk.2 was an absolute sonic jewel at an attractive price.

REF600 is not based on NCore NC1200 like Veritas and Prometheus, but on a yet unnamed NCore trickle-down module.... Sorry, I am still trying to find out some details....

REF600 utilizes an apparently standard Hypex NC1200/700 SMPS in each chassis. One thing unique about REF600 is that John Stronczer -- the designer -- has implemented a custom differentially balanced input stage to lower noise floor, raise common mode rejection ratio, and raise input impedance to 200KOhms.... I have not heard this amp yet, but outwardly it does look intriguing.

http://www.belcantodesign.com/eOne/products/amplifiers/ref600m-amplifier/

G.
yyzsantabarbara OP
4,903 posts
 
Thanks for your fantastic response. I had read your review about a month ago and I was looking for someone to do a comparison of the Veritas with the Theta. I cannot do this since I do not have my complete system yet (amp and speakers missing). How about you taking on the challenge? Your writing is excellent. Seems Veritas is keen for someone to do this,

"I would be happy to provide a pair of the Merrill Audio VERITAS Monoblocks for the comparison. I have also offered Stereophile the Merrill Audio VERITAS Monoblocks for review.

Perhaps there could be an independent, neutral place where the A/B comparison is done side by side. I understand some have done the side by side comparison and hope they will share their findings."

The above quote was posted on the Stereophile web site on the Theta review.

It would be great if Theta is interested in this comparison.
yyzsantabarbara OP
4,903 posts
 
These great response have me spending my day researching the Veritas amps. Here are some links that some reading this thread may appreciate.

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1380165366&openflup&94&4&&st0

http://positive-feedback.com/Issue68/merrill_audio.htm

http://parttimeaudiophile.com/2014/01/12/merrill-audio-veritas-monoblock-amplifiers

http://www.enjoythemusic.com/superioraudio/equipment/1213/merrill_audio_veritas_monoblock.htm
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