Tubes Asylum: REVIEW: Transcendent Sound Monoblock OTL T8 LN Amplifier (Tube) by C.B.

Model:	Monoblock OTL T8 LN
Category:	Amplifier (Tube)
Suggested Retail Price:	$4200/pr
Description:	Monoblock 80Watt OTL amps
Manufacturer URL:	Transcendent Sound
Model Picture:	View

Review by C.B. ( A ) on June 10, 2004 at 05:32:41
IP Address: 207.238.190.31

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for the Monoblock OTL T8 LN

I recently completed the construction of (2) of these, based on the schematic and parts list contained in Bruce Rozenblit's book Audio Reality . For those not familiar with this design, it is an 80W monoblock tube power amplifier with a so-called OTL (Output Transformer-Less) output stage. This means that the speaker is connected directly to the output tubes, in this case (8) EL-519s arranged in push-pull configuration. In addition, my amps have (2) chokes added to the B+ supply for addtional ripple filtering, which earns them the "LN" (low-noise) designation.
You can view pictures of my completed T8s by going to my website (see link). There is also a brief description there of sound quality, as well as notes pertaining to the construction techniques used. Since the article in Audio Reality is somewhat sketchy, much is left to the individual DIYer when it comes to layout, selection of parts, etc.
http://mywebpages.comcast.net/cbrodersen/T8OTL.html
My impressions and assessment of the T8 are pretty much in agreement with previous posters--this amp is one hell of a unit, with a clarity, transparency and ease of listening that will be hard to equal. I don't know if it is the best-sounding amp in the world, but in my system, it certainly beats everything I've had previously. As with all home audio gear, the actual difference is small, but significant, and I can't imagine ever going back to solid-state, even with the inefficiencies of tube-based design.
There are drawbacks. The T8 produces a lot of excess heat--about 300W of thermal load per monoblock. But this is considerably less than many OTL designs, due to the class AB operation and conservative tube biasing of the T8. And I worry about finding more of the EL-519 output tubes when it comes time to re-tube. If the Ei factory in Yugoslavia ceases production, I'll be in trouble.

Product Weakness: High thermal load, relative inefficiency, potential difficulty sourcing output tubes in the future
Product Strengths: Clarity, transparency, ease of listening, ability to drive just about any speaker made

Associated Equipment for this Review:
Amplifier:	T8 OTL monoblocks ([2] in system presently--to be increased to [4] in the future)
Preamplifier (or None if Integrated):	scratch-built Grounded Grid tube preamp (Bruce Rozenblit design)
Sources (CDP/Turntable):	Curcio CD12V DAC, home-made TT based on the old AR design
Speakers:	Newform Research NHB 45s ribbon hybrids--bi-amped
Cables/Interconnects:	home-made
Music Used (Genre/Selections):	Classical/jazz/folk
Room Size (LxWxH):	30' x 20' x 16'
Room Comments/Treatments:	none used
Time Period/Length of Audition:	3 months
Other (Power Conditioner etc.):	home-made power supply/speed control for TT
Type of Audition/Review:	Product Owner

Product Weakness:	High thermal load, relative inefficiency, potential difficulty sourcing output tubes in the future
Product Strengths:	Clarity, transparency, ease of listening, ability to drive just about any speaker made