SET Asylum: REVIEW: Yamamoto A-08 Amplifier (Tube) by cc998hi@yahoo.com

Model:	A-08
Category:	Amplifier (Tube)
Suggested Retail Price:	$2250 Finished/$1650 Kit
Description:	NFB SET Stereo Power Amplifer with 45 Output Tubes
Manufacturer URL:	Not Available
Manufacturer URL:	Not Available

Review by cc998hi@yahoo.com ( A ) on July 28, 2004 at 02:35:49
IP Address: 24.25.231.246

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I have the pleasure of owning a Yamamoto A-08 SET ampilfer for about a month now and I want to share my experience with my fellow inmates.
1. Background
I have enjoyed audio for about 40 years now since my high school days. The first 20 years was primarily with solid state gears and multiple driver speakers and the second 20 years was tubes and electro-static speakers. I got into SETs and single drivers about 3 years ago. You may say that I am a seasoned audiophile or an old man.
2. Yamamoto A-08 Stereo Power Amplifier
I was running a pair of high quality mono-block NFB SET 2A3s into my Lowther/Edgar horns for about 2 years. I enjoyed the low-powered, single-ended magic with high quality, high efficient single drivers a lot but like most audiophiles, I always find ways to further my audio journey, sometimes better and sometimes worse.
I was always interested in a 45 output amplifer because its sonic supremacy. However, I had my hesitations because of its high cost and low power. I came across the Yamamoto on the Audiogon and it was 'love at the first sight'. I was attracted to the extrememly classy fit and finish of the A-08 and had to have one. I ordered a kit from the authorized US dealer and waited for more than a month to have it shipped direct from Japan. I must admit that I gambled big time with this impulsed purchase as I had not seen or heard the amplifer. The dealer was very patient and helpful and the transaction was pleasant and easy.
3. Deviations
I am a firm beliver of cro'ying and I took apart the already assembled transformers, tube sockets and connectors for about a month's cro'ying. I cannot prove to you but my past experience was all metal conductors benefit sonically through cro'ying but the degree varies depends on the applications. I also opted to use solid core silver wires for internal hook-ups. I believe the wires come with the kit are of very high quality and so are teflon tube sockets, RCA jacks and speaker terminals but I just have a preference for 4N silver wires.
4. Assembling
It was a very interesting experience because I put the amp together primarily based on the excellent photographs in the manual. I was not sophisticated enough to understand the schematic that was provided in the manual and the english translated instruction was practically useless to me. I must say that this is a simple and straight forward kit to build and one basically has to connect the wires as most major parts are already installed. Soldering was not a problem using the apparently high quality solder that come with the kit (Yes! This is a complete kit including solder) except for the giant speaker terminals which required a super hot iron. I imagine it will take an experienced kit builder 8 to 10 hours to build the kit. It took me twice as long as I had to assemble all the parts back from cro'ying.
5. Up and running
I hesitated to turn-on the amplifer when completed because I built it per the photographs. As mentioned ealier, I am not good in reading schematics and know little about circuits. I checked the voltage of a few spots and they seemed to be a little low but not beyond the tolerance as suggested by the manual. I took another gamble and turned on the amp and it was making nice music. The hum level was a little higher than my other amps and I adjusted the hum pots at the bottom and it was pretty quiet since.
6. Audiotioning #1 (various pre-amps)
a. Art Audio high-gain phono stage with volume pot
b. Bottlehead Foreplay line and Seduction phono stage (both
souped up versions) and Wright Sound MC step-up transformer
c. DIY Bent Audio TX-102 MKII silver transformer volume
control with same Seduction and Wright Sound front-end.
The auditioning was with 6 other fellow audiophiles and through the Lowthers and Diatones.
First, hooked up to the passive Bent Audio TVC, the Yamamoto had no problem pushing the 98 db Lowther/Edgar horn. The sound was exceptional clean and clear and yet natural and involving. The highs were sparkling, mids were sweet and creamy, lows were tight and with good resolution although not as low and powerful like a self-powered subwoofer. Details, sound stage and image were excellent but the tonal balance was a little less hefty in the mid-bass and bass than the Diatone. Bottleline was that it was the most enjoyable listening experience I had with the Lowther PM-5A. My Lowther had a reconed (new folded edge whizzer cone) job early this year and is still breaking in.
Second, hooked up to the same passive Bent Audio TVC but with the Diatone, we were surprised by how the 2 watt Yamamoto drove the moderately efficient 91 db full range driver. With the Diatone, the Yamamoto exhibited its exceptional tonal balance with a more weighty mid-bass and bass. The overall sonic presentation was very transparent and convincing. However, the amp run out of steam occasionally in some real demanding contents but it was very graceful and barely noticable.
Third, hooked up to the active line stage Foreplay, the added gain provided even more dynamic and authority. One fellow commented that the sonic presentation has a scale and authority of real music which is very rare. Another fellow commented that the amp has huge dynamics which belied its 2 watt rating. The sound overall was very musical and powerful but not quite as open, transparent and airy as the TVC.
Lastly, the Yamamoto was hooked up to highly regarded Art Audio high-gain stand alone phono stage. With this, we did away with the Seduction and Wright step-up. This combination excelled in just about all areas. It has the powerful drive and dynamic of the Foreplay and the open transparency of the TVC. It was concenus among all 7 fellows that this was the best of the audioning session.
7. Auditioning #2 (various power amps)
a. A brand new 18 watt stereo NFB SET integrated amp made off-shore using
a chubby output tube made in Russia only.
b. A 2 year old 45/2A3 based stereo SET integrated amp made in East Coast
with a very unique chassis layout.
Auditioning #2 was done with 8 other fellow audiophiles about two weeks later. A majority of the fellows also attended Audition # 1 before.
The Yamamoto was much more lively and colerful (in good sense) music presentaion than amp 'a'. It had a almost silent background compared to the more grainy background of Amp 'a'. Amp 'a' was generally musical but more opaque and slow in transient. The Yamamoto was clearly more clean, clear, natural and relaxing despite its low power rating. It was concenus among all 9 fellows that the Yamamoto was much more enjoyable and involving. To be fair, we think Amp 'a' could sound better with tube rolling and more breaking-in.
Next, the Yamamoto was compared to the Amp 'b' fitting with old RCA 45s. Amp 'b' was very musical and involving but a litte dark and the tonal balance has some peaks and valleys. It was very revealing and has good micro-dynamics. However, the image was a little fussy and the sound was not as clean and clear compared to the Yamamoto. It also run out of steam and lost its coherence in demanding contents much sooner than the Yamamoto even they both used 45 outputs. The Yamamoto seemed to play cleaner, louder and has even better micro-dynamics and much more graceful when running out of steam. Subsituted the 45 with 2A3 bought more power and control to Amp 'b' but lost some of the fineness and the uneven tonal balance was more pronounced. Subsituted the RCA 45 of Amp 'b' with the Sylvania 45 of the Yamamoto improved the sound but not to a very great extent. Lastly, one fellow suggested that we subsituted the Yamamoto 45 outputs with 2A3. We tried it with the EH 2A3s of Amp 'b' and it worked beautifully. The 2A3s had more control and authority but not as full and natural in harmonic texture compared to 45. In both cases, it was concenus among all 9 fellows that the Yamamoto was a better performer in Audioning #2.
In conclusion, the Yamamoto A-08, with its limited power output, may not be the righ fit for most speakers in the market. It may not be the amplifer to own if you prefer thrilled highs and thundering lows. However, in the right system and set-up, it has certain quality and rightness to the sound that is very special and it certainly won my and 8 other audiophiles' heart handily in these 2 unscientific shoot-outs

Product Weakness: Output is low although surprising robust and it may not be the right fit for speakers with sub-90 db efficiency. Owner's manual is poorly translated in english. Access to the hum pots at the bottom is not convenient.
Product Strengths: Able to convey music convincingly in proper scale and harmonic texture. Sounds clean, clear and yet natural and not artifical with excellent tonal balance and dynamic range. Excellent fit and finish and high quality parts throughout although not boutique ones.

Associated Equipment for this Review:
Amplifier:	Amps X, Y & Z for comparison
Preamplifier (or None if Integrated):	Pre-amps A, B & C for comparison
Sources (CDP/Turntable):	Micro Seike air-bearing/vacuum TT with ET-2 and Kiseiki Argate Ruby low-output MC
Speakers:	Diatone 610MB/bass reflex, Lowther PM-5A/Edgar rear horn
Cables/Interconnects:	DIY solid core silver in sine wave pattern
Music Used (Genre/Selections):	Jazz, vocal, classical and pop
Room Size (LxWxH):	20 ft x 35 ft x 8'-6
Room Comments/Treatments:	Using the mid section of the 35 ft wide room, hard ceiling and hardwood flooring with 4 Corner Tunes and 2 stacked ASC Tube Traps.
Time Period/Length of Audition:	Owned product about a month/two 4 hours auditioning with 6 to 8 fellow audiophiles
Type of Audition/Review:	Product Owner

Product Weakness:	Output is low although surprising robust and it may not be the right fit for speakers with sub-90 db efficiency. Owner's manual is poorly translated in english. Access to the hum pots at the bottom is not convenient.
Product Strengths:	Able to convey music convincingly in proper scale and harmonic texture. Sounds clean, clear and yet natural and not artifical with excellent tonal balance and dynamic range. Excellent fit and finish and high quality parts throughout although not boutique ones.