SET Asylum: REVIEW: Yamamoto A-08S Amplifier (Tube) by chopper87@aol.com

Model:	A-08S
Category:	Amplifier (Tube)
Suggested Retail Price:	$3000
Description:	45 based single ended amplifier
Manufacturer URL:	Not Available
Manufacturer URL:	Not Available

Review by chopper87@aol.com ( A ) on September 22, 2005 at 17:37:51
IP Address: 205.188.116.71

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Review Purpose: To determine if AC filament heating the 45 tubes in a 2 watt SET amplifier is sonically preferable to DC filament heating.

Current Comparative Amplifiers: Wavelength Parallel Feed Gemini Mono Amplifiers (AC Heated), Yamamoto A-08S (DC Heated). New Type EML Solid Plate 45â€™s used in both amplifiers.

Preamplifier: Bent Audio TX 102 MK III Transformer Based Volume Attenuator with Remote Volume Control.

Source: Sony XA777ES SACD/CD Player. Analogue section feedback resistors have been replaced to allow 6 volt instead of standard 2 volt output. This affords an added 6 db of gain to the passive volume attenuation device.

Evaluation Speakers: Baltic Birch Medallion III back horns (All internal turns are curved) with Lowther DX-4â€™s.

Subwoofer: â€œWaveboxâ€ type utilizing a Dayton 10â€ light weight cone of high efficiency, and a 250 watt class a/b plate amplifier. High level input connections directly from amplifierâ€™s speaker outputs. Subwoofer designed and utilized as a corner loaded woofer.

Listening tests were performed with and without subwoofer to determine true bass potential of each amplifier.

Cables: Two 4â€™ pairs of DIY Fine Silver Interconnects, 2.5 Meters of Audience AU 24 Speaker Cables.

AC: Dedicated Audio AC Circuit with Quad Hospital Grade Duplexes. Four Eight-Foot Ground Rods Driven into the Earth Just Outside Of the Audio Room. SoundString AC cords through out. PS Audio P300 set to â€Sineâ€ for amplifiers and Sony XA77ES.

Both amps benefited sonically from the P300.

Rack: Mana 4 Tier Amp Stand.

Room: 13â€™ W x 19â€™ L x 8â€™.5â€ H. Strategically placed Room Tune devices through out

room.

Speaker Placement: Back of speakers Five feet in front of short wall and two and one half feet from sidewalls. Toe in to approximately 15 degrees out from apex of listening chair. Speakers are approximately seven and one half feet apart measured from center of DX-4 cones. Listening chair is placed between speakers and eight feet from their front center baffles.

This is a short review based on only three weeks of use with the New Yamamoto A-08 â€Sâ€. The â€œSâ€ version of the previous Yamamoto A-08 differs in a number of ways which can be clarified by reading about the new design at the, Venus Audio, web site. My interest was to determine if going from AC (45) tube filament heating to DC filament heating will degrade/dry out the sound of the Yamamoto amplifier. It has been stated on more than several occasions, (On the Asylum and other locations) that the 45 tube was designed for AC filament heating and that DC filament heating this tube type results in inferior and, specifically, a dry sounding amplifier when compared with that of a good AC heated design.

I am fortunate to own and enjoy a pair of Wavelength Audio PF Gemini amplifiers that AC heats the filaments of the 45 tubes used as outputs. After allowing the Yamamoto to play music at moderately loud levels non-stop for three days, I began my evaluation. I listen to lots of vocal jazz music and have used, CARMEN McRAE Sarah ~dedicated to you, as a reference recording for several years. A well-recorded cd with great vocal dynamics, air, detail, transparency, and good tight bass. This recording has good though not great dimensionality.

Any way, I have lots of experience listening to this cd through the Geminiâ€™s and was very anxious to hear how the A-08S would stack up. Have you ever heard someone refer to the sound of a guitar as having great TONE? In my experience, a guitar with good tone is usually very rich and full bodied with very good delineation of each note. You can feel the air around and between each clean or purposefully distorted note played. That is kind of how the DC heated Yamamoto dealt with music. Everything just felt more fleshed out and solid within the image field. I have not been a huge fan of recorded piano music because I never felt that any of my systems made the piano sound even close to real in my listening room. There is just so much dynamics to a hard hit piano note that is just really hard to get right, for me anyway. The Yamamoto made the piano come alive in my listening room more than with any other amplifier I have used. No, it still did not have quite the monster dynamics of the real thing, but, I listened to this whole cut for the first time in years. In fact, I never ever just sit and listen to my reference recordings all the way through. I have gotten into the really dumb habit of playing the same cuts or portions of cuts over and over again as comparison tools. With the A-08S plugged in, I listened to the whole cd all the way through without pausing or repeating once! This amp really helped my Lowtherâ€™s become much more listen able as well. It is no secret that Lowtherâ€™s, especially the stronger magnet ones can and WILL bite your head off from time to time. I havenâ€™t exactly figured out what it is that the A-08S does differently that allows me to listen to the DX-4â€™s at high volumes without cringing. No, it does not roll off the highs sooner or attenuate them more than the other amplifiers.

The mids and highs are very rich and a loooong way from dry. Vocals and cymbals sound more â€œin the roomâ€ than ever before. From every aspect that I can think of (from the midbass on up) this is the best sounding amp that I have lived with to date. However, I did not feel that its bass performance was better than that of the Geminiâ€™s or other good amps on hand. That isnâ€™t a bad thing at all though. Itâ€™s just that the damn thing was such an over achiever in almost all other areas.

I know that I have left a lot out because I am no professional reviewer or writer and have only been living with the Yamamoto amplifier for three weeks. However, I am satisfied that I have met the initial goal of this evaluation; Will the new DC filament heated Yamamoto A-08S compare sonically with a very good AC filament heated 45 SET amplifier? In my opinion, absolutely!

Lance A.

Product Weakness: The bass is as good as any low watt set amplifier that I have used ,but, I wish it's bass was as outstanding as the rest of its musical reproduction.
Product Strengths: Mesmerizing musicality with dead silence between notes. DC filament heating allows me to plug and play any 45 tube with no noise adjustment needed. The price is great and the thing is almost all made by hand by Mr. Yamamoto.

Associated Equipment for this Review:
Amplifier:	Wavelength PF Gemini's, Yamamoto A-08S amplifier. Approximately 2 watts each.
Preamplifier (or None if Integrated):	Bent Audio Passive preamplifier.
Sources (CDP/Turntable):	Sony Xa777ES SACD/CD Player.
Speakers:	Medallion III's with Lowther DX-4's
Cables/Interconnects:	DIY Fine Silver Interconnects, Audience AU24 Speaker Cables.
Music Used (Genre/Selections):	Lots
Room Size (LxWxH):	19' x 13' x 8'5
Room Comments/Treatments:	Room Tunes
Time Period/Length of Audition:	Three Weeks Total
Other (Power Conditioner etc.):	PS Audio P300
Type of Audition/Review:	Product Owner

Product Weakness:	The bass is as good as any low watt set amplifier that I have used ,but, I wish it's bass was as outstanding as the rest of its musical reproduction.
Product Strengths:	Mesmerizing musicality with dead silence between notes. DC filament heating allows me to plug and play any 45 tube with no noise adjustment needed. The price is great and the thing is almost all made by hand by Mr. Yamamoto.