Yamamoto A08-S Amplifier Kit
August 24th 2009 b
www.jacmusic.com
Horber Steige 25 * 72172 Sulz * Germany * Tel: ++49-1755382641
First we must say, for legal reasons it is not possible that our company JACMUSIC writes an official
manual for other companies products. However we answer often technical questions about the A08-S,
so we intend this document to be used only additional to what is officially supplied by the
YAMAMOTO SOUNDCRAFT COMPANY OF JAPAN.
An earlier version of this amplifier was called A08. This newer version is called A08-S, where the S
stands for the DC current meter, and lower hum of the output signal, and replacement of the 5U4G
tube with the Type 80 tube.
The A08-S is supplied by the factory as pictured above, with 8 Ohms output. A special version can be
ordered, such as amplifiers designed for Western Electric 205D tubes, or a 16 Ohms output.
Materials used
The wood is cherry, which is beautiful looking by itself, but not very suitable to construct a tube
amplifier directly. So before use, the wood is specially treated by Yamamoto, called the Shashih
process. This process significantly increases the hardness, and in this way, the thread of the screws can
be cut directly in the wood, even for very small screws like 3mm, this works excellent. Also the
Copyright by:
www.jacmusic.com * Horber Steige 25 * 72172 Sulz * Germany * Tel: ++49-1755382641
Copying of this document is not allowed, also not partially, and also not for private publication in the internet. In case of
copyright violation, we have the right to take legal action without notice.
Shashi process will give very good electrical isolation to the wood, and electrical components can be
mounted directly on the wood from the inside. It can be observed with tube amplifiers, having
wooden parts, those develop a crack after several years, or thick piano lacquer starts to crack, or chip
off. This is caused by the internal heat of tube amplifiers, and frustration can be very high if this
happens after some years. However with Shashi treated wood, this will never happen. Long term
stability of Shashi is excellent, and the extra costs are a good investment.
The feet of the amplifier are of Ebony wood, and are in line with the Yamamoto philosophy of using
Ebony stands for Audio Equipment. Some classical instruments like oboe, and the neck of a guitar
are made from Ebony as well.
The transformer cap is of brushed aluminium, cherry colour anodized.
Tubes supplied
The amplifier is supplied by Yamamoto with following tubes: 2x Type 45. 2x 717A 1x Type 80
rectifier. These are used tubes, but well tested by the Yamamoto company, care is taken that these are
also optically fine tubes.
Tubes replacement
Great care must be taken that the tubes for your A08-S are in good condition, since best sound can
only come this way. Saving money on tubes is the worst you can do, when good sound is what you
want. However buying triple selected tubes from obscure specialists is often a waist of money. So
buy good tubes from people that use good equipment, and make no secret about how they test tubes.
A non-documented tube test may be good, but a documented tube test may is more professional.
Here is some information on the particular tubes:
Tubes position
Believe it or not, but it is a classical mistake to put a rectifier in the 45 socket, or also put in a 45 or
the 80 rectifier with the pins in the wrong position. Do not orient the tubes position by the printing on
the tube! There is no relation. Always check the tubes pins first. The 717A, if it will not fit in, do
NOT force it. Check if you have the guide pin at the right position.
Type 45 tubes. We recommend you, not to use any Chinese 45. The recommended 45 tube from new
production is the Emission Labs 45 or 45 mesh. The mesh tubes may have best sound if you prefer the
high transparency that most horn speakers have, the solid plates are closer in sound to historical tubes.
However such audible differences are small.
Copyright by:
www.jacmusic.com * Horber Steige 25 * 72172 Sulz * Germany * Tel: ++49-1755382641
Copying of this document is not allowed, also not partially, and also not for private publication in the internet. In case of
copyright violation, we have the right to take legal action without notice.
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