Component Parts

Some manufacturers claim to have audio–grade components, but these are often standard products, re-labeled for the audio application use. Therefore it is necessary to approach to selection of parts very seriously. Not just the price can be used as a measure of sound quality of electrical parts, though it is more common. However is very important to sort out which types of components are critical to the sound by amplifier developing.

In my humble opinion three components are especially critical for sonics: Output transformers (OPT), coupling capacitors and volume potentiometer. So those parts choice I selected most carefully.

For OPT I have chosen Daburu DA-35X Output Transformer. This OPT contains high quality Double C-core Z11 Silicon Steel (legendary Tango Japanese steel quality). For bass amount and quality I am thankful to this transformer.

As a coupling capacitor I prefer Jensen NOS PIO sound quality. At first I tried Audio Note Tin Foil caps (modern production) — their sound was gentle and detail, but after changing to Jensen caps I have noticed better tonal balance in the mid range.

As an volume potentiometer I used 100K Noble. It is a black metal alloy encapsulated dual hi-end pot that is used in Audio Note Zero equipment. Actually TKD pot would be better here, but this can be a good reason for the next-step upgrade.

Few words about remaining components.

Resistors: I have refused to use metal film resistors in favor of carbon composite resistors. Also a film resistor always has inductance and drift, and their sound is a little harsh. Opposite carbon film resistors are non-inductive and characterized by lower noise and more natural warm sound than metal film resistors. I prefer japanese Kiwame brand. There is an opinion that their silicone insulated «body» is a primary reason for great sound properties. For cathode biasing and for PSU I have used non-inductive 1% wire wound power Mills resistors. Sonically is better to use a higher power resistor due to increased surface area.

Bypass capacitors: Because I use cathode biasing bypass capacitors are needed. For driver stage I took Elna Silmic II caps. According Elna site those are intended exactly for audio application and have superior acoustic characteristics provided by specially developed silk fiber. For output stage I used Black Gate standard grade series caps.

PSU capacitors: Power capacitor quality is also very important, because they are on the audio signal path. Therefore is it wrong way to spare money on it.
In power supply you can see hard to find (discounted) japanese Elna Cerrafine 220uF 500V cap. This is the best choice for PSU use due to its very top sonic performance and compact size. The other tank is Ansar film capacitor. As it is said in the British manufacturer review — they are produced specially for audio apps use and materials and production techniques have been selected for their acoustic as well as electrical characteristics, without a compromise. Both are the best sounding caps from all I heard.

Tubes: For 2A3 type I took monoplate variant. Monoplates are clear and moderately sweet with very fast and tightly bass. As input/driver tube I took the Russian 6H9C/6SL7 NOS 1975's for its quality and availability. For the beginning it is very good sounding option. As Rectifier I used vintage-looking 5U4G Tube for B+ (both channels).

Miscellaneous:

• 20awg, copper multistrand pvc shielded wire
• Solid core copper Kimber cable for input signal wiring
• Audio Note AN-SPR silver plated speaker posts
• Teflon insulated gold plated RCA phono sockets
• 5W Clarostat military linear potentiometers
  (for filament hum level eliminating )
• Sn95.5Cu0.7Ag3.8 1mm tubular solder with 2.5% flux

As power transformer I have used Hammond 302AX series trans which provides all the High Voltage and filament supplies to the stereo 2A3 amp.