Abbas phono

[jespera]

in reply to Artnet on the DAC page, here is something about a phono stage, due soon:
The Hephaestus RIAA will land I hope by the end of the year. Of course the war restrains progress, unsurprisingly. I will post findings.
I will wait for the RIAA to land before I experiment with EML regulation. I note you write -- concerning the EML mesh plate? -- "there is more body, air and separation in the music, but possibly dryer also". I found something similar with an EML AZ4 mesh vs period valve in my SET, the difference of impact, scale and clarity was remarkable. Out of respect for Abbas's design and judgement, I may resist EML regulation in favour of what he fits into the RIAA, or at least stick with 50's / 60's valves for richness of tone. My present relatively new RIAA --shoe box type case-- is with "GD rewound transformer" and Mullard EL84, EF 86 and EZ81. It sounds rich, full, and perfect ! I am guessing Hephaestus --full size case-- will render greater scale, yet retain character of tone.

I cant find much info on the new Hephaestus phonostage. Other than its full size. Do you have more that you can share?

Is it a full preamp with multiple inputs and volume control? Pictures?

 

[Paul49720]

Abbas sent me this description, below. He planned to place information and images on his website in the summer but, alas, the war ……

I attach a few quick pragmatic snaps he sent. The last image is of a shoebox format EF86 / EL84 which I use presently and I cannot imagine a more special sounding RIAA stage. I'm guessing Hephaestus will give more scale, yet reading the specifications again, perhaps there'll be more than scale.

Abbas most certainly knows what he is doing. The inverse of mass market boxes, his designs are nearly one-off artwork-instrument-machines that one must commission.Abbas wrote:

The Hephaestus Preamp is dual mono.

Input stage EF36 ( EF37) pair
Output stage 6BL7 pair
Tube rectifier 5U4 one

Gain is the same (as EL84/ EF86 model) , 45...46db at 1 khz
Output impedance 600 ohm
MC transformer 1:10, 20db ( MM- MC mode switched on back panel)
Input impedance 47 kohm ( MM) and 470 ohm ( MC mode)
4 wire-wound RIAA capacitors


Octal large tubes from the previous era (late 40s)

Inductive load + dynamic load, frequency band from 3...5Hz to 0.7

Capacitors between stages and at the output - hand-made( I make it), vintage copper foil, old paper, a special resin instead oil

The power transformer is now in a separate case in order to reduce hum. Double shielded.


I use a special output stage that nobody used before me. It is my invention. The first triode has a complex load in the form of a small inductance and a dynamic load by the second triode. This gives very low distortion, ultra wide frequency band, and excellent dynamic range.

Line inputs:
CD
Line 1
Line2

Remote control - YES
MC input 1:10- YES
weight 15...16 kg
sizes 400/440/200

Old preamp:
Two wire RIAA capacitors
NOVAL tubes
Inductive load
Frequency range from 15 Hz -3db
Indirect heating tube rectifier
Siemens capacitors between tubes



….here are a few more notes:

There are hand made capacitors, 8pc
4- RIAA circuits caps in glass tubes .
4- between tubes 0.2mf and 1mf output caps, in acrylic tubes .

There are 4 hand made coils
2- power supply
2- output stage

My capacitors will be made of copper foil with a dry dielectric (a special resin). No oil, no wax .

It is difficult to find capacitors of the required quality on the market. I do not like the modern well-known capacitors which don't convey the energy of the music well. I know this violates audiophile rules, but I do not believe wax and oil are the best impregnations for paper. Wax makes trebles too blurry. Oil reduces the energy of sound. However, oil in combination with aluminium foil sounds harmonious to my taste (Siemens, Bosch and other vintage capacitors) Oil combined with copper foil is too smooth, with loss of energy.

end.