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In the Forum: Analog Playback
In the Thread: Expressive Technologies Model 1 preamp
Post Subject: Expressive SU1 + Expressive preampPosted by Romy the Cat on: 6/18/2014
 Paul Costa wrote:
I have a PDF file of the manual if it interests you to read it, I can email it to you.
The unit weighs 80lbs, uses 6 6sn7's.
What I found a little odd was the spec for the phono is it says : MM Phono Stage Gain: 64 dB at 1 kHz

I own a Expressive SU-1 and can't imagine it getting much better than that for an SUT. I am very curious about the phono in it but that spec is very unusual for MM.

I read something on line that it uses a 2kva transformer for the power supply. It says it is heavily shielded but wouldn't there be a chance of magnetic fields potentially affecting the sound?

Thanks, for offering the manual, I really do not need it, if you want I can post it at the site but I do not think that there are a lot of people out there who would be interested, with exception  that it might have a schematics, which I think it does not have.

The 6 6SN7, that is interesting choose. I do not know if they  bridge those dual triode or use them in fully symmetric application, if the unit has phase switch then it might be later. The 3 stages of 6SN7 is kind of interesting chose and they are low gain tubes and usually people put in the first gain stage some kind of high gain triode (let say 12AX7 or 6SL7) and then follow with preamp-type of triodes 12AU7 or 6SN7.  It is perfectly possible to make 3 stage 6SN7  RIAA preamp  and I think RCA did it in past but I wonder how the hell they got 64dB gain. Each 6SN7 stage make 20dB and the RIAA network shall each 20dB, so where they got extra 4dB? I do not have an answer. Anyhow, if they do have  64 dB gain then I do not see why the spec should be odd.  Do not forget that phonostage on the unit does 40dB gain and you have extra 20dB gain by preamp section - sound completely reasonable to me. In fact when I see 40-50dB gain MM phonostage I always feel that it is not enough  - an MM stage shall have at least 60db gain and MC shall have 80-85dB gain - this is how I would like to have.

If you have Expressive SU1 then along with Expressive preamp you have near 90dB gain - so you are all set for any super low MC cartridge. I do not know how the Expressive preamp sound but it might be interesting to hear how Expressive people meant it to be. Expressive SU1 would not work its best with phono-correctors that have  high gain fist stage. I had my 7788 based two stage and I was not impressed how my SU1 worked with them. However, the same SU1 with EAR834PT was throwing the deglitzing, dynamic range and bass that was  absolutely mesmerizing. So, I might presume that when Expressive people did their preamp then knew what they are doing and I think it might be very educational to hear Expressive SU1 + Expressive preamp combination.

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