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A Russian Pass B1 FET Preamp/Buffer
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Author:  mwhouston [ 16 Oct 2010, 19:57 ]
Post subject:  Re: A Russian Pass B1 FET Preamp/Buffer

Gio wrote:
From the Enjoy the Music review:
Quote:
My unit was outfitted with an Ault +18V (70W) Model MW116 switching power supply specified for medical applications. No complaints so far, but I'm very curious to substitute a linear DC power supply such as the B+K 1671A in the near future.

Could be higher quality than mine if for medical, then again maybe not.

Author:  mwhouston [ 17 Oct 2010, 09:42 ]
Post subject:  Re: A Russian Pass B1 FET Preamp/Buffer

The Pass B1 is all finished and assembled. I'm listening on phones. Seems natural and falt across the audio spectrum. On SMPS and phones driver also on SMPS, dead quiet. No hum, buzz or anything.

It's 1:40am here. Time for bed. Two days from now I will have the chance to lace the B1 into my system for a listen on speakers with my 6AS7 SET.

Snaps to follow.

Author:  mwhouston [ 17 Oct 2010, 16:00 ]
Post subject:  Re: A Russian Pass B1 FET Preamp/Buffer

Forgot to add. The B1 draws under 20mA. And though I am running it on a 60W PS it would probably run well on batteries. Having another short headphone listen. Excellent. Good gain and just lets the music through un-coloured. Busting to listen through my main system.

Author:  dasfreak [ 17 Oct 2010, 20:51 ]
Post subject:  Re: A Russian Pass B1 FET Preamp/Buffer

Mark, I'm about to kick off a B1 build myself once I get the components assembled. Very much looking forward to seeing how your one will turn out.
I'm guessing the Hammond case you're referring to is the walnut sided one?

Cheers,
Graeme

Author:  mwhouston [ 17 Oct 2010, 22:03 ]
Post subject:  Re: A Russian Pass B1 FET Preamp/Buffer

No all back Al case. Snaps tonight.

Yes not like my to have an enclosure which has not been sprayed and straight off the shelf. I like the enclsoure though. Back and s*ex*y.

Author:  mwhouston [ 18 Oct 2010, 05:18 ]
Post subject:  Re: A Russian Pass B1 FET Preamp/Buffer

The Voka swilling Mr Pass B1 is complete and I have had time for some limited listening. I have listened both on cans and now as part of my main system.

Before I get into the prelim. review take a look at the finsihed product,
Attachment:
RussB1SS.jpg
Attachment:
RussB1RearSS.jpg

Quick description of the preamp: At the front there is the volume control with a 4oz solid brass black chrome knob on a 50K Alps blue velvet pot, to the left the on/off mini switch and the right: an Aqua led (yes genuine aqua led). As with all of my leds it barely glows when on.

On the back two sets of input RCAs. These are gold plated insulated RCAs, two pairs, so two switchable inputs and the output RCAs. The switch switches between inputs and there is also the power socket for the 19V 3.5A SMPS or any other PS.

Let’s get the bad parts over with first: On the HPs with Woody the HP driver in charge and being feed from the upgraded Oppo 980H, there was stacks of bass, good balance between mid and high frequencies. Mind you the preamp is barely hours old so a cap. and component settlement may change the audio landscape. BUT at this point with my SET and Osborns in place the sound is very tipped up. All I have done is replace my two stage valve preamp with the very new B1.

From upper mids through treble the sound is full of air and the sound stage has caused cracks in the plaster in the wall behind. The sound stage is so good and naturally etched I have been able to photograph it. But the bass appears way to lite. But as Dave from the Melbourne Audio club pointed out, this may be the true bass. Is the tube preamp adding something that is not there?

I think this preamp may suit a SS power amp. Dave has kindly offered to lend me his discrete component, all transistor, super tricked, dual mono, ultra low distortion power amp-rated 200W RMS. So my comments about bass etc. may change. And even as the amp settles, everything may change.

Now the good stuff: I have just been listening to Frank Sinatra “nice and easy” This is is a re-mastered, re-mix from original master tapes on a gold pressing.

IT IS ABSOLUTELY DREAMY, EVERY SOUND AND INSTRUMENT IS SOLIDLY PLACED ON
THE SOUND STAGE AND THE OVER-ALL “MUSIC” IS THE BEST I HAVE HEARD.


Yes very good. A big day of listening tomorrow so maybe some more gems to be dugout. One other problem is the preamp has not enough gain to play my SET at full level. But the mid-range, stereo image and sound stage is an “11” on any dial!!!!!

Author:  mwhouston [ 18 Oct 2010, 06:58 ]
Post subject:  Re: A Russian Pass B1 FET Preamp/Buffer

Forgot to add: Most of the hook-up wire/signal wire is cotton coated, tinned solid copper wire. Earth connections are with 0.7mm pure silver wire. All solder is silver based solder. Gold pins in the cct. brd. connect to the out-side world.

Once more I have to add the sound stage and imaging are very perfect!

Author:  dtsup1 [ 18 Oct 2010, 09:06 ]
Post subject:  Re: A Russian Pass B1 FET Preamp/Buffer

Mark,

Very nice review. Enjoyed reading. What is the 200W amp your friend is using ? Is it the Silicon chip class A amp?

Hmm light bass? It may be overdamped bass. Similar to my Aussie Amps. There is so much bass control that one wonders where the bass went to Lol.

-D-

Author:  Gio [ 18 Oct 2010, 09:59 ]
Post subject:  Re: A Russian Pass B1 FET Preamp/Buffer

Nice Mark. The black anodized aluminum Hammond chassis looks good. Thanks for sharing the review.
Cheers

Author:  mwhouston [ 18 Oct 2010, 16:03 ]
Post subject:  Re: A Russian Pass B1 FET Preamp/Buffer

dtsup1 wrote:
Very nice review. Enjoyed reading. What is the 200W amp your friend is using ? Is it the Silicon chip class A amp?

Hmm light bass? It may be overdamped bass. Similar to my Aussie Amps. There is so much bass control that one wonders where the bass went to Lol.

Dinesh: You maybe right. Very controlled for sure. The SET usually adds a bit to the bottom end with its lack of control but that appears to have gone. The SS amp amp is the Silicon Chip ULD amp. But Dave's has been extremely modded.

I hope to have a better listen today. I left the preamp on last night and will leave it on for a day or two to see if that helps. I'm also running music through it to bed the big Russian caps.

I may also put it under the CRO to see just how low the bottom frequencies go. I will report back here on what I find. The bass was extended last night just not a lot of weight.

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