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I called it Magnefest because it features a fest of Magnequest iron.
Very happy with my first DHT preamp. Dead quiet can't hear if it is off or on.Was hard work getting it quiet though. First I took away the filament transformers (one per channel) which were mounted below the chassisplate under the Abbies. After putting them in their own enclosure
I was still confronted with induced hum because of the power transformer. After taking it out...it turns out that the power transformer was in the worst possible spot I could have chosen. So that went into it's own enclosure as well.
Edited this post in 2023 - Not in use anymore. The three box solution was too cumbersome. Ended up getting noise somewhere... Never bothered finding the cause. Such is life sometimes. Nice thing about the hobby is you can re-use parts and chassis.
Edits: 05/26/15 05/26/15 05/26/15 05/26/15 05/26/15 05/26/15 05/26/15 05/27/15 06/17/15 07/25/23 07/25/23 07/25/23 07/25/23 07/25/23Follow Ups:
congrats, happy you are enjoying it.
g
if you find the name infringing on your name because people may think there is an association there is not.
To infinity and beyond!!!
Hello Bas.
From you I'm honored. If I ever do a small "show" say in Philly... Magnefest would be a good name!
Builder of MagneQuest & Peerless transformers since 1989
.
To infinity and beyond!!!
Very nice indeed!! Thank you for sharing. Beautiful shiny transformers!!
Please pardon my ignorance but in your description you said "outputs are hi-lo combo" is that output impedance or gain you were referring to? I assume the gain is about 4-6 ?
Cheers and thanks again.
Frank M
Hi Frank..Sorry for the confusion. It's a combination of high and low nickel core.
There is very little gain in this preamp. Step down ratio of the B7-15K is 5:1. Gain of the 801-A is supposed to be 8.
Not sure what that translates to in terms of total gain.
Kind regards,
Bas
To infinity and beyond!!!
Edits: 05/27/15
Thank you Bas. May I ask what type of amp you are using (or plan to use) with the 801A preamp? I always like to ask to get a better context on how people integrate their system components.
Presently I am using Mike's MQ-565's in a Baby Huey (PP EL-84) and am enjoying them immensely. These baby's really shine. I am building a 6V6 preamp (triode connected) to go with them but have always been interested in the 801A, however I need lots of gain for my MC phono set up.
Mike builds really nice stuff.
Cheers and thanks for sharing
Frank M
it's a case of diminishing returns.I had a 6v6 preamplifier and after building the 801A....one thing that crossed my mind was...was all the expense really worth it? I went pretty far on parts quality/cost on the 801A. Well you know what is in there. Probably 5-8 times more expensive. In the end its what we do. But the sensible thing for me would have been to stick to the 6v6. I could easily have been very happy with that for the rest of my life.I'm going to drive a full dht se amp with it. (One of the reasons I built the 801A is to go full dht)
4p1l input tube, 300b driver tube gm70 output.
The one thing the 801A appears to do better is letting through whatever is on the source. My NOS dac sounds even more natural now.
Kind regards,
Bas
To infinity and beyond!!!
Edits: 06/02/15
I've played with a 6V6 preamp (in triode) and really like the sound, but hard to tame the microphonics. Any microphonics problems with the 801a? Can you give op point (or maybe I missed it)? Thanks!
I've had no problems with the 801A. And not with the 6v6 either (unless I tapped on the amp itself) In that case both the 6V6 and the 801A are microphonic.
I had the 6v6 on a thin wooden top plate. The 801A on a 3mm aluminium top plate.
So it is hard to compare. Of the two I would say the 6V6 was the more microphonic.
6V6 are modern Russian versions. The 801A is RCA (don't know what year).
Still busy with the operating point. Initial impressions are that it there are no magic operating points..so far it sounds pretty much the same whatever operating point I've chosen.
To infinity and beyond!!!
nt
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