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Old 20th April 2009, 09:30 AM   #1
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Default MC prepre with submini tubes

Hello

does somebody tried subminiature tubes like 611,6112,6021,5703,... for MC prepre ?

Thanks

Best Regards

Pascal
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Old 20th April 2009, 11:02 AM   #2
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Hi,

IMO, the very low Gm inherent of the submini's mixed with a MC sounds like a baaaaaaaad idea to me

Cheers!
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Old 20th April 2009, 09:13 PM   #3
kevinkr is offline kevinkr  United States
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Most of the types listed have higher Gm than older garden variety audio tubes, however the 5842 and D3A will be much quieter, and have much higher Gm. I have used 5744 and 6021 in MM phono stages and found them barely quiet enough - I also did not like the sound that much.
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Old 20th April 2009, 10:27 PM   #4
tinitus is offline tinitus  Europe
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Didnt the Italian magazine TNT have a preamp design with nuvistor tubes, or is that completely different

But pure low output MC, isnt that still done with stepup trafo
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Old 21st April 2009, 12:48 AM   #5
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IMO, the idea of any tube in a LOMC prepre ("head") amp is very bad. S/N ratio is the diety in this situation and tubes simply are not up to the job.

Either you use a step up trafo (SUT) in front of a tubed MM level phono preamp or you use Allen Wright's hybrid cascode.
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Old 21st April 2009, 01:16 AM   #6
JesseG is offline JesseG  Canada
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The most recent UHF mag (No. 86) has a review of the Allnic H-1200 phono pre which uses 6112 and 6021 twin triodes. There is a fairly good photo of the innards in the review.

It uses step-up trafos for the MC stage - probably to get 'round the noise issue.

They had some nice thigs to say, but my overall impression was that they were trying to find nice things to say. However it was not a disaster.

So, it can be done
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Old 21st April 2009, 02:16 AM   #7
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Quote:
Originally posted by JesseG
It uses step-up trafos for the MC stage - probably to get 'round the noise issue.

So, it can be done
The original question was could submins be use for an MC preamp. Since the stepup transformer is the MC amplification stage, then they're not really doing it.

I believe that a transformer is the only really neutral sounding device. I've had the oppotrunity to use several active MC preamps including the AR MC-33 as well as SS battery powered units. All the active units, to my ears, added their own color or flavor to the overall sound as compaired to a good transformer. By good I mean a transformer specifically made for very low level signals from a MC cartridge like Lundahl's or the Cotter I still use. Not UTC's. And I'm willing to sacrifice a tiny tiny bit of speed for the neutrality of a transformer.
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Old 21st April 2009, 05:45 PM   #8
EC8010 is offline EC8010  United Kingdom
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The other huge advantage of an MC transformer is that the input can be made balanced and floating. If you use at a valve at MC sensitivity hum becomes a serious issue.
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Old 21st April 2009, 05:50 PM   #9
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Default Wouldn't touch nuvistors with a 12 foot mic boom!

They are too prone to oscillation. I used a AKG-Norelco C12 condenser microphone that used 7586 (I think). One mic howled right out of the box. The other one developed the same howl after about 50 hours. I used a Moviola-Magnasync dubber recorder that used the submin glass tubes with good success with long life. Ray
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Old 21st April 2009, 08:06 PM   #10
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Built with Nuvistors many times, --Never had any oscillation problems at all....

Great little devices, But the American ones suck big-time. Go for some nice quiet Russian ones.....
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