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Old 6th March 2014, 11:06 PM   #21
SY is offline SY  United States
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That was the point of my CMR statement. See my preamp article.

Let's run the numbers for noise of an SUT. In my aticle, I used a Sowter 8055, a moderately priced unit. Primary resistance is 0R72. Secondary resistance is 100R, with 1:10 stepup. So the input-referred ENR is somewhat over an ohm. Not noiseless, but well below the ENR of most MC cartridges.

At audio frequencies, the ENR of even the exotic tubes is 100R or more- usually a LOT more.
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Old 6th March 2014, 11:13 PM   #22
Bonsai is offline Bonsai  Taiwan
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BIC MC amplifiers are about 0.3 nV rt/Hz - pretty good.

But, they can't compete, without a lot of added complexity and noise degradation, with a transformer when it comes to CMR.

I'd give on balance to the transformer - but you need to spend a bit of money for a decent product.

IIRC the Jensens are about $300 each
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Old 6th March 2014, 11:19 PM   #23
kevinkr is offline kevinkr  United States
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The tube input ENR issue is further compounded by the fact that it is usually calculated based on measurements at frequencies tens to hundreds of MHz removed from the audio band. Tubes are usually significantly noisier than the ENR would seem to imply, particularly at the low end of spectrum where flicker (1/F) noise is usually the dominant noise source.

Generally by the time you are done with the cartridge resistance, primary and secondary resistances of the SUT will generally be significantly worse than the ENR of most good high transconductance triodes and perhaps on par with a quiet 12AX7A. Note that the ENR on the primary is multiplied by the square of the turns ratio and you have to add the secondary resistance as well. (As an approximation)

The quietest tubes I have used so far are the D3A, 5842/417A, and 6S3P-EV. There are others out there, particularly of Russian and European Post Office/Telecomm origins.
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Old 7th March 2014, 12:32 AM   #24
Bibio is offline Bibio  Scotland
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ooopppss, sorry i asked

from what i can see the SUT will only sound as good as the MM stage it's going into. ok so the SUT might be silent but the MM stage might be noisy so the end result will be a noisy stage.

on the other hand if you have a dead silent MM stage then i can see that a SUT would be good.

so if you have a noisy MM stage and want an MC cart then from what i can see you would be better off building a nice silent MC phono stage as the SUT will make no difference to the sound of a noisy MM stage.
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Old 7th March 2014, 12:38 AM   #25
sreten is offline sreten  United Kingdom
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Hi,

Its simple. Valves are pretty useless at MC step up.
Valve fans like transformers and don't like silicon.

Those that do like silicon you will have a hard time
arguing that transformers are a good idea, like
CMR remotely matters in any normal audio.

rgds, sreten.
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Old 7th March 2014, 01:00 AM   #26
kevinkr is offline kevinkr  United States
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I have both, and prefer the transformers, however the solid state unit (based on an AD multi-tan amplifier IC and not of my design) is much more versatile and more than quiet enough, it also manages to sound pretty good.

Bibio I did not mean to discourage you, in most cases the noise floor with any decent tube MM phono stage and SUT is still going to be lower than the noise floor of the actual recording.
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Old 8th March 2014, 07:52 PM   #27
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Hi,

Quote:
The quietest tubes I have used so far are the D3A, 5842/417A, and 6S3P-EV. There are others out there, particularly of Russian and European Post Office/Telecomm origins.
There are a few more out there that could be considered for MC headamp use.
What matters most to me is the linearity and noise figure in the region close to Vg0.
There's no point of building a tubed MC stage if you need a huge input cap to begin with.
When valves are carefully selected and controlled by CCS there is no good reason not to // them and take advantage of the lowered noise figures and reduced Rp.
I've build several valve based MC stages (one of them was publicized on this forum which is really cheap to build) that are absolutely dead quiet, have no cap input and would take all but the obscenely low output MC.

Valve noise is rarely a problem, RF often is and so is PS induced noise. Other than that it is fairly straightforward to build either a SE or a fully balanced MC stage.
The reason why it never got anywhere I suspect is that it's so much easier to use either a solid state input or a SUT.
I'd like to avoid SUTs as whatever they're qualities or shortcomings, you're just stuck with what you've got and that will determine everything that is attached to it.
IOW, I'm a bit of a control freak.

Ciao,
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Old 8th March 2014, 08:06 PM   #28
kevinkr is offline kevinkr  United States
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Good thoughts Frank, I'm actually thinking about a tube based MC head amp. Haven't really thought about the tubes, either moderate mu high transconductance triodes or perhaps a couple E810F/7788 or D3A pentodes connected in parallel.

Any thoughts on a tube with relatively low flicker noise?
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Old 8th March 2014, 08:18 PM   #29
andyr is offline andyr  Australia
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Quote:
Originally Posted by kevinkr View Post
Good thoughts Frank, I'm actually thinking about a tube based MC head amp.
Why bother - you will never get it as noiseless as a ss head amp. An Aussie guy named Trevor Lees came out with a tube-based head amp, phono stage and line stage in the 80s. I owned his head amp (which had been upgraded/recapped by someone who knew what he was doing) but, once I heard my current ss head amp - which just amplifies, without adding any noise - I got rid of it, as there was no contest.

By all means have tubes in your phono stage ... but use an ss device for head amp duties, IMO.


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Old 8th March 2014, 08:28 PM   #30
SY is offline SY  United States
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Quote:
Originally Posted by andyr View Post
Why bother - you will never get it as noiseless as a ss head amp.
All you have to do is get it as quiet or quieter than the MC's intrinsic noise. Past that, which is quieter is academic.
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