What would you want to see in a book on electronics for vinyl replay? Douglas Self.

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PRR

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> phono amplifiers and vinyl replay generally, add a bunch of new stuff which I have thought up since

My 2 cents (worth several bucks of sales) is in OLD approaches. Frankly obsolete designs. Humans can learn from the past. Although in this field, the bad lessons may be overwhelming.

Long ago we e-chatted this a wee bit, the 2-transistor phono preamps of late 1950s and too-far into the 1960s. You cited an influential English example. My side of the pond, a GE design was widely known. I even extracted 11 examples and composed some words on the good, bad, and very-bad/odd points of each; but never posted it. As 10 of the 11 look bad to me, I agree you should be "thinking up" instead of looking-back.
 

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Doug, what about actively driven shielded phono cable, virtually eliminating the capacitance of the cable, then using a known value of capacitance at the input of the phono amp so that the FR becomes more predictable. I've been thinking about making something like this myself, after Christmas.

See Post #22 above. The Neumann PUE-47 does this, but I am not aware of any other application, which is odd as it seems like a good idea.

It will certainly go in the book.
 
The cartridge is essentially a balanced device. It would be good to include some preamplifier design, MM and/or MC, with balanced input and output, if possible at least one simple and at least other more developed.

Surely the catridge coils are floating, except in some Shures where one of the grounds is connected to the cart body.

What's balanced about it?
 
Surely the catridge coils are floating, except in some Shures where one of the grounds is connected to the cart body.

What's balanced about it?
Shure, Stanton etc, yep removable little copper strap that grounds the cartridge body to one of the signal channel grounds.
The actual signal generating coils are indeed floating/balanced.

Dan.
 
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Most of the published data about maximum possible signal amplitude, and maximum possible signal frequency, comes from studies that focus upon moving magnet cartridges. Why not accumulate the same kind of information for moving coil cartridges too? I wouldn't blame if you chose to study only MC cartridges that were sold to the public after (let's just say) 2008. Older than that, becomes less and less relevant.

Received Wisdom / The Scuttlebutt / Loose Gutter Talk suggests that MC cartridges faithfully reproduce higher frequencies and greater amplitude pops, ticks, drum kicks, cymbal crashes, and cannon blasts than MM cartridges. But where is the line? What is the max possible in practice? Curious minds want to know.
 
Some real world data on the effects of AC coupling (and the lack thereof) of phono cartridges might be interesting too.

This was debated a few weeks ago at:

http://www.diyaudio.com/forums/analogue-source/288473-what-ideal-conventional-rumble-filter-douglas-self-20.html

in which some people seemed to be remarkably unconcerned about letting DC currents flow through their cartridges that were orders of magnitude higher than the signal. It is difficult to believe that that cannot have serious effects on cart linearity. Blocking caps are the way forward.
 
This was debated a few weeks ago at:

http://www.diyaudio.com/forums/anal...nventional-rumble-filter-douglas-self-20.html

in which some people seemed to be remarkably unconcerned about letting DC currents flow through their cartridges that were orders of magnitude higher than the signal. It is difficult to believe that that cannot have serious effects on cart linearity. Blocking caps are the way forward.
I wonder if cartridge distortion on very low level signals would be cleaner if a cartridge had a tiny bit of DC bias (polarity to be determined)? It would be interesting to test for that.

For the question of the ultimate rumble filter, I'd imagine that a spectral analysis sampling (3 sec.?) of the needle on the record during a blank spot (no program material) could tell a micro computer the best way to attenuate certain frequencies without just cutting all bass (?). Is a rumble filter actually needed anymore?
 
Seems to me the best way might be to implement the RIAA HF rolloff in analogue, to maintain good HF headroom and cut down ultrasonics that might cause aliasing, convert to digital, and then do the LF-boost in DSP with as much precision as required.
The SOTA on this is Wayne Kirkwood's system Pro Audio Design Forum • View forum - Pro Audio Design

ANY filtering will make digital processing of clicks & pops more difficult as it will both lengthen the fault and add wriggles on either side which will be impossible to remove w/o loads more processing.

But you do need an A/D with sufficiently high fs.

As to HF overload, so what? If the amp clips on a click but recovers instantly, no info that will facilitate removing it cleanly is lost. But ANY response shaping will slow down recovery bla bla.

But there are preamp topologies which behave more nicely under these conditions.

If there are no clicks & pops, I don't think it matters how you EQ apart from the cost, availability & size of 1% caps.
 
If you tap the load to ground at the pre-amp the signals are balanced i.e. using an instrumentation amplifier you get what you expect from a fully balanced source re: CMRR, etc.

Certainly, but the cartridge itself is not balanced, but floating. I don't see that 'floating balanced' is anything more than a contradiction. To be deprecated.

So far as I can see, if hum gets into the cartridge coils, then using a balanced phono amplifier is going to be of no help at all.
 
Certainly, but the cartridge itself is not balanced, but floating. I don't see that 'floating balanced' is anything more than a contradiction. To be deprecated.

So far as I can see, if hum gets into the cartridge coils, then using a balanced phono amplifier is going to be of no help at all.

With care the hum is common mode or mostly common mode, it does work numerous of us have done it. The hum is picked up at the cart but if you are careful to balance the cable capacitance and the source resistance in the two channels and use a fully balanced differential input to single ended output amplifier you can touch the cartridge and get no hum at the output. In fact center tapping the motor would defeat the benefit since induced hum on one side of the coil would be a fully differential signal again.

EDIT - To clarify, here is a picture from an Ayre Acoustics owners manual of my set up. Hum and noise were dramatically improved.
 

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With care the hum is common mode or mostly common mode, it does work numerous of us have done it. The hum is picked up at the cart but if you are careful to balance the cable capacitance and the source resistance in the two channels and use a fully balanced differential input to single ended output amplifier you can touch the cartridge and get no hum at the output. .

I think we may be at cross-porpoises here. I am thinking of hum getting into the cart coil via a magnetic field, whereas I think you are talking about electric fields, which are stopped dead by the simplest screening.

Seems to me that a magnetic field must produce a voltage across the ends of the coil, and balanced or unbalanced the amplifier will see that voltage. And magnetic fields are of course much harder to screen out.
 
I think we may be at cross-porpoises here. I am thinking of hum getting into the cart coil via a magnetic field, whereas I think you are talking about electric fields, which are stopped dead by the simplest screening.

Seems to me that a magnetic field must produce a voltage across the ends of the coil, and balanced or unbalanced the amplifier will see that voltage. And magnetic fields are of course much harder to screen out.

I was using a cartridge with an unscreened body. Kgrlee what are Mr. Kirkwoods reasons for going fully balanced?
 
Making MM cartridges with no electrical screening sounds like asking for trouble to me.

Anybody have a feeling for what % of cartridges are unscreened?

Well Doug it seems I get a new research problem all the time. I was using a wooden body Grado. Opening one with a broken cantilever I didn't notice any shielding (might have missed something) but rewiring differential reduced the notorious Grado hum noticeably. Now I see others also attribute it to magnetic pickup and I begin to think maybe I need to do a more careful experiment to separate the effects.
 
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