MM Input Stage working in inverted mode - not to find; why ??

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Here is really a shunt preamp compensating also for the v15type 3 cartridge inductance too.

There are some more patents made by japanese engineers in the 80's but the only patent that was executed in the real world in this:
US4470020A - Virtual ground preamplifier for magnetic phono cartridge
- Google Patents



modern reiteration with theoretical models:

Website of Wayne Stegall - Phono Equalization Calculations


the components values:

http://waynestegall.com/audio/spice-models/riaa/riaaci2st-psps.txt
 
Here is really a shunt preamp compensating also for the v15type 3 cartridge inductance too.

There are some more patents made by japanese engineers in the 80's but the only patent that was executed in the real world in this:
US4470020A - Virtual ground preamplifier for magnetic phono cartridge
- Google Patents

That patent is for all cartridges and includes "stylus stabilizing" in the description which IMO is mostly if not completely nonsense. Quoting a patent on a virtual ground tape pre-amp does not strengthen the case for it either.
 
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That patent is for all cartridges and includes "stylus stabilizing" in the description which IMO is mostly if not completely nonsense.
I see no reason why it shouldn't work.

If you'd read the patent you'd see that it is made for "stabilizing" specifically the Shure v15type 3 and it was built and verified...apart from that it is citing a number of similar patents.
It could be built easier around AD844 today.

I personally was a bit skeptical of using the current delivered by a Moving magnet cartridge, but some others tell that it can deliver good enough SNR.
As nobody built it yet , apart from the inventor, i wouldn't argue about it until i do it myself and check.
 
I see no reason why it shouldn't work.

Yes physics, a MM cartridge is not a reciprocal motor/generator system. They proved nothing that can't be explained by simple electrical circuit equivalents. Condensor mics and possibly ribbon mics are reciprocal, you simply need to look at the mechanical and electrical energy stored in the system. Every cartridge needs different values, a commercially nonviable situation. These types of pre-amps have turned up here off and on.
 
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Yes physics, a MM cartridge is not a reciprocal motor/generator system. They proved nothing that can't be explained by simple electrical circuit equivalents. Condensor mics and possibly ribbon mics are reciprocal, you simply need to look at the mechanical and electrical energy stored in the system. Every cartridge needs different values, a commercially nonviable situation. These types of pre-amps have turned up here off and on.
Well...it's DIY here, not Sony corporation...so we can tackle these problems one at a time :)
 
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And we have. I gave you the link to the thread where all the information is. Scott is right almost impossible to make a product from this unless it could measure the cartridge parameters on power up and select the right settings. This is not hard but would put off all potential purchasers anyway.
 
Claims of damping have been debunked: that is settled.

I discovered the patent after the fact - before that I came up with Aurak initially as a way to finally eliminate capacitance loading effects, and the general blight of MM loading.

What surprised me is how well it works, sounds and measures.

It's tempting to put a small series resistor in series with the cartridge to form a usable RIAA pole. The Barney Oliver preamp did this. But I went for 'true' zero input impedance, and it's not that hard at all to correct as part of the 1st stage.

So yes, it has been done and tested. Very good it is too, IMHO.

LD
 
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Well...Scott is also a master of the digital world, i've seen him working on digital RIAA , but unfortunately I can't understand a damn thing of his work so i'm stuck with the analog world where he's a master again.....Most probably he'd find a way if interested.
Analytical Weighing systems have automatic zeroing through injecting a current into a solenoid until the mechanical system reaches 0 position.After that you calculate the weight from the current you need to get the system in the same spot with your added weight . You have some mechanical characteristics of the weighing cell stored in a memory to help you get the system right over time too as each weighing cell have different elasticity parameters.When you buy a new weighing cell ( an elaborated piece of carved elastic metal) you're also given a 256kb memory with the cell parameter.So somebody can think of taring a mm cartridge too .
 
Well...Scott is also a master of the digital world, i've seen him working on digital RIAA , but unfortunately I can't understand a damn thing of his work so i'm stuck with the analog world where he's a master again.....Most probably he'd find a way if interested.

Thanks but not really, the takeaway from the article could be simply the RIAA coefficients for all the different variants, 6 numbers you can enter into any IIR filter capable DSP.

We could do the same for each brand of cartridge and just a few of the important ones, RIAA, ffrr, etc. Bill, LD what do you think? A little DIYaudio article since there is no more Linear audio?
 
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Well due to some slightly over exuberant ebaying I have rather a good selection of MM now :$


What I haven't got are real measurements of them yet. On my list of actions to do before losing all my marbles was a way of measuring cart inductance that you could do without needing a scope that was accurate enough. Now it turns out that, with a 300-500Hz turnover (depending on the version you build) you can be a chunk out and it makes IIRO 0.2dB difference to the overallresponse (and is easily corrected with a small LF shelf). So I suspect that a laptop audio port and a few passives will actually get one there. But not run any numbers yet.
 
Thanks but not really, the takeaway from the article could be simply the RIAA coefficients for all the different variants, 6 numbers you can enter into any IIR filter capable DSP.

We could do the same for each brand of cartridge and just a few of the important ones, RIAA, ffrr, etc. Bill, LD what do you think? A little DIYaudio article since there is no more Linear audio?
There's an exploit that makes a 'one fits all' eq possible: it turns out that the ratio L/R is near enough constant across most MM carts. When one thinks about it, there's reason for that.

Then a one fits all filter is practically possible, especially when f response of generator and mechanics is very probably level sensitive in any event. Well, the loss mechanisms within the gen/mechanics v prob are level sensitive for a given f, ie slew rate dependent. This is for normal loading as well as current loading, BTW.

Then it's not worth getting too fussy about exact RIAA response either, IMHO. A playback filter can be 'perfectly linear' and so was the RIAA encoder, but the electromechanical bits in between inconveniently v probably aren't. Part of vinyl's charm and perhaps why current loading is 'different' in terms of sound/performance, as it seems to be?


LD
 
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I don’t think feeding an MM cart directly into the summing junction of an inverting amp is at all practical. Scott has touched on some of the issues, but the main one is EQ has to be optimized for every cart. For a wacky-do DIY enthusiast project, but there it ends in my view.

If you are a dab hand at software/DSP you could do it automatically with a ref disc or some other clever technique, but really what precisely are you gaining over a classic 5534 all-active RIAA that can be built for probably $2 per channel using half decent passives? Nothing.

Maybe with MC because the coil resistance and inductance are so low but with that I prefer a discrete front end amp. Even a BF862 single ended gain stage can get you remarkable performance for the money.
 
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Sadly I've gone and bought all the carts that aren't ( for science of course*) but for a group of the most popular from ortofon and 21st century AT you can fit and forget. Just checking my spreadsheet and the range turnover frequency is 311-328Hz, which actually makes naff all difference down there.



@Bonsai. It works but I will add you name to the list of people who think its a daft idea. Up to 4 now :). What you are gaining is removal of the 4th order roll-off that MMs are hamstrung with. Flat electrical response as high as you want. Also superlative (turd polishingly good) noise performance. But the concept is so orthogonal to the way most people think about MM it seems wrong on first inspection.



*All my real oddities are long out of production so I only have myself to blame. Let me do a table of L/R values.
 
... Scott has touched on some of the issues, but the main one is EQ has to be optimized for every cart. For a wacky-do DIY enthusiast project, but there it ends in my view.
Our posts crossed, Bonsai. See my post above. That ratio L/R is almost constant for most MMs is very convenient for a one fits all filter.

Maybe with MC because the coil resistance and inductance are so low
The method suits MC particularly well. And no nasty pole to deal with. But beware cartridge=crispy fried duck in unlikely event of fault given that not much limits current except a few ohms of coil R. It's well documented for MC, anyway.
 
Our posts crossed, Bonsai. See my post above. That ratio L/R is almost constant for most MMs is very convenient for a one fits all filter.

I assume you would want to aim for a universal front end, something like a sub nV virtual ground input for MM, MI, or MC with only a gain adjustment all the rest in DSP. Handling the level dependent effects becomes more work, but they do it for speakers. There is work on time varying IIR filters, "The Time-Varying Bilinear Transform" by Able & Berners.
 
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