Simplistic NJFET RIAA - Page 1221 - diyAudio
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Old 10th March 2014, 03:03 PM   #12201
Salas is offline Salas  Greece
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Makes a difference for input loading and yes I used signal source modeling.
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Old 10th March 2014, 03:04 PM   #12202
AndrewT is online now AndrewT  Scotland
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Is that 22k or 1.22k
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regards Andrew T.
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Old 10th March 2014, 03:08 PM   #12203
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My simulations show that you need a buffer between the cartridge and the first JFET gain stage. Otherwise, the response is not pretty. The spice models I'm using are from the manufacturer.

You should put all the gain up front before the passive RIAA network in order to achieve the best S/N ratio. This one has a S/N ratio of 95dB @ 1KHz. Real world would be a little less than that.
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Last edited by dirkwright; 10th March 2014 at 03:11 PM.
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Old 10th March 2014, 09:40 PM   #12204
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Oh, and just to be clear. I don't mean to step on anyone's toes, or high jack this thread, or anything like that. I'm only trying to be helpful. This circuit is just something I threw together in 5 or 10 minutes. It's not "finished"....
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Old 10th March 2014, 10:38 PM   #12205
JimT is offline JimT  Canada
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I added your cartridge circuit to my Salas Folded Simplistic spice circuit. There is no problem.

Jim
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Old 10th March 2014, 11:30 PM   #12206
andyr is offline andyr  Australia
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Quote:
Originally Posted by Salas View Post
Nice. BTW, grab a UNI-T UT61E somewhere online on first chance. Easier to use than your Tenma bcs its auto ranging and It has a sensitive 0.1% spec frequency counter that extends far high, plus its true RMS and 22000 counts. Can datalog on a PC also. Keep the Tenma as secondary meter and Hfe tool.
Thanks, Salas, I shall go looking for one.

Finished the speed adjustment this morning BTW. The 33/45 speed controller I am using is put out by Steve Tuckett of "Number9 TT", here in Australia. It is designed for the 24v Premotec motor which Rega uses:
* mains frequency can be programmed to 0.001Hz,
* run-voltage & startup voltage can also be adjusted,
* as can the capacitance between the 2 pairs of motor windings (to minimise motor vibration).

Steve supplies a pulley for a Rega ... but I am using the speed controller with a Linn LP12 bearing & platter - so I had to get a pulley machined to suit the LP12 dimensions.

It turns out that this pulley is very slightly oversized; using a 1,000Hz tone (which is 1,350Hz when played at 45rpm), I needed 49.35Hz to get 33 1/3rd rpm and 66.60Hz for 45rpm. I had to use a 24dB bandpass filter (centred on 1KHz - which I made using Rod Elliott's P09 PCB) on the output of the phono stage, to stabilise the DMM reading, but it worked very well. At both speeds, I was able to get the DMM display to change only between -1 and +1Hz around the desired reading!

So thanks very much for all of your advice.


Andy
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Old 10th March 2014, 11:34 PM   #12207
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Quote:
Originally Posted by JimT View Post
I added your cartridge circuit to my Salas Folded Simplistic spice circuit. There is no problem.

Jim
It doesn't look that good to me, but opinions may differ.
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Old 10th March 2014, 11:51 PM   #12208
Salas is offline Salas  Greece
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You are simulating the MC configuration with an MM source model.
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Old 10th March 2014, 11:54 PM   #12209
Salas is offline Salas  Greece
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Quote:
Originally Posted by andyr View Post
Thanks, Salas, I shall go looking for one.

Finished the speed adjustment this morning BTW. The 33/45 speed controller I am using is put out by Steve Tuckett of "Number9 TT", here in Australia. It is designed for the 24v Premotec motor which Rega uses:
* mains frequency can be programmed to 0.001Hz,
* run-voltage & startup voltage can also be adjusted,
* as can the capacitance between the 2 pairs of motor windings (to minimise motor vibration).

Steve supplies a pulley for a Rega ... but I am using the speed controller with a Linn LP12 bearing & platter - so I had to get a pulley machined to suit the LP12 dimensions.

It turns out that this pulley is very slightly oversized; using a 1,000Hz tone (which is 1,350Hz when played at 45rpm), I needed 49.35Hz to get 33 1/3rd rpm and 66.60Hz for 45rpm. I had to use a 24dB bandpass filter (centred on 1KHz - which I made using Rod Elliott's P09 PCB) on the output of the phono stage, to stabilise the DMM reading, but it worked very well. At both speeds, I was able to get the DMM display to change only between -1 and +1Hz around the desired reading!

So thanks very much for all of your advice.


Andy
Its a minimal gear method but quite handy. Good experimental result.
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Old 11th March 2014, 12:37 AM   #12210
Salas is offline Salas  Greece
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Originally Posted by JimT View Post
I added your cartridge circuit to my Salas Folded Simplistic spice circuit. There is no problem.

Jim
Still there is the mechanical aspect to consider, which varies widely between MM models. "Clearly the electrical model is not telling us the whole story" Load the Magnets!!! - [English]
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