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Old 9th October 2008, 01:06 AM   #151
anatech is offline anatech  Canada
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Question I just saw your project

Hi Salas,
Nifty project. I may put one together for my Ortofon 540 and Thorens TD-126 MKIII.

May I ask if the 5 dB lift between 10 and 20 KHz is the Denon cartridge, preamp or test record? That would be very noticeable I would think.

-Chris
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Old 9th October 2008, 01:48 AM   #152
Salas is offline Salas  Greece
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Hi, thanx.

That last octave bump is common to MC with very few exceptions that they push it an octave higher, alas with a somewhat droopy response.
Its the tip mass - record surface resonance. There are bumpier than that! Not that noticeable given the lossy nature of many vinyl recordings and our ears. Plus power response of tweeters not usually strong. Get the VTA ok not to push it if with MC.
With MM the tip mass is higher, and the compliance higher normally, so other things usually mask it from prominence. Since your cartridge is MM with 200-400pF recommended load, I would urge you to avoid the above versions that produce 300-400pF Miller. Think that your cable may be 100-150 or 200pF additionally. Make the MM cascode version that I attach, with suitable gain, suitable overload margin, and very low Cinput. You may not attach at all the 100pF typically shown and start listening with just your cable capacitance, adding some Siver Mica for comparison. I have concluded that is the best sequence with MM. Or simulate what its inductance does with 47k and measure your cable pF to add. Then you know what you will need. You will not want to drive anything less than 30K line input or add a JFET buffer (better avoid if over 30k).
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Old 9th October 2008, 02:07 AM   #153
anatech is offline anatech  Canada
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Hi Salas,
Duh!! Brain fart on my part.

My cartridges are all replaceable stylus and high output. Someone did ask me recently about an MC preamp, so I mixed them in my mind. I haven't a clue what my acquaintance is using for a cartridge, or table for that manner. I think your circuit will solve his problem.

I would be driving an MM stage, or installing a buffer and run into a high level input.

Anyway, looks like a nice little circuit. Maybe not the best but probably better than a lot of things out there.

-Chris
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Old 9th October 2008, 02:26 AM   #154
Salas is offline Salas  Greece
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OK then. Here is your buffered version. From MM cartridge to line in. Can deliver up to 10mA to load. Lowest recommended is 20k with Cout 3.3uF. Make it 6.8uF for 10k load.

P.S. Don't drive an MM stage with 200-300mV that my 36dB stage and your cartridge will do. Sounds terrific for the little effort. A no brainer.
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Old 9th October 2008, 02:41 AM   #155
anatech is offline anatech  Canada
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Hi Salas,
This circuit will be amplifying a real MC cartridge, thank you. Your buffer is about as simple as it gets. I imagine that will drive most inputs with little trouble.

Quote:
Don't drive an MM stage with 200-300mV that my 36dB stage and your cartridge will do.
Nope. Didn't intend to. The Ortofon drives a MM input just fine, but this opens a possibility to use a preamp with no phono input.

Thank you very much Salas.

-Chris
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Old 9th October 2008, 02:52 AM   #156
Salas is offline Salas  Greece
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You will need 61dB for 0.2mV MC, 55db for 0.5mV MC, 40dB for 2-2.5mV high output MC like Denon 110-160 or Benz Micro MC Silver or Benz Ace Blue, 36dB cascode for 3.5mV MM.
All the versions are covered in the thread, and all are capable of driving a line stage. I recommend to avoid the extra buffer stage if the line input load has impedance (Z) over 10X the 2nd JFET's Drain resistor. Keep it simple.
Of course if it is made for a 3rd party, then the buffer is adequate since you will not always know with what is going to be connected, or future changes. The 2 stages sound great if the output is under 300mV and the load right. The added buffer will cloud it just a wee bit, but it will save the day by keeping the distortion very low and the drive strong in any adverse situation.
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Old 9th October 2008, 08:03 PM   #157
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Default Re: Currently under test

Quote:
Originally posted by salas
Plays very well with a finely tuned balance between full detail and no hardness at all. It is surprisingly dynamic even with low out MC (0.25mV). No noise. The local R-C decoupling of the first stage B+ for each channel is very audible. Focuses it. Batteries in general are good for noise but relatively Hi Z. Without the 10.000uF on their poles and the local JFET decoupling they create wide band interactions. I used 3X 12V 1.5Ah rechargeable batteries in series. I used Russian Silver Mica, Russian Polystyrene, Panasonic Electrolytics, & common metal film resistors. The 100R gate stoppers are Kiwame and optional. The output caps are Mundorf Supreme Silver/Oil. They were chosen as 0.68uF to create -10dB @ 5Hz to battle record warp. This is when they feed the 50K input resistance of the following Salas 6V6 line stage.

The black thing attached is the schematic. It will turn white when you click.
Hi Salas

I followed this link http://www.diyaudio.com/forums/showt...54#post1628754
and found your wonderfull work.

I will implement this with a PSU using superregs instead of batteries !

What should be the minimun voltage to feed your design ?

I am using a Benz ACE Medium output (Clear body)... should I make some adjustments or your design is good for this cart?

Please be pacient with me (I am no electronics wizz)... but in time I will surelly build this RIAA stage.

Best regards

Ricardo
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Old 9th October 2008, 08:28 PM   #158
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Salas have post all the info you need back
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Old 9th October 2008, 08:30 PM   #159
RCruz is offline RCruz  Switzerland
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Quote:
Originally posted by nicoch46
Salas have post all the info you need back
Thank you again.

I edited my post after back reading.

I do not know if I can find a suitable 36v spower... could I use a lower voltage ?
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Old 9th October 2008, 08:42 PM   #160
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