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Old 12th January 2004, 06:34 AM   #11
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TL 431 is not " classical " zener diode, but ( as I know ) band gap regulator, which have lower noise.
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Old 12th January 2004, 06:46 AM   #12
Werner is offline Werner  Europe
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I object, your honour.

The circuit as detailed above runs the 431s at a noise gain of about 5, in which case they emit horrible sounds almost on a par with that other noise generator, the LM317. This can not be optimal with a payload circuit with lacking PSRR. Moreover, used as above the 431 will have an output impedance of 500-1000mOhms, a figure you can also attain easily with a well-configured BJT zener-follower (series), or its shunt equivalent.

By the way, I have a suitable breadboard with 5 or 6 styles of (simple) voltage regulators on it, all connected to a low-noise gain stage that allows me to listen to the noises on the voltage rails. (non-unity-gain) 431 and 317/337 are the worst possible solutions of the simple v-regs.

To Aiace: I think you better start with an even simpler and well-known circuit like the Pacific RIAA, or else perhaps the Pass Pearl.
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Old 12th January 2004, 07:56 AM   #13
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I have never say, that 431 is best solution, only that have lower noise than zener diode .
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Old 12th January 2004, 10:52 AM   #14
Aiace is offline Aiace  Italy
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To Werner:
Who has said you that I am to the beginnings?
On TL431 yes, I'd nevere used. Many people say that TL431 is great but if it's not true .... I'll use zener, mos, and cap multiplier with any feedback.
Have you a "great" schemetic for power supply?

Bye
Aiace
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Old 15th January 2004, 10:12 PM   #15
Aiace is offline Aiace  Italy
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This is my last schematic, now I'm going to build it.
I try to apply several of your advice, pleas can you tell me is somthing is wrong?
Thank you
Aiace
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Old 15th January 2004, 10:17 PM   #16
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Don't know how much it will matter in this particular design, but
perhaps pots on the CCS JFETs since JFETs tend to vary quite
a lot. You could select them for appropriate IDSS too, of course.
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Old 16th January 2004, 01:50 PM   #17
KlausB is offline KlausB  Germany
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I assume this is a MM phono stage. The design looks nice and interesting and I am very much looking foreward to read a first comment on its sonic performance.

A few comments:

For more stable current sources I would recommend the BF246 (high IDss) plus a source resistor instead of the BF244.

Instead of the input BF244 you might have chosen jFETs with a higher transconductance like the 2SK369 (40ma/V) or a 2SK289 dual FET (20ma/V).

I cannot read from the schematic what currents the transistors draw. However, you should consider a battery or accumulator based power supply to eliminate the problems mentioned in the last posts.

The symmetric output allows you to place a phase switch at the output, which might be a nice option.

Good luck
KlausB
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Old 16th January 2004, 02:12 PM   #18
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Aiace, I suggest that you simulate the amp because I suspect that the low gain can be a trouble for you when it comes to RIAA accurancy.
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Old 30th January 2004, 08:32 PM   #19
Aiace is offline Aiace  Italy
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This is the final schematic that finally I built.
I've done some measures:
Gain (20Hz) = 46.6dB
Max error from RIAA +/- 0,4dB (With a little patience it can be improved but I think it's enoght for my hear)

Now I'm going to build the power supply. I'm going to post my listening impressions.
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Old 30th January 2004, 09:57 PM   #20
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That is just too much capacitance for this poor little diff amp to slew.
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