Solid state phono preamp design philosophy

[PMA]

Interesting, Janasek was my competitor in solution of isolation amplifiers for power transients monitoring systems, some 11 years ago. Noise was not important, but immunity against fast CMV voltages was VERY important.

 

[john curl]

PMA, the examples were very primitive, nevertheless, at least 40 years behind. I hate to remind everyone, but we in the USA went to the moon in '69, and we had lots of heavy engineering behind it, some of which spilled out into the audio sector. When I look at such examples, it only reminds me as to how far ahead hi end design generally is over what people even know exists.

 

[Lumba Ogir]

Hi,
regarding MC, not just noise is a problem, the extremely small amount of energy involved as well. Just a very few devices have the ability to handle so weak signals satisfactorily, others cause (considerably) more losses and distortion. Parallelling does not help, means sonic degradation. However, such annoyances usually don`t make simulation data less fabulous.
For the orthodox minded only battery supply is acceptable.

 

[john curl]

This is not helpful.

 

[Lumba Ogir]

Mr. Curl,
did you mean my post, Sir?

 

[CBS240]

Hi

Just out of curiosity, would the KSK595H transistor work well as a phono input stage? I think there is a TO-92 version also. Good linearity with high input impeadance.

 

[john curl]

Yes, paralleling of parts does not lose information, and is often necessary for lowest noise. Power transfer is NOT the same as signal transfer. We have known how to do this since 1966, due to a paper in the IEE's 'Electronic Letters' found in research labs and in technical libraries at the time, and even today.

 

[john curl]

ksh device is OK for microphones, lousy for phono in general.

 

[PMA]

PMA, the examples were very primitive, nevertheless, at least 40 years behind.

I just opened the paper - you are right, of course. The designs were mainly for cheap PC based measuring cards, I know the story.

 

[CBS240]

ksh device is OK for microphones, lousy for phono in general.

It does state "capacitor microphone applications" in the data sheet. I assume it is has to do with the phono pickup being inductive? Or is this another point of insight chalked up to "experience"?

 

[PMA]

Absolute maximum Id is only 1mA.

 

[john curl]

Have you finished college yet? Serious question.

 

[CBS240]

I don't quite understand why that is such a problem, it is not a power amplifier. It does have a relatively small transconductance but wouldn't linearity be of concern? I am thinking in terms of a source follower driving a bjt follower, as a buffer.

 

[Lumba Ogir]

Mr. Curl,
sonic degradation in paralleled (even if matched) devices occurs due to the effects of differences in signal processing. Another significant deteriorating factor is multiplied capacitances.

 

[PMA]

Rt 50 ohm is quite typical load for MC. Often Ct 10n in parallel is added. Would there be any issue with JFET input capacitance??

 

[john curl]

I have been producing world class pre-preamps for the last 35 years. Most here are rank amateurs, without experience, understanding, or even having done the computations necessary to determine what they are stating. I just can't cope with this disparity in understanding and experience. It is pointless. Also, 50 ohms is usually too low, 100-200 ohms is usually better with modern cartridges. Capacitance is optional and should point out the silliness of worrying about the intrinsic capacitance of the input devices.

 

[PMA]

Just for the record, 100 ohm with such high as 10nF in parallel makes F(-3dB) = 159kHz.

 

[Onvinyl]

But to me, this is so elementary that it's not worth wasting much time on. If your circuit has trouble driving the EQ network, then you shouldn't be designing circuits. There are much more subtle points to work on and achieve real improvements than to waste time on these types of basic problems that have been understood for decades.

So, which of the designs testet by audiophile didn't reflect the 'basic problems that have been understood for decades'?

thanks,
Rüdiger

 

[jacco vermeulen]

to cover and switch

Is that a problemo ?
Moving coil stage on the left side of the picture. (RIAA is not on it)
The various combinations are PIC stored and push button selected, same-same for the MM stage on the right.

 

[PMA]

I do not understand why you speak about problem. All I meant is I just made a proto to verify circuit function.