Parasound JC3 Phono

[john curl]

Thanks Jacco, Joe knows his 'stuff'.

 

[john curl]

RCruz, your question is an interesting one. Perhaps, you really are getting the addition of
EXCESS NOISE in resistors from your Source resistor. This is the perfect place to bring it out.

 

[scott wurcer]

Thanks Jacco, Joe knows his 'stuff'.

I would disagree that shunt capacitors are not in the signal path. An RC high pass and low pass are complimentary and at crossover ALL the "distortions" of the capacitor are seen equally no matter if it is series or shunt. This bit of flawed reasoning appears everywhere.

 

[john curl]

I don't think that your criticism is very important to the design. While I believe that capacitors are VERY IMPORTANT because of their aberrations, I have not found you, Scott, to believe them so, in recent years.

 

[scott wurcer]

I don't think that your criticism is very important to the design. While I believe that capacitors are VERY IMPORTANT because of their aberrations, I have not found you, Scott, to believe them so, in recent years.

Not a criticism of the design but the reasoning that contributes to the folklore. All capacitor abberations are measurable, it's the measuring under one set of conditions and use under another set that bothers me. No comment on the 5 op-amps per side. 🙂 ?

 

[simon7000]

I would disagree that shunt capacitors are not in the signal path. An RC high pass and low pass are complimentary and at crossover ALL the "distortions" of the capacitor are seen equally no matter if it is series or shunt. This bit of flawed reasoning appears everywhere.

Scott,

It has to do with the discontinuities you don't believe in. In series they remove low level information, as a shunt they leave in more than they should at low levels. 🙂

ES

 

[john curl]

I use 6 op amps per side, for my phono stage.

 

[scott wurcer]

I use 6 op amps per side, for my phono stage.

WOW, you've gone hog wild!

 

[scott wurcer]

Scott,

It has to do with the discontinuities you don't believe in. In series they remove low level information, as a shunt they leave in more than they should at low levels. 🙂

ES

Quite true, but there's a little thing like KT/q and bandgap voltages at room temperature that make uV barriers an extraordinary claim.

 

[john curl]

I have always used 4 IC op amps, even with my Vendetta SCP-2 phono stage. I just make the 'important' stuff, discrete.

 

[Bob Cordell]

Bob, somewhere there might be an MC cartridge with more inductance than nominal. Sometimes for MORE output, they use a ferric ring to the coil to raise the output. This might give you the 'aberration' you seek. However, since the early days, more than 35 years ago, we could not find any significant change with variation in resistor loading, as far as frequency response is concerned, in most MC cartridges.

Hi John,

I'm certainly not seeking to find an aberration, just hoping to better understand if there is the potential for one. I also understand that there are some higher-output MC's that are likely to have more inductance. Those I am not talking about (that's why I mentioned MCs in the range of 400uV).

So anyway, bottom line, what kind of inductances have you measured on typical MC cartridges? Is it less than 500 uH?

Thanks,
Bob

 

[SY]

Some typical numbers:

Denon DL-110 high output (1.6mV/5cm/s) 380uH
Denon DL-304 low output (0.18mV/5cm/s) 50uH

 

[simon7000]

Quite true, but there's a little thing like KT/q and bandgap voltages at room temperature that make uV barriers an extraordinary claim.

pV or nV suspected uV or mV who knows!

However on corroded contacts absolutely up to V!

 

[RCruz]

RCruz, your question is an interesting one. Perhaps, you really are getting the addition of
EXCESS NOISE in resistors from your Source resistor. This is the perfect place to bring it out.

Hi John

I have two 48dB builds with exactly the same topology but different components.

One of them uses special Japanese carbon film as Rs on the jfet first stage (needed to reduce THD and miller effect) and it is dead quiet.

The other one uses a kiwame for Rs and it produces some residual noise (Woosh at full power without signal in).

Am I reasoning correctly ?

 

[RCruz]

It has to do with the discontinuities you don't believe in. In series they remove low level information, as a shunt they leave in more than they should at low levels. 🙂

This is a very good way to explain it indeed.

I am used to "voice" my builds by choosing and mixing the shunt caps (I call them decoupling caps).

As for series caps.... I tend to use the best I can afford (Teflon, SMica, Polystirenes, MKP) but I always feel that these act like filters.

 

[john curl]

Hard to say, but resistor is a problem.

 

[RCruz]

Thank you John... is there a way to avoid the resistor in that place ?

I know some precision resistors with low ppm are less noisy but I really could never grasp the relation between low ppm and noise.

 

[Bob Cordell]

Some typical numbers:

Denon DL-110 high output (1.6mV/5cm/s) 380uH
Denon DL-304 low output (0.18mV/5cm/s) 50uH

Thanks, SY; that's just what I wanted. Looks like a 400uV MC would be in the range of 100uH for cartridges like the Denon. No influence to speak of in the audio band due to a 100 ohm load against that amount of inductance.

Cheers,
Bob

 

[john curl]

Look for the term: EXCESS NOISE. LOWER THE BETTER.

 

[john curl]

Use wirewound, and be safe.