Sony C800G polarization scheme

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pasarski

Well-known member
Joined
Jan 29, 2010
Messages
292
This thread http://groupdiy.com/index.php?topic=55792.0 reminded me of my plans to build a C800G clone. Also reminded me of the unusual polarization scheme this mic seems to have.

The R101/R102 (180K/47K) voltage divider for the backplate and a 47uF from backplate to the ground. Eliminates one big resistor but adds a big electrolytic. In the signal path or not? This "warthread" http://groupdiy.com/index.php?topic=53620.180 got me confused.

What do you think is the idea behind this kind of a polarization scheme? Cost issue? (Really doubt it in a $10 000 mic)

http://gyraf.dk/schematics/Sony_C800G_Schematic.gif
 
Dear pasarski,

C101 is a decoupling cap thus has nearly no effect on sound despite Misha's posts.

you can use any electrolytic cap, like sony's tech did, as long as it has standard specs .You can't go wrong with Elna or Nichicon caps.

regards
 
pasarski said:
This thread http://groupdiy.com/index.php?topic=55792.0 reminded me of my plans to build a C800G clone. Also reminded me of the unusual polarization scheme this mic seems to have.

The R101/R102 (180K/47K) voltage divider for the backplate and a 47uF from backplate to the ground. Eliminates one big resistor but adds a big electrolytic. In the signal path or not? This "warthread" http://groupdiy.com/index.php?topic=53620.180 got me confused.

What do you think is the idea behind this kind of a polarization scheme? Cost issue? (Really doubt it in a $10 000 mic)

http://gyraf.dk/schematics/Sony_C800G_Schematic.gif
Click to expand...
Hi pasarski, I'm glad you are also here, on this forum:
I think that:
This "decoupling" cap is also coupling input cap for this schematic. The same situation is in U47. Fred will not admit it - but there are physical laws. AC current is also flowing through this "decoupling cap"  is connected in series to earth with a capsule. Because of its huge capacity in alignment with the capacity of the capsule, its effect is small, but it can not be ignored.  However, if you want the best sound is achieved and smaller distortion, then I would advise shunted electrolytic cap with film capacitors of small capacity.
 
Thanks for the answers guys!

Both of you kind of missed my point though. Maybe I didn't make it clear enough: why a small resistor and a big cap, and not a big resistor and a small cap like in many other mics?

But hey, why not try to use your arguments for solving it for me?

If granger.frederic is right, and the cap has no significant effect on sound, then Sony's aproach makes sense. Rather a small resistor and a cheap cap vs. a small cap and a expensive large resistor. But then, why so many mics do it the other way? And many times there is a film/PIO/styroflex or some other "better" cap.

If o3misha (and so many others) is right, it get's more complicated. Did Sony engineers like the sound of a 47uF electrolytic in that posotion? Did they want to cut the cost at the expense of good sound? Probably not.

Regarding your argument. I kind of believe o3misha (and others) on this matter, even though I haven't tested it myself. Even granger.frederic admitted in the other thread that a wrong kind of cap in this position ruins the sound. Why it should be black and white: ruined or good? There must be semigood in the middle?

BTW: If you like to continue the argument here on my thread I don't mind. I actually enjoy following it. But please try to keep the tone of the conversation friendly. This is a great forum and one reason I love it so much is, that there is no flame wars, but a mutual respect between forum members and a friendly atmosphere. Nobody's ridiculed or bad mouthed for differing opinons, lack of knowledge, typos or anything. Let's try to keep it that way :)


 
pasarski said:
Thanks for the answers guys!

Both of you kind of missed my point though. Maybe I didn't make it clear enough: why a small resistor and a big cap, and not a big resistor and a small cap like in many other mics?

But hey, why not try to use your arguments for solving it for me?

If granger.frederic is right, and the cap has no significant effect on sound, then Sony's aproach makes sense. Rather a small resistor and a cheap cap vs. a small cap and a expensive large resistor. But then, why so many mics do it the other way? And many times there is a film/PIO/styroflex or some other "better" cap.

If o3misha (and so many others) is right, it get's more complicated. Did Sony engineers like the sound of a 47uF electrolytic in that posotion? Did they want to cut the cost at the expense of good sound? Probably not.

BTW, regarding your argument. I kind of believe o3misha (and others) on this matter, even though I haven't tested it myself. Even granger.frederic admitted in the other thread that a wrong kind of cap in this position ruins the sound. Why it should be black and white: ruined or good? There must be semigood in the middle?

BTW: If you like to continue the argument here on my thread I don't mind. I actually enjoy following it. But please try to keep the tone of the conversation friendly. This is a great forum and one reason I love it so much is, that there is no flame wars, but a mutual respect between forum members and a friendly atmosphere. Nobody's ridiculed or bad mouthed for differing opinons, lack of knowledge, typos or anything. Let's try to keep it that way :)
Click to expand...
For filtering of polarisation it is the same: big resistor+small cap=small resistor+big cap. But, for coupling capsule and the tube it is better to have small influence of the cap. So. I think Sony made good decisiion to choose bigger cap. But I think, that it is better to put small good film cap in parallell with electolytic. Who knows : maybe Sony engeneers love the sound of electrolytic caps, or they just use as biggest cap as possible for avoiding of its influence on sound path? I heard that a few old very famous microphones equipped with electrolytic caps in output coupling cap position (C2 in U47). It is only the matter of taste which type of capacitor to use: electrolytic, film or something else. Who does care if the mic is good sounding with eletrolytic C2? Did I answere your question?
 
i admit that i could sometimes be sarcastic but not in a bad way.

things are simple.
Neumann and sony's tech have understood that decoupling caps, even in high impedance parts, are not impacting much the sound as long as the caps are efficient.
If you choose in this case a good electrolytic , and if you take care to make it work at 80% of its nominal voltage, you shouldn't have a major non-linearity, thus no issue.Even if electrolytic caps are not loved by some audio techs.

in other words, if you respect the original conception, you will achieve the best sound of your beloved microphone
 
granger.frederic said:
i admit that i could sometimes be sarcastic but not in a bad way.

things are simple.
Neumann and sony's tech have understood that decoupling caps, even in high impedance parts, are not impacting much the sound as long as the caps are efficient.
If you choose in this case a good electrolytic , and if you take care to make it work at 80% of its nominal voltage, you shouldn't have a major non-linearity, thus no issue.Even if electrolytic caps are not loved by some audio techs.

in other words, if you respect the original conception, you will achieve the best sound of your beloved microphone
Click to expand...

So why do you think so many manufacturers want to waste money for a ~1G resistor if they could as well choose the Sony way?
 
you're touching a very mysterious point.

some techs say that the THD of a capsule is lower with gig ohms resistors.

but if you analyze the schematics of an elam 251 or C800 , you will see some lower value.

i suspect that it depends of the capsule conception.
 
pasarski said:
granger.frederic said:
i admit that i could sometimes be sarcastic but not in a bad way.

things are simple.
Neumann and sony's tech have understood that decoupling caps, even in high impedance parts, are not impacting much the sound as long as the caps are efficient.
If you choose in this case a good electrolytic , and if you take care to make it work at 80% of its nominal voltage, you shouldn't have a major non-linearity, thus no issue.Even if electrolytic caps are not loved by some audio techs.

in other words, if you respect the original conception, you will achieve the best sound of your beloved microphone
Click to expand...

So why do you think so many manufacturers want to waste money for a ~1G resistor if they could as well choose the Sony way?
Click to expand...
Both ways have its advantages and disadvantages. 
 

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