Scott Dorsey article on mic mod - full version, anyone?

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volki

Well-known member
Joined
Jun 9, 2004
Messages
178
Location
Berlin
there's this article by scott dorsey, "making mic's better", at

http://www.pfarrell.com/music/shanghaimic.html

originally published in recording magazine. it has this interesting xformerless balanced circuit in it, but some of the explanations are skipped on the website version. since i'm located in germany, it would be quite expensive for me to get the back issue in which it was published... do any of you have it by any chance? would it be possible to get a scan? that would be really great.

cheers,
volker
 
[quote author="volki"]there's this article by scott dorsey, "making mic's better", at

http://www.pfarrell.com/music/shanghaimic.html

originally published in recording magazine. it has this interesting xformerless balanced circuit in it, but some of the explanations are skipped on the website version. since i'm located in germany, it would be quite expensive for me to get the back issue in which it was published... do any of you have it by any chance? would it be possible to get a scan? that would be really great.

cheers,
volker[/quote]

Volker,

I don't have original article, but FWIW, I don't quite understand why it is a "Scott Dorsey mod". It is a Schoeps schematics (I sent original to Zebra50, but cannot find it on his website), stolen and used by many Chinese mics, such as MXL603, 990, 991, 2003, MCA, Aphex, and many others. You could as well get any of those mics, replace caps for good ones, with the same effect.
The part on FET is a phase splitter, followed by symmetric emmiter follower on 2 BJS, with bias set by resistors R4-R5. Emmiter resistors are part of phantom power.
 
Hi Marik,
obviously not looking hard enough this morning!

http://www.omnipressor.com/MicSchLib/Schoeps.pdf

:thumb:

Dorsey did design and build some PCBs for this so I guess that's why it has his name. Like the 'Royer' mod is very similar to some old tube schematics but Grizz brought it to the masses (and that voltage tripler idea is pretty neat).

Stewart
 
Scott Dorsey is a Saint and DGMM..... he freely admits to borrowing the Schoeps design, but he did this mod years ago....well before the Chinese borrowed it from Scott.

peter
 
great, thanks people! i was looking for that schoeps cmc series schematic anyway. :thumb:

so the web article obviously contains a simplified schematic? such as power derivation from phantom via zeners, the associated smoothing circuit, etc. at least the original schoeps schematic completely makes sense to me, while the simplified schem didn't.

anyway... so i finally got some schoeps in my collection thanks to zebra (is there more interesting stuff at that link?!?), now all i need is some b&k or dpa...

cheers!
volker
 
The schematic isn't simplified, the circuit is. I've used it, works fine except for two things-
Not enough filtering on the zeners; use 100uF instead of 10uF.
With my batch of 2sk107BL FETs I only get about .4-.5 volt across the source resistor. I put a voltage divider across the source resistor to take Vgs a little less negative. Some of the Schoeps circuits I've seen use a trimpot for that.
 
It?s nothing you can?t easily bread-board if you have the schematic. Just be sure and clean the flux off good or it?ll be noisy.

On another note, this circuit doesn?t work well on mics using capsules from 797 (Studio Projects, Behringer, and some MXLs to name a few). These capsules need a voltage multiplier to generate a higher bias voltage, so you?re better off just up-grading the capacitors on the original circuit board.
 
[quote author="Marik"]. Emmiter resistors are part of phantom power.[/quote]

ahhh, i think i get it - you mean the 2x 6k81 resistors that actually feed the phantom from the supply to the signal lines? that's pretty ingenious...
- where, isn't an emitter resistor of 6k8 that a little very much series feedback?

regarding the original schoeps schematic - the a/b switch (gain +2/-3db) does introduce some kind of ac feedback via the capsule...?!? whew...
 
[quote author="volki"] (is there more interesting stuff at that link?!?),
volker[/quote]


http://www.omnipressor.com/MicSchLib/


:wink:
 
I know this is a super old thread but I was wondering if any of these Kludge mike boards have been used as a DI?  I have one I recently acquired in a box of goodies and it looks like it is setup to be a start to a DI.




 
I remember some talk about that , have you googled yet ?
Also last time someone asked about the board for mics
a few people poo poo'd it  but it was certainly better
than what it replaced  not sure if the issue was starting from scratch ?
 
Greg i got 2 boards i bought from you.
i modded then 1 mxl v69 and it now sounds at least 50x better than before...
i even prefer that sound to a royer tube mod..

Thanks
 
okgb said:
I remember some talk about that , have you googled yet ?
Also last time someone asked about the board for mics
a few people poo poo'd it  but it was certainly better
than what it replaced  not sure if the issue was starting from scratch ?

I did google it but didn't find anything about it being a DI?  If it works I may throw it in a box.  I have a number of mics that I like a lot so I'm just trying to figure out how to use it.  Any reason it wouldn't work like a DI?
 
I just tested it out.  It works and it sounds pretty darn good!  I think I will put it in a case and maybe throw a 20db pad on it as well.  It sounded better then the DI in my vintech x81 so that makes me smile!

 
Vintech DI's are just a switchning 1/4" jack.
they bypass the mic input transformer, sending the DI line straight to the gain switch.
It sounds okay to me, but not great as if you were using a good DI to input trasnformer...
good luck..
 
3nity,
What is the board you are using in the mxl v69 that makes it 50x better?
I have one of these mics stock and I would really like to improve it.
Dan
 
Ok thanks, I guess you put a Dorsey / Kludge Audio board in the v69, switching it from a tube circuit to a FET circuit.
 
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