How Would You Modify or Simulate the Studio Projects C1 circuit???

[Paul678]

Here it is:

http://www.flickr.com/photos/drslick/8557187493/sizes/l/in/photostream/


I've read some people tune these to particular voices.

I know increasing C4 and C3 to 1uF will certainly help
the low end, and that R4 and C21 create an RC time
constant, and thus a low pass filter.

But I assume the best simulator for this would be
some sort of Spice simulation? I'm an RF guy,
so I could also use Microwave Office, but that
might be over-kill.

Thanks in advance...

 

[ricardo]

Are you certain you've traced the circuit correctly?

Not sure where this one comes from.

 

[Paul678]

Are you certain you've traced the circuit correctly?

Not sure where this one comes from.

Someone else reverse engineered this from their C1.

Do you have a better, more accurate schematic?

 

[ricardo]

I'm suspicious of both schematics.  I don't have a C1 so can't confirm.

But your circuit shows a single switch when the Studio Projects data shows 2 switches.  One for 10 & 20dB pads and another for 75 & 150Hz filters.

 

[Paul678]

I'm suspicious of both schematics.  I don't have a C1 so can't confirm.

But your circuit shows a single switch when the Studio Projects data shows 2 switches.  One for 10 & 20dB pads and another for 75 & 150Hz filters.

Good point.  It may be an older model, that only had one switch.  Not sure....

 

[Gus]

Looks something like the MXL2003 schematic
I traced my 2003

 

[ricardo]

Good point.  It may be an older model, that only had one switch.  Not sure....

OK.  Now makes more sense.  I think your schematic switch is the wrong way round.

C19 in parallel with the capsule reduces sensitivity without changing response.

The other network involving C8 is similar to the HPFs on the other schematic but seems to be fed to the wrong end of the capsule.

Steve Bore of Neumann describes how this works in my MicBuilders directory under ChinaMod+U87hybrid

Is your switched actually marked 'low shelf'?

 

[Paul678]

Good point.  It may be an older model, that only had one switch.  Not sure....

OK.  Now makes more sense.  I think your schematic switch is the wrong way round.

C19 in parallel with the capsule reduces sensitivity without changing response.

The other network involving C8 is similar to the HPFs on the other schematic but seems to be fed to the wrong end of the capsule.

Steve Bore of Neumann describes how this works in my MicBuilders directory under ChinaMod+U87hybrid

Is your switched actually marked 'low shelf'?

    Well, I don't have the mic yet.  I'm just doing some research to see if the
circuit can be improved, before I plunk down another $150 (used) or $250 new.

    However, maybe people are happy with this microphone totally stock....they
don't modify anything.  Some supposed professionals even compare this mic
favorably to the U-87.

 

[ricardo]

Well, I don't have the mic yet.  I'm just doing some research to see if the circuit can be improved, before I plunk down another $150 (used) or $250 new.

Some very experienced recording engineers whom I trust and who have much experience with vintage Neumann & AKG in some very famous recordings, like the standard C1.

If I was modifying a mike or speaker, I would always have 2 and check first that they sound identical.  Then modify one and compare with the unmodified.  That way you don't fool yourself that whatever Golden Pinnae stuff you swap in (including new capsules) sounds better.

Its unlikely you will hear a difference with bigger C3/4 except the bigger caps might overload the mike earlier with subsonic rubbish.

C20/21 are for RFI reasons.  There are better ways to tame a K67 capsule's HF screechiness.  eg my ChinaMod+U87hybrid in MicBuilders

 

[Paul678]

Well, I don't have the mic yet.  I'm just doing some research to see if the circuit can be improved, before I plunk down another $150 (used) or $250 new.

Some very experienced recording engineers whom I trust and who have much experience with vintage Neumann & AKG in some very famous recordings, like the standard C1.

If I was modifying a mike or speaker, I would always have 2 and check first that they sound identical.  Then modify one and compare with the unmodified.  That way you don't fool yourself that whatever Golden Pinnae stuff you swap in (including new capsules) sounds better.

Its unlikely you will hear a difference with bigger C3/4 except the bigger caps might overload the mike earlier with subsonic rubbish.

C20/21 are for RFI reasons.  There are better ways to tame a K67 capsule's HF screechiness.  eg my ChinaMod+U87hybrid in MicBuilders

My method for my SP-1 was to record each stage of the modifications, to see their effect, while singing
the same song, and playing the same acoustic guitars.

You can definitely hear an improvement, but as I said in my other thread, the old capsule
is usable for sure.

 

[RuudNL]

There is certainly something missing in this schematic.
Both the DC converter and the FET stage are not getting any supply voltage!