A very versatile input stage for SDC mics

[kingkorg]

Kingkorg's example from a plosive into an SDC produced over 22Vpp. I would think close miking a drum, trumpet, or vocal without a suitable screen would necessitate some means of limiting the signal or deal with a 30 to 140+ dBspl dynamic range.
In that scenario a step down conversion may be useful.
My schematic had two caps in series with the signal where only one is needed to avoid DC magnetization of the core.

There are some real benefits from very close miking sources like snare drums and combining takes with traditionally placed snare mics. People have mostly stayed away from this because of phase issues (which i never understood as you can phase align stuff in post) and because each and every condenser i tried craped out at this position (milimeters away from the head). Dynamics are too bulky, and don't have enough high end detail.

Combining these mics by mixing them at different levels, playing with ADSR, and placement you get a sort of snare design tool and can avoid bleed and control different aspects of the sound such as initial snap transient, ring, rim....

My latest project for a band i produced lead me to this approach as the drummer was a total wuss on the snare, and as usual every cymbal's worst nightmare. Needless to say, the absolute non-negotiable thing was NO SAMPLES!

Just when i thought i was covered with mics, this opened another can of worms.

 

[abbey road d enfer]

each and every condenser i tried craped out at this position (milimeters away from the head).

I use a dpa2011 and have no such issues.

I'm not sure I understand what you mean by "the drummer was a total wuss on the snare"...
Do you mean he didn't hit hard enough?
The customer says "no samples", which I accept (I'm not particularly a fan of drum replacement) and lets you with a bad drummer, it's a recipe for disaster.
No mic is capable of solving this.

 

[kingkorg]

I use a dpa2011 and have no such issues.

I'm not sure I understand what you mean by "the drummer was a total wuss on the snare"...
Do you mean he didn't hit hard enough?
The customer says "no samples", which I accept (I'm not particularly a fan of drum replacement) and lets you with a bad drummer, it's a recipe for disaster.
No mic is capable of solving this.

Exactly that. Extreme close miking saved the day. I used one close mic just for the attack + HF boost, another one for the decay, this one was close to the rim and had tons of ring. Kind of caveman's Transient Designer. Both had miniscule amount of hi hat bleed. Then I phase aligned these two to a traditionally placed sm57, and used them to enhance the snare sound without introducing additional bleed. It was a botch job, but gave excellent results.

Needless to say both of these close to the head mics sounded terribly on their own, but blended in with sm57 did wonders.

Couple of months ago I didn't have ideal mics for the job, and now i'm obsessing about making this a permanent setup.

 

[Cqwet Dbdfte]

Exactly that. Extreme close miking saved the day. I used one close mic just for the attack + HF boost, another one for the decay, this one was close to the rim and had tons of ring. Kind of caveman's Transient Designer. Both had miniscule amount of hi hat bleed. Then I phase aligned these two to a traditionally placed sm57, and used them to enhance the snare sound without introducing additional bleed. It was a botch job, but gave excellent results.

Needless to say both of these close to the head mics sounded terribly on their own, but blended in with sm57 did wonders.

Couple of months ago I didn't have ideal mics for the job, and now i'm obsessing about making this a permanent setup.

How did you get the 22Vpp into the mic pre?

 

[Khron]

Probably external mic psu and audio going into a (padded) line input?

 

[kingkorg]

How did you get the 22Vpp into the mic pre?

I didn't get most probably anywhere close to that, he was playing softly which was the issue to begin with. On the other hand, i have mic pres with pads so that is unlikely to be a problem. I just want to prepare myself for these kinds troubles in the future.

 

[abbey road d enfer]

I just want to prepare myself for these kinds troubles in the future.

IMO you should warn your customers GIGO. They shouldn't expect a good production from lousy musicians.
You may lose a few customers but keep your hair.

 

[schsz]

If you are interested in "repair kits" (board and all components together in a package) send a PM

It's been a while since MicUlli made these boards.
Has anyone made similar ones since? I'd be very interested. I have several EM21 capsules I'd like to revive.

 

[MicUlli]

It's been a while since MicUlli made these boards.
Has anyone made similar ones since? I'd be very interested. I have several EM21 capsules I'd like to revive.

Yes I made these boards a long time ago. Several kits are still available.
You have to be aware that the boards deliver a polarisation voltage around 39V. Using Primo EM21 capsules may cause problems with voltages above 25V (membrane collapse). Decoupling at the input with a 1nF 50V NP0 ceramic cap can help, still not tested yet..

 

[micro1_de]

Ulli has been so kind to give me 6 boards. Here are the boards (5) and the finished mics. Buildung is very easy and the sound and technical data are really outstanding! Thanks Ulli! Reiner

 

[MicUlli]

Hi Reiner,
thanks for your kindness
I am glad to have an additional MBHO-Fan in this forum. The boards you have manufactured look very fine, enjoy recording with these outstanding microphones.
Best regards MicUlli

 

[Caviar]

Yes I made these boards a long time ago. Several kits are still available.
You have to be aware that the boards deliver a polarisation voltage around 39V. Using Primo EM21 capsules may cause problems with voltages above 25V (membrane collapse). Decoupling at the input with a 1nF 50V NP0 ceramic cap can help, still not tested yet..

Hi, i'm interested to revive mics i have with Primo em21 and em23 capsules. Do you have tested your circuit with the decoupling cap with these ?
Thanks !

 

[MicUlli]

Hi, i'm interested to revive mics i have with Primo em21 and em23 capsules. Do you have tested your circuit with the decoupling cap with these ?
Thanks !

Yes i did some minutes ago But: you have to spend an additional BAV199 dual diode. One side connected to the 1nF cap and the electret capsule wire and the other side to the node of R2 and R3..
This gives a pol voltage of 13V at the capsule resulting in a sensivity rise of 1,7dB for EM21 and EM23. Works very fine.
Best regards MicUlli