U87 with a breakout box?

[mateus]

Hello guys,

I'm not sure if that's possible but an idea came to my mind. Lots and lots of times I like checking how each pattern of my U87 sound in each source before recording, cardioid, omni and fig. 8, going for the one I liked the best. Ok, that takes me to problem 1, getting out of my chair, changing it, listen again, back and forth and I already lost perspective... It would be nice if I could change it without moving out of my listening position, since sometimes you just lose the momentun comparison, yeah, I could record and listen each one, but then comes performance issues, asking for someone change it on site? Won't work for me, there's pops and other noises sometimes. Problem 2, what if I set for one and during mix down I start feeling "argh, omni would have been best"... You get my point? So I started thinking about building a new U87 where I could have a breakout box close to me, or even better, 2 channels, 1 for each backplate...

Am I dreaming or is it possbile?

Cheers!

 

[abbey road d enfer]

Am I dreaming or is it possbile?

Of course it is. You would have to make two pieces of head amp, which is not terribly difficult, but you would need to make a specific enclosure, unless you opt for a different, more compct design. There are a few similar projects going at the micbuilders group.

 

[RuudNL]

Maybe I don't get your point, but IMHO it isn't necessary to add an additional circuit.
The front membrane is always active (also in the omni- and figure-8 setting).
So what you would have to do is:
- Switch the rear membrane on or off. (In cardioid the rear membrane isn't connected)
- Vary the polarisation voltage on the rear membrane, so you will get omni-cardioid-figure-8 and any pattern in between.

You could eventually keep the rear membrane permanently connected, but in that case you offer a few dB signal to noise ratio (and sensitivity) in the cardioid position.
As long as you change the polarisation voltage on the rear membrane 'slowly' (R-C filter), there should be no pops. Only a minimal delay of a few seconds.

 

[abbey road d enfer]

Maybe I don't get your point, but IMHO it isn't necessary to add an additional circuit.

Indeed it would answer the first question, but having two signals would answer "problem Nr2".
Allowing to choose pattern at a later time is a big selling argument for the proponents of recording both sides of the capsule separately.
However, I'm not a big fan of delaying decisions. If there are too many choices at mixdown, one gets lost and loses focus IMO.

 

[mateus]

Indeed it would answer the first question, but having two signals would answer "problem Nr2".
Allowing to choose pattern at a later time is a big selling argument for the proponents of recording both sides of the capsule separately.
However, I'm not a big fan of delaying decisions. If there are too many choices at mixdown, one gets lost and loses focus IMO.

Totally agree! I try making decisions as I go but there have been far too many times I would rather making the decision after seeing the big picture during a rough mix.

Cheers!

 

[Gus]

This has been posted about at this forum. look for the TLM67 thread with two outputs and other microphones with two amps
set gain for each, mix, mix inverted to change the pattern after you record with both cardiods.
Some modeling microphones have two outputs. IMO the only way to do real modeling is two have both outputs.
And something a little different
http://www.josephson.com/pdf/srs7.pdf

 

[mateus]

Cool! Ok. This will sound dumb but I need to make sure... Can I power both circuits simultaneously with my phantom right? Should I think about some special output trafo for avoiding using 2? Any idea on how could I squeeze 2 U87 boards into a single body or do I need to draw a new dual board for avoiding longer cables?

Cheers!

 

[soliloqueen]

Cool! Ok. This will sound dumb but I need to make sure... Can I power both circuits simultaneously with my phantom right? Should I think about some special output trafo for avoiding using 2? Any idea on how could I squeeze 2 U87 boards into a single body or do I need to draw a new dual board for avoiding longer cables?

Cheers!

You'd need to edit the circuit a bit. depending on how you did it, you'd probably end up with something more like 2 km84 circuits with HF feedback

 

[abbey road d enfer]

Cool! Ok. This will sound dumb but I need to make sure... Can I power both circuits simultaneously with my phantom right? Should I think about some special output trafo for avoiding using 2? Any idea on how could I squeeze 2 U87 boards into a single body or do I need to draw a new dual board for avoiding longer cables?

Well, if you want to retain the possibility to change pattern after the fact, you need to record two signals, so you need two channels, each powering one head amp.
Now it you just want to control on the take, you should use RuudNL's suggestion. You can change the pattern remotely by just changing the voltage and polarity of the rear capsule, and of course, you need only one channel and one head amp.

 

[mateus]

For now I have a pair of U87s I built using all resources from this magic community, Dany's PCBs, Chunger bodies, AMI trafos, Heiserman's capsules and all the good stuff. Amazing sounding mics and huge compliment to my humble mic locker.

What I'm thinking is about building a 3rd one, this time one that can allow me recording both backplates isolated.

I just have no idea how to do it hehe

Cheers!

 

[RuudNL]

Maybe first think about how the pattern of the C12 can be changed remotely.

 

[abbey road d enfer]

What I'm thinking is about building a 3rd one, this time one that can allow me recording both backplates isolated.

I just have no idea how to do it hehe

You need two head amps, one for each side of the capsule. As I wrore earlier, the first challenge is finding an enclosure large enough for two PCB's. An alternative is to use an Alice circuit, which is much smaller, but it's not the same sonic signature as the original U87 circuit.
Typically, this type of construction uses a 5-pin XLR and an adapter for 3-pin XLR's.

 

[ubxf]

this project by Kingkorg might be helpful
https://groupdiy.com/threads/quick-diy-dual-output-ldc.69193/

 

[k brown]

How about having only the two FETs in the mic's body, and the rest of the circuit in an external enclosre?

 

[mateus]

Cool, I was going for an Alice anyways so I guess I'll start with it, once I get a good look at the idea I see what else I can think of.

Maybe a C12 style long body would work? maybe I can try getting the SYT Gen 3 head basket installed in one of those bodies. If that would work I would need 2 trafos too right?

Cheers!

 

[abbey road d enfer]

Maybe a C12 style long body would work? maybe I can try getting the SYT Gen 3 head basket installed in one of those bodies. If that would work I would need 2 trafos too right?

Alice is transformerless, that's why it makes for a very compact PCB.

 

[mateus]

Alice is transformerless, that's why it makes for a very compact PCB.

Sorry, I was referring and brainstorming about the idea for a possible dual output U87. Maybe I could fit all the boards inside a C12 style long body and still use the correct U87 headbasket, for that I would need 2 trafos too right?

As for the Alice I'll get one spare fake U87 bodies aliexpress have.

 

[abbey road d enfer]

Sorry, I was referring and brainstorming about the idea for a possible dual output U87. Maybe I could fit all the boards inside a C12 style long body and still use the correct U87 headbasket, for that I would need 2 trafos too right?

Of course.

 

[emrr]

https://groupdiy.com/threads/tlm67-modification-to-dual-output.68096/

 

[mateus]

Cool! Thanks a lot guys! I'll make a dual Alice 1st and then I'll start gathering the needed pieces for my dual U87 idea and gonna try document it here once I get started.

Cheers!