SE Electronics SE 2000

[Tim Parkes]

Thanks LevinGuitar - I read about another suggestion for C3 at 680pf with someone saying:
Replace the stock C3 cap (220 pF) with a 680 uF one. This acts as a high-shelf EQ starting just before the siblant region. Around a -3 db shelf. This really brings that hyped high end back down to something listenable.

I might try this at a later date also just to test the theory. My soldering skills are improved since beginning this project.

 

[Khron]

Sounds (no pun intended) a lot like this:

https://groupdiy.com/threads/akg-perception-p220-to-neumann-u87-5-min-mod-p200-p100-p400-p420.67473/

 

[LevinGuitar]

Yes, very good thread with a lot to learn from, but 680 pf is quite a lot, try it.

Best you could do is to remove all pnp section and use the rest to implement original U87 circuit. With the stock circuit mods there will be changes, yes, but never good enough to be truly happy with it (at least for me).

https://messageboard.tapeop.com/viewtopic.php?t=81385

 

[Tim Parkes]

Sounds (no pun intended) a lot like this:

https://groupdiy.com/threads/akg-perception-p220-to-neumann-u87-5-min-mod-p200-p100-p400-p420.67473/

Thanks for this!

I ordered an electrolytic 680pf cap for this - i’m on 48V so went for 50v because of dimensions and as I’d used one elsewhere and I’m a fan of them from a basic valve amp repair I did last year. (Pots change and Capacitors for Panasonic)

So could you clarify which to change - C3 from 330pf currently to 680pf
or
C6 as the linked thread to Perception circuits?

They are a different circuit aren’t they?


On a final note, I had a listen again today through the mic and found that it is when the gain is increased that the white noise increases (obvs) but i seems to be about keeping the gain low.

 

[Tim Parkes]

Yes, very good thread with a lot to learn from, but 680 pf is quite a lot, try it.

Best you could do is to remove all pnp section and use the rest to implement original U87 circuit. With the stock circuit mods there will be changes, yes, but never good enough to be truly happy with it (at least for me).

https://messageboard.tapeop.com/viewtopic.php?t=81385

Thanks for this,
I’m quite enthusiastic about the idea of changing the front end. Thanks .

 

[Tim Parkes]

Thanks for this,
I’m quite enthusiastic about the idea of changing the front end. Thanks .

Replying to self:
Here’s where my autism makes me miss nuance. @LevinGuitar
I understand exactly now what you mean.
As I like to follow one thing at a time, I hope you’ll be pleased to know that I’m doggedly sticking to method as you suggested, in reverse from 330pf to 230pf.
I’m way below biasing FETs in my skills and understanding so far, and I suppose if I don’t like the results I could go further.
I’ll try the 680, but not until I’ve really assessed as above. - and clarified C3 or C6?
Thank you

 

[LevinGuitar]

I would leave 270 or 330pf in C3, instead of the original 220pf and improve rest circuit to achieve more low end and less distortion.

C6 is the cap of the low cut, forget it.

The output of this mics is on the low side unless you completly change the biasing (not only adjusting) but I'm unsure if there are unwanted side effects.

 

[Tim Parkes]

Thanks @LevinGuitar - I tested the mic on a demo recently. Vocally it sounds more like I want with the 330pf Cap in there and the electrolytic cap you suggested too. It sounds much better than when I started out, a little ‘pinched’ in some way, not a bad sound, just different.
I expect it is in biasing that I could change more of the colouration.

So far so good

 

[Tim Parkes]

I took the chance and installed a 680pf Film Cap at C3.
it sounds loads thicker and actually very sensitive. Running through DBX 286s, nice preamp compression.

I have a question about potential wiring the capsule for omni (both sides connected to circuit.
I wonder if this circuit has appropriate voltage to power both diaphragms at once to achieve the Omni sound?

It’s now a really usable mic, RK47 Capsule, and two caps changed so far.

@LevinGuitar - this u87 front end mod, I think I found the thread a little confusing, a couple of comments swept-in with suggested changes that confused the heck out of me.

I’m very interested in getting more signal and sensitivity from the mic.

I’ll try and post sound samples soon.

 

[LevinGuitar]

I would not use a k47 in this kind of circuit, but you loose nothing trying it. The polarization voltage will be same in cardioid or omni. After the change of the circuit into a U87 style, you can use original value on C3. Also you can try a jumper over the imput cap (1000pf).

The only thing I don't see in the Front End mod thread is the change to a higher gain fet like the 2N3819 is. Guess the original one will give you a very low output.
Good luck!