Schoeps vs Alice

[LevinGuitar]

I'm trying to understand how affect using a capacitor to feed the output PNP transistors (C9 in original Schoeps) versus not using it like Alice circuit does.
I find that this cap affects the curve response and increase THD (the 47uf seems to be a selected value for this circuit, I tried different values and this one works the best) but removing it makes the mic cleaner and way brighter at first (I'm talking about any Chinese mic that uses this circuit). Increasing the value of C2 and C3 as the Alice does from the original 0.1uf helps to bring the low end back but here there is a problem, the bigger value, better low end, and after 4.7uf is hard to find a film capacitor that would fit any mic. Maybe 10-20uf would be enough to have a similar low end to a circuit with that C9 47uf cap or not, I don't know. 3.3-4.7uf are quite ok and there are some 50v caps that are small enough to fit in many mics. Using a electrolythic, even a good one, results in a downgrade of the sound, no matter what value we use (I tried up to 100uf), so it must be a film one.

Does anyone have experimented with this?
I definately like more the sound removing that cap and increasing C2 and C3 value, but in some mics, without the respective C9 cap, there are a low noise. Where it can comes from? In the old NT2 there are no noise issues with this mod.

 

[Екатерина]

In my impression, C9 only filters the noise generated by D3 and D4 Zener diodes, maybe it is the noise that makes the low-end bad. The default value of C2 and C3 in this circuit is 0.3μF instead of 0.1μF. In addition, removing or reducing C4 and C5 can expand the high-end frequency band. Reducing the noise can change the triode model to remove the Zener diode, in general, this is a plain and straightforward sound, with a suitable infinity electrolytic capacitor 4.7μF instead of C2 and C3 will make the sound warmer and softer, I wish you have fun

 

[abbey road d enfer]

I'm trying to understand how affect using a capacitor to feed the output PNP transistors (C9 in original Schoeps) versus not using it like Alice circuit does.
I find that this cap affects the curve response and increase THD (the 47uf seems to be a selected value for this circuit, I tried different values and this one works the best) but removing it makes the mic cleaner and way brighter at first (I'm talking about any Chinese mic that uses this circuit). Increasing the value of C2 and C3 as the Alice does from the original 0.1uf helps to bring the low end back but here there is a problem, the bigger value, better low end,

Do you have evidence of it, like frequency response graphs or noise measurements?
It seems quite strange to me.
As mentioned in the previous post, this cap should affect only noise. If it affects frequency response, I would think it shows a sign that something is not correct in the overall implementation.

I definately like more the sound removing that cap and increasing C2 and C3 value, but in some mics, without the respective C9 cap, there are a low noise.

That is to be expected.

Where it can comes from? In the old NT2 there are no noise issues with this mod.

Do you have a schematic of this "old NT2" to show?

 

[LevinGuitar]

I found the schematic of the NT2 on KingKorg's post here:

https://groupdiy.com/threads/nt2-upgrades-which-is-better.72611/post-919641
No, I have no measurements, so I set this question here if someone want to check it out, my ears can betray me and bigger C2 and C3 maybe just smooths high end that is smoothened otherwise with C9. But there are definately more coloration

I tried removing D3 and D4 and it made no change with that noise, also tried a filter after D5, but neither it help, only using a cap over 1uf. It was in a B2pro mic with some mods triying to turn it into a B2.

 

[abbey road d enfer]

I found the schematic of the NT2 on KingKorg's post here:

https://groupdiy.com/threads/nt2-upgrades-which-is-better.72611/post-919641

This schemo shows a 47uF capacitor there.

I tried removing D3 and D4 and it made no change with that noise

D3 and D4 are there for protecting the transistors base junctions. Without them, the transistors may become noisy.

, also tried a filter after D5, but neither it help,

Do you mean an additional RC filter? That would not work very much.

 

[LevinGuitar]

This schemo shows a 47uF capacitor there.

D3 and D4 are there for protecting the transistors base junctions. Without them, the transistors may become noisy.

Do you mean an additional RC filter? That would not work very much.

Yes, the 47uf is the same value I found in all Schoeps inspired mics. The idea is what happens just removing it (when there are no noise issues as side effect). In this mic (NT2) it worked without issues. I started having noise increasing D3 zener from 6.2v, but up to 7.5v it was ok

 

[ct.waveform]

I'm trying to understand how affect using a capacitor to feed the output PNP transistors (C9 in original Schoeps) versus not using it like Alice circuit does.
I find that this cap affects the curve response and increase THD (the 47uf seems to be a selected value for this circuit, I tried different values and this one works the best) but removing it makes the mic cleaner and way brighter at first (I'm talking about any Chinese mic that uses this circuit). Increasing the value of C2 and C3 as the Alice does from the original 0.1uf helps to bring the low end back but here there is a problem, the bigger value, better low end, and after 4.7uf is hard to find a film capacitor that would fit any mic. Maybe 10-20uf would be enough to have a similar low end to a circuit with that C9 47uf cap or not, I don't know. 3.3-4.7uf are quite ok and there are some 50v caps that are small enough to fit in many mics. Using a electrolythic, even a good one, results in a downgrade of the sound, no matter what value we use (I tried up to 100uf), so it must be a film one.

Does anyone have experimented with this?
I definately like more the sound removing that cap and increasing C2 and C3 value, but in some mics, without the respective C9 cap, there are a low noise. Where it can comes from? In the old NT2 there are no noise issues with this mod.

0.47uF into 100k gives you 3.4Hz as your -3dB point. That should be plenty low enough. 4.7uF is obviously 0.34Hz. First of all I would be amazed if you can hear the difference between the two, however low your speakers go (and that's not usually much below 40Hz) but, more importantly, there are a number of good reasons not to try and press things this far electronically. You are likely not getting a more faithful transcription of the audio (or more actual bass on the recording) and are probably introducing all sorts of other deleterious possibilities. And if you are using film caps then you want them to be as physically small as possible or they'll pick up all sorts of fields. The mic body should not be your limiting factor. LOL. If you really are intent on pushing it, I would say 1.6uF is the absolute limit, which is a round 1c/s.