Adding de emphasis to tube mic circuits

[ln76d]

Interesting Isnt the vintage U87 i polarisation voltage around 46V ish, lower than the 60V in the more modern Ai U87.
I read several peoples opinions that that is the reason its sounds better, better low end more musical sound due to more relaxed diaphram, Im aware or the noise penalty.I was thinking maybe thats why this crappier capsule sounds good in the 87i circuit.

ehhh...
Less read more work.

Reading about someone subjective feelings, for me, is worth the same as reading teenage girl diary...
These statements could be worth anything if they will be about flat circuit.
Two main capacitors in deemphasis circuit are different for both version of U87...

A while back when I got the cheap K67 I tried it in a valve mic with 60V polarisation voltage & plate to ground caps installed & it didnt sound good, to me all my DIY tube mics have more detail in the high end than any of my FET mics I thought this well contributing to making it sound shrill.

Because all depends on the circuit. That's why i don't agree with all universal "recipes".
For example my G7 with k47 "type" capsule is polarised by 50,5V. In this circuit it sounds the best. Same capsule in other circuits sounds best at 60V, 65V, 70V etc.

Im going to re try the cheap K67 in a Ela mic I have as I said I already have the plate ground caps installed I have a 3 way switch cant remember the values I those, think one value same as K49 other same as original Ela s cap value & maybe something inbetween, i will check.

What's the "value same as K49"?

If you want a hi-end mic don't spend time here go to tweak

 

[afdobbert]

I'm not so sure about that 150p cap in the C-800G

http://www.freeinfosociety.com/electronics/schematics/audio/pictures/sonyc800g.gif

dangit, foiled again!

 

[gary o]

Interesting Isnt the vintage U87 i polarisation voltage around 46V ish, lower than the 60V in the more modern Ai U87.
I read several peoples opinions that that is the reason its sounds better, better low end more musical sound due to more relaxed diaphram, Im aware or the noise penalty.I was thinking maybe thats why this crappier capsule sounds good in the 87i circuit.

ehhh...
Less read more work.

Reading about someone subjective feelings, for me, is worth the same as reading teenage girl diary...
These statements could be worth anything if they will be about flat circuit.
Two main capacitors in deemphasis circuit are different for both version of U87...

Less read more work done both I read many time people saying prefer the lower vintage 87 for various reasons they are not my opinions and so I do go and build & draw my own humble opinions & build to my taste, that is why I am here.
I happen to prefer the vintage 87 weather its because of lower polarisation voltage I dont maybe because of lower OP you hear mic pre more, but thats just my preference in sound.

A while back when I got the cheap K67 I tried it in a valve mic with 60V polarisation voltage & plate to ground caps installed & it didnt sound good, to me all my DIY tube mics have more detail in the high end than any of my FET mics I thought this well contributing to making it sound shrill.

Because all depends on the circuit. That's why i don't agree with all universal "recipes".
For example my G7 with k47 "type" capsule is polarised by 50,5V. In this circuit it sounds the best. Same capsule in other circuits sounds best at 60V, 65V, 70V etc.

Im going to re try the cheap K67 in a Ela mic I have as I said I already have the plate ground caps installed I have a 3 way switch cant remember the values I those, think one value same as K49 other same as original Ela s cap value & maybe something inbetween, i will check.

What's the "value same as K49"?

600pf as in M49b

After more more experiments tonight , I prefer my cheap k67 in the u87 circuit with its de emphsis rather than a tube mic with the plate to grounds caps

If you want a hi-end mic don't spend time here go to tweak

I think I tweaked enough for one night I tried 4 different capsules in 4 different mic circuits I have my favs

have a good day

 

[micaddict]

You're doing just fine, Gary.

And keep it coming.

 

[gary o]

Thanks henk 

Do keep us posted. 

What Chinese mic did you rescue the capsule from?

I couldnt remember where I got it but then afdobbet s post reminded me, I think it came from chunger.....& now I realize its not your usual china K67 , it sounds quite nice fantastic for the money in fact.

The reason I took mine out of the draw is I have this spare U87i circuit with the real deal neumann tran inside it & i thought the capsule will have the honk & I will iron it out with the de emphasis. Turn out it doesnt need it, its sound good as is. A friends wants me to mod a cheap mic he has I will build U87 front end in his mic ,thats another project.

Thanks.

 

[micaddict]

Yes, the one chunger offers seems to be a good one. Kidvybes is pretty fond of it and he has a good eye/ear for value for money capsules and microphones.
Here's the info from chunger's site:

35MM K67 Type Center Terminated Capsule:

We also offer a high quality 35mm K67 based capsule manufactured in China. This 6 micron capsule is well regarded by a number of microphone manufacturers and the sound quality is excellent.

The larger diameter and other improvements to the backplate design create less of a pronounced treble lift than the original K67 design allowing this capsule to be 100% useable and quite nice in flat response circuits.

This would imply it's usuable with standard Ela M and M49 circuits, but not with the standard U87 circuit. Unless you ligten up the de-emphasis in the latter, of course.  Or if you're looking for a darkish mic.

 

[micaddict]

Found a picture in chunger's White Market thread.
It doesn't seem to have isolated backplates.

 

[Gus]

I posted a circuit years ago.

 

[micaddict]

I posted a circuit years ago.

Then you probably have it close at hand. 

 

[gary o]

Yes, the one chunger offers seems to be a good one. Kidvybes is pretty fond of it and he has a good eye/ear for value for money capsules and microphones.
Here's the info from chunger's site:

35MM K67 Type Center Terminated Capsule:

We also offer a high quality 35mm K67 based capsule manufactured in China. This 6 micron capsule is well regarded by a number of microphone manufacturers and the sound quality is excellent.





The larger diameter and other improvements to the backplate design create less of a pronounced treble lift than the original K67 design allowing this capsule to be 100% useable and quite nice in flat response circuits.

This would imply it's usuable with standard Ela M and M49 circuits, but not with the standard U87 circuit. Unless you ligten up the de-emphasis in the latter, of course.  Or if you're looking for a darkish mic.

Regarding the U87 circuit personally I like it  without the de emph you get the bonus of higher op better sn ratio too.

Found a picture in chunger's White Market thread.
It doesn't seem to have isolated backplates.

Yes not isolated back plates but can wire accordingly.I cant believe how good it is for the money very usable, I bought to play with expecting to pull it apart, but will use it now.

 

[ln76d]

without the de emph you get the bonus of higher op better sn ratio too.

Could you elaborte, how this is possible?
Neumann deemphasis is basicaly feedback, so with the feedback you should have higher output, better self noise.

 

[micaddict]

I do believe the reasoning behind the design was similar to that of Dolby noise reduction.

 

[ln76d]

I do believe the reasoning behind the design was similar to that of Dolby noise reduction.

I do believe, that i don't know what you tlking about

Could you also elaborate?

 

[micaddict]

I mean lifting (or making more sensitive to) treble first and then attenuate it, in order to reduce noise.

 

[ln76d]

aaa, ok, now i get it

I believe that Neumann designed k67 for easier manufcturing.
It's much more simple (cheaper?) design (resonator pattern) than k47.
Then they had to find the way to reduce hf bump.

 

[micaddict]

I'm pretty sure the HF lift was deliberate.

And the Neumann technicians at the time were first class to say the least.

The double backplate was for easier matching of both sides, but that's another matter.

 

[gary o]

What I mean by SN ratio is mic has higher output than with de emph I engaged so you dont have to have your mic pre/ compressor whatever is in your chain up as high, if Im misunderstood then Im sorry , Im here to learn & do DIY 

 

[ln76d]

What I mean by SN ratio is mic has higher output than with de emph I engaged so you dont have to have your mic pre/ compressor whatever is in your chain up as high, if Im misunderstood then Im sorry , Im here to learn & do DIY 

As most of us, that's why debate like this is usefull for everyone i think.
I hope, that you don't think it is about who have the right

But, about the deemphasis, did you mean whole feedback or capacitor only?

 

[ln76d]

I'm pretty sure the HF lift was deliberate.

And the Neumann technicians at the time were first class to say the least.

The double backplate was for easier matching of both sides, but that's another matter.

Probably you are right

http://www.vintagewindings.com/gen%20pop/8299543VW8335/ProAudio1/Neumann%20Tube%20Mic%20History.pdf

 

[micaddict]

Actually, the pre-emphasis/de-emphasis, negative feedback design in a U67 goes a step further than  just lifting and rolling off. And perhaps that's why some experience it as darker than the frequency plots for the three patterns suggest.
The louder the trebles you throw at it get (particularly transients) the harder (darker) it fights back.