ln76d

Re: Mic Project Idea
« Reply #20 on: December 24, 2016, 09:49:44 AM »
Thanks everyone for your suggestions.  Something came to mind tonight.  I think that the AKG capsules polarize at 62V, but I believe that the KM84 circuit is 48V.

Will the AKG capsules work with the Neumann voltages, and if so, will this affect the sound?  Perhaps the pcb for this project would have to have a voltage converter for the proper AKG polarization voltage.

Capsule will be working without any problem with 47Vbut can sound different (maybe even better in hi freq area).
You can also add simple DC converter for KM84 circuit.

You might look at using 0.1uf C0G capacitors in parallel. Mouser carries both 50V and 100V parts in the 1206 form factor. If you're willing to do a little SMD, you should have no trouble fitting 10 in parallel on the back of the PCB.

IIRC, they're around a buck each, so at $10 for a 1.0uf cap you're still well in under the price of most fancy foil caps.

WHAAATTTT FOOORRR??????


gabasa

Re: Mic Project Idea
« Reply #21 on: December 24, 2016, 10:41:49 AM »
Lol....!  Just last night I was looking at 1uf MKC 1860 metallized polycarbonate capacitors on eBay. 
Any thoughts?

ln76d

Re: Mic Project Idea
« Reply #22 on: December 24, 2016, 10:49:00 AM »
MKC have poor dielectric, much worse than MKT.
You need also think about capacitor size, since it's sdc.

Look for Evox Rifa MMK, believe me you want it.

lso it don't have to be 1uF. Look from 470nF-1uF range.
From my experience lower capacitances before transformer works better.
Should be no difference in low end response.

Dylan W

Re: Mic Project Idea
« Reply #23 on: December 24, 2016, 04:28:37 PM »
WHAAATTTT FOOORRR??????

Maybe sounds a little crazy, but they're guaranteed to fit and should be the best dialectric that will fit, about as good as polyprop or polystyrene and much better than polyester, at least quantitatively (see the CB articles).

Then again, I haven't compared polyester and polypropylene head-to-head in mic coupling applications. Interested to know what you heard with polypropylene that made you dislike it. (My fav DIY mic has a tantalum coupling cap... so lower distortion, lower dissipation factor, etc, is obviously not always better, though in a semi-scienctific blind test I did once--preamp output coupling cap--I found a polyester box cap to be subjectively musically inferior to polypropylene).

Dylan W

Re: Mic Project Idea
« Reply #24 on: December 24, 2016, 04:29:49 PM »
Also, I was wrong about the price--in quantity 10, the 50V part is $0.30.

3 bucks ain't bad for a 1u C0G cap.

gabasa

Re: Mic Project Idea
« Reply #25 on: December 24, 2016, 08:23:47 PM »
Look for Evox Rifa MMK, believe me you want it.

so it don't have to be 1uF. Look from 470nF-1uF range.

Ok thanks, if I use a metallized cap here, then the MMK seems to be the way to go.
Would a great foil cap be massive overkill?  I actually think that a 100V RelCap TFT could fit inside with a small cutout in the pcb.

I'm not an EE, and I was wondering how that cap value affects the frequency response.  It's not wired up as a filter, is it?

ln76d

Re: Mic Project Idea
« Reply #26 on: December 25, 2016, 07:40:02 AM »
Maybe sounds a little crazy, but they're guaranteed to fit and should be the best dialectric that will fit, about as good as polyprop or polystyrene and much better than polyester, at least quantitatively (see the CB articles).

Then again, I haven't compared polyester and polypropylene head-to-head in mic coupling applications. Interested to know what you heard with polypropylene that made you dislike it. (My fav DIY mic has a tantalum coupling cap... so lower distortion, lower dissipation factor, etc, is obviously not always better, though in a semi-scienctific blind test I did once--preamp output coupling cap--I found a polyester box cap to be subjectively musically inferior to polypropylene).

You will don't get any improvement using ten SMD capacitors than one good film cap.
First of all - connection - man - make ten SMD in parallel is  totally mess.
Also it's 18 additional soldering points.
Make even only one colder joint...
I wouldn't be so much afraid "distortions" from datasheets...
If you have read CB articles, find comparison measurements between Evox Rifa MMK and Electrolytic cap.
Of course the best capacitor is no capacitor at all. But sometimes ├╝ber capacitors or higher values are not corresponding to the overall sound quality. All A/B tests i did with several different capacitors at the output, before transformer, gave me same result.
Polypropylene sounds worst (Wima, ROE, JB, Mundorf, Hovland and many more). Sound was just more dull in whole audible spectrum.
MKC was the worst, but in different way than polypro.
Polyester was better but the best always was metal paper. In many other applications and circuits polypropylenes were usual better. Also i'm using C0G/NP0 and many other different types.
Never found any improvement using tantals. Rather unpleasant sound.  Big improvement in C414EB P48 is replacing output cap from tantal to MMK polyester. It's audible difference, not only subtle "something".
Even in simple fiiters in dynamic Sennheiser MD441 polyester sounds better than tantals. Or D202, D224 etc.
Get few caps, rotary switch (few positions) and make A/B in working circuit then you will know what you like or dislike or do you hear any difference. Don't trust me, CB or any one else - find your own sound ;)
For some time there was a hype for oversized capacitors in blind "modifications". Usual it sucks. If you will take 470nF and 1uF for comparison in most of the circuits you will probably get the same low end response at leat to 20Hz. But overall sound in whole spectrum can be really different. You can also make A/B and measure electronic response of the circuit.
For electrolytics i never found anything better than Elna Silmic.

Ok thanks, if I use a metallized cap here, then the MMK seems to be the way to go.
Would a great foil cap be massive overkill?  I actually think that a 100V RelCap TFT could fit inside with a small cutout in the pcb.

I'm not an EE, and I was wondering how that cap value affects the frequency response.  It's not wired up as a filter, is it?

Think first about the sizes of capacitors, make PCB model in eagle or similar software.  You can be surprised how much size simple circuits can eat. Especially if you would like to use additional dc converter.
It's high pass filter. For the rest see above.
For SDC i would also use MKT for C3 - 2.2uF or 3.3uF is enough.

gabasa

Re: Mic Project Idea
« Reply #27 on: January 04, 2017, 07:53:57 PM »
Thanks everyone for your help; I'll let you know how it all goes!