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Project Specific Discussions => Microphones => Topic started by: squarewave on June 15, 2017, 03:21:58 AM

Title: I need a microphone
Post by: squarewave on June 15, 2017, 03:21:58 AM
Hopefully I don't start a flame war with such a perilously vague question but I really need a mic to record just about everything including vocals, acoustic guitars, speakers (eg e-guitar). Right now I have one SM57 and that's it!

If you could have only one mic, what would it be?

I was thinking of a large-diaphragm cardioid FET + transformer a la U87 type mic but I have never used such a fancy mic so I will try to be open to anything.

Also it would be fantabulous if there were a $300 USD version of whatever it is. For example, does anyone have the Studio Projects C1? How does it compare to high-end large-diaphragm cardiod mics? Capsule, transformer, housing, ...?

I am a very capable builder so if there is a particular kit that everyone seems to like I would appreciate a pointer. But I would be equally happy to just buy something. I already have a few projects in the queue and I really just need a pro-level mic now.
Title: Re: I need a microphone
Post by: micaddict on June 15, 2017, 03:46:46 AM
Quote
I am a very capable builder so if there is a particular kit that everyone seems to like I would appreciate a pointer. But I would be equally happy to just buy something.

You're a very capable builder and you're asking this in the microphone section of a DIY forum.

"Just buy something" will likely not be the answer. ;D

Title: Re: I need a microphone
Post by: tmuikku on June 15, 2017, 04:22:13 AM
Whats wrong with the 57?:)
Best bet would be to buy used, any mic. If it doesn't work for you sell it and try another one. You can make profit or get even with most used mics you buy.

Any mic can be good or bad with given application. DIY mics don't have very good resale value i think (in general).
Title: Re: I need a microphone
Post by: micaddict on June 15, 2017, 04:24:14 AM
LOL

Seems I was wrong.
Title: Re: I need a microphone
Post by: Khron on June 15, 2017, 04:40:00 AM
Be it DIY or bought - "it's how you use it"... ;D
Title: Re: I need a microphone
Post by: tmuikku on June 15, 2017, 04:45:45 AM
LOL

Seems I was wrong.
  8)

DIY mics can be really good and cost less than a original classic. Very good capsule can cost 300$ alone though, which must be the most important factor for good sound.

If cost is not a problem one should build every classic mic, in pairs of course! These will last a lifetime and be a joy
Title: Re: I need a microphone
Post by: RuudNL on June 15, 2017, 04:53:00 AM
Buy a cheap LDC microphone (SP-1, MXL440 etc.) and exchange the capsule for a real good one.
That will give you an excellent microphone for a very reasonable price!
Optionally you can tweak the circuit, optimize the bias of the FET etc.
Title: Re: I need a microphone
Post by: micaddict on June 15, 2017, 05:05:23 AM
The fun factor anyone?  :P
Title: Re: I need a microphone
Post by: ln76d on June 15, 2017, 06:03:55 AM
From the cheap FET mikes  without need of modification last Rode NT1 (black) is really decent.
It's the first NT1 which stock  sounds ok. Of course it's specific like all Rode mikes but previous versions were nasty.
For mods, if you live in Europe,  i would go for t.bone sct 700 (tube) and rebuild the circuit (potentially change capsule for k47 or make eq for original capsule) or Fame C05 (FET) and change it for U87 circuit. Stock capsule is really decent if you make circuit properly. 3U Audio 10:1 transformer fit very well. Size is rather similar to U89 but it doesn't make huge difference.
For start those are pretty good options.
In SP C1 except pretty well made body but there's nothing exciting inside. Capsule is pretty good, but it use schoeps circuit.
Title: Re: I need a microphone
Post by: micaddict on June 15, 2017, 06:28:01 AM
OK, I'll play.
You mentioned $300. Is that a reference price point or could it cost somewhat more?

A used mic for 300 could be a 600 dollar mic or more if bought new. Depending on how much hurry there is.

If you buy new, I'd seriously look at 3U Audio microphones. The name was already dropped regarding transformers. But the owner, Guosheng Zhuang, makes whole microphones, too. He's a veteran capsule maker, so you shouldn't worry in that department. And his mics have discrete electronics of good quality. Furthermore, you buy directly from the maker, so there are no middlemen (wholesale, retail). I personally don't know better bang for the buck new mics.
His Warblers come in six different flavours, all with a large diaphragm capsule, either centre or edge terminated, and all tuned or voiced differently.  Plus they have one of the aforementioned trannies.
Cardioid only is about 270 including shipping and multipattern is 349, from the back of my head.

He also offers trannyless LDCs, for even less (129 single, 199 for a pair!).
http://www.3uaudio.com/ (http://www.3uaudio.com/)

Yes, modding is a good option, too. E.g. we recently had a long overdue thread about modding a Behringer B2 Pro.

All that said, if I were a very capable builder, which I have to admit I'm not (yet?), I wouldn't think twice and build myself a dream microphone or two.  :P :P :P
Title: Re: I need a microphone
Post by: micaddict on June 15, 2017, 06:56:28 AM
Oh, and a few workhorses to "bang around" (where 57s won't do).

8)
Title: Re: I need a microphone
Post by: granger.frederic on June 15, 2017, 07:08:16 AM
for me, putting a high end capsule in a MXL,Fame,Apex,etc... is like putting a V12 in a WV polo, or like changing the pickups on a fender Squier, it will sound better but never sound like an USA
don't expect it to work like a high end mic even if you rebuilt the headamp (resonances inside the body, in the HighZ section, among others things...) or you need to  deeply modify the body...
my 2 cents
buy a good body (flea for ex) and take care of ALL the details, or stay with a cheap but decent stock mic like SE 2200a or NT1a
Title: Re: I need a microphone
Post by: RuudNL on June 15, 2017, 10:23:06 AM
It depends what you are going to use a microphone for...
Remember that his budget is only $300.
I'm afraid that isn't enough for a Flea body and a high quality capsule!
(Anyway, compared to an SM57, I suppose any microphone is an improvement...  :P )
Title: Re: I need a microphone
Post by: granger.frederic on June 15, 2017, 10:55:33 AM
i guess it's for audio recording ...  ;)
i'm kidding...
i agree , for 300euros , i wouldn't bother me to buy a cheap chinese capsule and cheap mic for modification, but i would choose a decent stock mic
today cheap mics are good enough to make some semi pro recordings

here's a big shootout but you must be leery as it can't be very impartial : https://www.sweetwater.com/feature/vocal-mic-shootout/
Title: Re: I need a microphone
Post by: DerEber on June 15, 2017, 12:55:37 PM
If I'd have the one mic choice it would def be an EV Re-20.
It's a great mic on so many things.
Title: Re: I need a microphone
Post by: squarewave on June 15, 2017, 07:03:58 PM
What great answers! Just the right mix of know-how and comedy.

So it sounds like the capsule is rather important. I guess my budget is whatever it needs to be to get the critial parts right. If that means something with a $300 capsule in it then so be it.

Honestly the rationale behind just buying something as opposed to DIY-ing a mic is that it seems like there's a lot of voodoo and BS going around the web. How do people test their mics? Do you have an anechoic chamber and a spectrum analyzer? Probably not. Mics (and voice coils) are a little hard to test. It's limited to relative measurements (before / after replacing a part) or only analyzing electonics after the capsule (which says nothing about the basket, capsule, polar pattern, etc). So a lot of information about DIY mics is highly subjective. This means you have to trust the manufacturers which means either just buying a known good mic from a respected manufacturer or the buying the the parts from a well known respected manufacturer (where do you buy a genuinely good capsule?)

At this point it sounds like buying a cheap mic and then swapping out the capsule might be a decent strategy.

What donor mic?

Incidentally, as described here http://www.rane.com/note165.html (http://www.rane.com/note165.html) are there mics that are known to have an issue with pin1 to the shell? You can see in this pic:

(https://4.bp.blogspot.com/-6EsPH0BtvGw/WWG1TgvCdGI/AAAAAAAAAPE/8QDXuKjILYgjc3LN9znwgj2r6fQlVTglACLcBGAs/s1600/SdeCABd.jpg)

the SMD version of MCA SP1 is actually correct with the little piece of buss wire between pin1 and the shell (assuming that solder lug is actually screwed into the shell properly). Even though the PCB is SMD, is there a good kit for this body that would warrant just replacing the PCB entirely?

Other than the capsule, what do you consider to be critical parts?

I saw a website that claimed changing the coupling cap to poly or mica improved distortion significantly. Reality or voodoo?
Title: Re: I need a microphone
Post by: Tubetec on June 15, 2017, 10:26:28 PM
Hi Square ,
Heres a link to a great article by Dave Royer on making your own tube mic .
http://tapeop.com/tutorials/25/dave-royer/
Theres a lot of talk on forums about  using this or that body, capsule  ,the reality is even a budget off the shelf transistor
large membrane mic can be converted for pocket change into very decent tube mic .
Granted it will have a different response than say something with a very expencive Neumann capsule ,but thats not to say it wont sound good either.
The first tube mic I made was using a behringer B-2  capsule and body , I ripped out the all the the transistor  electronics ,
then mounted a ptfe 9 pin tube socket onto the underside of the detachable mic head , I used a sowter mic input transformer in reverse through a coupleing cap from the anode of an Ef86 ,circuitwise its a bit like a u47 ,100kohm anode load ,diaphram connected to grid directly ,polariseing voltage(60volts) applied to the back plate ,swapped out the 3 pin xlr for a seven pin and of course the powersupply had to be constructed .
Theres many hybrid tube transistor mics out there they of course come with powersupply, 7 core cable etc all you really need to do is ditch the transistors and find a decent transformer and do a small rewire of the tube circuit .Of course theres many third parties offering off the shelf upgrades for easily available mics too ,thats another option.
The resulting recordings Ive got from my modded behringer compare very favourably with mics costing into the thousands . For me at least going the diy route was well worth the extra effort and saved me a packet .


Title: Re: I need a microphone
Post by: granger.frederic on June 16, 2017, 11:30:13 AM
Sorry but i totally disagree ...
please keep in mind that my post is not a personal attack but more a passionate testimony...

when i see a probable 1 giga ohms resistor (red one on right) touching the metalwork (body) , your microphone can't work nicely...
all the vibrations are going to pollute the capsule signal...
i add that a 8230 sowter has a 5:1 ratio and is not the best choice for a ef86 even in triode mode

building mics is almost lutherie because of the ultra high impedance section, the transducer principle and the presence of a tube that can be microphonic, among A LOT of other things ...

i'm not saying that you can't achieve a good microphone with a cheap body but i say that i will more difficult and it will need some deep modifications and a lot of knowledge to take care of all the details...

it's not impossible at all, but it seems to me more complicated than putting everything inside without attentions or just changing the  capsule , and posting on various forums after, pretending that it sounds like a thousands $ mic...

with a small budget , i would stay  with a good stock LDC , the net is full of shoutouts and reviews,
however if you plan to build a very good one because you are passionate and you want to approach  the sound quality without paying 5 to 10k$, then you need a good body (1500$) or a chinese but with deep modifications (400$ + lot of time + knowledge)
you need a good capsule (thiersch,campbell,beezneez,heiserman,dan bouchard...) around 300-500$
a good transformer (cinemag,lundhall,haufe,samar,sowter,ami...) min 300$
a good PSU 150$ min (you must mod the original noisy stock one)
a good and suitable (selected) tube 100$ min
good cables 50$
good connectors 100$ min
good components around 300$
total around 1800$ and it's the ABSOLUTE MINIMUM to have a good result,  and i don't talk about the time spent...
Title: Re: I need a microphone
Post by: Recording Engineer on June 16, 2017, 01:57:46 PM
I suppose it comes down to what "good" really means... But an absolute minimum in caps at $1800 for good? I would easily say around half that is a sufficient minimum; though certainly not an absolute minimum at all.

And as for lower than that good ones, one off the top of my head is the Jim Williams AKG C414 B/ULS mod.

I do agree that minimum is taking a used mic with a decent circuit and components and at least replacing with a good capsule, most-likely not Chinese, though they've been getting closer every year for a longtime now.
Title: Re: I need a microphone
Post by: granger.frederic on June 16, 2017, 02:26:25 PM
I agree
chinese capsules and mics are better these days, and that's a good thing ...
however,(fortunately)  there's still a big gap between a good 300$ mic and an high end mic (elam 251 for ex...)
i'm trying to say that this  gap is quite difficult to pass in DIY world, without a specific knowledge  and a substantial budget
i can also say that i'm still searching the gap between a stock c414 b/uls and a 300$ good chinese mic, but i admit that i've never tested one with a jim's mod...
i have in my stock two recent akg nylon ck12 type capsules and i can say that it isn't in the same league than a campbell CT12, but i'm doubtful that just a capsule swap could change a c414 b/uls into a classic mic which can compete with a healthy vintage C414eb with a brass CK12 (3000 to 3500$)
if jim's achieved that then : respect..
this is pure speculation because i know that jim has the mics  knowledge ,i don't know the mod price and details , and i've never tested one...
Title: Re: I need a microphone
Post by: Recording Engineer on June 16, 2017, 03:46:51 PM
Agreed, the Chinese are still far from achieving even a decent CK12.

By the way, Jim's mod of the C414 B/ULS uses the stock capsule. It's amazing to anyone I've ever heard of use one. It makes me wonder if the non-brass CK12s get their bad-rap from an application standpoint even though they are designed specifically for C414s!

In fact, I have to admit my favorite stock C414 are the newest ones since the brass EBs and I think I've convinced myself it's these newest capsules!

But you're absolutely right, you do need to have some intimate knowledge of what's going on (even if it's exclusively from extensive trial and error) to achieve a good mic, but that's regardless of what it costs you in parts!
Title: Re: I need a microphone
Post by: squarewave on June 16, 2017, 05:11:22 PM
Well I just bought a used MXL 440 for $65 USD shipped.

I assume this is the usual Schoeps circuit.

What should I do with this?

Traditional U87 pcb kit + transformer?
Title: Re: I need a microphone
Post by: Tubetec on June 17, 2017, 09:40:27 AM
Hi Fred,
Your making quite a few assumptions here,
First, its not a 1 gig resistor
Second, even though it may look from that angle that the resistor touches the metalwork ,it doesnt.
Third, the sowter 8230 matches 25kohm into 200 ohm, at a very minimum the mic will feed an input of 1200 ohms ,and on higher level sources I usually terminate with 10 kohms into a line stage with variable gain.
Fourth, Im well aware that the high impedence nature of the grid wiring and associated components is crucial to a good design,thats why I mounted the Ef86 pins up and as close to the capsule as I possibly could .
Fifth, of course 'good' is a totally subjective term but I have 20 or more years experience in sound and recording , over that time Ive used all kinds of condenser mics .When I designed and made this mic I wasnt trying to clone or copy the sound of any mic in particular,Im  willing to accept that the capsule geometry and case dimensions of the B-2 will impart its own signature on the final result.
Sixth, maybe if you were  willing to post details of your own efforts in mic design along with your criticisms of other peoples work you might come across as slightly less judgmental.
Title: Re: I need a microphone
Post by: Tubetec on June 17, 2017, 10:11:41 AM
Hi Square,
I'm kinda fond of tube mics personally ,so I couldnt really give much advice on the fet stuff.Great news  that your getting stuck into a project though.
Technicalities aside, one of the really nice things about diy/modding is the sense of satisfaction it gives,and Ive found it to draw in the interest of the musicians and people you might be recording .None of these things are measurable with scopes and probes ,but they do have an effect on the vibe and feel of the end result.
Title: Re: I need a microphone
Post by: Gus on June 17, 2017, 11:04:39 AM
Well I just bought a used MXL 440 for $65 USD shipped.

I assume this is the usual Schoeps circuit.

What should I do with this?

Traditional U87 pcb kit + transformer?


http://cdn.recordinghacks.com/images//mic_extras/mxl/mxl-440-circuit.jpg (http://cdn.recordinghacks.com/images//mic_extras/mxl/mxl-440-circuit.jpg)

There is a web site that has good information about upgrading the circuit that microphone looks to have.
I use the stock PCBs and install 1 new part(cut a trace and add some wire) and remove 4 stock parts from the circuit and rewire some connections
I also select new transistors for the JFET and PNPs
Then adjust for min distortion
you can then change caps values and types to taste
Then adjust the DC to DC section
All of this is on the web you just need to look.
I am not a fan of capsule if it is the same as the MCA one(I have a MCA)

There is different China built (not sure where the circuit was designed)transformerless circuit that sounds good stock.
I bought some microphones for the bodies last year (easier than building bodies)and one surprised me. I need to get around to changing the capsule and improving the capsule grill environment. The stock capsule sounds like it was improved over older models.


 
Title: Re: I need a microphone
Post by: RuudNL on June 18, 2017, 03:50:37 AM
Hi Fred,
Your making quite a few assumptions here,
First, its not a 1 gig resistor
Second, even though it may look from that angle that the resistor touches the metalwork ,it doesnt.
Third, the sowter 8230 matches 25kohm into 200 ohm, at a very minimum the mic will feed an input of 1200 ohms ,and on higher level sources I usually terminate with 10 kohms into a line stage with variable gain.
Fourth, Im well aware that the high impedence nature of the grid wiring and associated components is crucial to a good design,thats why I mounted the Ef86 pins up and as close to the capsule as I possibly could .
Fifth, of course 'good' is a totally subjective term but I have 20 or more years experience in sound and recording , over that time Ive used all kinds of condenser mics .When I designed and made this mic I wasnt trying to clone or copy the sound of any mic in particular,Im  willing to accept that the capsule geometry and case dimensions of the B-2 will impart its own signature on the final result.
Sixth, maybe if you were  willing to post details of your own efforts in mic design along with your criticisms of other peoples work you might come across as slightly less judgmental.

+1
Title: Re: I need a microphone
Post by: Khron on June 18, 2017, 06:21:32 AM
Hi Fred,
Your making quite a few assumptions here,
First, its not a 1 gig resistor
Second, even though it may look from that angle that the resistor touches the metalwork ,it doesnt.
Third, the sowter 8230 matches 25kohm into 200 ohm, at a very minimum the mic will feed an input of 1200 ohms ,and on higher level sources I usually terminate with 10 kohms into a line stage with variable gain.
Fourth, Im well aware that the high impedence nature of the grid wiring and associated components is crucial to a good design,thats why I mounted the Ef86 pins up and as close to the capsule as I possibly could .
Fifth, of course 'good' is a totally subjective term but I have 20 or more years experience in sound and recording , over that time Ive used all kinds of condenser mics .When I designed and made this mic I wasnt trying to clone or copy the sound of any mic in particular,Im  willing to accept that the capsule geometry and case dimensions of the B-2 will impart its own signature on the final result.
Sixth, maybe if you were  willing to post details of your own efforts in mic design along with your criticisms of other peoples work you might come across as slightly less judgmental.

+1

+1
Title: Re: I need a microphone
Post by: Tubetec on June 18, 2017, 01:31:42 PM
Saluts Ruud and Khron !  cheers guys
What I might do is upload a tune I recorded with the modded B-2 and see what people think.
Is it possible within the group diy site to upload music ?
Alternatively I can use file hosting and post a link .
Title: Re: I need a microphone
Post by: granger.frederic on June 19, 2017, 08:15:49 AM
 Dear Tubetec, Ruud and Krohn,

thanks for the attacks...

as you are demanding, here's an example of a U47 clone that i'm building right now, for a very famous French Producer with a K49 Neumann, Flea Body.

look at the Hiz section , it's built on custom milled plexyglass , point to point and on silent blocks, the tube as well...
the hiZ section is encapsulated between the top plexyglass plate and the tube/foam, like in the original U47.

that's what i do...
but you are free to do your own way of course...

Tubetec , could you post a picture of the red resistor please ? to see the value ...
7:1 min for an EF86 would be better for me but ,once again , you are the only judge...
Title: Re: I need a microphone
Post by: granger.frederic on June 19, 2017, 08:17:34 AM
here's some pictures of some of personal mics
of course , i've restored it (near museum shape for certain...) and i use it for comparative listening...
Title: Re: I need a microphone
Post by: granger.frederic on June 19, 2017, 08:18:16 AM
again
Title: Re: I need a microphone
Post by: granger.frederic on June 19, 2017, 08:19:40 AM
and again
Title: Re: I need a microphone
Post by: granger.frederic on June 19, 2017, 08:21:02 AM
i hate self promotion thus i'm stopping and it's not very interesting for the other forum members...
regards
Fred
Title: Re: I need a microphone
Post by: Khron on June 19, 2017, 08:48:13 AM
So then why'd you do it? ;)

i hate self promotion thus i'm stopping and it's not very interesting for the other forum members...
regards
Fred

What you choose to name "attacks" were just a polite(?) attempt at sort of "getting you off your high horse", or "knocking you down a peg", in case you're familiar with the phrases :)

You have to admit, you came across a bit... perhaps arrogant, some might say, with that whole "it's gotta be expensive to be good" attitude. Noone likes a "snobbish" know-it-all, especially in DIY circumstances, i think :D And bragging about owning(?) expensive mics, indeed, serves no (constructive) purpose. But i could be wrong...

Just to make it 100% clear - no offense or insults were intended, i come in peace.
Title: Re: I need a microphone
Post by: granger.frederic on June 19, 2017, 08:52:51 AM
i do it because you asked me ...
now you're upset
sorry, it was not my intentions
i just want to share my knowledge and push builders to think about details (expensive or not, no matter), but i think i won't do it anymore
these days people seem too susceptible...fortunately i'm not, even after your insults

ps:i have also cheap but good mics:
Title: Re: I need a microphone
Post by: KrIVIUM2323 on June 19, 2017, 09:21:44 AM
Hi,
Frederic don t be touchy about comments, this is probably a problem of translation about tone of your initial comments. And everyone his own choice! This is why diy is interesting!

Anyway, your rubbermount of tube/hi z plate is interesting. What did you use for the rubber?
I always ask for myself why the use of acrylic as there is better insulation material available?
Title: Re: I need a microphone
Post by: granger.frederic on June 19, 2017, 09:43:15 AM
Hi
the rubber cames from an old tube socket damping system
but i often use sorbothane rings

plexyglass when perfertly cleaned seems to isolate enough for me and most important ,it doesn't transmit well vibrations,  it's easy to mill and easy to check if it's clean


regards
Title: Re: I need a microphone
Post by: ln76d on June 19, 2017, 09:59:56 AM
I always ask for myself why the use of acrylic as there is better insulation material available?

PTFE ;)
Title: Re: I need a microphone
Post by: KrIVIUM2323 on June 19, 2017, 10:19:30 AM
Yes. ;)
But this have some drawbacks: at same thickness it is softer not as stiff than other material, it is sometime difficult to have consistency when you cut it ( not stable with higher temp), can be dangerous/lethal if you produce temp high enough for it to produce smoke...

Obviously if you have access to water jet cutting(which i don't)... most drawbacks are irrelevants.
Title: Re: I need a microphone
Post by: Murdock on June 19, 2017, 10:42:06 AM
Here is a great little table I found online. It states the most important characteristics of the most common plastics.
It's in german but I think you can understand everything with the use of google translator and by looking at the unit table.
7) and 8) are the electrical characteristics:

https://www.hug-technik.com/inhalt/ta/kunstoff.htm#PTFE

Wish I had found this before I build my U67 Pleximount...
Title: Re: I need a microphone
Post by: Tubetec on June 19, 2017, 02:55:42 PM
My take on the subject of insulation resistance is that the weakest link in the chain is always going to be the limiting factor.
In the case of the Vf14 it used a low loss base material and underwent special testing for suitability  in high grid resistance situations such as tube mics . The Ef14,which is a very similar valve wont always perform as well in place of the Vf14,and careful selection will be nesessary to find a usable specimen. Insulation resistance between the pins of the tube being the limiting factor no amount of special precautions/or exotic materials is likely to improve matters a great deal.In models like the Neumann M49 and M50,which used an all glass sub mini wire ended tube ,plexiglass is used to good effect.

I did notice that the original post decrying my work on the B-2 tube mic conversion was edited later, criticisms constructive or deconstructive  I have no issue with ,being accused of lying is another matter completely.

Anyway I hope this post finally puts a lid on it ,and hope we can move on to a more constructive approach
Title: Re: I need a microphone
Post by: KrIVIUM2323 on June 19, 2017, 06:00:30 PM
Quote
Insulation resistance between the pins of the tube being the limiting factor no amount of special precautions/or exotic materials is likely to improve matters a great deal.

I do agree from an electrical point of view. But as Frederic pointed from a mechanical point of view this can have an effect (microphony). I like PTFE for electrical properties and mechanical properties: very low friction factor and used with some damping material it has nice effect i think.

I've used silicon glue (for aquarium) to make more or less same thing that Frederic showed in pictures of 47 to limit vibration transmission to the socket for an ef14. Not really scientific  and a real mess to do the 'pads' but it work well.

I'll probably couple that with ptfe plate for next build.
Title: Re: I need a microphone
Post by: Tubetec on June 19, 2017, 06:55:06 PM
I was lucky enough to pick up a bunch of  ptfe valve bases from a man who breaks old military gear down ,some used some nos ,but with a bit of a clean and a polish as good as new . I havent used ptfe much for structural work though. I was thinking that some kitchen heat resistant cooking tools etc might be a good place to find it on the cheap , I must check into it more.
Title: Re: I need a microphone
Post by: KrIVIUM2323 on June 19, 2017, 08:18:37 PM
I would be careful about kitchen ptfe: there is different kinf of ptfe, some with additive making it much less interesting for electrical insulation properties. Don t know if that is the case for the kind used for food tools though.
Title: Re: I need a microphone
Post by: Tubetec on June 19, 2017, 09:07:43 PM
Yeah you probably right about that ,the real stuff  costs alot more , and tends to be pure white in colour . must be other stuff added to the standard kitchen variety . Just as a guide 1200x1200x2mm  310 pounds sterling but thats an awefull lot, must try and source some in smaller quantities locally .
Title: Re: I need a microphone
Post by: Tubetec on June 19, 2017, 09:11:30 PM
Hmmm forgot to add the vat ,so all up 372 quid
Title: Re: I need a microphone
Post by: KrIVIUM2323 on June 19, 2017, 09:22:32 PM
You can find small quantity at ebay.
If i remember correctly in eu there is some offers from germany.
2mm is a bit thin from my experience, 3mm is stiffer and more useful for structural duty imho.
Title: Re: I need a microphone
Post by: cyrano on June 20, 2017, 08:26:39 AM
PFTE is abundant in the terabrik caps...

Easy to melt down and press into slabs. See Dave Hakken's channel:

https://www.youtube.com/watch?v=76AFNIxYjUE
Title: Re: I need a microphone
Post by: Tubetec on June 20, 2017, 09:33:20 AM
Thanks Cy,
Interesting video ,makes alot of sense to re-cycle/upcycle wherever possible.
Im gonna try a few local engineering supply places and see if they have any off cuts of sheet ptfe,Im sure they will be willing to let it go cheap .
Title: Re: I need a microphone
Post by: KrIVIUM2323 on June 20, 2017, 09:53:17 AM
Quote
Im gonna try a few local engineering supply places and see if they have any off cuts of sheet ptfe

Makes sense. Just be sure they are not loaded with bronze or other fiber to strengh them up. 
Title: Re: I need a microphone
Post by: granger.frederic on June 20, 2017, 10:03:34 AM
My take on the subject of insulation resistance is that the weakest link in the chain is always going to be the limiting factor.
In the case of the Vf14 it used a low loss base material and underwent special testing for suitability  in high grid resistance situations such as tube mics . The Ef14,which is a very similar valve wont always perform as well in place of the Vf14,and careful selection will be nesessary to find a usable specimen. Insulation resistance between the pins of the tube being the limiting factor no amount of special precautions/or exotic materials is likely to improve matters a great deal.In models like the Neumann M49 and M50,which used an all glass sub mini wire ended tube ,plexiglass is used to good effect.

I did notice that the original post decrying my work on the B-2 tube mic conversion was edited later, criticisms constructive or deconstructive  I have no issue with ,being accused of lying is another matter completely.

Anyway I hope this post finally puts a lid on it ,and hope we can move on to a more constructive approach

no problem tubetec...
concerning the grid leaks , the tubes (EF14 or 12 or everything else)  must be cleaned also , the socket as well , especially after soldering...
my experience is that 1 tube of 5 usual  mics tubes is unsuitable if you have a good tube dealer ...
if the tube in its datasheet has enough inter-electrodes insulation (let's say a bit more than the grid resistor), chances that it will work are pretty good.
high insulation  sockets are preferable of course
but at the end, i notice that the mechanical insulation (ALL the components of the highZ section) affects the sound more than the electrical insulation (mainly on low end)
Title: Re: I need a microphone
Post by: KrIVIUM2323 on June 20, 2017, 10:54:04 AM
I just watched the video Cyrano linked.
Re use of plastic material is really something good and we should do everytime possible ( i can t stand all sorts of plastic items i encounter each time i go bodyboarding in Atlantic ocean... and it s a relatively protected ocean).

Nevertheless, i won t do that with ptfe without being supervised by someone who know is stuff: melting point is relatively high and i repeat if it release smoke it can kill you.
Trying to machining some using a friend s lathe i ve experienced it.  Won t do that again.
Title: Re: I need a microphone
Post by: cyrano on June 20, 2017, 12:51:06 PM
Thanks Cy,
Interesting video ,makes alot of sense to re-cycle/upcycle wherever possible.
Im gonna try a few local engineering supply places and see if they have any off cuts of sheet ptfe,Im sure they will be willing to let it go cheap .

I get leftovers for free. I buy perspex and stuff like that from one local supplier. Asked them if I could do some dumpster diving. Sure, OK.

Had to prove that to police, once. Doing it at around 1 pm on a sunday night wasn't one of my brightest moments.

And tetrabrik caps are clean. Food safe. Unlike some of the mil spec stuff...
Title: Re: I need a microphone
Post by: squarewave on June 24, 2017, 01:07:59 AM
I got the MXL 440 donor body. It's SMD and the capsule has visible corrosion on it. So I'm going to just gut it. Sounds pretty good though for such a cheap mic (as does the 441 that came with it). Zero hum anyway.

So now I'm thinking of doing a KM84 pcb with a Peluso P-K47 capsule and an AMI T13 transformer (basically same as T84 from micparts).

Does anyone see a problem with this?

The T13 is 9.5:1 so with a 1.2K / 300R mic pre input thats going to make a load of around  108K / 27K on the FET.

Will a 34mm capsule fit in the 440 body? Will the Peluso mount work with the 440 body? The 440 body seems a little small.

Anyone have any experience with zenproaudio.com?

ZenPro claims both the capsule and transformer are "Stock Item, Usually Ships Same or Next Business Day", free shipping and no sales tax.
Title: Re: I need a microphone
Post by: RuudNL on June 24, 2017, 04:25:22 AM
A 34 mm. capsule will fit the body. I did it before.
(The mounting post should not be too high.)
Title: Re: I need a microphone
Post by: G-Sun on June 24, 2017, 04:37:28 AM
My suggestion:
- Fet 847 (diy)
- Aston Origin (new)
- Miktek MK300 (new)
- any diy U87 kit

Provided that you have a good tracking-room.
If it's just need a mic, then I'd buy new (or used)
if you like the diy-challenge then diy :)

btw: I have a C1 jj mod for sale
Title: Re: I need a microphone
Post by: micaddict on June 24, 2017, 05:37:39 AM
Yes, the 847 was the first one that came to my mind, too.
https://groupdiy.com/index.php?topic=61057.0 (https://groupdiy.com/index.php?topic=61057.0)

Title: Re: I need a microphone
Post by: Gus on June 24, 2017, 08:57:31 AM
Why don't you adjust the SMD circuit using the information available on the web for the Schoeps like circuit.
A properly adjusted circuit like that can sound fine.
Title: Re: I need a microphone
Post by: squarewave on June 24, 2017, 12:23:59 PM
Yes, the 847 was the first one that came to my mind, too.
https://groupdiy.com/index.php?topic=61057.0 (https://groupdiy.com/index.php?topic=61057.0)
This is interesting.

But why did they DC couple the capsule to the JFET?
Title: Re: I need a microphone
Post by: RuudNL on June 24, 2017, 03:56:43 PM
But why did they DC couple the capsule to the JFET?
To avoid the effect of the capsule coupling capacitor.
(Many people think a coupling capacitor has an audible effect on the sound quality.)
Title: Re: I need a microphone
Post by: squarewave on June 24, 2017, 06:03:53 PM
To avoid the effect of the capsule coupling capacitor.
(Many people think a coupling capacitor has an audible effect on the sound quality.)
I'm not even sure that makes sense. They just moved the cap to the other side of the capsule so any distortion in that cap is still reflected as a difference across the gate and drain of the JFET.
Title: Re: I need a microphone
Post by: RuudNL on June 25, 2017, 03:54:40 AM
The capacitor at 'the other side of the capsule' has to be there anyway, to obtain an AC ground for the polarisation voltage.
So it is still one capacitor less...
Title: Re: I need a microphone
Post by: squarewave on June 25, 2017, 01:17:04 PM
The capacitor at 'the other side of the capsule' has to be there anyway, to obtain an AC ground for the polarisation voltage.
So it is still one capacitor less...
That's not what I see. Although they could use one less capacitor they don't. They added the AC ground cap to make what is also a 3rd filter stage. And 1G/100n is a much lower RC than the two previous 10M/100n. So yes, they removed the 470p but added a 100n.

I can only guess this was done to be more like a U47 circuit with how it applies polarization to the backplate AC coupled to ground and then grounds the diaphragm where it also takes signal. But in this case you might as well drop one of the 10M/100n stages and make the 1G/100n more like the 100M/10n of the U47. Otherwise it will take a loooong time to charge (and what is the leakage current of a 100n film cap?).

I think I'll use the stock KM84 circuit but with the K47 capsule. Just swap it in. No changes in capacitors. No changes in polarization. Does anyone see an issue with that? The capacitance is quite different (36p for K84 vs 72p for K47) but does that matter? Sorry to tear down someone's project but I just want to make sure I understand this correctly because these parts are expensive. Any and all criticism is welcome.
Title: Re: I need a microphone
Post by: RuudNL on June 25, 2017, 03:08:46 PM
Yes, the 0.1 uF/1G.ohm would give a ridiculous long time to charge. (Over 1 minute...)
So you could omit those components.
But for audio, the effect would stay the same; it doesn't matter if you have the one 0.1 uF in the circuit 'at the other side of the capsule', or the other 0.1 uF.
Title: Re: I need a microphone
Post by: squarewave on July 16, 2017, 11:09:54 PM
I'm building a KM-84 mic with a Peluso PK-47 capsule but it's not obvious to me which side is the "front" or how to wire this precisely. The KM-84 schematic doesn't make it obvious either and I have never worked on mics so I want to make sure I understand this perfectly.

The PK-47 capsule has a wire attached to each diaphragm and screw holes for the mount that are slightly offset to one face. Included are 3 small screws that appear to be for mounting. There is no wire attached to the ring. I also have the correct mount which also has holes offset to one face.

Just to be crystal clear, the capsule is mounted so that the offset holes complement each other such that the capsule is centered correct?

Which side is the "front"? Do I want the front diaphragm wire to be the input and thus gets the bias? And then attach a wire to the ring which is the "back"? And then the other wire is simply left unconnected? There is no eyelet or wire for the ring. Why? I can salvage this from the donor mic but I am confused as to why it was not included.
Title: Re: I need a microphone
Post by: ln76d on July 19, 2017, 05:15:58 AM
You should ask manufacturer why he didn't add third wire for capsule.
https://io.groupdiy.com/file/gdiy-2017/u/39511/58d1402a088e3.pdf
Use this schematic, front diaphragm should be connected to the R1/C1/Q1 node, backplate ("ring" i guess) to R2/C11.
If you are buildng cardioid only mike, then the rear diaphragm left unconnected (isolate wire).
Title: Re: I need a microphone
Post by: squarewave on July 19, 2017, 12:00:36 PM
How do the Neumann mic capsule schematic symbols work?

In this graphic which network is connected to the the backplane and which is connected to the input of the mic circuit?

(https://2.bp.blogspot.com/-9yRjA_fbJGQ/WW-BAeg776I/AAAAAAAAATM/Gj8d8uWALxw3fZsbTXUgHzPzfbAUyEwSQCLcBGAs/s1600/capsule.png)

Is the thick rectangle the backplate/mounting ring and the thinner bar a diaphragm?

So in this particular mic (KM84) the diaphragm is grounded and the signal is taken from the backplate as well as charged with bias?
Title: Re: I need a microphone
Post by: ln76d on July 20, 2017, 03:45:48 AM

Is the thick rectangle the backplate/mounting ring and the thinner bar a diaphragm?

Yes

So in this particular mic (KM84) the diaphragm is grounded and the signal is taken from the backplate as well as charged with bias?

Yes, like in most of SDC microphones (schoeps was one of exceptions), where due to capsule design, diaphragm have permanent connection to the microphone body which is grounded.
In case of LDC, where the capsule don't have to be connected to the ground better is to use connection with dipahragm connected to the circuit input and polarize backplate. This allow to remove input capacitor. Both changes are improvement.

Title: Re: I need a microphone
Post by: squarewave on July 20, 2017, 12:32:10 PM
(https://groupdiy.com/index.php?action=dlattach;topic=66205.0;attach=51855;image)
What schematic is this from? Clearly it's a Neumann schematic but which mic is this?
Title: Re: I need a microphone
Post by: ln76d on July 24, 2017, 06:29:05 AM
I just redrew  your pic in ms paint :D :D :D
Title: Re: I need a microphone
Post by: Recording Engineer on October 16, 2017, 03:51:15 PM
You know, this whole thread has got me thinking... Is there still not yet a cheap Chinese mic out there (tube, FET, transformer, transformerless, or otherwise) that at least has a circuit and parts that most would agree doesn't need modification (or at least not more than 1 or 2 stupid-simple changes); capsule, transformer, tube,  or body swapping aside?
Title: Re: I need a microphone
Post by: ln76d on October 17, 2017, 11:15:47 AM
You know, this whole thread has got me thinking... Is there still not yet a cheap Chinese mic out there (tube, FET, transformer, transformerless, or otherwise) that at least has a circuit and parts that most would agree doesn't need modification (or at least not more than 1 or 2 stupid-simple changes); capsule, transformer, tube,  or body swapping aside?

Still not :D

Akg perception could be good candidate (this time it's U87Ai mixed with C414 PNP follower) but aslo screwed up and need modification to sounds pretty good.

Current Rode NT1 (black) is pretty decent (first NT1 which doesn't suck!!!) and there's nothing to change inside.
What's funny is that it have all the "mods" which i was doing for years in NT1a - coincidence? :D
Still you need to like it sound, because still it's very specific but much better than all the previous versions.
Title: Re: I need a microphone
Post by: Recording Engineer on October 18, 2017, 01:44:52 PM
Wow! You'd think after however many years and however many renditions of the same things over and over again, I would have thought at one of the Chinese manufacturers or importers would have made at least one!