What's a good "raw" electret capsule?

[szegedin]

I asked about this years ago but now I've forgotten the explanation.

I understand there are those electret capsules out there that have a FET built in.

That's not what I need. I'm looking for a 0 volt electret. This type was used in many of the high-end measurement mics by Bruel&Kjaer and others.

Are there any really good capsules (aside from B&K) available out there for this kind of mic? I have an extra B&K preamp. It should be just signal and ground leads - not ground, output and DCv. It looks like some of the $3 capsules on JLI are this type. Are there any good ones? Cardioid would be great, but I'll take an omni.

Any rec's appreciated.

 

[bremusound]

https://groupdiy.com/threads/cad-equitek-e100-capsule.77061/
Primo EM21 is good but you‘ll have to buy a used mic with that capsule

 

[k brown]

The Primo EM23 omni is even better. An insanely quiet capsule for an electret of it's size.

You didn't say if SDC or LDC - if SDC, A very good (if rather bright) omni comes as part of the Monoprice 'Stage Right' SC100 set
https://www.amazon.com/Monoprice-Pencil-Condenser-Microphones-625907/dp/B08T4V3ZMG. The card is not bad either; they're both made by Transound, and they have best selection of FET-less electrets (available from JLI, as it looks like you know). The cards in the Monoprice mics appear to be TSB-160a; the TSB-165a has a flatter response and is used in a lot of commercial mics (none of these are very quiet, though). The omni SC100 capsules are a bit of a mystery as neither JLI or Transound show anything like it on their sites; maybe OEM-only? They are clearly stamped with the Transound logo.

For a smaller omni, the Primo EM4052 show up on eBay now and then (though not at the moment). They are a nice, flat 14mm machined brass capsule that screws onto a tiny body containing a simple 2SK118 circuit, with a 'captured' cable (see attached). A selected version of the capsule was used by Nakamichi as the 'pin-point' omni (CP-3) for their CM300 mics. Very quiet for their size.

A very nice smooth, SDC card I've been playing with can be used FET-less if you're willing to do a little 'surgery'- the capsules in the long-discontinued Audio Technica AT825 and AT822 one-piece stereo mics (I just bought another one). They have built-in FETs (2SK660), but they are contained on a little circular board right behind the capsule proper (bad place for a smooth, hard, flat surface). To say the backs of these capsules are operating in a hostile environment is putting it mildly! The frame containing these boards is easily cut away, leaving a beautiful machined brass 18mm card with gold-sputtered 2 micron diaphragm. The same capsule was used in the AT4031, which later became the AT4041. To me they sound more like a 'big buck' mic than the EM21 (the bottom of which rolls off at a higher freq); a little noisier, though (should see if they would be quieter with a little external polarization).

I put two of these into very shortened BM700 bodies as side-address mics - with their backsides now freely singing into the open air : - )

 

[szegedin]

The Primo EM23 omni is even better. An insanely quiet capsule for an electret of it's size.

You didn't say if SDC or LDC - if SDC, A very good (if rather bright) omni comes as part of the Monoprice 'Stage Right' SC100 set
https://www.amazon.com/Monoprice-Pencil-Condenser-Microphones-625907/dp/B08T4V3ZMG. The card is not bad either; they're both made by Transound, and they have best selection of FET-less electrets (available from JLI, as it looks like you know). The cards in the Monoprice mics appear to be TSB-160a; the TSB-165a has a flatter response and is used in a lot of commercial mics (none of these are very quiet, though). The omni SC100 capsules are a bit of a mystery as neither JLI or Transound show anything like it on their sites; maybe OEM-only? They are clearly stamped with the Transound logo.

For a smaller omni, the Primo EM4052 show up on eBay now and then (though not at the moment). They are a nice, flat 14mm machined brass capsule that screws onto a tiny body containing a simple 2SK118 circuit, with a 'captured' cable (see attached). A selected version of the capsule was used by Nakamichi as the 'pin-point' omni (CP-3) for their CM300 mics. Very quiet for their size.

A very nice smooth, SDC card I've been playing with can be used FET-less if you're willing to do a little 'surgery'- the capsules in the long-discontinued Audio Technica AT825 and AT822 one-piece stereo mics (I just bought another one). The have built-in FETs, but they are contained on a little circular board right behind the capsule proper (bad place for a smooth, hard, flat surface). To say the backs of these capsules is operating in a hostile environment is putting it mildly! The frame containing these boards is easily cut away, leaving a beautiful machined brass 18mm card with gold-sputtered diaphragm. It's been said they are a slightly different version of the capsule used in the AT4041 (and possibly the 4033). To me they sound more like a 'big buck' mic than the EM21 (the bottom of which rolls off at a higher freq); a little noisier, though (should see if they would be quieter with a little external polarization).

I put two of these into very shortened BM700 bodies as side-address mics - with their backsides now freely singing into the open air : - )

Thanks for all that info, that's very useful.

I just thought I would put this unused preamp mic body to use - designed for an SDC but willing to mod it to use it with a larger capsule. It's not worth much to sell because it's not for current DPA mics, so I want to DIY something.

That stereo mic looks good. Maybe if I can do a figure-8 pattern mic with two caps it could be a useful addition for M/S mic'ing.

I guess if the capsule can't manage <18db self noise, it's probably a non-starter.

I'm still confused about which of these work on the same principle as traditional 0v electrets, and would work with my preamp, which shows 0.2v on +.

 

[Icantthinkofaname]

The Primo EM23 omni is even better. An insanely quiet capsule for an electret of it's size.

You didn't say if SDC or LDC - if SDC, A very good (if rather bright) omni comes as part of the Monoprice 'Stage Right' SC100 set
https://www.amazon.com/Monoprice-Pencil-Condenser-Microphones-625907/dp/B08T4V3ZMG. The card is not bad either; they're both made by Transound, and they have best selection of FET-less electrets (available from JLI, as it looks like you know). The cards in the Monoprice mics appear to be TSB-160a; the TSB-165a has a flatter response and is used in a lot of commercial mics (none of these are very quiet, though). The omni SC100 capsules are a bit of a mystery as neither JLI or Transound show anything like it on their sites; maybe OEM-only? They are clearly stamped with the Transound logo.

For a smaller omni, the Primo EM4052 show up on eBay now and then (though not at the moment). They are a nice, flat 14mm machined brass capsule that screws onto a tiny body containing a simple 2SK118 circuit, with a 'captured' cable (see attached). A selected version of the capsule was used by Nakamichi as the 'pin-point' omni (CP-3) for their CM300 mics. Very quiet for their size.

A very nice smooth, SDC card I've been playing with can be used FET-less if you're willing to do a little 'surgery'- the capsules in the long-discontinued Audio Technica AT825 and AT822 one-piece stereo mics (I just bought another one). The have built-in FETs, but they are contained on a little circular board right behind the capsule proper (bad place for a smooth, hard, flat surface). To say the backs of these capsules is operating in a hostile environment is putting it mildly! The frame containing these boards is easily cut away, leaving a beautiful machined brass 18mm card with gold-sputtered diaphragm. It's been said they are a slightly different version of the capsule used in the AT4041 (and possibly the 4033). To me they sound more like a 'big buck' mic than the EM21 (the bottom of which rolls off at a higher freq); a little noisier, though (should see if they would be quieter with a little external polarization).

I put two of these into very shortened BM700 bodies as side-address mics - with their backsides now freely singing into the open air : - )

For the SC100, do you know if those capsules are the same ones as the iSK CM-10? They look identical (aside from logos and pattern icons) but the CM-10 had a supercardioid capsule.

 

[k brown]

Sorry, no - I've never dissected any iSK mics.

They certainly 'look' like the same mic. Anyone know the difference between CM10 and Little Gem - they look like the same mic.

 

[k brown]

Continuing to experiment with those groovy little AT stereo mic capsules, I noticed that (ignoring the outer ring) the capsule in the AT4033 looks like maybe an updated version of those in the stereo mics. Most noticable difference is the presence of a hole in the center of the 4033 and 4041's capsules' faceplates, which the others don't have. According to AT's Bill Balmer (in e-mail to Ty Ford) the AT4031 had the same capsule as the AT822/825 stereo mics . Since the 4033 and 4041 have a flatter top-end than the strereo mics, I tried drilling a hole in the center of the faceplate; it indeed does now have less top-boost, but doing it with a hand drill, the hole isn't precisely centered. Any specu-loose about affect on sound? I don't have kingkorg's fancy-pants analysis tools.

Wondering about enlarging the outer holes as well . . . I imagine the response would be smoother if the space between holes is slightly smaller that the diameter of the holes, as appears to be the case with the 4033 capsules?

 

[k brown]

Here it is in it's final home, my most 'shrunken' BM700 yet.

No body tube at all - just the bottom ring screwed right up against the head basket. Only FET and RF caps in basket, below and behind the capsule, with captive cable; rest of electronics in remote power module. Attached swivel/clamp is re-purposed from the shock mount supplied with most of these mics (this was a Neewer). Basket and bottom ring damped with Coax-Seal (it's amazing how little of this stuff it takes to completely eliminate 'ring' from these parts).

Weighs little more than most full-size SDCs with an XLR cable attached.

I'm a bit surprised there aren't more side-address SDCs in generously-sized head baskets, like the Schoeps V4U.

 

[szegedin]

Here it is in it's final home, my most 'shrunken' BM700 yet.

No body tube at all - just the bottom ring screwed right up against the head basket. Only FET and RF caps in basket, below and behind the capsule, with captive cable; rest of electronics in remote power module (rather like tube mics). Attached swivel is re-purposed from the shock mount supplied with most of these mics (this was a Neewer). Basket and bottom ring damped with Coax-Seal.

This is still lighter than most SDCs with an XLR cable is attached. Greatly increases the range of rigging possibilities.

Speaking of tube mics, ye hijacker, what about a tube version of a prepolarized electret?

I saw this design out there:
DIY Microphone Design

I wonder what the noise spec on this kind of mic would be. Frankly I don't understand the point of DIY mics that don't end up with the frequency response and noise level on par with professional mics, ie, maybe 20db self-noise maximum. What would be the use of them?

 

[k brown]

Speaking of tube mics, ye hijacker, what about a tube version of a prepolarized electret?

I saw this design out there:
DIY Microphone Design

I wonder what the noise spec on this kind of mic would be. Frankly I don't understand the point of DIY mics that don't end up with the frequency response and noise level on par with professional mics, ie, maybe 20db self-noise maximum. What would be the use of them?

Though it doesn't say on the schem, the capsule used for this was the Primo EM21 electret; it apparently 'didn't mind' the several volts of grid leak from the tube:
https://www.jensen-transformers.com/wp-content/uploads/2014/08/as076.pdf I did the same thing (using 6205 tube) with the little CP-3 'pinpoint' capsule for the Nak mics (also a Primo electret) - worked great.

As far as the Naiant, most of the noise would come from whatever capsule was used, assuming a decently quiet tube was used.

 

[k brown]

Here it is in it's final home, my most 'shrunken' BM700 yet.

No body tube at all - just the bottom ring screwed right up against the head basket. Only FET and RF caps in basket, below and behind the capsule, with captive cable; rest of electronics in remote power module. Attached swivel/clamp is re-purposed from the shock mount supplied with most of these mics (this was a Neewer). Basket and bottom ring damped with Coax-Seal (it's amazing how little of this stuff it takes to completely eliminate 'ring' from these parts).

Weighs little more than most full-size SDCs with an XLR cable attached.

I'm a bit surprised there aren't more side-address SDCs in generously-sized head baskets, like the Schoeps V4U.

New black/grey livery for these guys - all that glittering chrome wasn't going to cut it before a live audience. This metallic grey for the front grille is a great color called 'Soft Iron', in a new line of rattle cans from Behr. A little too 'metal-flake-y' for my taste for use on smooth body tubes, but hardly noticeable on the mesh.

A bit of a 414 look.

 

[Icantthinkofaname]

New black/grey livery for these guys - all that glittering chrome wasn't going to cut it before a live audience. This metallic grey for the front grille is a great color called 'Soft Iron', in a new line of rattle cans from Behr. A little too 'metal-flake-y' for my taste for use on smooth body tubes, but hardly noticeable on the mesh.

A bit of a 414 look.

Did you add any mesh inside the headbasket? Unless somethings changed the headbaskets of the BM-700s are really open right?

 

[k brown]

Did you add any mesh inside the headbasket? Unless somethings changed the headbaskets of the BM-700s are really open right?

Depends on which you get; 'Zramos' I got on Amazon had coarse plus fine mesh, and I removed the fine mesh from the front only - 'Neewer's I got on eBay had only coarse mesh, but these AT capsules' FET boards have a substantial metal ring around them which I ground, so not getting hum at all with the coarse mesh only.

 

[k brown]

Stereo pair - just light enough to securely shock mount with a single Shure 'donut'.

 

[k brown]

Now an exercise to see what's the smallest side-address SDC I can make.

Capsule from an AT813 (a broken pair on eBay for $40), in the head off a Teac ME-50 (with one of the vertical support bars cut out). Again, all that's inside is FET and RF caps.

Turns out the AT822/825 stereo mics' capsules are just upgraded versions of a capsule AT used for their very first microphones - the 800-series (1978). The list of mics containing some version of this capsule is long, and runs a good three or four decades:

AT811, AT813, ATM11, ATM10a (omni; same capsule w/o vented rear plate), ATM31a, ATM33, AT833; among others. All have the exact same internal parts and construction; only the housing/faceplates are different. The earlier, cheaper versions are in stamped aluminum housing with no internal FET; later ones had FET board attached to back - and the stereo mic version is machined brass. The difference between all the mic models is, some have mesh ball pop screen, and the internal circuitry improved considerably over time; first mics ran off AA batt only, later phantom was added.

When connected to identical circuitry, I actually like the sound of these capsules better than the
Primo EM21s that I have, though the ATs have more noise (about the same as TB165a).

The look is a bit reminiscent of the head of the original version of the Neumann KM88.

 

[k brown]

Interesting history on the capsules used in these first mics by AT; after a little digging, it seems they were (long since discontunued) Primo EM68B that were custom-spec'd for AT by replacing the stock aluminum-sputtered diaphragm with a thinner 6 micron gold sputtered one (or maybe AT was making the diaphragms themselves - I've never encountered a Primo with a gold diaphragm). Probably better FETs as well (one of the later examples I have came with a 2SK660; older ones were 'J30' or 'I03MI' (?). The AT version also had the circular pcb mounted on the inside of the rear casing, instead of 'tabbed' onto the bottom.

The Tascam ME-50 (and at least one Radio Shack model) used the stock version of the EM68, as analogguru mentioned in this thread: Cad Equitek E100 Capsule

In the later brass-bodied versions used in the AT822/825 stereo mics and the AT4031, the diaphragm was reduced to 2 microns.

 

[Tubetec]

I think we were looking for the Country Boy article sometime back , either way handy to have the schematic .
In this design the transformer is back in the PSU , the cathode drives the cable unbalanced ,

In the B&K cathode follower mic and PSU you have the option to tap the signal directly off the cathode , ie no transformer ,
it works best into high z and I think at least 250k load is recomended .
For 600 ohm balanced output a single transistor buffer and transformer are included in the very specially screened PSU .
Ive done a mock up of a circuit similar to the B&K , its unbalanced out on the multicore cable , the HPF is done by switching the coupling cap at the PSU end , I used a 12 way rotary switch , I adjusted on listening test the values of the caps to give a pleasing sweep in the response with regards proximity effect ,
I find it really effective for dialing in the right 'weight' into a sound ,
I used a Behringer B1 body and capsule and self biased the CF which also provides capsule bias .

 

[k brown]

Very nice!