MSH-1 Omni SDC

[cannabis]

how are you matching the pairs?

 

[mshilarious]

how are you matching the pairs?

First I measure their sensitivity, then I take two that match for sensitivity, and I compare their response to white noise on an FFT. Panasonic's specs for the capsules is +-2dB, but I find the vast majority are +-0.6dB, so it usually takes between 6 and 8 mics to find a pair. Of course the more mics I have made, the more pairs I can get from a batch.

Something to keep in mind if you are rolling your own, is that you will probably need 4 capsules to get reasonably close, and I've found about 1 in 20 capsules is totally off. I mean it will work, but will have no bass or something like that. So order a couple more than you think you will need.

 

[Adam P]

I just "ordered" a pair on Sunday night. I can't wait to get them!

 

[cominginsecond]

I got my pair, and I like them! Mic bargain of the year!

 

[Harvey Gerst]

More news! I have finally succeeded in building an "active" prototype and fitting it in the XLR Early results show stability down to 600 ohm input impedance, still need to do a long cable test to see how much that matters. I will publish that circuit when I'm sure it really works and actually fits, although I will warn you it's significantly more difficult to build

Even better, I have an idea for a "tube simulation" circuit. Oh yes, there are more good things to come.

PM me if anybody wants to be a tester (free samples!) for models #2 & #3, probably towards the end of the month. I do ask an .mp3 in return

I'll buy a pair of the "active" mics when you're ready to sell them.

 

[MadAudio]

I'll buy a pair of the "active" mics when you're ready to sell them.

Me, too.......

 

[mshilarious]

Me, too.......

Patience, Monty, climb the ladder

I'll have prototypes by early next week to send out for testing

I did max SPL testing on the MSH-1 today. Kinda fun sitting in my studio wearing -36dB earmuffs I don't exactly have a high-end lab here

Anyway, 1 kHz @ 115dB with 2% THD, 121 @ 4%, and 125 @ 20%. I was pretty sure that 125dB was gonna be the limit, because the capsule doesn't get fed more voltage than required for that, it was pretty cool to see that result in real life

Oddly enough I didn't test down to 1% THD, because I made an error in my first set of calculations, and I thought 115 was 1% I'll try again tomorrow, but figure on 112dB. Even so, for fast transients, 120dB would not be objectionable.

The MSH-2, among other benefits, might be able to as much as 6dB better than that.

 

[mshilarious]

OK! I have 4 pairs of MSH-2s ready to send out to testers, so look for 'em in the mail next week. I'm doing more testing myself tomorrow (including max SPL), but so far I think the goal has been met; essentially the same sound as the MSH-1, with the ability to drive low impedance pres. I tested down to 150 ohms, even that wasn't too bad, 600 ohms only loses about 2dB or so (vs. about 7dB for the MSH-1). Frequency response is essentially unchanged irrespective of input impedance.

Here's the schemo. Added in v2 is a transistor stage basically used as a current source, physically it sits on top of the stack of caps, where the RF filter cap was in v1. That cap was dropped in v2 in the interest of space. The single transistor with the impedance balanced output seems to be working fine, I have noted no difference in THD from v1, about 0.4% @ 94dBSPL @ 1kHz. That is a good thing, because I still can't find a way to fit the typical long-tailed pair arrangement, and one transistor is cheaper than two

 

[Minion]

Hi MS, Your design Looks Simple enough, I hope you don"t mind but I think I will try it out?? But I was wondering about the Orientation of the Transistor, Which way is it Faceing (I think the Flat Part of the Trans is Faceing the XLR But not sure) and can any Transistor be used?? also is that Diode a Zener??

Also are the Only Crossing Leads that are Joined the Ones with the Black Dot at the Intersection of the Crossing leads?? for instance does the Diode connect to the Horizontal Leads that connects to Pin 2 of the XLR or does it also connect to the Negitive lead of the C1 10uf Cap?? (I hope you understand??)

So this Circuit works with 48v Phantom power without any extra Noise??

In your Mics do you use PCB"s or PerfBoard/Vertoboard or just Direct point to Point Wireing?? If you want I could probably Design and Etch some Small PCB"s for you to Try out in your Mics?? ....You might even be able to Incorporate a couple small Poly bypass caps in there also, If you want to Incorporate them into the design I can see how small I can Make the PCB"s...It will probably be easier to wire and save on space, i could Probably work out some sort of Small Trade or something if you are interested...



ThanX a Lot!!!

 

[mshilarious]

Hi MS, Your design Looks Simple enough, I hope you don"t mind but I think I will try it out??

Yep, the circuit is free for all to try

But I was wondering about the Orientation of the Transistor, Which way is it Faceing (I think the Flat Part of the Trans is Faceing the XLR But not sure)

Actually, the way I build them, the transistor pins face down towards the XLR, at least until they are bent. If you're looking at the round side of the transistor, pin 1 is the gate which goes to the capsule. For 2N5457, source and drain (pins 2 and 3) are interchangeable. I used 2N5457 just because I have them laying around (and they are easy to get and cheap), 2SK170 is popular for mics, and is quieter. However, the capsule itself is kinda on the noisy side, 22-24dB, so the added noise is only about 0.3dB.

also is that Diode a Zener??

Yes.

Also are the Only Crossing Leads that are Joined the Ones with the Black Dot at the Intersection of the Crossing leads?? for instance does the Diode connect to the Horizontal Leads that connects to Pin 2 of the XLR or does it also connect to the Negitive lead of the C1 10uf Cap?? (I hope you understand??)

OK, for some reason the dots got messed up when I exported the picture. Here is how it should work:

Pin 2 to R2
Pin 3 to R1
Drains of D1 and C1 to Pin 1
Drains of C2 and C3 to U1

Hopefully that makes things clear

One other thing, R4 and R5 could be 680 or 470; that would probably even out the response between different input impedances some more. I just have lots of 1Ks because the MSH-1 uses them. I wouldn't go lower than 470 though.

So this Circuit works with 48v Phantom power without any extra Noise??

Well I don't have anything non-phantom powered to compare it to, but it does work well.

In your Mics do you use PCB"s or PerfBoard/Vertoboard or just Direct point to Point Wireing?? If you want I could probably Design and Etch some Small PCB"s for you to Try out in your Mics??

It's all point to point. I appreciate the offer, but there is *zero* room left inside the XLR connector. There is simply no way to fit a PCB without using surface mount caps. Also PCBs in small quantities are expensive to have manufactured, so it would drive up the cost.

....You might even be able to Incorporate a couple small Poly bypass caps in there also, If you want to Incorporate them into the design

There is room for two 0.01uF poly caps in the connector of the MSH-1; I also use a 0.001uF cap for RF filtration there. The earliest versions of the MSH-1 I made had the bypass caps, but I stopped using them because they took too much extra time for not that much benefit. But if I was building for myself, sure, toss 'em in.

However in the MSH-2, fitting the bypass caps and the transistor would be a much more difficult task.

 

[mshilarious]

Also, I finished SPL testing today. No additional SPL handling on the MSH-2 Seems to be between 105-110dB for 1% THD for both models, and 120-125dB to clipping. It varies mic to mic, and seems insensitive to (reasonable) power supply variations, so I imagine it is a characteristic of the capsule.

 

[JonSinger]

Yeah I'd like to see Behri try to take me on!

Or if you're too cheap for even Behri, roll your own! I posted the schemo here earlier.

Hi.

I find the schemo of the MSH-2 on page 2 of this thread, but I have not yet found the schemo of the MSH-1, which you mention in this posting. Can you point me to it?

I also have a quick question: do you modify the WM-61A capsules the way Siegfried Linkwitz suggests? ( http://www.linkwitzlab.com/sys_test.htm#Mic )

Many thanks --
jon

 

[mshilarious]

Hi.

I find the schemo of the MSH-2 on page 2 of this thread, but I have not yet found the schemo of the MSH-1, which you mention in this posting. Can you point me to it?

It's buried in an older thread. Here is the final MSH-1, below.

I also have a quick question: do you modify the WM-61A capsules the way Siegfried Linkwitz suggests?

I experimented with the Linkwitz mod, but chose not to use it in production, for a couple of reasons: first, in my experiments, I could not show a difference between the stock and modded capsules. This may be because my design uses a floating capsule, I am not sure.

Second, the mod involves soldering to a very small tab on the case of the capsule, which results in an occasional capsule failure, and substantially increases the amount of time required to assemble a mic. Since my goal was to keep costs low, and there was no demonstrable performance gain, I do not use it.

Edit: rereading that I see there is more than one "Linkwitz" mod out there. I think there is a long thread here where Marik experimented with it, that reorients the circuit around the existing FET. That is the mod I tested. Also note that WM61 has an improved FET from WM60AY.

Edit #17: OK, I just saw the little picture on the Linkwitz site. I thought you were referring to the entire mic circuit, so never mind

Also note that in my mic it's not possible to obtain a 9V supply, nor would it be desirable without adding an external FET (as in v2). Even so, when you commit to that kind of voltage, you have to be able to drive low impedance pres with a pretty good amount of current, which would require a circuit that would be more expensive and difficult to fit in an XLR connector.

These mics were born out of a desire to mod the Tape Op mic for use of phantom power, secondly to be more flexible, and finally to be very inexpensive, so the final design primarily reflects those considerations.

 

[Adam P]

I just want to cut through the electrical mumbo jumbo for a second and say that I used one of my new MSH-1s as a drum room mic on a quick session a couple weekends ago and was pleased with the result (aside from a slightly noisy delay unit, which of course isn't the mic's fault in any way). I'm looking forward to using them more extensively.

Thanks again!

 

[JonSinger]

Many thanks!!

Gotta run to rehearsals & a performance; will give you a better response when I get back.

Again, thanks --
jon

 

[tmix]

MS
Theese look really coool!

How quiet are they compared to other small diaphram mics like the Behrries?

I had to send behrs back because they were sooooo noisey.

Tom

 

[Sloan]

Any hopes to make a cardioid or other pattern version?

 

[mshilarious]

MS
Theese look really coool!

How quiet are they compared to other small diaphram mics like the Behrries?

I had to send behrs back because they were sooooo noisey.

Tom

Well anything with that small of a diaphragm is gonna be comparatively noisy. I do believe, however, that Behri is using a slightly inferior capsule than the WM61A, although I could be wrong there. WM61A is a few dB quieter than Panasonic's older WM60AY, but it's still probably in the 22-24dB range. The MSH-1 does not have any other transistors, so there is only a few small resistors adding noise, so at least there is that.

Quite honestly I haven't put the MSH-1 to a detailed noise test yet, you're actually the first to ask. I'll do a comparison vs. my Apex 220 when I get home, sometime next week.

 

[mshilarious]

Any hopes to make a cardioid or other pattern version?

No, not really. The available directional capsules have inferior noise, frequency response, and sensitivity, and I'd also have to work out drilling holes into the XLR connector . . .

 

[Minion]

MSHilarious....You might want to take a Look at some of the Cardioid and Uni Capsules made by "Primo" ...

Thay have a few models that have much higher SNR than the Panasonic Capsules....They have at least one Cardioid model with a 78bd SNR but I can not remember the Model number but I have heard of poeple talking about these Capsules on the Mic builders Yahoo group and they have been very impressed with them......

I also just finnished designing a PCB for your MSH-1 Design and I have gotten it pretty small (I haven"t etched any yet but will probably try some this weekend)....

I have the design down so I should be able to make the PCB about 2.5cm x 1.5cm or maybe a Bit smaller and by putting the Parts on both sides of the PCB and laying the Caps on there sides I think i will be able to Fit it in a XLR but I will also exchange these circuits with my Battery powered ones which I have been haveing Noise problems with.....


ThanX