Primo EM204 to EM200 modification

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kingkorg

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Hello!
EM200 has been one of my favorites lately, and probably one mic desert island SDC capsule.

They can be pricey with import and shipping, however a guy on Ebay has lots of EM204 at lower price.

EM204 is same as EM200 but it has built in source to ground resistor (470ohm) and can't be biased properly for loud sources. Even with vocals it clips easily.

So i sacrificed one capsule to find out where this resistor is, and if it's easy to just cut the trace from the outside. Turns out it's quite easy, and this is the place where you need to make a tiny hole to do it.

Measure source to ground resistance after you are done to make sure you did it right. Hole should be sealed afterwards because of polar pattern.

While we are here, does anyone know which FET this is, the one on the bottom image? Marking seems to be DJ but i am not sure. 2sk4027?

4Z6d2tG.jpg



This is the trace we are cutting:

Er6suwB.jpg
 

Gus

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Do you run a vacuum cleaner as you drill to remove anything that might get in between or do you drill upward  and let the material fall down?
 

kingkorg

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I do some gentle vacuum cleaning, however tiny amount of dust won't do damage because of the construction.

There is cloth between layers underneath, there is no way dust could reach diaphragm or backplate.
 

kingkorg

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Khron said:
That sounds to me like "ye olde" Linkwitz mod for Panasonic 1/4" electret capsules :)

Sure, it helps to know where to cut :)

One other thing is that one of the backplates, the one found directly under those tiny holes is connected to the diaphragm, and thus the gate of the FET. So topology can relatively easily be changed to "charge amp" discussed in Richard Lee's simpleP48.doc and Henry Spragens' site. This by adding capacitor from mentioned backplate via tiny spring, for example, to drain connection. For even better THD, but sacrificing some S/N.
 

rogs

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craigmorris74 said:
Just curious, has anyone compared the Primo capsules to Transound capsules?
Depends which Transsound capsules you mean?
Certainly the EM204 has a much smoother and extended frequency response than the standard TSB165A style electret from Transsound, but how the Primo capsules compares to Transsound's new 34mm LDC capsules (the TSC-1 and TSC-2) I don't know?
Those look like 'standard' Chinese K.67 style capsules, but I'm assured they are actually made by Transsound themselves, so they may sound better?
Sadly, shipping costs make Transsound capsules too expensive to buy, here in the UK.
 

craigmorris74

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rogs said:
Depends which Transsound capsules you mean?
Certainly the EM204 has a much smoother and extended frequency response than the standard TSB165A style electret from Transsound, but how the Primo capsules compares to Transsound's new 34mm LDC capsules (the TSC-1 and TSC-2) I don't know?
Those look like 'standard' Chinese K.67 style capsules, but I'm assured they are actually made by Transsound themselves, so they may sound better?
Sadly, shipping costs make Transsound capsules too expensive to buy, here in the UK.
I was thinking something like the TSB-2555B or TSB-25AXZ3.  Something comparable to the Promo EM204 or 200.
 

rogs

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craigmorris74 said:
I was thinking something like the TSB-2555B or TSB-25AXZ3.  Something comparable to the Promo EM204 or 200.
I read good reports about TSB-2555B, so it may well compare well with the EM204 or 200?
Here in the UK the TSB-2555B is likely to be more expensive than a Chinese 34mm LDC capsule, so probably not worth going for?...
Even the EM204/200 capsules are expensive when compared to 34mm Chinese LDC condenser capsule prices here in the UK, but there are projects where that style of higher quality electret can be more usable.
I used 3 x EM204 capsules for a Mid-Side (M/S) mic project, where it was easier to fit 3 x 16mm capsules into a single mic body than it would have been to try and accomodate 3 x 34mm capsules!
 

kingkorg

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Honestly i would pick em200 or em204  over any chinese LDC for anything. I love them that much. Even more than my favorite k67 from 797 audio. Unless i need multi pattern that is. Only possible downside is that they are a bit sensitive to plosives. But nothing that pop filter wouldn't fix.

Those capsules perform so well both on axis and off axis, noise, consistency.

They can't really be compared to TSB-2555B, as it doesn't have FET built in.
 

rogs

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kingkorg said:
Those capsules perform so well both on axis and off axis, noise, consistency.
I have to say I was pleased with all 3 of those qualities when I used 3 x EM204 for my 'BM800 donor bodied' Mid-Side mic.....

MS.EM204.capsules.jpg


Not sure I don't prefer at least one or two of my Chinese LDCs to the EM204s? -- Although 'consistency' is not exactly a strong  feature of most cheap Chinese LDCs  :)
 

rogs

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kingkorg said:
That mic looks great!
Thanks! -- It was just constructed as a 'one off' experiment just to see how it performed.
I was hoping that the 2 x EM204s mounted side by side - and facing in opposite directions - would be close enough to a genuine double sided capsule for the figure of 8 'side mic'.
Seems they are.... an offset of only about 20mm is not really a problem in 'real world' side channel audio pick up.

The 3rd EM204 faces forward, and is used as the cardioid 'mid channel' mic.

The EM204s turned out to work way better than the EM184s I had tried in my first attempt....
As you say, they are quite impressive capsules - especially as they are only electrets!

I used a very simple circuit, put together on stripboard. Seems to work pretty well....

MS.EM204.Sch.900.jpg
 

kingkorg

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Thanks for the schemo!

I cut the source resistor on them so that i can use internal resistor in place of Q5 and skip the rest. If i use Schoeps type circuit.
 

Recording Engineer

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For years, I’ve been liking the idea of an M/S in a 47-type grill/body as well, with SD capsules, but who is doing great fig-8 SD capsules? Les Watts was supposedly offering some, but I’ve never heard of anyone actually  picking one up. I’ve tried for some years now to get a hold of him, all different ways, to no avail. I sure hope he’s doing well.
 

rogs

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kingkorg said:
Thanks for the schemo!

I cut the source resistor on them so that i can use internal resistor in place of Q5 and skip the rest. If i use Schoeps type circuit.

EM200 would probably be a better choice for ultimate simplicity  - I don't think I would be as brave as you though  -- I'm not sure I could trust my 'aim' when it comes to cutting that resistor on the EM204 from the outside...
 

kingkorg

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I salvaged two of these tiny boards from Aliexpress mini u87. So this is the idea, based on Josephson e22s, basically to have least possible acoustical interference around the capsule. We'll see how it turns out in the end with the sleeve.

The good thing is the capsule housing is grounded so there is no emi even when used like this with no sleeve.

xgZ8tpK.jpg
 

k brown

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The underside view seems to show two caps to gnd from the drain; these would seem to actually be EM204N, that had RF caps inside. I just e-mailed Primo, and they said those two caps are 10pf and 33pf, for a total of 43pf. Would probably be a good idea to add 43pf on both drain and source on EM200 (drain only on EM204) in any DIY mic to filter RF/EMI.

He said EM204N is longer in production, but they have a lot of stock left. Odd that micbooster doesn't sell them. Even odder that they are charging twice as much for 204 than for the 200, when a much better mic can be made with the 200, without having to mod the capsule.
 

rogs

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..... Even odder that they are charging twice as much for 204 than for the 200, when a much better mic can be made with the 200, without having to mod the capsule....
For some reason, the Micbooster listing for the EM204 now defaults to the price for a matched pair? ...
A single EM204 capsule is still the same price as the EM200...
 

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