Jerry Lee Marcel:

You can reduce gain of the internal jfet to unity if you disconnect capsule gnd from ground and instead connect it directly to capsule drain.
That way you make it a charge amp just like the km84, just with lower gain (unity).
This works the same way as the simplep48RCA.?
This also works very well for reducing gain of pip mics, by the way.
This works only with 3 wire or linkwitzed capsules.
I wish had figured this out in the old days when I went out and recorded live concerts...

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"decreasing", not recreasing.

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Have you tried recreasing the resistor ?

1kohm should reduce level by 6dB, 620 ohms by 10dB, and so on.

I've got this problem also, but with a two-wire Primo em258 capsule — since I believe drain and ground are already connected inside the capsule, is there another way to reduce the sensitivity, or is that an impossibility for such a capsule?

Here's the diagram from the em258 spec sheet:

You can reduce gain of the internal jfet to unity if you disconnect capsule gnd from ground and instead connect it directly to capsule drain.
That way you make it a charge amp just like the km84, just with lower gain (unity).
This works the same way as the simplep48RCA.?
This also works very well for reducing gain of pip mics, by the way.
I wish had figured this out in the old days when I went out and recorded live concerts...

Hi Milan, you may try the suggested schematic in the datasheet, something like this.
?

The EM200 is capable to manage SPLs up to 136 dB, maybe a good windscreen is enough in most cases.
At first glance the resistors values in your schematic seem too big
my 2 cents

On Sun, Jan 7, 2024 at 08:26 PM, <mildavaca@...> wrote:

Also, do I understand correctly that the EM200 is a three cable capsule, so there is no need to do the linkwitz mod?

That's right, you don't need to do the mod.
Just remove the 22uF capacitor across the 5k6 resistor.

On Sun, Jan 7, 2024 at 08:37 PM, jack wrote:

Primo recommend 5.6KOhm but you can adjust that value to change the sensitivity.

Increasing this resistor would not change the sensitivity if the capacitor is still there. It would just decrease headroom.

Just disconnect the 22uF capacitor across the 5k6 resistor.

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One of the challenges here is that this methodology lowers the voltage out of the FET ?it may reduce output but not headroom/maxSPL ? Ideally we want to lower the signal going into the Fet. ?It’s easy with a fetless capsule. Not sure the best methodology for one with built in FET?

Here is my actual schematic:
/g/MicBuilders/message/32232

Do you have a resistor between drain and source?
Primo recommend 5.6KOhm but you can adjust that value to change the sensitivity.
Cheers
Jack

I apologize for not being more specific about the capsule type and microphone circuit. I need to reduce the sensitivity of the Primo EM200 capsule in the KM84 circuit. I have a working microphone, but it is very sensitive for "normal" studio use.

I don't know if I understand correctly from the mentioned documents, can I achieve the sensitivity reduction by adding an RC link between drain and source?

Also, do I understand correctly that the EM200 is a three cable capsule, so there is no need to do the linkwitz mod?

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You can do the "Jerry Lee Marcel" mod. Check Stefano's or Ricardo's files. It will reduce sensitivity by about 10dB and about 15dB more max SPL, with a 2.2k resistor.
But you need to make the 3-wire "Linkwitz" mod.

You can also drop the value of the drain resistor. Output level is directly proportional to the drain resistor value. However, this will not increase the max SPL.

Migs - sure thing, here you are:



This is FAQ, I guess the easiest way to navigate this huge thread on DR-70D in general and there are links to couple of known mods and Jim Williams' mod in particular.
As far as I remember this mod's subject pops up all along the thread from time to time.
Cannot be more precise, it's a huge thread and although I read it all, it was some time ago.

That's precisely the problem, as you said - no proper A-B'ing. Just "I modded the recorder and it performs better".
Sure, if you have only one, it's a bit difficult to A-B it properly due to amount of time the mod takes (especially if you send the device to be modded by some else). Otherwise one needs two devices - modded one and not, to record the source at the same time.

Glad you liked my Falc-Boya ? mic idea. Have fun making the mics.
The hardest part is to get the body apart. You canbsee on the photos that one looks... hmm... well used ;)
I had to sand down the burrs after first, failed (2) attempts. The second one is nice - I made the jigs/holders already.
Note that you absolutely need to cover cut outs with something sticky or rubbery. Thin layer of silicone sealant or glue that stays rubbery after drying. Otherwise MDF just slides around the body, no matter how strong you clamp it.
AND do not drill to far!
5-6 mm is enough to seat the capsule properly still leaving a ridge to support it from below. You drill to far and you're left with a clean through hole with no support for the capsule.
The Boya white markings can be cleaned off with solvents like acetone, toluen or nitro. The body is powder coated. Sure, the lettering remainscstill visible but darker, not bright white.

Pawel

Hi folks and "Merry New Year! " (as one E.Murphy would say)

@pmfalcman when you say "I found a long thread on this mod and I got less excited ;)?No one made proper side by side comparison yet."
Could you tell us where you found the long thread you are talking about and/or share a link? I'm just curious to read a bit on it.
That is often the problem with "mods", not making proper A-B comparison of before and after or with and without.

Well done BTW for the BOYA body find and the excellent DIY job!
I might give it a try soon.

M

"I'm thinking the longer one may give a bit more holding area if using a mic holder and windscreen, yes?"

I clip the XLR plug in mic holder when using windscreen.
But yes - extra 10 mm might be useful.
My next pair will go into longer bodies. Probably Primo 272 this time.

Brian - I don't know, havent compared them yet. Tascam's mics are noisier for sure.
As for the Jim's mod - I was excited at first when I read about it. Them I found a long thread on this mod and I got less excited ;)
No one made proper side by side comparison yet.
I even bidded on a "broken" DR70 recently, aiming at modding it Williams' way but the price went to high and I gave up.

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How do these mics compare to the built in DR-70d mics? Asking because I have the same unit. I think the built in ones sound pretty decent.