Harvey Gerst
New member
I promised Marik I would take some pictures of the circuit inside my original ECM8000. Here they are:
I think he did use a WM61. The schematic reads WH61, but he probably meant WM61Swapmaster said:Does this mod change the response graph of the mic? If not, would using a WM61 capsule be possible?
Marik said:Jon,
Yes, the capsule is quite sensititve to the noise. In fact, I spent a great deal of time to quiet it down. The 15K and 220um cap are sufficient to suppress it to minimum, however the voltage regulator should be definitely better. Higher voltages ( I tried up to 14V) on the capsule make situation worse.
<7808. (wouldn't) Too bad there isn't a common 10v version.>
Do you know the trick with diode in the middle leg? Two diodes should do.
<What do you think? I'd add a load resistor to provide maybe 5-10 mA of current thru the regulator, they quiet down a bit with some load, the capsule and resistor divider would probably only load it a mA or so.>
We cannot do it. Don't forget, here we have barbarian practice to put two 6.81K resistors at the phantom rails for 14ma total current. The circuit current is already about 5 ma, which is a lot for the mic. The further increase will drop the voltage significantly.
Anyway, I gotta try it and see...
Rossi said:Another difficulty is the Linkwitz mod. It's virtually impossible to solder a wire to the housing of the capsule as it is made of aluminum. I'd be happy for suggestions how to solve that problem.
Marik said:Naw DJL, the noise of this capsule is an electronic one and comes from the internal FET. That's why I want to open it and see if will be able to replace the FET.
Marik said:<It's a silver ink pen. More than enough conductance. That path is a _very_ low current path. I coat the trace with silicone or E6000 after the ink dries. Beware of closing off the vent hole.>
Bob,
I was thinking of using it, however prices on this stuff are high.
I believed that besides of acoustic dumping resistance noise, the FET contributes into overall noise in significant way. If you have other thoughts please share.
Ha! You think it's bad now, wait until you have kids! Not that they're not worth it, but they greatly limit your time, which is why you're doing all this and I'm not helping.Marik said:...So far to me it cost at least 50 hours of trying different things, soldering, listening, recording, comparing etc. Plus some scandals and accusations like 'your mics are more important than me' etc. And.... parts cost.
arcanemethods said:I believe the bias in microphone FET's such as are used in the WM60 or WM61 is done via the leakage current through an integrated diode connected from source to gate and that the bias voltage is essentially zero regardless of the voltage on the can.