ECM8000 Mods

Swapmaster,

>Got a good connection now and it is about 5 db down from the stock mic and I am very happy with it. I don't have a mic preamp yet so I removed the preamp from the mic and made a steel adapter to mount an RCA jack in the bottom of the Behringer. I feed it into a modified Radioshack SPL meter which has a reasonably clean and very flat preamp then from the line out of the meter to the laptop.>

Good! I am glad it works for you. I am little bit puzzled, though. The modified WM61 should have same output as stock connected WM60. I think you have 5db drop because you don't use a preamp in the mic, which should give gain around this figure.

<Marik, how will the preamp in my mic with the transformer compare to the newer ones without the transformer? And can it be modded to the same characteristics you are getting with yours?>

Although I never heard the transformer coupled one, I wouldn't trust cheap Chinese trannies. Since there are much less traces on the board, I think it would be much easier to make a new PCB.

<Did some searching around on Digikey last night.. there are a few Linear low noise regulators that would be interesting to try, (only 20uV of noise!) and in smal SMT packages as well.. but only no good values fixed, have to use a variable.
And 10v isn't that rare of a value as I thought, for the more everyday 78Lxx series of TO-92 parts..>

Jon, on the second thought, I am not sure how much reduction of noise you will get using regulator, but I am sure then you can use smaller value of filtering capacitor. I tried to use caps here up to 6800uf and did not get any further improvement.
 
Ok, I did a compare between a stock WM61b and one with the Linkwitz mod and the modded one is about 13db down from the stock WM61b. Which puts it about 6db down from an unmodified WM60ay. Does this sound about right?




edtited for additional information
 
<Ok, I did a compare between a stock WM61b and one with the Linkwitz mod and the modded one is about 13db down from the stock WM61b. Which puts it about 6db down from an unmodified WM60ay. Does this sound about right?>


How do you connect it to the preamp? do you use blocking cap?
 
Swapmaster said:
Ok, I did a compare between a stock WM61b and one with the Linkwitz mod and the modded one is about 13db down from the stock WM61b. Which puts it about 6db down from an unmodified WM60ay. Does this sound about right?
Click to expand...

This is entirely possible. The transconductance spread on FET's is notoriously wide and the sensitivity in the common source (as shipped) configuration is entirely dependant on that transconductance.

Going to the source follower via the Linkwitz mod, the gain from the gate is pretty close to one. The sensitivity in this configuration, while lower, is likely to be much more consistent from capsule to capsule because the diaphragm/gap/backplate geometry that determines the sensitivity measured at the gate is much more controlled than the transconductance of an FET.


Bob
 
Take away resistor R26, replace C15 with highest possible value----thousands uf would be fine. Connect Drain of modded capsule to R15--C15 junction. Source to C1 with 10K resistor to ground, and ground the capsule.
 
Marik

About the mod you suggest to my meter preamp. What will it do?

I do not understand what the drain or the source are. I assume the drain is the positive and the source is the negative connection from the capsule.

Do you mean to connect modded capsule drain to C15/R25 junction? You stated connection to C15/R15 junction which does not exist.

This is what I understand so far but it's probably wrong

1. Remove R26

2. Increase C15

3. Cut ground from FET on a new capsule, connect factory capsule - to C15/R25 junction

3. Connect factory capsule + to C1 positive side

4. Connect 10k from C1 positive side to ground

5. ground capsule case.

Will this change the gain settings for VR1 ? I need to keep it to adjust calibration.
 
<I do not understand what the drain or the source are. I assume the drain is the positive and the source is the negative connection from the capsule. Do you mean to connect modded capsule drain to C15/R25 junction? You stated connection to C15/R15 junction which does not exist.>

OK,

The drain is unmodified pin of the capsule. Connect it to positive of C15 (where it is connected to R25). The pin which you just cut from the capsule case is a source--connect it to positive of C1, and from this connection run 10K resistor to the ground. Ground the capsule case. It is the correct way of connection. On the second thought, you cannot connect the capsule through RCA connector, as you need to do it with THREE wires, so it might be a better idea to use existing XLR, and modify connector on RS. This might be the case why you loose 5db of sensitivity.
If something is unclear feel free to contact me.
Let me know (or post on the board for everybody's benefit) how it came out.

Best, Marik
 
Ok, I will try the mod this weekend and see what happens. There is no room for an XLR plug on the meter so I will use 1/8" sterio plugs.

Thanks
 
One last thought before I do the mod. Is this still considered a Linkwitz mod? Do we want to reverse the fet connection to the board as the Linkwitz does or is cutting the ground from the FET is all we are after?
 
Ok, I just looked at the sketches on Linkwitz's site and you are using the source follower 3 wire hook up. I understand now.
 
<Ok, I just looked at the sketches on Linkwitz's site and you are using the source follower 3 wire hook up. I understand now.>

The way you use it, you cannot make two-wire connection, because it requires opposite polarity of battery from what you get in your RS meter.
 
Marik

I found my db problem. With the Linkwitz 2 wire mod I had terminals 1 and 3 going to ground and terminal 2 going to C1/R26 junction. I reversed connection on the capsule and it is just a few db down from the stock WM61b. Will your suggested mod be of any benifit or should I leave well enough alone. I am happy with it now.
 
Swapmaster,

As I wrote before, the resistor R26 should be taken away. I never tried 2 wire connection before, but in this configuration the battery polarity should be reversed and actually, I don't really understand how did you connect it now. I would suggest you to connect the way I did, as I know for sure this way it works right.
 
After the Linkwitz mod I connected the pin that I soldered the capsule to C1/R26 junction and the pin that was detetched from the capsule to ground. It is connected the way Linkwitz shows it as a source follower 2 wire connection. The db's are down just a few from the factory RS capsule so VR1 allows me to recalibrate it easily.
 
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Modified ECM8000 listening trials

I visited Marik today and compared a few microphones in use on lightly picked acoustic guitar. We compared two mic's at a time directly during each pass and tried to play in a similar style for reasonable consistency to other passes. Included in the tests were his modified Behringer ECM8000 microphones and an unmodified, stock ECM8000.

The modified microphone really proved itself as a very good acoustic instrument microphone. Within a few seconds of playback, no matter what we compared it with (MXL 603s, modified Oktava MC012, unmodified ECM8000, NADY TCM-1050, and a custom mic similar to a Neumann U67, I believe) we both knew it stood out in this application.

It has a very even, open, natural response, but it is still interesting and compelling. Flat, but not boring. I think it shined in the high-end, with the harmonics resolved very well.

The room sound was minimized by our 12" mic'ing distance. Noise was increased slightly from the cardiod microphones, when we cranked the monitors to listen for it, but it is probably a result of room noises and traffic noises. The modified mic had a different, slightly more subdued character than the noise of the unmodified mic. I don't really know exactly how much was actual mic noise and how much was external noise, but either way it was not really objectionable.

It's a certainly a nice microphone, and, I think, safe to say outright better than the others for natural-yet-involving-sounding recording of solo acoustic instruments.

Thanks to Marik for his work on this microphone. I think many people will appreciate it.
 
Marik is working on that. It was his intention to have .mp3 soundfiles posted on the webbernet.

I'm not sure if he'll have all the files (not necessary, in my opinion) or just the Behringers head to head.

I think he will post to this thread when he's got that set up. We both agreed that the differences would still be noticable through .mp3.
 
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