Mavis Prima MPA-81s is a very nice donor mic platform

[Khron]

Resembles this "Alice" schematic? https://groupdiy.com/threads/need-help-troubleshooting-a-pimped-alice-circuit.86068/

Yep, apart from the added high-frequency attenuation parts (R14, R15, R16 & C2, in the schematic in the linked thread).

 

[AdamFrisen]

More I look into microphone discussions (I just scraped on the surface), it seems to be about "coloring" the sound so it is pleasing to your ears or should I dare to say "larger than life". When it comes to voices, I tend to prefer the way it sounded when I listened to FM radio decades ago (not too much compression though).

I enjoyed the presentation of microphones made by Jim Lill:



Keeping the same electronics/body and alternating between "compatible" capsules should be very fun.

 

[AdamFrisen]

I finally got some time to replace the capsule with Arienne K47 flat. I see the capsule will be positioned much higher using the included together with Arienne's. I ended up using the one I ordered as it was little lower (but still higher than the default in MPA-81).

https://www.aliexpress.com/item/100...UwAR7zyA&utparam-url=scene:search|query_from:

I read the position of the capsule in the grill can affect the sound noticeably?

 

[rock soderstrom]

I read the position of the capsule in the grill can affect the sound noticeably?

...way more than any super duper capacitor. The situation reminds me of close miking of a guitar amp speaker, small changes in position result in big changes in sound.

 

[AdamFrisen]

Monday-soldering? How did this pass QA...



Little fiddly as I needed to unscrew both circuit boards in order to access the mounting screws for the grill. The switches were in the way.

 

[AdamFrisen]

Arienne K47 flat to left, MPA-81 capsule to right

 

[Khron]

Monday-soldering? How did this pass QA...

Well, just because it looks like ass, doesn't mean it doesn't make a sound electrical contact. Not that it needs to pass any meaningful current anyway...

 

[micolas]

Arienne K47 flat to left, MPA-81 capsule to right

View attachment 132161

It seems to me or is MPA-81 a capsule frequently found on Ali...?

https://a.aliexpress.com/_EwOVXuJ

 

[AdamFrisen]

...way more than any super duper capacitor. The situation reminds me of close miking of a guitar amp speaker, small changes in position result in big changes in sound.

Ok, maybe I should try to correct the height of the new saddle later.

It seems to me or is MPA-81 a capsule frequently found on Ali...?

https://a.aliexpress.com/_EwOVXuJ

The white plastic parts looks different, I can post more pictures little later.

I have to amplify 20-25 dB more than before when using default MPA-81 capsule to get good level using Arienne K47. Now my mic preamp is at +60 dB.

Is this as expected? I checked the pad (-20dB) on the mic is not enabled.

 

[micolas]

I have to amplify 20-25 dB more than before when using default MPA-81 capsule to get good level using Arienne K47. Now my mic preamp is at +60 dB.

Is this as expected? I checked the pad (-20dB) on the mic is not enabled.

MPA-81 is a capsule from the k67 family.
A normal K67 capsule at the same polarization voltage can deliver 5...6dB more than a normal k47 (at 10kHz for example)
Considering that the MPA-81 can be even brighter by a few dB than a classic k67,
and the Arienne K47flat is even darker in the most sensitive sound area, and also that there are cumulative tolerances, it is possible that the perception of loudness differs by probably 10...12dB, but not by 20...25dB.
Everything must be carefully checked. The character of the sound differs so loudness can be subjective.
Does the circuit have de-emphasis?

FR graphics are made by @soliloqueen.

 

[AdamFrisen]

Thanks.

MPA-81 is a capsule from the k67 family.
A normal K67 capsule at the same polarization voltage can deliver 5...6dB more than a normal k47 (at 10kHz for example)
Considering that the MPA-81 can be even brighter by a few dB than a classic k67,
and the Arienne K47flat is even darker in the most sensitive sound area, and also that there are cumulative tolerances, it is possible that the perception of loudness differs by probably 10...12dB, but not by 20...25dB.
Everything must be carefully checked. The character of the sound differs so loudness can be subjective.
Does the circuit have de-emphasis?

Thanks. That explains why I need to amplify more than before. So expected more gain required but not the amount of it (maybe add a pot and trim the bias?).

Except for +60 dB required, it sounds nice so maybe I should leave at that for now. I am happy my soldering skills could be retrieved with little exercise beforehand.

Regarding de-emphasis, I don't know, but according to Khron's comment earlier in this thread, I assume no. Correct me if I am wrong.

 

[AdamFrisen]

I put the microphone in cardioid mode and turn it around while recording my voice. I don't hear any attenuation off-axis. Except the overall gain gets higher in figure 8 and omni.

 

[Khron]

I put the microphone in cardioid mode and turn it around while recording my voice. I don't hear any attenuation off-axis. Except the overall gain gets higher in figure 8 and omni.

Photos of which capsule wire goes where?

 

[AdamFrisen]

I put the red wire from the center of one side of the capsule to pad on the circuit board with letter 'F'. The white wire from the center of the other side of the capsule to the pad with letter 'B', The blue wire in the picture was connected to the side of the capsule so I attached that to the side of the new capsule as well.

Note: I actually didn't do this test with the microphone before changing the capsule.

I see in the photos I posted that the blue wire seems to be soldered to what is referenced as mic+.

 

[Khron]

How can you be sure "B" stands for "back", and not for "backplate" ("the side of the capsule")?

 

[AdamFrisen]

How can you be sure "B" stands for "back", and not for "backplate" ("the side of the capsule")?

I don't know. I just put the wires how they were soldered with the original capsule. The original one has two white wires coming from the center of the both sides of the capsule. The blue wire was connected to the side of the capsule.

 

[Khron]

I put the red wire from the center of one side of the capsule to pad on the circuit board with letter 'F'. The white wire from the center of the other side of the capsule to the pad with letter 'B', The blue wire in the picture was connected to the side of the capsule so I attached that to the side of the new capsule as well.

In the photo that's in the first post in this thread, i can see a wire pad marked "F" right next to one marked "R".....

With the fig-8 being the center detent of the pattern switch, and with those light-brown i'm suspecting 51meg(?) resistors around the pattern switch, that part of the circuitry reminds me a lot of the CAD GXL3000.

http://recordinghacks.com/images/mic_extras/cad/gxl3000-schematic.png

Something miswired somewhere...

 

[AdamFrisen]

Sorry, the letter is not "B" but "R". It looked like this before replacing the capsule.

 

[AdamFrisen]

I remember reading some incident with XLR writing being wrong on BFL V47...

@Wordsushi - Would you care to do off-axis test in cardioid mode on your modified MPA-81s? And also interesting, how was your mic wired before the mod?

 

[Khron]

Here's a thought - reinstall the original capsule and see if it behaves the same way.