iSK BM-600 as a donor mic?

[Icantthinkofaname]

Also looking at a 680pF, that seems to be the recommendation on Gearslutz too. I definitely want a neutral sounding mic with a slight presence boost since that's what works for me.

Is anyone able to give me an idea of how it sounds stock? I can't find any decent audio samples of it in English. The frequency graph if it's accurate looks like the mic would already be pretty flat. Looks like a slightly less smooth Warbler MKID (no idea if it would sound like it though), so it looks like even stock could be as usable as my Black CM1. I do plan to do the capacitor upgrade though.

 

[Icantthinkofaname]

Would a (used!) Behringer B2 Pro with an upgraded C3 be a better choice (if it has a negative feedback circuit), or would it be relatively similar? The BM-600 has the benefit being really cheap buy also having great electronics in it and the specs seem a bit better with less self noise, and specs in greater detail, plus there's the transformer but I don't know how important that is to the U87 sound.

 

[Icantthinkofaname]

I guess that makes a certain amount of sense, then.

As you may or may not have noticed in one of the links i've posted before (namely this one - https://groupdiy.com/index.php?topic=61084.msg773828#msg773828 ), i've lifted the schematic of the whole thing, albeit didn't really bother renaming all the parts to fit the designations in the actual BM600, so the HF de-emphasis cap value is 220pF, and is (fortunately) located on the bigger signal board (as opposed to the preeeeeeetty cramped input / switch board).

I myself am kinda skeptical about the whole "this film cap sounds worlds better than that film cap", although i do try to not have ceramics in series with the signal path. In other words, just about any film cap is preferable to a (non-C0G / NPO) ceramic, imho

820pF might be a bit heavy-handed, starting from 220pF, but i suppose it's worth a shot. Worst case, you'll end up with a dark(er)-sounding mic - ribbons anyone?
Might want to consider also getting a 470pF one, or perhaps a 680pF one too, and see which value you like best. Or if you're feeling particularly adventurous, MacGyver a switch for that, too ;D

Bumping because the mic should arrive within the next few days. Which capacitor value would be better if I wanted as close to a U87ai sound I can get with the stock capsule?

 

[Khron]

A starting point: https://groupdiy.com/index.php?topic=67473.0

Bumping because the mic should arrive within the next few days. Which capacitor value would be better if I wanted as close to a U87ai sound I can get with the stock capsule?

 

[Icantthinkofaname]

The microphone arrived today. C3 has a value of 10uF/50v and C13 next to it says 4.7uF. These are cylindrical black capacitors. I'm not sure if they changed the PCB layout, labelling, or components, but I'll upload a couple photos. Or the labelling is just different from other mics where C3 is the HF rolloff.

I can write more about it tomorrow because I'm off from work then.

http://recordinghacks.com/images/mic_extras/neumann/u87ai-schematic.gif

C106 in the U87 schematic.

https://groupdiy.com/index.php?action=dlattach;topic=61084.0;attach=38337;image

C2 in my version of the BM600 schematic (the part designations may not match the silkscreening in the mic).

Further details: http://www.audioimprov.com/AudioImprov/Mics/Entries/2014/2/7_Mic_Electronic_Eq_Pt.1.html

Looking at your schematic the capacitor for the HF rolloff is C1 in this mic. The values for a lot of marked stuff on the PCB matches the labeling in your schematic so it seems like it could accurate for my BM-600.

 

[Icantthinkofaname]

And heres the photo of the back PCB.

UPDATE: Got C1 removed (but broke the pins) and got a 680pF/100v WIMA cap in there, accidentally damaged the gray capacitor next to it, and burned the solder that was in the C1 spot (it really wasn't coming out, had to jam a super fine soldering tip in there), the new cap in C1 is sitting slightly on the resistor next to it. Got a lot of new static in Omni mode so I opened the mic again, saw a lot of smudging on the PCBs because I'm a ******* and forgot to wear gloves, so I cleaned the boards with 99% isopropyl alcohol. Once it dries and I reassemble the mic I'll update my post. Next time I think I'll just leave it to the pros.

 

[Icantthinkofaname]

And heres the photo of the back PCB.

UPDATE: Got C1 removed (but broke the pins) and got a 680pF/100v WIMA cap in there, accidentally damaged the gray rectangular thing (unlabeled) next to it (a bit of burning on the side so that may need to be replaced), and burned the solder that was in the C1 spot (it really wasn't coming out, had to jam a super fine soldering tip in there, I know ot was a bad idea), the new cap in C1 is sitting slightly on the resistor next to it. Got a lot of new static in Omni mode so I opened the mic again, saw a lot of smudging on the PCBs because I'm a ******* and forgot to wear gloves, so I cleaned the boards with 99% isopropyl alcohol. Once it dries and I reassemble the mic I'll update my post on whether or not this his is there. Next time I think I'll just leave modding to the pros.

 

[Khron]

I don't suppose you bothered removing the board out of the body before attempting the removal of C1, did you? :-\

It would've been quite trivial to remove C1 by melting its joints from underneith.
Or if you weren't planning to reuse it anyway, you could've just flexed it back & forth until its legs broke ;D

PS: If anything, finer tips are actually worse at transferring heat into the solder (joint)...

UPDATE: Got C1 removed (but broke the pins) and got a 680pF/100v WIMA cap in there, accidentally damaged the gray capacitor next to it, and burned the solder that was in the C1 spot (it really wasn't coming out, had to jam a super fine soldering tip in there), the new cap in C1 is sitting slightly on the resistor next to it.

 

[Icantthinkofaname]

I don't suppose you bothered removing the board out of the body before attempting the removal of C1, did you? :-\

It would've been quite trivial to remove C1 by melting its joints from underneith.
Or if you weren't planning to reuse it anyway, you could've just flexed it back & forth until its legs broke ;D

PS: If anything, finer tips are actually worse at transferring heat into the solder (joint)...

I disconnected it to the point I could hang the board out and easily reach the back to solder/de-solder, probably should've de-soldered everything, oh well.

I did try to de-solder from underneath but I was having a lot of trouble. I tried it the same way I did with wires on a crappy mic, but there actually wasn't much solder there.

The hissing is constant in bi and omni mode and on and off in cardioid.

That gray piece worries me since it's giving off a very bad smell. Anyone know the manufacturer or where I can source a replacement?

EDIT: I guess it's just a .47uF 100v film capacitor so it should be easy to replace. I'm gonna order a replacement. But other than that what else should I check to try to fix this new loud hiss?

 

[Khron]

Adding some extra / new solder to the joint helps, not in the least due to forming / being some extra heat-transfer medium

A 63v cap will do just fine there, you'll never see more than 15v or so on that JFET drain.

 

[analogguru]

what a poor microphone....

 

[Khron]

... And that's an assessment based on...?

what a poor microphone....

 

[analogguru]

... And that's an assessment based on...?

Its based on reading carefully.

Obviously this innocent, defenseless microphone is tortured with a soldering iron:

I did try to de-solder from underneath but I was having a lot of trouble. I tried it the same way I did with wires on a crappy mic, but there actually wasn't much solder there.

So the capacitor was apparently "desoldered" from the component side:

and now:

That gray piece (rem.: capacitor) worries me since it's giving off a very bad smell.

 

[Icantthinkofaname]

First I tried removing C1 from the back where you're supposed to, but had no luck. Shouldn't have tried from the front obviously, but live and learn. I just ordered 5 similar (same capacitance, same max voltage) pieces on eBay, so I should be able to replace it when those arrive. The seller has great feedback and says they're located in Australia, and Australia Post seems to be super fast.

I was pretty sure it was a capacitor, but I called it a piece because it was unlabeled on the PCB so I wasn't 100% sure.

 

[Icantthinkofaname]

I've finally got the mic working again. I'm still getting a lot of noise (maybe from bad soldering/residue or just something like skin oil getting on the PCB) but the mic now functions in all polar patterns and there's no additional hiss or whine when changing polar patterns.

https://app.box.com/s/9em7tbugpteqih6jul8cyl12c57qu3rj here's a quick sample.

 

[Icantthinkofaname]

Bumping because I ordered a couple more, and a better soldering iron and a slightly better solder sucker (still a pump, can't justify $300 on the gun ones until I have more experience).

I'm gonna do the same basic capacitor swap. Is there any reason to replace the transformer or is it decent as is?

 

[Impala]

I have modified several BM600 microphones.
Yes, the BM600 uses a K67-style capsule but it sounds less bright than most Chinese microphones do.
There is some signal to noise ratio improvement possible, the transistors aren't the most quiet ones.
Never used a C12 style capsule in this microphone, but as far as I remember there is no EQ in the circuit, so this should be possible. It might be a good idea to change some capacitors, because the frequency response drops at low frequencies.
But the microphone isn't really bad as it is delivered. (Keeping the price in mind.)

Dear Ruud,

Are you still willing to do a mod on a brand new Devine BM-600?
What mod do you propose and what will be the cost?

Greets from Antwerp Belgium

Alfons

[email protected]

 

[mrgrooves666]

So will anyone having one of these BM600 mics handy would kindly let me know the measured distanced between the 2 pcb screw holes please? Appreciated it!

 

[Icantthinkofaname]

So will anyone having one of these BM600 mics handy would kindly let me know the measured distanced between the 2 pcb screw holes please? Appreciated it!

I have a couple of them, I can measure later. I won't get home until 11:00 PM or 12:00 AM EDT though.

 

[Icantthinkofaname]

So will anyone having one of these BM600 mics handy would kindly let me know the measured distanced between the 2 pcb screw holes please? Appreciated it!

They're about 3 cm apart, from the right edge on the left hole to the left edge of the right hole. I'd say 30.5mm. The holes don't exactly line up with those in the body though.