<Details and photos can also be found in the "part 1" and "part 2" posts over on my blog 
>
Because of Mr. Spencerleehorton, i decided to spring for a few of these uber-cheap BM800 / BM700 electret mics - primarily as body donors.
I went for the blue/silver version, at least because it seemed less garish than the black/gold one And i specifically looked for one with METAL shockmounts because plastic shockmounts (would) just give me the heebee-geebees... So i ended up grabbing four of these:
http://www.ebay.co.uk/itm/291654240021?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
They updated the price since i had bought'em, at the end of january. So four of these, including shipping to Finland, ran me a grand total of 71,13$ / 47,52gbp, so roughly 18$ / 12gbp each. They were sent as two separate packages - one arrived this week apparently without getting checked by customs, while the second one arrived into the country on friday (12.02) and DID stop at customs. Go figure... On the bright side though, it only took about 2 weeks to get here from China, so still - could be worse
Either way, moving on: first impressions.
1) Cast chassis - quite impressive, in fact. Most of the body is one cast piece - from the XLR connector "neck", all the way to the top plate to which the capsule mount is fixed. This means it's pretty much (mechanically) dead, as opposed to mics like the Apex 435 / Alctron HSMC001, which are highly resonant (ie. if you knock them with a finger, you'll feel the vibrations for a good quarter/half a second).
2) Gold ring is quite loose. Purely a decorative / an aesthetic component, it's a bit too narrow for the space between the tube of the body and the headbasket, so it jangles a bit when you move the mic. Couldn't care less, it will get removed anyway, to allow room for the cutouts for the pattern / pad / high-pass switches.
3) Two-layer headbasket mesh - this is a slightly "mixed bag", as it were. The inner layer isn't soldered in or anything, only fixed with one(!) dab of glue, near the top of the headbasket. Bad side = long term, it might(?) be prone to wiggling loose and/or rattling. Good side = removing it is easy as pie
4) Circuitry's no big deal - an analysis & tests can be found over here: http://audioimprov.com/AudioImprov/Mics/Entries/2014/12/18_Another_Chinese_mic_Circuit.html
5) This one's a bit of a downer - the capsule mount's just a crap little moulded piece of plastic, so... I'm gonna have to get a bit creative when it comes to mounting the new capsules
I tried to make a half-decent "montage" of various views of the mic. The mic itself pictured is already with the inner layer of mesh removed.
Now, the plan is to stick a pair of group-buy CK12's into two of these bodies, along with a modified version of the stock circuitry (which is itself a modified Schoeps circuit). I decided to keep the input design, only with a J305 FET. The "separate" high-pass / phase-splitter PNP there makes for an easy implementation of a switchable high-pass with a single-pole switch. Later i think i might also post the circuit, for the scrutiny of minds brighter than mine ;D
I'm planning to get a few PCB's manufactured (signal board, dc-dc converter & switch-board), and designing those has been what i've spent the bulk of the last couple of days on LTspice for tweaking component values and topology details, and then cramming everything onto suitably-sized boards, while keeping an eye on mechanical constraints (mounting holes, board width, component height etc).
Not a whole lot to show just yet, but i'll post updates as soon as i have any
>Because of Mr. Spencerleehorton, i decided to spring for a few of these uber-cheap BM800 / BM700 electret mics - primarily as body donors.
I went for the blue/silver version, at least because it seemed less garish than the black/gold one
And i specifically looked for one with METAL shockmounts because plastic shockmounts (would) just give me the heebee-geebees... So i ended up grabbing four of these:http://www.ebay.co.uk/itm/291654240021?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
They updated the price since i had bought'em, at the end of january. So four of these, including shipping to Finland, ran me a grand total of 71,13$ / 47,52gbp, so roughly 18$ / 12gbp each. They were sent as two separate packages - one arrived this week apparently without getting checked by customs, while the second one arrived into the country on friday (12.02) and DID stop at customs. Go figure... On the bright side though, it only took about 2 weeks to get here from China, so still - could be worse
Either way, moving on: first impressions.
1) Cast chassis - quite impressive, in fact. Most of the body is one cast piece - from the XLR connector "neck", all the way to the top plate to which the capsule mount is fixed. This means it's pretty much (mechanically) dead, as opposed to mics like the Apex 435 / Alctron HSMC001, which are highly resonant (ie. if you knock them with a finger, you'll feel the vibrations for a good quarter/half a second).
2) Gold ring is quite loose. Purely a decorative / an aesthetic component, it's a bit too narrow for the space between the tube of the body and the headbasket, so it jangles a bit when you move the mic. Couldn't care less, it will get removed anyway, to allow room for the cutouts for the pattern / pad / high-pass switches.
3) Two-layer headbasket mesh - this is a slightly "mixed bag", as it were. The inner layer isn't soldered in or anything, only fixed with one(!) dab of glue, near the top of the headbasket. Bad side = long term, it might(?) be prone to wiggling loose and/or rattling. Good side = removing it is easy as pie
4) Circuitry's no big deal - an analysis & tests can be found over here: http://audioimprov.com/AudioImprov/Mics/Entries/2014/12/18_Another_Chinese_mic_Circuit.html
5) This one's a bit of a downer - the capsule mount's just a crap little moulded piece of plastic, so... I'm gonna have to get a bit creative when it comes to mounting the new capsules
I tried to make a half-decent "montage" of various views of the mic. The mic itself pictured is already with the inner layer of mesh removed.
Now, the plan is to stick a pair of group-buy CK12's into two of these bodies, along with a modified version of the stock circuitry (which is itself a modified Schoeps circuit). I decided to keep the input design, only with a J305 FET. The "separate" high-pass / phase-splitter PNP there makes for an easy implementation of a switchable high-pass with a single-pole switch. Later i think i might also post the circuit, for the scrutiny of minds brighter than mine ;D
I'm planning to get a few PCB's manufactured (signal board, dc-dc converter & switch-board), and designing those has been what i've spent the bulk of the last couple of days on
LTspice for tweaking component values and topology details, and then cramming everything onto suitably-sized boards, while keeping an eye on mechanical constraints (mounting holes, board width, component height etc).Not a whole lot to show just yet, but i'll post updates as soon as i have any
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