#19 Takstar / Gear4Music WPM-200 Wireless Monitor System part 3: transmitter mods

And at long last(?), we've reached the point where we take a look at the transmitter end of this wireless monitoring system. Not a whole lot to see on the outside, really: power switch, power LED, channel select rotary switch (1 to 6) on the front, and the DC input barrel socket and the 1/4" stereo input jack socket on the back.

#18 Takstar / Gear4Music WPM-200 Wireless Monitor System part 2: receiver mods

Ok, turns out i lied in the previous post, as this part 2 won't be about the transmitter - so sue me...

Either way, into the meat of it: upon some listening tests with music, it turned out the expanders were misbehaving just awfully. They made the volume jump up and down virtually all the time, in a very disconcerting manner - basically briefly increasing the volume (noticeably) upon every louder bass note (and only for the duration), and dropping back down in between.

I took apart one of the receivers, and lifted the schematic of the expander chip and the associated passives around it. Pretty much exactly what's in the datasheet of the TA31101, with the exception of having omitted the coupling capacitor going to the "Comp In" (pin 11), thereby turning the compressor side of the chip into another 1:2-ratio expander, just like the other half.

#17 Takstar / Gear4Music WPM-200 Wireless Monitor System part 1: receiver teardown / li-po upgrade

This "part one" will be dealing only with the WPM-200 receivers and the lithium-upgrade pertaining to them. The transmitters and subsequent mods will be dealt with at a later date.

Fine, i'll admit, i miiiiiiiight be ever so slightly guilty of the whole "if all you have is a hammer, everything around you looks like a nail" thing, what with these nifty little one-cell charger & protection boards, but hey - at least it kinda validates(?) my "stockpiling" of laptop and phone batteries along the years. Now, i finally have the excuse to put some of them to good use and all that...

During my UK eBay browsing sessions a month or two (or seven?) back, i happened to come across a few listings of faulty wireless monitor sets (transmitter & bodypack-receiver) from this British music gear retailer. A bit of googling later, revealed to be straight rebadges of Takstar WPM-200 sets - nope, they hadn't even bothered changing the model number. The one thing they might've customized, though, are the radio frequency ranges / channels (since there are different regulations on different continents, and so on).

#16 Cheap chinese BM700 / BM800 microphone modding / upgrade, part 2 (CK12 & K47 capsules)

<Continuation from part 1>

After quite a while, i "finally" got around to modding the other three BM800 mics i had. Just for the hell of it, i decided to make a matched triplet (to use as, say, three overheads on a big drum set).

I went with more of my modded-Schoeps boards, and matched components between them, as closely as i could (within reason, at least). Resistors were no big deal, and neither were the capacitors; one of those cheapo chinese ATMega328-based "component testers" helped with matching the JFETs and PNP transistors. No, i didn't necessarily care about the absolute values, just that they're the same (or as close as reasonably possible).

#15 Alesis io|26 repair & modding

So, i got my hands on one of these Alesis io|26 interfaces for pretty cheap (50 bucks delivered). "Of course", i bought it as faulty (can you see a pattern yet?), with the already "classic" issue of dead Firewire chip (the ubiquitous Texas Instruments TSB41AB2).

I went for it mainly for two reasons. First, because i knew it was based on the TC Applied Technologies Dice II chip, and as such, should have flexible enough mixing / routing options; second, due to the ADAT inputs available. The sort of "added bonus", one might say, were the gain adjustments for the 8 analog (mic/line) inputs.