#25 Behringer ADA8000 "Ultragain Digital" revival

I got my hands on one of these Behringer Ultragain Pro-8 Digital a few months ago, as faulty (as in, totally dead) for about 50$ shipped. Having done some preemptive googling before going for it, i was expecting the transformer to be toasted. Sure enough, that's exactly what the problem was - one half of the center-tapped primary measured in the hundreds of kohm, so pretty much open-circuit (as opposed to the 50-odd ohms the remaining good half measured).

Initially i was planning on finding / getting a "drop-in replacement" toroidal transformer, ie. similarly sized physically and power-wise, but with less insanely-high secondary voltages. The stock one, according to some "inspection notes" i found online, seems to have had roughly 2x20VAC windings for the analog +/-15V (meaning the voltage regulators had to "burn off" uselessly much power / voltage), 12VAC for the 5V regulators, and a whopping 58VAC winding for the phantom power regulator. That's about a 50% overkill across the board. One can only wonder just what possessed them to spec the transformer quite like that, especially since it must've been a custom order - you'll rarely find retail units with more than two (identical) secondary windings, and when you do, expect to pay a pretty penny for'em.

#24 SM Pro Audio TB202 dual tube preamp / channel strip modding & upgrade, part 4

On the note of front panel switches, you might've noticed two extra ones, in the previous post (the part 3). One other idea had crossed my mind, already long before this second stage of modding. It took me a little while, but i managed to get my head around how to implement this. The idea was to be able to swap the order of the two processors in the signal path.

From the factory, as described in the "part one" post, the processing order is input - gain - tube - compressor - EQ - output. But in some cases, it can be desirable to have the EQ come before the compression stage. That way, one can attenuate certain frequency ranges that one would not want the compressor to react to (or conversely, boost ranges for the compressor to react to).

#23 SM Pro Audio TB202 dual tube preamp / channel strip modding & upgrade, part 3

Even before having received the thing, i had already started thinking of daisy-chaining the two channels. In the context of something like a bass preamplifier, for example, one would want a "clean" channel, perhaps with some heavy compression, in order to have a consistent signal (especially in the lower registers), as well as a "dirty" channel, with a high-passed signal having some distortion applied to it.

#22 SM Pro Audio TB202 dual tube preamp / channel strip modding & upgrade, part 2

Once the "adventures" from the previous post were completed, i proceeded to hook up one channel to my audio interface and feed some test-signals into it. This revealed a few things which didn't sit with me all that well.

First of all, the compressor didn't seem to be doing much of anything. No level reduction with the knob turned up to full (even with full input gain and clipping the snot out of the tube), the associated LED stayed green (instead of going red), nothing. A bit of oscilloscope-probing in the signal rectifier area quickly pointed out the issue - there was no real rectification going on. The signal coming out of that stage was still largely sinusoidal, albeit with a small kink at the zero-crossings. Well, that's no good...

Removing the diode in the signal-rectifier for testing didn't reveal anything, it measured as a normal 1N4148 both in and out of circuit. My aforementioned buddy pointed out that the arrangement they had used in this design, a "precision diode" circuit, was somewhat flawed as a concept, as is described in this link over here. I then proceeded to upgrade both channels to the "precision rectifier"circuit (see link above).

#21 SM Pro Audio TB202 dual tube preamp / channel strip modding & upgrade

<Further developments can be found in parts two, three and four>

I'll admit, this was a bit of a lucky catch, in that it was mistakenly listed in the wrong eBay category, but one i "stalk" for good deals on certain faulty bits of audio gear. It was up for auction, there didn't seem to be much demand for it, and i ended up winning it for a mere 21 euros. About as much as the shipping for it ended up costing, oddly enough.

But still, even for some 40-odd bucks, not a bad little unit. Two channels, a (bare-bones-ish) compressor on each (1.5-10:1 ratio, 1ms/5ms attack, 500ms/1500ms release, at least according to the specs in the manual), as well as 3-band EQ (80Hz shelving / 1.8kHz bell / 8kHz shelving), and there's a tube / valve involved in the circuitry as well. If nothing else, i figured it would do nicely as a bass DI (or even an overdriven preamp, once some internal re-wiring is figured out and done).

#20 SM Pro Audio TB202 power supply repair

<Some sort of continuation from another post>

Buuuuut that brings us to what might as well amount up to the proverbial "elephant in the room" - the power supply. No markings or label anywhere on it - if i didn't know any better, i could almost say it never had any (no adhesive residues or anything). Fortunately, it was held together with four Phillips-head self-tapping screws, so "disrobing" it wasn't unecessarily traumatic. That being said, what greeted my eyes, sort of WAS.

#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.

#14 TC Electronic Studio Konnekt 48 "Dice II STD" replacement / transplant

A couple years ago i got my hands on a faulty one of these. Details of the revival process can be found over here; photos visible only for forum members though. Buuuuut since i'm in a good mood, OVER HERE you can find the link to a Google Drive folder with all the (relevant) photos i had posted on that particular thread - you're welcome...

The last issue i had to take care of, back then, was the (apparent?) shorting to ground that some of the I2S clock signal lines, coming out of the Dice II chip. Fortunately, it has several sets of these clock output signals in use, so between cutting a couple traces and adding some wire jumpers, i managed to put together and distribute a healthy set of clock signals to all the ADC & DAC chips that required them.

PS: It seems that the original link for the schematics of this unit is dead nowadays ("thank you", Music Group?), but for the sake of completeness and posterity, i've reuploaded it right over here.

#13 Fisher RS-1022 rehabilitation and bling-ification

So i had this old Fisher RS-1022 Studio Standard stereo receiver brought in, with one of the fuses in-line with the speaker outputs blown. Fair enough, that was easy enough to replace, they made it quite easy, with the fuseholders being mounted right on the rear panel. The clamps were nowhere near as elastic (or firm) as they might've once been, but with a pair of needle-nose pliers and a bit of creativity, that was no biggie.

Second issue, five of the six lamps that illuminate the tuning scale and the radio signal level were dead. In four of the dead ones, the fillament was attached only at one end, and in the fifth, it was attached at neither end. Interesting little lamps, 6.3v AC, 250mA, in a similar casing as 6x32mm glass fuses. Good luck finding replacement ones (which may very well just end up dying again anyway); these will get replaced with a few white LEDs recovered from a laptop display's backlight.

#12 Cheap chinese BM700 / BM800 microphone modding / upgrade (to say the least).

<Part 2 can be found right over here>

Last year, after hearing (or rather, after reading) about these cheapo BM700 / BM800 microphones, over on the GroupDIY forum, i decided to get a few myself. They were cheap enough (under 20 bucks a piece), and i figured they would, at the very least, make for reasonable enough donor bodies.

Some credit is due in no small part to Mr. Henry Spragens, whose microphone section on his blog served as a considerable portion of inspiration for this endeavour. Said blog is a fountain of knowledge, testing and ideas for anyone interested in condenser microphone modding or even building from scratch.

#11 sE Electronics sE X1 rebuild

It's been a good few years since this mic (sE Electronics X1) came into my possession. As many others i have, i bought this one as faulty. The main problem was, it was noisy as hell (think wind-noise, or the sound of blowing straight into a microphone).

Once i had another capsule to test this with (a temporarily removed capsule from a Shure KSM27), i figured i'd hook it up to the X1 to see whether the capsule was the source of the noise. Nope, the noise was still there. After i ruled out the (stock) capsule, i replaced it with a 100pF styroflex capacitor, for minimal hassle (and risk of damaging a capsule) during subsequent testing of the electronics.

#10 A litle K67 (microphone capsule) fun

From among my microphone collection, as a result (or rather, a consequence) of various upgrades and capsule replacements, i kept the stock ones (which were still good), for later experiments or "just in case". Today, that day arrived.

Among a few others, i had a some stock single-sided K67-type large diaphragm condenser capsules out of the several AKG Perception 200's i've collected these last few years. Fortunately, they're actually assembled out of two nearly-identical halves. The front has the gold-sputtered Mylar / PET diaphragm, and the rear one (since they're cardioid-only capsules) is skinned with a plain, non-metallized diaphragm.

#9 Revisited: Amphion Impact 500 (DB Series DB5004) subwoofer amplifier - DONE!

Got the fresh parts the other week, and installed them all. That, plus rebuilding the two blown and "distressed" traces, respectively.

#8 Low battery blinking indicator

This thought came out of the LED ring flash li-po mod, since the battery indication programmed into the microcontroller was "calibrated" for 100% being the 6v coming out of four full AA batteries, and (close to) 0% around 3.8-4v. Obviously, since a single lithium cell is only 4.2v when full, the stock battery indicator's out of whack.

Next step - i wanted a blinking indicator. Partially, because a solidly-lit LED would be a constant drain, and partially because a flashing light is more noticeable - think turn-signals on cars, or the emergency lights on police cars & ambulances.

#7 Cheapo ring LED flash / light teardown & li-po mod

I had been thinking about grabbing a LED ring flash for my camera for quite some time, but finally last week, i pulled the trigger on one. Cheapest of the cheap (from what i could find on the British eBay), but still cost me a bit under 30 bucks.

That being said, it's a reasonably well-featured package: four different coloured diffusers (that go onto the front of the LED ring), eight different size adapter rings (for lens/filter threads, and onto which the light clamps on to), and the control unit that mounts into the camera flash "hot-shoe". Also, the LEDs in the light "head" are split into two halves (ie. left and right), for <ahem> creative effect when using the ring flash for macro work.

The thing normally works on 4 AA's, buuuuuut... given some of the previous posts here, you oughtta have half an idea about my feelings regarding disposable power sources... <wink-wink, nudge-nudge>

#6 Canon EOS 400D / Rebel XTi troubleshooting & repair

I got this old EOS 400D from a friend for about 35 bucks. She said it won't power on, even with a fully-charged battery. Might as well have a crack at it, eh?

On the outside it seems to be in pretty good shape. A bit of dust here and there, but hey, it's about a decade old, whaddya expect? Battery checks out fine, reading 8.15v, so that's definitely not it.

As chance would have it, between being offered the camera and receiving it, i did some digging around online, and i came across this little story here (scroll down to the second half of it). Could i (also) be fortunate enough to only need to swap out some fuses?

#5 Another Li-ion Upgrade - Cordless Trimmer

Due to my openly-admitted laziness, a while back i got myself a trimmer - it's way quicker and easier than a full shave, and i rarely need (or want, for that matter) to be totally clean shaven. But that's enough background babbling, on to the nitty-gritty. This one's mainly "what for increasing the chooch factor", as it were - thank you AvE, you crazy canuck.

#4 Dunlop Zakk Wylde ZW45 wah pedal teardown & repair

Ok, this one's a real quickie. One of the guitarists in my band got this wah (Dunlop ZW45 Zakk Wylde Cry Baby Wah) as a gift a number of years ago, and in the last few weeks it developed crackly and intermittent sound (regardless of being on or off).

Initial fiddling with the power / input / output jacks pointed towards a questionable patch-cable, but even that soon stopped working, which then turned my suspicions towards cracked solder joints (rather than the jack sockets themselves).

#3 MOTU 8Pre teardown & gain adjustment pot replacement

On the latest drum tracking session i surprisingly discovered that channel 8 on the MOTU 8pre in my recording rig was noisy and useful-signal-less. This same unit had a similar issue with channel 6 when i bought it (as faulty, with a shot Firewire chip).

Fortunately, when i was about to take care of ch6, i got two replacement pots. When investigating the issue, i had read it's a relatively common occurrence, so i figured that as long as i'm contacting the local MOTU distributor, might as well get an extra / spare one, just in case (especially since i had two 8Pres at the time).

#2 Amphion Impact 500 (DB Series DB5004) subwoofer amplifier autopsy (and repair, hopefully)

Right, so i've had this amplifier brought in last week (sans the subwoofer enclosure itself). When i noticed the brand, i remarked to the owner that, to the best of my knowledge, Amphion stuff is anything BUT cheap. He confirmed, this whole thing having costed him something over a grand(!!!), a couple years ago.

It had allegedly been serviced before, and he pointed at an electrolytic cap. A ChemiCon SXE - totally out of place on a board otherwise full of CapXons. Yep... Oh joy...

#1 M-Audio Fast Track (mk1) gain and 18650 Li-Ion mod / upgrade

So i had this old, pre-"facelift" M-Audio Fast Track since 5-6 years ago, which had been lent to a bandmate for the last couple of years. A few weeks ago, i traded him up to a Scarlett 2i2, and i got my Fast Track back.

And then i got thinking - it has the convenient mono/stereo switch on the front (to have both inputs in mono, or input 1 on the left and 2 on the right), a headphone output, doesn't need a specific power supply (it being bus-powered)... 😏