Long time no press, I’ve been busy finding a job and again noticed that doing things is generally much more fun than documenting the doings, but here we go again.
I’ve been planning for a sort of home studio for a long time. This is what I’ve come up with during past few weeks and well, studio is a bit too hi-fi expression for the current state, but it’s a start and it works. Equipment now includes couple of nice dynamic microphones for vocals, Korg D4 multitracker, basic mixing abilities, power amplifier and close-range monitor speakers. This can now serve for singing, synth (or multitrack) backings, karaoke – whatever the need.
And it wouldn’t be mine if it wasn’t something home-made. I built the amplifier enclosure from what was once a cd-tower, so it’s recycled! Amplifier is a Tripath chip based ”Class-T” module with stated power of 2 x 100W @ 4ohms. I bought it for testing earlier this year and it surprised me with both being quite clean and quiet sound-wise but also by delivering almost the specified wattage to a load. So I made a power supply for it and put it to good use. It’s actually impressively efficient too. Amp delivers pretty much the promised wattage per channel to 4ohms with very nice THD figures and generates very little heat, shoebox has no air-holes at the moment and I can still keep the volume cranked up for several hours with no problems.
This is how it looks.
No extra bells and whistles. Switch to turn it on, power and audio in and speakers out. All you really need 🙂
Audio processing is now only done with a small Behringer mixer I purchased second hand. It still needs some nicer preamp for mics and perhaps a dsp for mix-out, more on those later when I’ll find suitable device(s) to fill the needs.
Mixer has seen it’s better days for sure, but nothing a little cleaning up wouldn’t take care of. All the channels and features work and the best part is – no noticeable humm or hiss at the output – it’s quiet!
And the microphones. Bought them based on some reviews to try them out. T-Bone MB-85Beta (Shure imitation) and Beyerdynamic Opus 29-S. I like them both for what they are, affordable dynamic microphones with solid build quality and natural sound reproduction (in my case the singer will be the main problem anyway 🙂
Last (and least) the speakers. They’re small Behringer passive close-range monitors I removed from my surround setup couple of years ago. I’ll propably upgrade these soon-ish, but as the room is quite small and they handle the available power well, result is actually quite good. Overall when considering how little money I spent on these components, this is a superb solution.
Tested this also as a karaoke setup last night, works very well indeed!
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First snow – 2010
A tad late posting because I was replacing HDD to my main computer and didn’t download photos from my camera until now.
Anyway we were visiting my parents in Karvia last weekend (23.10). There was no sign of snow when we arrived there Friday and when I woke up saturday morning, almost couldn’t believe my eyes, there was ~15cm of snow!
And my niece Elina got on to creating her very first snowman.
Let there be light
One of the things too long on my to-do list was some nicer night-lightning to my home and leds would be the perfect solution for that. They’re cheap and practically last forever. Like usually, I couldn’t find anything that would fit my purpose from stores, so I decided to make the led-strips myself. It’s made from triangle shaped wooden strip. Drilled the holes (by hand at this point, which is very visible :P), milled a groove for wiring in the back side and soldered the leds in place. Leds are 5mm, white, driven with constant current of up to 50mA. Lightning output was around 15000 mcd @ 20mA. Not very much in lumens, but it is enough for this sort of purpose.
And first installation of strips fitted in place, this is how it looks now in stairs. Photo is actually quite dark compared to what it is in reality. There’s well enough light now to see where you put your foot on.
EPROM data lost forever?
I got myself an interesting bit of museum-grade hardware last week from a friend of mine. Little (not in size, though) Z80-based industrial computer, four A4 sized cards on a back plane, 8KByte of battery-backed up SRAM. Device seemingly worked – one could read data (programs) from memory, but saving didn’t work correctly or at all. My first suspicion was of course software Eprom(s) as the computer originates from somewhere 1980’s. As I hadn’t instant access to a prommer, I first decided to check possible hardware-faults in address decoding logic of memory card as the fault was hinting to that sort of problem as well. I didn’t find any faults in there, couple of potentially hazardous design-flaws, but as the device had already worked 20+ years, those had perhaps been proved to work after all.
So I loaned a simple prommer from a friend and started verifying the eprom contents. One out of the three eproms was outputting random-ish bytes here and there. I could read out 4-5 different commonly repeating binary images out of the one Eprom, but none of these worked at the actual hardware. With any of the tried images the computer stays dead silent, with original supposedly-corrupted rom, it atleast starts up. As the prommer-software lacked any control parameters over the reading, I decided to do what I had planned to do for some time now, my own prommer (well, memory-reader at this point atleast). I was hoping that with settable read-speed, I could perhaps still salvage the lost contents somehow. On to the matter… few hours and roughly 100 lines of C later, I had Atmel mcu interfaced to eprom and could read it’s contents over serial port to PC.
Good news, after slowing down the read operations and precise control over the vcc, I could now get more consistent data out of the eprom. Bad news, none of these images was even close to the ones read with the commercial prommer. At this point I verified that my prommer was actually reading the data correctly and not outputting any garbage – it worked, so the fault was really the ROM itself. I read the contents for about 30 times, out of the results there can be found three commonly appearing binary patterns. Looking at these three patterns more closely, reveals there is difference between them only in three address locations, so I can now atleast get quite consistent garbage out of the chip.
Too bad for more testing, the commercial prommer decided to stop working at this point (what seems like timing problems with the PC, it’s one of those using programmed I/O through parallel port), so I couldn’t test all of the read images on the actual hardware. So I’ll propably have to continue with adding the write operations and some kind of terminal functions to my own prommer.
What troubles me at this point, is that despite the more consistent data, I can’t be sure if the the idea of slowing the read was correct at all or if I did end up with more garbage than with the commercial prommer anyway. Disassembling the rom contents doesn’t immediately reveal anything as there are no illegal opcodes or non-sane parameters at the differing address locations and digging through thousands of lines of disassembled code to understand it, is too much trouble to do for just plain curiosity. Anyway, should this test succeed, it would propably be a nice bit of information as the much used eproms are getting older every day in all kinds of equipment.
Long story short – if you have a car, refridgerator, tv or anything useful (and old) equipment you have containing eproms, back the data up before it’s too late. They’ll fail eventually to point of no repair.