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vainajala

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Everything posted by vainajala

  1. Response graph.... The extra parts L5 and R6 in schematic are supposed to perform baffle-step compensation, to attenuate the midbass-midrange quite a bit.
  2. <bump> I understand this is not really a forum about loudspeakers, but here's some updates... This might be the final crossover's circuit... I just need to wait until the drivers arrive to me (about 2-3 weeks maybe). And when I get my "testing gear" (a speaker measurement jig+microphone+computer) ready, I can actually measure how well or bad these drivers perform in this application. And tweak the crossover if needed. Before that, I must trust my ears ;D The Jig: http://www.gti.net/wallin/audio/audua/audua.html
  3. Hello Audioguru, and thanks for your reply :) Actually, I was going to connect the drivers with opposite polarity. This really got me thinking of using 18dB filters, for their better performance. My amp is a Sony's model STR-DE585, not a welding machine ;D But seriously, I think it's rated for nominal impedances between 6-16 ohms... If I use the filter component values determined by the basic calculations (with no Zobels), and simulate that with 7spice, the freq. responese has very large variations, caused by the inductance at the driver... I see no other way than using the Zobels :P Of course this is a bad thing, especially when one wants only the highest quality and performance. But you see, my goal with this design is to create small 2-way loudspeaker pair with decent soundquality and complexity... So I think a natural choice for me is a passive crossover. That's a great suggestion, but when using woofer's coil inductance as a 0,60mH inductor, I get crossover frequencies about 930 Hz for 18dB crossover... with formula taken from speaker design book. L=(80*Z)/f --> L=(80*~7ohm)/930Hz = 0,6mH IMHO, this could work well with 3-way's, but bit too low for 2-way :( I'll see what I can do! :) These both filters have -6dB points at 3,05 kHz according to 5spice... should there be some "gap" between them, for example, -8dB at 3,05 kHz? I think it's an interesting article... But for the bi-amping, I understand it is a great technique because there is no need for passive crossovers, but unfortunately I don't have resources and equipment for that kind of system...
  4. Hi, I have in mind building small 2-way loudspeakers to my stereo system, because the old speakers are in so bad condition. The bass-element's foam surround has come really "weak" and it has many holes even though the surround hasn't been touched by hand practically at all! The loudspeakers are at least 15 years old, so it's really not a wonder :) I'm considering Vifa TC14WG49-08 as bass/midrange: http://www.d-s-t.com/vifa/data/tc14wg49-08a.htm and (maybe) Vifa D20TD-05-06 as tweeter: http://www.d-s-t.com/vifa/data/d20td-05-06a.htm They are most propably to be installed in 14 liter bass-reflex box tuned at 43 Hz. I knew something about different loudspeaker enclosure types (and how they work) before I was even thinking of starting this project. But I must admit that i'm quite a new-bie when it comes to crossovers. I haven't designed these before and I thought it might be wise ask you will they work before I start buying the crossover parts. They are quite expensive, you see... The pictures from analysis program 5-Spice follows. They are (at least they should be ;D) -12dB/octave filters, with Zobel circuits. Any comments are appreciated...
  5. Thanks, Ante! :) So it's a 5V regulator (like 7805), but with slightly higher max. output current and lower max. input voltage...
  6. Hi all, These components are from old PC power supply, the problem is that I can't find any info about the left component in the picture. The right one seems to be PNP Darlington transistor... Could someone help a bit?
  7. Andy, If you don't have very new (=power-consuming) PC then this article might interest you... ;) http://home.concepts-ict.nl/~cybersake/carmp3/ Ante, do computers need voltages other than +-12V and +-5V? Because I remember there was also +3,3V... ???
  8. Check out this... 8) http://www.lsdiodes.com/5mm/5mmflash.htm
  9. AJB2K3, I agree also to Ante's suggestion. it's a simple and powerful circuit, and with good heatsink it doesn't need any pass transistors for this application. There's many circuit examples in the datasheet of LM338, I suggest you to take a closer look... :)
  10. Audioguru, thanks for information! I must try this when I have more time for this project... Ante, maybe the MAX626/627 driver could be used to drive the dual P-channel FETs then? And, should I get inverting (MAX626) or non-inverting (MAX627) driver? Also the max. 18VDC supply must be arranged for the MAX62*, that's one concern too. I'll maybe use 2-3 of IRF9540N FETs...
  11. I decided to test N-channel MOSFET as a switch transistor, and it worked well! Typical efffiency was 77% with 21W and ~74% with 55W. The heatsink was so small that the FET heated pretty quick with 55W and higher loads, so effiency in these loads is more "approximate". I had to make modification to circuit to drive the FET: I tied the emitters to the FET's gate (instead of collectors) and collectors to Vcc. This is very promising result, and at least using FETs, the base resistors can be eliminated. So I'm considering to use two or three N-ch FETs in parallel instead of BJTs... NTP45N06L N-ch FET http://www.onsemi.com/site/products/summary/0,4450,NTP45N06L,00.html
  12. About darlingtons... I tried a darlington transistor configuration with dual MJ15004 transistors. 55W halogen served as a load, again. Unfortunately I didn't measure the performance of that circuit (Iwas in bit of a hurry...), but the output-transistor got very hot (i almost burn my finger when touched it ::)) I experimented some different base resistors from 330R to 10K with little or no impact on "heating-effect". I see you're discussing about darlingtons, well how about Sziklai configuration (also known as the complementary Darlington)? I suppose that the Sziklai-type has lower saturation voltage when compared with ordinary Darlington... I found this information from some finnish electronics website. Text was in finnish, so I put a translation in a form of a picture :) Some more Sziklai info here: http://www.ampslab.com/c200cfp.htm
  13. I found this simple "OAUGDP" plasma panel experiment. It's quite a simple device but it looks cool in my opinion! ;D Has anyone tried to built anything like that? Anyway, nice use to a unused ignition coil lying in a junkbox... http://jlnlabs.imars.com/plasma/html/s_gdp1.htm http://jlnlabs.imars.com/plasma/html/oaugdp.htm
  14. First of all, thanks for your help, it's surely needed ;) Audioguru, What do you think about using three MJE2955's in parallel, with 0,1R emitter resistor in each? By the way, are the "equalizing resistors" needed in switching applications? As far as I can understand in this transistor's datasheet, the HFE=~40 at IC of 3A. So with three transistors, max. 9A could be drawn with HFE ~40. So base resistors: 45V / (3A / 40 * 1,3) =460 ohms, and wattage: P = 0,075A2 * 460 ohms = 2,58W. Am I correct? 9A would be actually more than enough, the circuit's current limit start at ~7,5A... MOSFET(s) might be good idea. Could P-channel fets be easily used in this circuit? IRF9540 or IRF5305 maybe? ??? MJE2955: http://www.onsemi.com/site/products/summary/0,4450,MJE2955T,00.html
  15. Some testing with 30VAC 300VA transformer... I have made some changes to the device: I put transistor and diode into heatsinks, and added a trimpot to adjust the voltage. The 150R base resistor heats up very quickly! I changed it to a 11W 150R power resistor and it got up to 70
  16. I have now built the powersupply and tested it a little bit. I unfortunately can't test it thoroughly, because I don't have a variable DC-supply. I'll try it tomorrow with two car batteries in series, resulting 24V. I did some tests with a car battery charger as a mains supply, trying some 12V bulbs and small fans as a load. It did work quite nicely, and it lowered the output voltage to about 8-9V (charger's voltage is about 18V when not loaded). I also measured volts and amperes & calculated effiency "n": With 21W car bulb: n=74% small 12V/100mA fan: n=68% 55W car halogen: n=46% (charger's max. current sets the limit here, it's only 4A) It definitely needs more testing, fine-tuning and of course heatsinking, but if it works after that, I think it will be worth of it :)
  17. This is what the original version looks like...
  18. Sorry, but I forgot to add one wire (from second counter's last output pin to first counter's reset pin) :P It might still contain errors, but I think this is the way to go... :)
  19. Hi gamerscloset! I found this application from Philips' HEF4017 datasheet, and modified it a bit for dual counters... I think this would work nicely for you ;)
  20. That's OK, if you say so! You know, I'm just trying to make it "even better" and easier to use... ;) I posted a picture about a thing which confuses me. I hope you can answer. What do you think about the R12's value? Is it correct? The TL494 needs supply current of 15mA MAX. My transformer gives about 45VDC, so can I calculate resistor value like this?: (45V-39V)/0,015A=400 ohms? Would be glad for help! :)
  21. Heatsinking of the MJ15004 (in TO-3) is a problem, should I do a mofidied version with, for example, parallel-connected two or three BD912's (in TO-220)? Because TO-220 is way more easier to heatsink than the TO-3 in my opinion... If I end up using the BD912's, I don't think that the TL494 has current capability to drive paralleled transistors. So driver transistors might be a mandatory addition in that case... [glow=red,2,300]OR[/glow] Should I just stick with the original design?
  22. OK, time to flood the forum again with my pictures ;D Well, actually it's the same circuit, with a soft-start feature that should limit inrush current when starting. The board measures about 10,5 x 7,5 cm, and I designed it with the soft-start components in place. If I ever get this thing to work, could this be added to the "projects" -section....? ::) If you will take just one more Powersupply circuit! ;)
  23. Maybe with current sense resistor + op-amp + transistor driving the "FB" pin low, would that work? At least it might (and most propably will) interfere with output voltage setting resistors...
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