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 14th May 2003, 11:33 AM #2 Mad_K   diyAudio Member     Join Date: Sep 2002 Location: Norway The 0,4W is good for the circuit, even with increased bias. For the source resistors, 5% is not good Not to worry though. What you need to do is to match the 5% the same way as you matched the output mosfets. -> Send a known amount of current (0,5A-1A or thereabout), and note the voltage drop across the resistor. This I would do even with 1% resistors.. It is essential that the resistors match as much as possible, so that the outputfets share the load equally. This has more to do with reliability than sonics. -You can easily get 1% tolerance from 5% parts this way __________________ Mads K
 14th May 2003, 11:45 AM #3 Duck-Twacy diyAudio Member   Join Date: Oct 2002 I'm afraid I didn't match the mosfets myself Can't I just measure the Vishays with my Fluke 111 multimeter? Oeps checked the specs. resolution 0.1 ohm, so guess not __________________ Is that all there is?
 14th May 2003, 11:58 AM #4 Mad_K   diyAudio Member     Join Date: Sep 2002 Location: Norway This is not difficult! I use an old psu (wall-wart or what you call it) from my pc-sub (2A, 15VDC) and two 47R 17W resistors in paralell. Then you put your mosfet or resistor in series and measure VGS or V (=U) across the part. I take the measurment after 5 seconds. Measure the voltage across the two 47R, and you know the current, I. Then it's a simple R=U/I for your source resistors __________________ Mads K
 14th May 2003, 12:15 PM #5 Duck-Twacy diyAudio Member   Join Date: Oct 2002 Still If I decided to replace them with the 1% Caddocks MP816, would it be sufficient to only replace the twelve 1 ohm resistors and leave the eight 0.47 ohms 5% Vishays, or are these just as important? __________________ Is that all there is?
 14th May 2003, 12:49 PM #6 Mad_K   diyAudio Member     Join Date: Sep 2002 Location: Norway You could use the 5% for the 0,47R, and replace only the 1R with 1%. This will be good enough __________________ Mads K
 14th May 2003, 08:36 PM #7 Duck-Twacy diyAudio Member   Join Date: Oct 2002 So if I first try to match the 1 ohm resistors, how do I group them? In 2 sets of 6 resistors for left and right channel, or maybe also within each channel two sets of 3?? What if one channel has about 0.95 ohm and the other channel around 1.05 ohm?? __________________ Is that all there is?
 14th May 2003, 10:50 PM #8 Nelson Pass   The one and only     Join Date: Mar 2001 I wouldn't worry about the 5% on the Vishays, even if they were really 5%. More likely they are 1% or better. As to the .4 watt BCCs, they look awfully tiny....
 15th May 2003, 08:06 AM #9 Duck-Twacy diyAudio Member   Join Date: Oct 2002 Thank you mr Pass. Still, I will try to measure them. As for the little BCC ants . Try reading the colour code on these thingies (I have -5 lenses! ). But now I'm worried again. What is the worst that can happen if one of the liitle resistors on the PCB gets fried? Can that result in a unduly death of my mosfets?? __________________ Is that all there is?
 15th May 2003, 08:41 AM #10 Duck-Twacy diyAudio Member   Join Date: Oct 2002 Edit. Btw according to the datasheet (see PDF abopve) the 0.4 watt is for 40 degrees celcius ambiant temperature. At 60 degrees C (more typical for an Aleph) it is only 0.3 watt. Is this bad? (My PCBs will be attached perdendicular to the heatsinks, at 2 or 3 cm distance minimum, so for most resistors the distance wil be greater) (couldn't edit the above message anymore) __________________ Is that all there is?

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