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Old 6th August 2009, 02:04 AM   #1
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Default silly question: diodes

You'll have to forgive me... I'm really not an EE. I'm a matsci who works in nanomechanics....


I'm about to put together an F5 an antek 300VA 18V toroid. The 'biggest' diodes I have is the MUR1560, 15 Amps max current. I modeled my PSU in PSUD and saw that the startup current is well below an amp. I'm seeing up to 6 amps/channel current draw (3 amps peak per device into 8 ohm speakers)

Nelson uses 35 amp parts, I see other people using the 30 amp MUR diodes. I have some heatsinks here that I could put on the diodes to keep the T down.

I'd hate to pay shipping for 4 pieces, but I'd hate to start a fire as well. Am I grossly undersizing my diodes?
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Old 6th August 2009, 04:15 AM   #2
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Default 1560 diodes

The 1560's will be just fine - 15A at 600volts and a Trr of about 60nS will give you a fairly "fast" sound but still quite "smooth" - not many "nasties".

Suggest using a R-C-R-C configuration with ) 0.1R's (non wirewound, if possible) and 10,000 (ripple cap) and 22,000uF (2nd power cap) - bit different than the Duncan specs, but good results.
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Old 10th August 2009, 12:44 AM   #3
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I'm trying to use stuff I already have. I had modeled a CRC with a 12mF initial cap and then had planned on using inductive wirewounds in parallel with some of the 3W panas. Then a pair of parallel 12mF caps for 24mF of power capacitance.

I actually found a place that carries the irfp9240 locally! Then I dug through my parts and found that I have 75 ztx450 and no 550s. Hopefully the local joint has that part in stock or I'm going to have to go begging from people I know. Goes to show what I know when I thought I had everything I needed.
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Old 10th August 2009, 01:51 AM   #4
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I wouldn't get too concerned about the difference between the wirewounds and the Pana resistors - they do have an effect on the amps sound, but it can easily be later upgraded if offensive.

What amp and speakers? - they are a system, you know- room requirements (and acoustics), speakers to suit (sound, size, volume), amplifier to drive them.
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Old 10th August 2009, 02:30 PM   #5
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well, the F5 obviously. powering a pair of diy proac 2.5 clones. i do most of my listening nearfield in a smallish room so I'm not too worried about having only 25 watts.
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Old 10th August 2009, 03:49 PM   #6
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Not sure if jackinj is still supplying kits for this, but he has matched IRFPs and other things - well worth the money.

The proac clones, eh? perhaps you got some really good crossover componenets, yes? and good wire, maybe silver?
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Old 10th August 2009, 04:09 PM   #7
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goertz foil inductors and music caps. for wire i'm using 12 Ga oxygen free copper. i've matched my own transistors though.
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