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Old 6th October 2005, 10:07 PM   #21
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Location: Dallas, TX
Quote:
Originally posted by wayne325


A delta of 34 is about as high as you want to go. That will
give you a temp of about 55C in the winter - approaching 60C
in the summer if you keep your apartment at 80F. Keep in mind
also those are free air figures and not stacked.
The other heatsink solution gave me a delta of 16 degrees but I had to give up too much back panel space and the connectors would have been jammed all together in a 4" by 5" area...

--Chris
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Old 7th October 2005, 03:35 AM   #22
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Quote:
Originally posted by Nelson Pass


The line capacitor should be specifically rated for AC line - it
will say so in the catalog and it will bear the appropriate
safety markings.

I'm assuming the value isn't critical since its just here to filter high frequency noise from he AC line? I looked up the part number you used in your Pearl Phono design on pasdiy.com "Digikey part P4603-ND" .. But the closest they have in the panasonic Interference Suppression Metal film type is 0.0047uF.

I'm assuming the0.0047 will be fine so the BOM and shopping list is done! Now I just have to wait a week for all the stuff to get here

--Chris
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Old 7th October 2005, 06:23 PM   #23
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You can get higher values if you want. We usually use .22 uF
across the line at PL.

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Old 10th October 2005, 03:00 PM   #24
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Gents,

Many thanks to Mr. Pass, Wayne, Alain Dupont! I've placed my order for parts with PEX, Mouser, and Digikey. I've read Mr. Pass's article "Mosft Testing for Audio" (http://www.passdiy.com/pdf/mos.pdf) and I think I'm all set. I plan to make a breadboard with jumpers according to figure 5 in the article for matching my FETs. I'm assuming the bi-polars don't need to be matched? Anything else I need to know before I get started?

Thanks again guys, I think this is going to be one heck of an adventure

--Chris
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Old 17th December 2008, 05:25 PM   #25
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Location: San Jose
Default F1 Transistor matching

Which of the 5 IRFP's need to be matched together?

Q1 IRFP240
Q2 IRFP240
Q5 IRFP240
Q3 IRFP9240
Q4 IRFP9240

Also do the the ZTX550's Q5-6 need to be matched?

Thank you for the help!

-David
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Old 17th December 2008, 08:00 PM   #26
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1 = 2, and 3 = 4. Q5 is the single current source as I recall.

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Old 17th December 2008, 08:28 PM   #27
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Location: San Jose
Thank you Nelson.

Here's the BOM I'm using with WIMA 1uf signal caps.

Sounds like I need to match the IRFP240's Q1 & Q2 to each other. Also match the IRFP9240's Q3 & Q4 to each other, and the ztx550's Q5 & Q6 don't need to be matched. The single Q7 IRFP240 current source does not need to be matched to anything.

Thank you for any oversight help.

-David

Click the image to open in full size.
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Old 17th December 2008, 11:10 PM   #28
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I'd appreciate any thoughts on the BOM above before I heat-up the iron.

Thank you,

-David
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Old 18th December 2008, 12:22 AM   #29
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Aren't IRFP P-channel devices possessed of some unwholesome type of distortion when used common drain?

The Fairchilds are rumored to better (by those who really know mosfets). There is a secret device number -- I think it is SFH9240 from Fairchild that is a good sub for the Vishay (aka IRFP).

JJ
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Old 18th December 2008, 11:39 AM   #30
cfcubed is offline cfcubed  United States
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Here's my thoughts based on my recent F1 clone build:

* I'd trouble sourcing the little PS C9 "interference" cap that goes across A/C IN so I just pulled one from one of the dead PC pwr supplies I had around.

* Even tho I'd purchased (supposedly) matched FETs, I needed R27*,R28* (RES 10 OHM 1W metal - ordered 10) supplementary resistors to attain < 50mv offset. Somewhere around are details about these, essentially you may need a couple paralleled on R27 OR R28 on each channel based on its direction of offset (*if* you find it > 50mv on initial build).
Even if your matching turns out better than mine did, I'd have them on hand.

* AFAIK, the 20V zeners are for static/hookup protection only, *think* I read somewhere that NP leaves them out of his personal builds and that removing unnecessary zeners is a good thing.... So I left them out of my build.

* Tweaks:Can't say about specific MOSFET devices... I used the ones in your BOM & they sound good to me Some have pushed building bridges out of "better" diodes VS using bridge rects (I've not gone there - used bridge rects in my builds).

Good luck!
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