IRFP240's on E-Bay???? - diyAudio
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Old 26th March 2005, 10:39 PM   #1
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Default IRFP240's on E-Bay????

There is a guy obviously selling matched sets plus six "free" 9610's with each order and this for a pretty hefty price at this site. 100.00 for 24 matched fets..... Man, I should be in his buisness!
http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

Mark
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Old 26th March 2005, 11:44 PM   #2
jleaman is offline jleaman  Belgium
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Default Re: IRFP240's on E-Bay????

Quote:
Originally posted by Mark A. Gulbrandsen
There is a guy obviously selling matched sets plus six "free" 9610's with each order and this for a pretty hefty price at this site. 100.00 for 24 matched fets..... Man, I should be in his buisness!
http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

Mark

jump on it then : O) ANd jump on selling parts i bet you make more money : O )...
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Old 27th March 2005, 01:06 AM   #3
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Yep thats me. Thanks Mark!!! I like being in this business considering it takes me hours to do this sort of thing. The irf9610's are included and matched to +-1mV and shipping is included, and i do not charge paypal fees. So, if someone feels like buying 100 fets to get a group of 12 matched to within spec, thats fine. But hopefully i'm saving a few bucks and time for people on this board. I use my fets in my Alephs, and the matching is excellent. Just fyi Oh, my fets (irfp240's) are matched to the closest tolerance i can match them to. Thanks for the plug Mark!

-Matthew K. Olson
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Old 27th March 2005, 02:03 AM   #4
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Matt,
You don't have to buy 100 to get 12 matched close enough for an Aleph. If you buy twice the number needed and they all come from the same lot code you will find typically that you are still buying too many and end up with many spares. Digi-Key is always very cooperative to sending out semi's with the same lot code.

In 100 quantities which you are obviously dealing with they cost 1.50 each. Those 24 transistors in the "buy it now auction" cost you 36.00. 100.00 -36.00 = a hefty profit of 64.00. Ok, lets toss in the 9610's and say thats another 4.00 worth so that nets you 60.00, less shihpping and paypal should still net you a 55.00 profit . For you this is clearly a make money venture, not a hobby. Were it a hobby you would be selling those semi's for 1.50 each.... matched!

Now I once read in these threads that we are allowed to graciously use other peoples designs and circuits for our own use, not commercially. Personally, I see your E-Bay add as a commercial venture free extras or not. If those generous people allowing us to use their designs in our hobby some day decide to pull that option then I guess we would all point our fingers at you....

Mark
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Old 27th March 2005, 02:35 AM   #5
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Wow, I'm a dumbass. I could have proffited $600 on the batch I matched and sold in March. I think I pocketed $15.00 and 12 oddball IFRP 244's (good thing I kept my day job).

More power to you if you can find buyers.
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Old 27th March 2005, 02:51 AM   #6
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Ok. Lets see here...hmm.... what to do. I match 300 at a time since i can't possibly stand to sit more than 4.5 hours at a time staring at a clock. I believe that these need to be matched within 100mV to be adequate. I don't go for adequate. I go for perfect. Out of the batch of 300 that i matched, i got ONE group of 24 that matched perfectly, and some groups of 10-16. When i mean perfect, i mean w/in 10mV. So, if you are going for perfect, then by my estimation, you need to have a bunch more fets than you might think. Now, i realize you (Mark) said that you do not have to buy lots of fets to be adequate for an aleph. I'm a perfectionist, so i don't go for adequate. Is it easier for someone to set up a testing jig, buy a bunch of extra fets at digikey's price of $3+ each, and spend hours matching fets, or to buy mine which come matched as accurately as i can possibly get them. Not a hobby? well, lets see...sure i make gas money off these fets, but i didn't buy 10k of these. I do it because it will work great for people wanting to build their own amps, and because NOBODY HAS OFFERED THESE ON EBAY that i have EVER seen, and because I get the leftover fets for my own projects. I have Pass Aleph 2's that i just finished ...biased at 8A and they have 16 fets (2 groups of 8) per monoblock. These amps will have their debut at DIY Connecticut April 9th. Come on down, i'd love to meet ya!

As I see it, this is a win win for everyone here. If Nelson himself tells me that i shouldn't be doing this, or Brian or Peter, I'll shut up right away, and my wife's credit card will take this whole purchase up the butt.

Amps i have built w/ my own cash earned at $10/hr selling bicycles for the past 9 yrs

mult gainclones lm3886, lm3875
DOZ high power 50wpc
BPA-300 lm3886 (my own mods)
Anthony Holton Symmetrical 400's w/ extra output fets and higher power driver transistors
8 channel Rod Elliot p19
8 channel p3a/gainclone
Aleph 2's
aleph x's pending, 8 channel p3a pending, high power DOZ pending

not a hobby (that list obviously doesn't include speakers hehe)?

-Matthew K. Olson
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Old 27th March 2005, 03:47 AM   #7
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There's no problem here. Matt is selling transistors on Ebay. Nowhere is the name or brand Pass used or any info as to what to do with the transistors. If he wants to try to make a few bucks in the deal, go for it. I would doubt that he'll have many takers ar his price though.

I did a big order and sold the excess because me and a friend need 4 sets of 12 and 4 sets of 8, so we needed a large batch and sold the extras at cost. We also wanted to do the matching, not because of cost, but because it's DIY. I would never consider matching fets as a n occupation. It was quite tedious, but a learning experience.

I got my jab in because it didn't feel right to me. But after reconsidering, Matt is doing nothing wrong. Nobody is forced to buy from him, and he's not trashing other sources of fets or anything. And you do need to have a large quantity of fets to get good matches. And to Mark... I found that the variation within a tube or lot number is as wide as from 1 tube to the next. I buoght 300 or 350(I cant remember) that was from 2 lots, and both lots had the same range and distibution. you can easily find 3 pairs of 9610's in a 10 pack, but you'll need much more than 50 to find 4 groups of 12

BTW My Aleph's also have 16 fets/channel and 3.5A bais +-55V with a final temp of 155 degF without a fan.
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Old 27th March 2005, 04:16 AM   #8
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Thanks Brian. I appreciate that. If you think my prices are high, thats opinion, and thats fine I can handle that. Someone telling me i'm being unrealistic or unreasonable...i can handle that too. Telling me i'm not a hobbiest, that doesn't fly. So, thanks for the gentler words Brian, i do appreciate it. Maybe i won't get anyone to buy at this price. On the other hand, i have never seen matched transistors offered anywhere for sale EXCEPT a place online called "the company store" and i believe they are $5+ each matched...though it doesn't mention how close the tolerances are. When I was buildling my amplifiers, i was considering buying from them, but when i asked for a price quote, they just refered me back to the website basically telling me to purchase the stuff first, ask questions later. On the other hand, i appreciate that website b/c they have other transistors etc for sale that aren't readily avail anywhere else, they also have the transistors for Rod Elliots new p101. I'm off topic. Anyway, seemed easier for me to match the transistors myself, and do like you did, get rid of the extra somehow. Now that i know how to do it, i figure that most hobbiests (here on the board and elsewhere) that need matched fets might like to have a place to buy them where prices are straightforward, the fets are as accurate as possible, and i like to think they get to deal w/ a reaosnable guy (me ) I answer emails quickly and as quickly and as straightforward as possible, and i have had repeat buyers. I won't be able to do this forever because i will not have the time, but a few people will be able to have some matched fets

some info about me, i'm 25 years old and i live in Connecticut. i go to UCONN Dental School and i'm currently a 4rth yr student (1.5 months to graduation!). I've built amps for most of the last 4 years, as well as being the only one to hold a part-time job through most of dental school (9 years of selling bikes was enough, i quit a month ago). I spend most of my free time building or thinking of building or reading about building. I start a residency in July and will have very little free time for matching fets etc, but i'll try my best for those that want em. I have a nice regulated PS, a jig for matching different fets, an excel spreadsheet that i use for organizing all the fets etc. Tomorrow i'll spend another 4 hours and match 300 more fets ( i got 600 total), and then spend 4 hours ontop of that organizing and packaging all of them. so, if anyone needs anything specific, let me know. Thanks again for the kind words Brian, i appreciate it!

-Matthew K. Olson
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Old 27th March 2005, 04:19 AM   #9
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oh, my alephs are running +-44VDC rails (i think) 4A bias per rail) and the sinks are approx 120 F w/o fans i have close to 4000 sq in. heatsink PER channel hehe

ROCK ON MAN these amps are just CRAZY good

-Matthew K. Olson
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Old 27th March 2005, 09:18 AM   #10
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I have taken Matt up on his offer and have done so in the past. I don't have the time or the patience to do the matching on my own, so Matts service is appreciated and he delivers a quality product. I don't see many places I can get matched IRFP240's (matched to a few millivolts) at less than $4.00 a pop except for a group buy that may happen only occasionally. With Matt, if I need matched pairs, I email him, and I can get matched fets anytime. No waiting for a group buy, no fuss, no muss, no mess. He is just trying to make a few bucks while going to dental school and isn't bothering anyone or abusing anyones IP (these can be used on amps other than Pass). Geeeesh.......give the guy a break. He gives those of us too lazy to do it, a quality service.
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