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First Watt J2 installed
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Old 10th October 2017, 10:06 PM   #51
Nelson Pass is offline Nelson Pass  United States
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Quote:
Originally Posted by JeffYoung View Post
I got a quote for SJEP120R100's: $122 each at qty 12. That's $1500 for 3 amps. (They each take 4, right?)

Yowza. But those FETs were expensive to begin with, right?
Who is charging that? I want to thank him.....

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Old 10th October 2017, 10:16 PM   #52
JeffYoung is offline JeffYoung  Ireland
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Well, I'm already building an F5 with IRFPs. I like to try different things, so the SemiSouth's piqued my interest.

The quote I got was from Sierra IC in North Carolina.
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Old 10th October 2017, 10:52 PM   #53
2 picoDumbs is offline 2 picoDumbs  Australia
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Originally Posted by grimberg View Post
Careful Dave, you may be approaching 3 picoDumbs today! Cloning is not just for scared cats. It is also a way to create an audible reference and better understand what the product designer hears.
Very true.
That is why I purchased a Firstwatt F5.
Someone has to pay Nelson a wage.
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Old 11th October 2017, 04:49 PM   #54
JeffYoung is offline JeffYoung  Ireland
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Quote:
Originally Posted by JeffYoung View Post
.... They each take 4, right?
Turns out only 2, really:

Quote:
Originally Posted by Nelson Pass View Post
You can build a perfectly fine version with something else, like the IRFP240, on the current source. I have done it for test, and there were no complaints.

The output stage sound is dominated by the gain device on the negative rail. The mu follower is quite neutral due to it's own local feedback.

I just used JFETs all around for consistency, and to avoid the internet troll accusation "It's not really a JFET amp", which I saw in a posting once regarding the F3. (Not on this site)

So if anyone else is interested in a pair (or four) at extortionate prices, drop me a PM.
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Old 11th October 2017, 05:40 PM   #55
Nelson Pass is offline Nelson Pass  United States
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"I just used JFETs all around for consistency, and to avoid the internet troll accusation "It's not really a JFET amp", which I saw in a posting once regarding the F3. (Not on this site)"

The troll didn't know what a cascode was.

Not usually a problem on this forum...
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Old 12th October 2017, 08:35 AM   #56
nicoch58 is offline nicoch58  Europe
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Old 12th October 2017, 09:40 AM   #57
Vix is offline Vix  Yugoslavia
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Quote:
Originally Posted by Nelson Pass View Post
... I have, however, built some
nice versions with IRFP240's.
Somebody may not agree with me, but my approach to Diy audio is to try to build the best sounding (it could be just 2w amp, no problem) with parts that I happen to find in my drawer or that I could easily find at the local market. In this case, I have IRFP250, and would happily use it with no regret
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Old 12th October 2017, 04:31 PM   #58
needtubes is offline needtubes  United States
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Quote:
Originally Posted by JeffYoung View Post
I got a quote for SJEP120R100's: $122 each at qty 12. That's $1500 for 3 amps. (They each take 4, right?)

Yowza. But those FETs were expensive to begin with, right?
They weren't that expensive when new...

I just got a quote from them for $157.54 each for SJEP120R100 from Sierra IC. They must like you more than me. To add to the hilarity, they quoted me $9.85 each for the tiny little 2SK715 JFET by ON Semi, which recently went EOL and can still be bought from Rochester Electronics for pennies (albeit for a couple thousand of them).
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Old 12th October 2017, 04:51 PM   #59
Nelson Pass is offline Nelson Pass  United States
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I recall buying a few thousand R100's at slightly more than $10 each.
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Old 12th October 2017, 05:16 PM   #60
JeffYoung is offline JeffYoung  Ireland
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Well the good news is another member came through and sold me some for considerably less than $122.

The bad news is they were still considerably more than Nelson's $10.
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