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PPA v2 construction discussion

post #1 of 1039
3/11/05 at 3:49am
Thread Starter 
Talk about building PPA v2 here.

Tangent's PPA v2 site
Morsel's PPA v2 site
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post #2 of 1039
3/11/05 at 4:29am
Are there alternative transistors you can use for the buffer stage? Some of those resistors are hard to source in europe, so a european transistor list might be handy.
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post #3 of 1039
3/11/05 at 4:35am
BD139/BD140 are easily found in Europe.. oh you probably meant the TO-92 parts.. instead of 2N5087/2N5088 you can use BC849/BC859 or BC850/BC860, the pinout is however slightly different.. another choice would be 2SC1815/2SA1015 if you can find them, these have the same pinout..
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post #4 of 1039
3/11/05 at 4:37am
Quote:
Originally Posted by Glassman
BD139/BD140 are easily found in Europe..
PN4392,2N5087,2N5088 aren't though
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post #5 of 1039
3/11/05 at 4:44am
instead of that JFET you can use for example some from the BF24x series with higher Idss, about 30-60mA is about right there.. they come in various pinout versions, you might find one that fits the PN4392 pinout, otherwise you have to bent legs.. oh and btw. PN4392 is the same as 2N4392 if that helps..
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post #6 of 1039
3/11/05 at 5:29am
r24, r34 are 2.2 ohm resistors? Is there a mouser part number for that? I'm going to build one using the vishay dale resistors.

thanks
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post #7 of 1039
3/11/05 at 9:15am
Quote:
Originally Posted by phobus
r24, r34 are 2.2 ohm resistors? Is there a mouser part number for that? I'm going to build one using the vishay dale resistors.
Yes, but Vishay Dale RN55's start at 10 ohms, look at their datasheet.
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post #8 of 1039
3/11/05 at 10:52am
doh. ok thanks.
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post #9 of 1039
3/11/05 at 1:56pm
Quote:
Originally Posted by phobus
r24, r34 are 2.2 ohm resistors? Is there a mouser part number for that? I'm going to build one using the vishay dale resistors.

thanks
I found this.... It's not vishay but it's metal film and 1% and IN Stock

660-MF1/4DLT52R2R21F from mouser

Here's a vishay brand 1% metal film 2.21 ohm But it doesn't state the wattage.

594-9B14064A2R21FCT Stock is coming
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post #10 of 1039
3/11/05 at 3:37pm
Quote:
Originally Posted by Glassman
oh and btw. PN4392 is the same as 2N4392 if that helps..
PN4392 and 2N4392 are the same electrically, but in different packages and pinouts. PN4392 is plastic TO-92 while 2N4392 is metal can TO-18.
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post #11 of 1039
3/11/05 at 3:55pm
Quote:
Originally Posted by amb
PN4392 and 2N4392 are the same electrically, but in different packages and pinouts. PN4392 is plastic TO-92 while 2N4392 is metal can TO-18.
The 2N4392 is also a 1.8W device isn't it? Whereas PN4392 is 625mW
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post #12 of 1039
3/11/05 at 4:07pm
Quote:
Originally Posted by individual6891
The 2N4392 is also a 1.8W device isn't it? Whereas PN4392 is 625mW
The TO-18 metal can has better heat dissipation than the plastic package hence the higher power rating. BTW the Vishay-Siliconix datasheet for these devices says the 2N is 1.8W as you state, but the PN is 350mW.
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post #13 of 1039
3/11/05 at 4:18pm
Quote:
Originally Posted by amb
The TO-18 metal can has better heat dissipation than the plastic package hence the higher power rating. BTW the Vishay-Siliconix datasheet for these devices says the 2N is 1.8W as you state, but the PN is 350mW.
Ahh you're right, Fairchild's datasheet says the PN4392 (TO-92) is 625mW, but it's surface mount equivalent MMBF4392 is 350mW... I guess different manufacturers datasheets can be all over

Well at the moment someone's ordering me some of the 2N5087/8 and PN4392 with their digi-key order to europe so yay

As for a replacement to the 2N5087 / 2N5088 available very easily to the UK.. would:
BC337-40 : NPN, 2N5088 replacement
BC327-40 : PNP, 2N5087 replacement
...be appropriate?
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post #14 of 1039
3/11/05 at 5:24pm
Quote:
Originally Posted by individual6891
As for a replacement to the 2N5087 / 2N5088 available very easily to the UK.. would:
BC337-40 : NPN, 2N5088 replacement
BC327-40 : PNP, 2N5087 replacement
...be appropriate?
The BC550C/BC560C are better, and more favored in audio use. Note that these have reversed pinouts than the 2N5087/2N5088.
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post #15 of 1039
3/11/05 at 8:52pm
Is there much of a difference between the "recommended" and the "alternate" part. Eg. Output transistor MJE243OS, BD139OS vs 511-BD139.
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