OK, I have these also that will work there : Mouser Part No 871-B32529C104K189. They are only 2.5mm wide. But it is an Epcos Polyester, and not a lot of DIYers like them that much.
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So you can change capacitors—shmapacitors, or practice your alcohol tolerance and boost up those 3.5% ;-)
If R27 is the equivalent of the bias resistor in the Aleph 2 (R19), couldn't we just leave R27 open, and adjust bias with the source resistors? I ask because R27's connection between Q4 B-C is different in the AJ schematic than all others I've seen.
-john
-john
R27 has a direct correlation to output bias. I would leave it in.
Your question is probably best answered by Nelson...
Your question is probably best answered by Nelson...
typing on fluffy eee pc , which I hate , so not having my own files handy
whatever , R27 role - explanation of - is trivial
Pa put it there , there is no need that he must explain it , too
:
whatever , R27 role - explanation of - is trivial
Pa put it there , there is no need that he must explain it , too
:
No sure if this is the right thread ...
In the spirit of being universal ...
Just curious if anyone has built an "upside down" Aleph J;
using the more easily available and less risky to acquire dual N-JFET from Linear Systems (or a matched pair of singles) and flipping the polarity of all the other semis and caps as appropriate.😉
I think I saw in a related thread where someone paid almost $9 each for 2SJ74 - that seems a bit much to me ...😱
I'm just saying ...
mlloyd1
PS I might be showing my age again here
I know sometime in the past it was "preferred" to use P devices in front end because they were a little quieter and N devices in the next stage (VAS) because they were faster with lower capacitances. Semi processes have advanced a bit over the years and this is a power amp instead of a MC phono preamp.
In the spirit of being universal ...
Just curious if anyone has built an "upside down" Aleph J;
using the more easily available and less risky to acquire dual N-JFET from Linear Systems (or a matched pair of singles) and flipping the polarity of all the other semis and caps as appropriate.😉
I think I saw in a related thread where someone paid almost $9 each for 2SJ74 - that seems a bit much to me ...😱
I'm just saying ...
mlloyd1
PS I might be showing my age again here
I know sometime in the past it was "preferred" to use P devices in front end because they were a little quieter and N devices in the next stage (VAS) because they were faster with lower capacitances. Semi processes have advanced a bit over the years and this is a power amp instead of a MC phono preamp.
Aleph builder required reading: http://www.diyaudio.com/forums/pass-labs/12923-top-ten-ways-better-aleph.html
In all the Alephs I've built, I've always left R19 (R27 in AJ) open. It allows Q4 to run bias 'wide open'...generally increases overall bias by about 500mA. The resistor just trims the bias. But this connection in AJ scheme is slightly different, so I'm wondering if this same mod applies.
In all the Alephs I've built, I've always left R19 (R27 in AJ) open. It allows Q4 to run bias 'wide open'...generally increases overall bias by about 500mA. The resistor just trims the bias. But this connection in AJ scheme is slightly different, so I'm wondering if this same mod applies.
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Instead of going through the brain damage of building the Aleph J upside down, just build an Aleph 30 with the Fet front end...
Anyway, the 2SJ74 are still cheap compared to tubes.
Anyway, the 2SJ74 are still cheap compared to tubes.
No sure if this is the right thread ...
In the spirit of being universal ...
Just curious if anyone has built an "upside down" Aleph J;
using the more easily available and less risky to acquire dual N-JFET from Linear Systems (or a matched pair of singles) and flipping the polarity of all the other semis and caps as appropriate.😉
I think I saw in a related thread where someone paid almost $9 each for 2SJ74 - that seems a bit much to me ...😱
I'm just saying ...
mlloyd1
PS I might be showing my age again here
Mlloyd,
I have some dual die N channel samples coming that I plan to try in a preamp with a similar configuration. Not difficult to try other options and sooner or later the J74 will be extinct. Nelson has stated that they are not necessary in power amps anyway, being more important in line level and low noise designs.
NOT that anyone will believe me but I would like to hint that people should keep their eyes on the diyAUDIO store as within a month we'll be making an interesting JFET announcement.
Would be even better if it were the original Toshibas, desoldered from the beast with the 10.000 JFets 😀
I think they left the leads long enough in the Beast that the FETs could be clipped out if they ever needed to be harvested.
This is what the website of Linear Systems says:
What would be a new year without new products? In 2013, we will be introducing three new products, all of which are JFETs specifically designed for the professional audio markets: LSK489, LSJ74, and LSK186.
I hope the diyAudio store can deliver the LSJ74's 🙂