You may also want to increase the values of R7/8 to increase the gain so that you can take advantage of those higher rails.
Also, watch the values (and dissipation) of R25-28, adjust them to keep the voltage across the jfets reasonable. I'm thinking of using 20V zeners in place of R27/28. You can increase the values to reduce dissipation.
Good point. But how do you calculate the gain increase? NP says with 220 there the gain increases to 22dB from the 15dB at 100ohm.
Ah, I always use this great post from Jacco to calculate F5 gain:
From 25W to 50W is +3dB.
50W in 8 Ohm is 20V.
22 dB gain is about 12.6 times. (18dB+4dB = 8 times ~1.58)
20V divided by 12.6 is ~1.6v input
100 ohm divided by 2 is 50 Ohm.
50 + 10 = 60.
60/10 = 6
20 log (6) = 15.6 dB
220 divided by 2 is 110.
110 + 10 = 120.
120/10 = 12
20 log (12) = 21.6 dB
Difference is 6 dB [220/100=2.2 20log(2.2) = 20log(2) +20log(1.1) = ~7dB]
6dB minus the 3dB extra to reach 50W is extra 3dB gain left.
The gain margin is for stability, read Bode plot papers (the name Bode is Dutchie lingo for messenger)
You may not need the extra 3dB gain with single outputs, but if you leave gain as is, you need close to 5V in to reach 100W peak in 8.
(for dB estimates, it's handy to have the gain factors for +1dB to +5dB in head)
Hey....here it is. Sorry about the late reply, I wasn't sub'd to this thread.
http://www.diyaudio.com/forums/pass-labs/188691-illustrated-guide-building-f5.html
Buzz and Co.:
Success, glorious success! Thank you, thank you, thank you! The first monoblock is responding just as it's supposed to -- an incredible relief after the last frustrating week. As clearly demonstrated over the past 30 posts or so on this thread, I really couldn't have done it without your continued support. Many, many thanks.
But please don't disappear on me: there's still the matter of this monoblock's twin and two more stereo V2 amps to be dealt with. I shall report on my efforts with them, good or bad, as appropriate.
Warm regards this cold season,
Scott
Success, glorious success! Thank you, thank you, thank you! The first monoblock is responding just as it's supposed to -- an incredible relief after the last frustrating week. As clearly demonstrated over the past 30 posts or so on this thread, I really couldn't have done it without your continued support. Many, many thanks.
But please don't disappear on me: there's still the matter of this monoblock's twin and two more stereo V2 amps to be dealt with. I shall report on my efforts with them, good or bad, as appropriate.
Warm regards this cold season,
Scott
F5T as compared to the Aleph J
I'm hoping someone here that has built the F5T, that has also built the Aleph J could post a reply on their impression of differences between the two. What was good? What was not as good?
I'm hoping that the evaluation was done with all other components the same...
(not asking for much....
)
Thanks...
I'm hoping someone here that has built the F5T, that has also built the Aleph J could post a reply on their impression of differences between the two. What was good? What was not as good?
I'm hoping that the evaluation was done with all other components the same...
(not asking for much....
)Thanks...
I can't figure out the other answers (cockroaches, nerdy librarians) as I haven't swilled back enough Sam Adams yet.
I kinda like the "sultry woman". Not into the too athletic type as I could spill my beer trying to keep up.
Just one further question. Anyone here been able to successfully get more output power (even a few watts) from their Aleph J without deviating from the "as designed" sound? If so, what was the final rail voltage, bias & output power?
Thanks!!
any Aleph (smallest one to biggest one ) can be made to have J in name
and it will sing with same character
for possible differences , going from small to big , read F5T article - same approach* , sans diodes in output
*Jfets on input , cascoding them when going up in PSU , more oomph in output stage etc.
and it will sing with same character
for possible differences , going from small to big , read F5T article - same approach* , sans diodes in output
*Jfets on input , cascoding them when going up in PSU , more oomph in output stage etc.
ZM, buzzforb, thanks for your replies. Looks like both input (cascoding for more current) and output (adding more devices) should be considered along with rail supply voltage.
http://www.diyaudio.com/forums/pass-labs/241729-aleph-j-illustrated-build-guide-7.html#post3652028
is there possible end of my wittiness .......
with F5 , you'll see cockroach wandering behind Violin player's feet ;
with J , cockroach will smile on you ......
is there possible end of my wittiness .......