as buzz already told you - that's nature of the (caged) beast ; normal behavior for all Alephs , at least from my experience
in fact - nothing to worry
all you can and need to do is - to obtain as much airflow through case itself, to minimize temp diff between cold and hot amp , speaking mostly about input LTP
not necessarily ; do not observe lower and upper output parts independently ; they're part of combo (think FW SIT-2)
all you need is to set Aleph CCS AC gain , to your liking ; because it's driven from lower one , it will track Semisouth's way of thinking , so to speak
buzzforb says
"I think the Jango is a bad idea. While you can get the offset and Dc conditions set and stable, the AC conditions are going to be non ideal. If the SS was loaded with a simple CCS, like the F2, i would expect an improvement in performance equal to the improvement of the SS fet vs standard mosfet. With the ACS, we have something completely different. You have an active current source that is basically trying to track/follow the output of the lower fet and contribute equally, or as close as determined by ACS setting, as possible. If you had two identical fets, like in the original, I would expect excellent results, as both fets are matched and respond to the same signal in similar ways. With the Jango, you have very different fets, with different operational parameters when fed the same AC signal. While I am sure the top fet can do the job and the amp can sound nice, it seems limited from the beginning, simply because the fets will respond differently due to fact that they are different. I can see cohesive effort with similar fets, but a sort of battle, with dissimilar fets."
Can a SS be used in the top as well as bottom position? I only have 4 but I noticed that ZM in his Babelfish J uses one pair of IRF 150s in each channel and I guess the real question would be can I use one pair of SS per channel biased at 2 amps?
Thanks
"I think the Jango is a bad idea. While you can get the offset and Dc conditions set and stable, the AC conditions are going to be non ideal. If the SS was loaded with a simple CCS, like the F2, i would expect an improvement in performance equal to the improvement of the SS fet vs standard mosfet. With the ACS, we have something completely different. You have an active current source that is basically trying to track/follow the output of the lower fet and contribute equally, or as close as determined by ACS setting, as possible. If you had two identical fets, like in the original, I would expect excellent results, as both fets are matched and respond to the same signal in similar ways. With the Jango, you have very different fets, with different operational parameters when fed the same AC signal. While I am sure the top fet can do the job and the amp can sound nice, it seems limited from the beginning, simply because the fets will respond differently due to fact that they are different. I can see cohesive effort with similar fets, but a sort of battle, with dissimilar fets."
Can a SS be used in the top as well as bottom position? I only have 4 but I noticed that ZM in his Babelfish J uses one pair of IRF 150s in each channel and I guess the real question would be can I use one pair of SS per channel biased at 2 amps?
Thanks
yes. It's called the j2
Slightly different version of same concept.ZM pointed out my erroneous thinking. Figured out what is wrong with my Jango, even if I don't know what's causing it. I removed LTP pot and set to 300R. Inserted back into board and it reads 50R. Something is wall somewhere and causing it to be in parallel with some other resistance, but I can't figure out what. It has pth to bottom rail, so it shouldn't bee too complicated. The mystery continues.
buzzforb said
:I removed LTP pot and set to 300R. Inserted back into board and it reads 50R. Something is wall somewhere and causing it to be in parallel with some other resistance, but I can't figure out what. It has pth to bottom rail, so it shouldn't bee too complicated. The mystery continues."
I set my pots at 390. Just raid resistance across the pot and I also get 50 ohms on my boards
__________________
:I removed LTP pot and set to 300R. Inserted back into board and it reads 50R. Something is wall somewhere and causing it to be in parallel with some other resistance, but I can't figure out what. It has pth to bottom rail, so it shouldn't bee too complicated. The mystery continues."
I set my pots at 390. Just raid resistance across the pot and I also get 50 ohms on my boards
__________________
Realized quickly that I was wrong about that. I believe it is in parallel with the other leg of the LTP. I can get my offset down to 160mV, but no lower. Biased at 1.2A. I can turn the LTP pot, but run out of turns before zeroing offset. I haev a 1k pot in the LTP leg. THe cs is set to 10mA. THE jfets are matched at 10.6mA. I may have another clue, but I have to hook it up to check. Even though the gain of the Jango is very similiar to the F5T, being 10V or 20dB, THe jango is much quieter at same volume setting. So it seems I am losing my gain somewhere. I need to make sure first, but I thought this was strange.
Got it working. Problem lies in poor connection of Ikebana fet leg extenders as seen here. I could touch the wires and the offset would wonder. I am hoping that har mounted will change things and allow perfect offset. I have to test distortion, but it sounds a little griity on "The Hobbit Soundtrack" that have been listening to with F5T for last couple weeks. THis may improve with direct contact as well.
Attachments
if you're ever going to use depletion mode , especially unobtanium , never-never-never use lousy sockets , or lousy contact upstream in circuit
I'm still recuperating , after TA-5650 nightmare ; not just T0-3 sockets for 8 Vfets , but numerous sockets and wire-wrap contacts
all of them demanding redo , with proper soldered contact
I'm still recuperating , after TA-5650 nightmare ; not just T0-3 sockets for 8 Vfets , but numerous sockets and wire-wrap contacts
all of them demanding redo , with proper soldered contact
So hear goes subjective foo foo part. Jango is very nice. It seems to maintain that wonderful Aleph sound, like warm bubble bath or big bosommed woman, or both
. But,,,,,,,you gain the SS ability to resolve detail. It seems to me they have a very crisp controlled nature. Capable of rendering space so well. Makes me want to know how orchestra is arranged in Hobbit soundtrack recording. Heard same thing in the F6. Perhaps you would call it bright, but it isn't. Too smooth for that. I have to keep this mounted and then compare with both F6 and j2 bastard. Foo foo portion off.
. But,,,,,,,you gain the SS ability to resolve detail. It seems to me they have a very crisp controlled nature. Capable of rendering space so well. Makes me want to know how orchestra is arranged in Hobbit soundtrack recording. Heard same thing in the F6. Perhaps you would call it bright, but it isn't. Too smooth for that. I have to keep this mounted and then compare with both F6 and j2 bastard. Foo foo portion off.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.