Just repeating ZM below. I did not fully follow your build. Just noticed that you have higher rails and don't remember what they were before the new transformers. Mine has 18V secondaries. I don't know if the resistor values in the snip below are correct for your setup. The point being P102 for Iq and P101 for offset; Increase series resistor as appropriate. And readjust pots and measure before power up.
And Denver, CO ? Small world.
And Denver, CO ? Small world.
Last edited:
Hi BA. Yeah! Small world indeed! Are you in Denver as well?
I did base my resistor changes on that post but Semisouth down has a different starting point for R118. I did my own math there but probably shouldn’t have. 😕
I did base my resistor changes on that post but Semisouth down has a different starting point for R118. I did my own math there but probably shouldn’t have. 😕
just lloking at my morning coffee
even sight still mushy, let alone brain
so - if you didn't solved it already, please recapitulate, for us little handicapped
("I want that Iq, but now I still have just this Iq and DC Offset is this; resistors are(not) changed")
🙂
Good morning ZM! Latest resistor values and measurements in post #499. With a little guidance I’ll give it another try tonight.
Currently:
R118 = 499R
R123 = 510R
Iq max = 775mV - I would like to get to at least 850mV
DC Offset min = 435mV
Currently:
R118 = 499R
R123 = 510R
Iq max = 775mV - I would like to get to at least 850mV
DC Offset min = 435mV
Last edited:
just one more detail - at which resistor group you are measuring Iq (as voltage sag)
which figure (in A) you are shooting for?
which figure (in A) you are shooting for?
Using this schema for Semisouth down with .68/1R resistor groups. Iq measures the same at all source resistors. A little update too. Just remeasured. Iq settles at max 758mV. DC offset is actually -358mV with pot turned all the way in.
Attachments
Last edited:
So in addition to the last post I did some more math. Source resistors for Semisouth down total .405R. I would like 1.8A Iq. So 1.8x.405=.729mV. Looks like I'm fine on R123. I'll readjust and see where that puts me on DC offset.
Okay. Readjusted Px02 for 729mV for Iq of 1.8A. Offset went to -400mV. Iq seems good but Offset is heading in the wrong direction.
if you're good with Iq, and DC offset is a problem, that means:
- offset positive - increase R118
-offset negative - decrease R118 (or just short it, do everything with P101)
- offset positive - increase R118
-offset negative - decrease R118 (or just short it, do everything with P101)
Eureka! Offset is dialing in nicely now. I paralleled 1.05kOhms with the 499R I have at Rx18. Thanks for the guidance ZM. A little more dressing of wires and I should have the BabelJ2 singing again.
BabelJ2 is fully operational. It is a little tricky to really dial in the offset on this one. Bias is 1.8A. Heat sinks on the 5U 400 hold steady just a smidge below 50C. I had an Antek 400va with 22V secondaries but voltage seemed a little too high. Swapped out for 400va with 20V secondaries. The SLB is 23.4V +/-.
And the sound. Ooo the sound. I’ve only tested with my workshop speakers with a cheap Bluetooth receiver as the source. Dayton PS95-8 is karlson foamcore enclosures. So far this amp has phenomenal imaging. Listened to A few tracks from Roger Waters, Amused to Death. I have never heard a soundstage like that. I didn’t know it was possible. Also, Eric Clapton Unplugged. Very nice. Can’t wait to get this into my main system with a real pre-amp. Will report back again soon. Here are some photos of the final product. Glad I really took my time with the wiring on this one. Those BabelJ2 boards really deserve it. Thank you ZM! I had the prescribed 270R in Rx18’s but I couldn’t adjust offset enough. Paralleled the 499 with 1.05k because I got a little lazy to look for any 330R in my parts stash and I didn’t want to risk lifting any pads on desoldering those again. Worked out well in the end. 😀
And the sound. Ooo the sound. I’ve only tested with my workshop speakers with a cheap Bluetooth receiver as the source. Dayton PS95-8 is karlson foamcore enclosures. So far this amp has phenomenal imaging. Listened to A few tracks from Roger Waters, Amused to Death. I have never heard a soundstage like that. I didn’t know it was possible. Also, Eric Clapton Unplugged. Very nice. Can’t wait to get this into my main system with a real pre-amp. Will report back again soon. Here are some photos of the final product. Glad I really took my time with the wiring on this one. Those BabelJ2 boards really deserve it. Thank you ZM! I had the prescribed 270R in Rx18’s but I couldn’t adjust offset enough. Paralleled the 499 with 1.05k because I got a little lazy to look for any 330R in my parts stash and I didn’t want to risk lifting any pads on desoldering those again. Worked out well in the end. 😀
Attachments
Last edited:
thank you for kind words
even if I'm mainly clueless, sometimes I'm successful in compensating that, with sheer love for what I'm doing
You’re welcome ZM. I am perpetually in awe of your talents. And don’t worry, more kind words on the way. Starting the Singing Bush very soon!
Singing Bush is for Sissies
or to comfort you - SBush is SissySIT on steroids - gain some, loose some
but as I sad last night to my Bubba Uncle Bob - we are way past a point of needing to build an amp to have it ..... now we have totally other set of reasons
or to comfort you - SBush is SissySIT on steroids - gain some, loose some
but as I sad last night to my Bubba Uncle Bob - we are way past a point of needing to build an amp to have it ..... now we have totally other set of reasons
jwjarch - Congratulations! Love the clean / tidy build.
It's no secret that I'm a Babel J2 fanboy. Hope you enjoy yours as much as I enjoy mine.
It's no secret that I'm a Babel J2 fanboy. Hope you enjoy yours as much as I enjoy mine.
Then don't put two perfectly spaced holes in your PCB's ZM!!! Haha!!! 
I hear you though. El cheapo fast-ons almost fried my whole build. I spent a few more cents and bought some legit locking fast-ons from Mouser. All are crimped and soldered and they have a very positive connection to the tabs. That said I may go back and solder wires straight to the board at some point. I still have to see if this wiring layout is the best with high sensitivity speakers. Hooking up to Lii-Audio Crystal 10's very soon.
Thanks for the complements ItsAllInMyHead. I had to go back and read your posts on your build and impressions. Are you still using the Iron Pre with yours? The BabelJ2 is up to some stiff competition against my F7 clone paired with a WHAMMY pre. I recently swapped the LM833 for a Burn Brown OPA2134 in the WHAMMY. Less DC offset and a little more detail. I will try it with the J2 and compare vs F7.
I hear you though. El cheapo fast-ons almost fried my whole build. I spent a few more cents and bought some legit locking fast-ons from Mouser. All are crimped and soldered and they have a very positive connection to the tabs. That said I may go back and solder wires straight to the board at some point. I still have to see if this wiring layout is the best with high sensitivity speakers. Hooking up to Lii-Audio Crystal 10's very soon.
Thanks for the complements ItsAllInMyHead. I had to go back and read your posts on your build and impressions. Are you still using the Iron Pre with yours? The BabelJ2 is up to some stiff competition against my F7 clone paired with a WHAMMY pre. I recently swapped the LM833 for a Burn Brown OPA2134 in the WHAMMY. Less DC offset and a little more detail. I will try it with the J2 and compare vs F7.
