Got these BPA300 boards in the mail today, one for each channel:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Has traw tested these? I'd hate to see a repeat 
The one thing I don't like about designs like that are how the power traces are routed with the thin power trace running down between the legs of the other chips. In a parallel design each chip should draw the same current from the supply rails. The last chip on the rail will see the most voltage drop across the power trace because not only is it farthest away from the supply caps but all of the other chips are drawing current through the same trace as well. I'm not saying it won't work, just that it's not the most optimal.
The one thing I don't like about designs like that are how the power traces are routed with the thin power trace running down between the legs of the other chips. In a parallel design each chip should draw the same current from the supply rails. The last chip on the rail will see the most voltage drop across the power trace because not only is it farthest away from the supply caps but all of the other chips are drawing current through the same trace as well. I'm not saying it won't work, just that it's not the most optimal.
yep they work. i wouldn't had suggested or offered them to mayday if didn't, that would be utterly cruel. i was hoping to see the original boards focused on in this thread be rememdied to a working state and not sidetrack those efforts.
have made 3 iterations of these, first 2 not noticing a major error. there are 2 flaws that i am providing remedies for. one being a missing trace from the voltage regulator output side cap to to the 0.1uf cap on the + rail (or lm317 side) another on the outter/global feedback resistor - onboard feeds back to the output side of the opamp output rather than going to the non-invert input.
i know what you mean on the power traces. in that respect 'pa150' board approach may be better. i have seen a different approach bending legs around creating larger space for running thicker traces. i havent't tried running a 2-3 ohm load at full tilt but made one using +/-39 volt rails playing stuff heavy for good period of time. i should try to do some rough measurements to see if last in line chips suffer.
another regretful thing is not providing place for 0.1uf or similar caps at each chip.
in general this version works very well, has that nested feedback stuff i'd inquired with a couple members offline about.
have made 3 iterations of these, first 2 not noticing a major error. there are 2 flaws that i am providing remedies for. one being a missing trace from the voltage regulator output side cap to to the 0.1uf cap on the + rail (or lm317 side) another on the outter/global feedback resistor - onboard feeds back to the output side of the opamp output rather than going to the non-invert input.
i know what you mean on the power traces. in that respect 'pa150' board approach may be better. i have seen a different approach bending legs around creating larger space for running thicker traces. i havent't tried running a 2-3 ohm load at full tilt but made one using +/-39 volt rails playing stuff heavy for good period of time. i should try to do some rough measurements to see if last in line chips suffer.
another regretful thing is not providing place for 0.1uf or similar caps at each chip.
in general this version works very well, has that nested feedback stuff i'd inquired with a couple members offline about.
All in a days work:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Traw: Have you tested the boards?
By looking at the pictures of the board I get that it is connected like this:
RC in series as feedback? I think those should be parallell to each other...
By looking at the pictures of the board I get that it is connected like this:
An externally hosted image should be here but it was not working when we last tested it.
RC in series as feedback? I think those should be parallell to each other...
The resistor and series cap you're mentioning is in parallel with the resistor that sets the amplifier gain. You can shape the high frequency gain and phase characteristics of the amplifier with those two components. It is most likely used to increase stability since traw mentioned that this board uses nested feedback.
there's a 22k series'd with 47pf paralleled with 56k for the feedback at chipamp. the outter feedback is a 56k... really cranks the gain of the chipamps up. sounds a bit different than some other multichip configs i've tried without the nested feedback. seems to produce a more solid clear sound, or at least from my own perceptions.
Work is coming along nicely on traw's boards.
The mox output resistor are huge one those boards
Now I'm just waiting for some more 47pf caps, ordered to few by mistake But they should arrive on monday.
And then there's the LM3886's, kinda hard to get it to work without em
The mox output resistor are huge one those boards
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Now I'm just waiting for some more 47pf caps, ordered to few by mistake
But they should arrive on monday.And then there's the LM3886's, kinda hard to get it to work without em
As soon as I get the driverboard populated I'm gonna continue work on my other boards as well. The issue of V+ to the lm3886's is solved so hopefully it'll work. Haven't been building much these last days to to family problems, but I'll get on with it.
Still waiting for some more chips to get traws boards populated too.
Still waiting for some more chips to get traws boards populated too.
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