They might not be "true" balanced outputs, but there should still be an inverted signal on the negative output (pin 3). This is done by taking the positive signal and inverting it using an op-amp; exactly what has been suggested here but it's already done inside the unit.
Why not just try it?
I asked the guy who did an upgrade to my DAC. He says this will result in one channel being dead quiet.
That doesn't make any sense to me. The user manual for the BMC-2 says it has balanced outputs. To be balanced there has to be an inverted output.
Did his upgrades include modifying the output stage?
EDIT: I see the list of mods on the LC Audio page...
I'm confused.
Did his upgrades include modifying the output stage?
EDIT: I see the list of mods on the LC Audio page...
I'm confused.
Last edited:
I actually do not know. But he explained that it would not have worked on the unmodified version either.
Will have to try capacitance. If that does not work. Phase shifting.
Will have to try capacitance. If that does not work. Phase shifting.
Ok, now that really doesn't make sense.
Do you own a multi-meter? Play a 50-60Hz sine wave and measure the voltage of the output from pin 1 and 2 and then compare it to the output of pin 1 and 3. If it's roughly the same, then measure from pin 2 to pin 3. You should get double the voltage.
Last edited:
Won't hurt trying. I own several multi-meters.
Will try with capacitors first, and keep a look out for bus pumping. I have read a lot of places I might not even get a problem...
Finally figured out why I have to put - on the capacitor to -55V, and "+" to GND.
Found this picture in a IRS2092 amp ad.
Will try with capacitors first, and keep a look out for bus pumping. I have read a lot of places I might not even get a problem...
Finally figured out why I have to put - on the capacitor to -55V, and "+" to GND.
Found this picture in a IRS2092 amp ad.
Attachments
I did not add any capacitance or do any phase inversion. - And I still have no bus pumping! Yay... Played well above my toleration for volume, and measured 99,5V. I played rap, rock, heavy metal and EDM. Never above 100V.
Sorry for the thread revival, however I do not feel it would be worth while starting a new thread.
I plan to build a few of the L15D amps, starting with 2 channels and then increase to 6 channels. I will be using 2 of the channels to run subwoofers so the bus pumping is a bit of a concern and this would be my first amp build, so want to make sure I understand everything before making the purchases. My knowledge is still a bit limited but that has been and will continue to improve, especially after getting this build done.
I have a MiniDSP on its way and was wondering if I could use that for the phase inversion? Also how would the phase inversion work with 4 or 6 channels if they were to all be connected on the same PSU - which amp boards would I need to invert the phase for and which would remain the same?
Also just to clarify, the signal would be phase inverted and then on the speaker outputs I can reverse the polarity there to get everything back in phase?
I plan to build a few of the L15D amps, starting with 2 channels and then increase to 6 channels. I will be using 2 of the channels to run subwoofers so the bus pumping is a bit of a concern and this would be my first amp build, so want to make sure I understand everything before making the purchases. My knowledge is still a bit limited but that has been and will continue to improve, especially after getting this build done.
I have a MiniDSP on its way and was wondering if I could use that for the phase inversion? Also how would the phase inversion work with 4 or 6 channels if they were to all be connected on the same PSU - which amp boards would I need to invert the phase for and which would remain the same?
Also just to clarify, the signal would be phase inverted and then on the speaker outputs I can reverse the polarity there to get everything back in phase?
You don't need to invert a second time.
To get bridge mode the two outputs must be out of phase.
It is already out of phase due to inverting input.
Don't forget that in bridge mode the load must be twice normal impedance, so for an 4 ohm amplifier bridged it must be 8 ohm load.
That would only be if I were to bridge the amps, which I do not plan on doing.
Unless I am misunderstanding something?
Alright, I understand that. However as I mentioned I do not plan on briding the amps as I would then need to double the amp boards to get 6 channels of output.
I'd like to look at phase inverting to try solve any bus pumping issues I may run into, hoping that with the MiniDSP being able to invert the signal it will be easier and not require any phase inverter boards.
Edit: I'm still learning here, so its possible I might have missed something and am being a bit daft.
Sorry for the double post, but let me try clarify.
So if I have 2 channels running off the same PSU, I simply invert the signal on the one channel which will cancel out the bus pumping effect. This I understand and makes sense.
If I have 4 channels or even 6 channels running off a single PSU, how does the phase inversion work then? Which amp channels do I invert and which do I leave?
Is it possible to use phase inversion to resolve bus pumping issues if I are running 4 or 6 channels off a single PSU?
So if I have 2 channels running off the same PSU, I simply invert the signal on the one channel which will cancel out the bus pumping effect. This I understand and makes sense.
If I have 4 channels or even 6 channels running off a single PSU, how does the phase inversion work then? Which amp channels do I invert and which do I leave?
Is it possible to use phase inversion to resolve bus pumping issues if I are running 4 or 6 channels off a single PSU?
Hi Mortenhoe: I just came upon this post of yours about eliminating bus pumping. Two questions: if that is a negative symbol on the caps to added to the output shouldn’t the bottom caps polarities be reversed so the “-“ is on the negative rail? Secondly, did this technique actually work for you?
Thanks, Pete
Sorry, I just saw posts #13 and #15. My question was already answered. Should have read the whole thing through.
P
P
I would try a capacitor multiplier . Like this one from Allo.
The multiplier behaves the same as it would have 1000 000 uF .
The cost is about 20 dollars each. You need one for every amplifier.
Only max 30 V input, though.
The multiplier behaves the same as it would have 1000 000 uF .
The cost is about 20 dollars each. You need one for every amplifier.
Only max 30 V input, though.
Attachments
Last edited: