Interesting, but what does that look like practice. I always thought the advantage of monoblocks was the separation of everything by channel…including the PSU.
Last edited:
Hello, running SE for testing purposes. JFets from diyaudiostore kit, all parts tested before installation. Solder joints inspected and look good to me, as does the part positioning. Do you know what input voltage for a 1kHz sine wave would cause clipping? The distortion is definitely reduced at lower input voltage.
With a 24 volt supply and 8 ohm load you should be able to get to around -/+10 volts output voltage (so around 7 volts rms). Input voltage for that would be around -/+3 volts on a scope.
That assumes R12 is 39.2k. If you have fitted 68k then the input voltage would be around -/+ 2 volts.
(the results deviate from what theory might suggest because of the very high output impedance of the ACA and its very low open loop gain)
That assumes R12 is 39.2k. If you have fitted 68k then the input voltage would be around -/+ 2 volts.
(the results deviate from what theory might suggest because of the very high output impedance of the ACA and its very low open loop gain)
The different parts of different psus modulate the signals different. The earing does listen these differences.
Try: set some cables and a switcher between the psus. Listen and switch;-)
If anybody looks for more separation of channels: Move the speakers further apart.-)
No, the offset is set to 0mV.
Question, though... based on the topology of this amp, if I feed a signal only into the left input, should I get an output at both speaker terminals? I'm thinking yes, because the reds are tied together (to ground), but if that's the case, it makes it tough to troubleshoot which one is my problem channel.
Question, though... based on the topology of this amp, if I feed a signal only into the left input, should I get an output at both speaker terminals? I'm thinking yes, because the reds are tied together (to ground), but if that's the case, it makes it tough to troubleshoot which one is my problem channel.
OK... maybe my test rig/method is the issue. Could my oscilloscope actually be what is bridging the left and right output? Because when I hook up a separate volt meter to each output, I only get voltage out of the one whose input is being fed.
Assuming you’re still working on the left channel… scope probe to left output black, scope ground lead to left output red.
scope is most likely (safety) grounded, so you need to take care of that, when measuring bridged amps
floating output doesn't like any end being grounded
floating output doesn't like any end being grounded
@KevinHeem
@Zen Mod
BINGO... no distortion when hooked up as Kevin suggested. Zen, I think you're dead on. This is the first bridged amp my test rig has encountered.
Thank you all so much for helping me reason through this.
@Zen Mod
BINGO... no distortion when hooked up as Kevin suggested. Zen, I think you're dead on. This is the first bridged amp my test rig has encountered.
Thank you all so much for helping me reason through this.
No, in stereo mode, but in that mode, the positive speaker outputs are tied to ground, which (if I'm understanding correctly) is different from most amps.
My test rig routes the black speaker wires to oscilloscope ground, not the reds, which has never been an issue before now.
Maybe I'm misusing the term "bridged"...
My test rig routes the black speaker wires to oscilloscope ground, not the reds, which has never been an issue before now.
Maybe I'm misusing the term "bridged"...
ok then
connect scope probe gnd to whatever gnd you can find in amp, positive scope probe to whatever output terminal is giving you gigglywiggly
did you confirmed proper DC voltage of output node, and proper Iq?
connect scope probe gnd to whatever gnd you can find in amp, positive scope probe to whatever output terminal is giving you gigglywiggly
did you confirmed proper DC voltage of output node, and proper Iq?
Thanks, Zen, I'm good now. No distortion. ACA is working perfectly. It was an error introduced by my testing process, which I've sorted... thanks.
The red terminals are grounded because this is an inverting amplifier. It is typical of a common drain if I am right.
The only reason that the terminals look confusing is because for topology correctness, they are not reversed, since the amplifier is inverting and so is the polarity of the output. Switching around the jack colours would do nothing in terms of driving it (except that when doing parallel you still need to connect the right terminals regardless of colour. )
The only reason that the terminals look confusing is because for topology correctness, they are not reversed, since the amplifier is inverting and so is the polarity of the output. Switching around the jack colours would do nothing in terms of driving it (except that when doing parallel you still need to connect the right terminals regardless of colour. )