Hang on...
So I went to the bench and grabbed an ACA 1.6 and placed DMM on GND and Q1 pin 2 and looked at the DC voltage from a cold start; yes, it actually does show a large rise and fall, but it also stabilized after 90 seconds. No load, inputs open.
I suggest turning it on and letting it sit for a few min as it warms up and all the caps stabilize, then adjust. Small movements in the pot make big changes, so go slow. It should be straightforward and well damped. If it’s still making big consistent changes, then suspect something amiss.
So I went to the bench and grabbed an ACA 1.6 and placed DMM on GND and Q1 pin 2 and looked at the DC voltage from a cold start; yes, it actually does show a large rise and fall, but it also stabilized after 90 seconds. No load, inputs open.
I suggest turning it on and letting it sit for a few min as it warms up and all the caps stabilize, then adjust. Small movements in the pot make big changes, so go slow. It should be straightforward and well damped. If it’s still making big consistent changes, then suspect something amiss.
Thanks again for the responses. I adjusted the dc bias. Listening to high sample rate Miles Davis via Plex, a PCM5242 preamp, the ACA monoblocks and my 86dB Apogee Slant 8 speakers. I am happy the power is enough for my small living room. Not sure I need a pair of F5-turbo monoblocks, but I am excited to see how they compare.
Hi All,
Noob question here: when running the ACA as a monoblock via the XLR input, is the amp running as a Differentiated Balanced Amp? (Note: I know the balanced XLR input has nothing to do with the output being “Balanced Differntiated”)
My understanding (and please correct me as I may be completely off base) is that a balanced differentiated amp does not have a speaker connection that goes to ground: the the terminal that you connect your black speaker connection to is actively pulling the inverse of the terminal you connect your red speaker cable to.
There is voltage on both terminals of the amp.
Is this correct? And, is this what is happening with the ACA when run as a monoblock via the XLR input?
The reason I ask is because I plan to hookup 2 Rel subs (one per monoblock) and, because Rel subs connect via the power amp output, knowing how the ACA is operating influences how the Rel’s are connected.
Thanks!
Noob question here: when running the ACA as a monoblock via the XLR input, is the amp running as a Differentiated Balanced Amp? (Note: I know the balanced XLR input has nothing to do with the output being “Balanced Differntiated”)
My understanding (and please correct me as I may be completely off base) is that a balanced differentiated amp does not have a speaker connection that goes to ground: the the terminal that you connect your black speaker connection to is actively pulling the inverse of the terminal you connect your red speaker cable to.
There is voltage on both terminals of the amp.
Is this correct? And, is this what is happening with the ACA when run as a monoblock via the XLR input?
The reason I ask is because I plan to hookup 2 Rel subs (one per monoblock) and, because Rel subs connect via the power amp output, knowing how the ACA is operating influences how the Rel’s are connected.
Thanks!
You are talking about feeding the ACA with a balanced source: Correct?
Electrically what happens when you do that: is you are feeding one amp of the pair (Call it left or channel 1) with one side of the balanced signal. And the other amp (Call it right or channel 2) with the other side of the balanced signal.
They are equal in amplitude and opposite in phase, the same way you describe the speaker connection.
Just wanted to make sure you are talking about feeding the amp with a balanced source, too.
Electrically what happens when you do that: is you are feeding one amp of the pair (Call it left or channel 1) with one side of the balanced signal. And the other amp (Call it right or channel 2) with the other side of the balanced signal.
They are equal in amplitude and opposite in phase, the same way you describe the speaker connection.
Just wanted to make sure you are talking about feeding the amp with a balanced source, too.
This really explained and fixed why the REL sub didn't sound right with the ACA. I'd forgotten the red and black were reversed on the amp and hooked up the sub wrong. It never sounded right so it was disconnected and sat unused.
After your post it got hooked up with the REL positives going to the ACA black post and all was well.
I built the amplifier and knew very well it reversed those posts yet did a complete brain dump when hooking up the sub. All I can say is that I've done worse.
tjw,
I believe you are correct if you mean a tiny bit of the output of one channel is tapped with a resistor to the input of the other channel, which has no other input signal. That low level from the output is inverted since the amp output is inverting, so you end up with each channel being out of phase creating, in effect a “balanced” input..
not sure what the confusion is. If I’m wrong the I hope others will correct me
One comment is about what the input is and one about how to hook up the output IMHO
Perhaps “signal” is part of the confusion as it usually pertains to the input, not output of an amp?
I believe you are correct if you mean a tiny bit of the output of one channel is tapped with a resistor to the input of the other channel, which has no other input signal. That low level from the output is inverted since the amp output is inverting, so you end up with each channel being out of phase creating, in effect a “balanced” input..
not sure what the confusion is. If I’m wrong the I hope others will correct me
One comment is about what the input is and one about how to hook up the output IMHO
Perhaps “signal” is part of the confusion as it usually pertains to the input, not output of an amp?
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The Parts Kit is sold out right now, which effectively makes the whole kit sold out - go through the workflow in the store to purchase and you will get a notice once you are in the cart.
Jason said somewhere in another thread it may be 3 months until it is back in stock.
Sorry! I thought that the whole kit was still available. Looks like everything except the parts kit is still in stock. The pcb, power supply and chassis can be ordered. You'd have to source the parts yourself.
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