nothing easier than mod it and try
Wasn't expecting much of a change but there was very noticeable different between 2.21k and 2.67k. Sounds fine tuned.
Some finishing touched.
Attachments
After seeing several ACA's with linear supplies I think I'll go ahead and build a separate
PS chassis for my store kits and run umbilicals to the amps.
Anand, have you seen this one: https://www.dvatp.com/tech/aca_project
PS chassis for my store kits and run umbilicals to the amps.
Anand, have you seen this one: https://www.dvatp.com/tech/aca_project
Ahh...yes, thanks for the reminder, that fella even designed his own PCB boards...I completely forgot!
Best,
Anand.
gents a PS question: I put together a pair of ACA from diyaudio store kit. I used them to take a measurement on a speaker and the turn off thump is pretty bad; also there was some noise in large sensitive drivers (it could have been coming from my signal generator too, not sure yet).
> anyways I am looking at adding a large capacitor to prevent/reduce the depowering thump. I also have a pair of 0.68mH inductors lying around and they could each fit into the ACA housing; so i was wondering if I could use them in an L-C?
Can somebody recommend a capacitor size for an L-C after the SMPS DC voltage in, so the store smps can charge it and it can provide some noise attenuation with that size choke? (also if I need to add a resistor and a diode at the cap plus).
by the online calculators it looks like the LC impedance goes down with larger caps. to me 0.68mH with 22,000uf looks good, but Papa makes a reference to "lesser values"? so I have no idea if my coils could be used with what size cap to add anything to it, and how to size a resistor and a diode if I need them:
http://www.diyaudio.com/forums/pass-labs/215392-amp-camp-amp-aca-197.html#post4152611
Mucho appreciated!
> anyways I am looking at adding a large capacitor to prevent/reduce the depowering thump. I also have a pair of 0.68mH inductors lying around and they could each fit into the ACA housing; so i was wondering if I could use them in an L-C?
Can somebody recommend a capacitor size for an L-C after the SMPS DC voltage in, so the store smps can charge it and it can provide some noise attenuation with that size choke? (also if I need to add a resistor and a diode at the cap plus).
by the online calculators it looks like the LC impedance goes down with larger caps. to me 0.68mH with 22,000uf looks good, but Papa makes a reference to "lesser values"? so I have no idea if my coils could be used with what size cap to add anything to it, and how to size a resistor and a diode if I need them:
http://www.diyaudio.com/forums/pass-labs/215392-amp-camp-amp-aca-197.html#post4152611
Mucho appreciated!
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after smps at the front switch as in the ACA build guide. when taking speaker measurements I ended up trying to flip the switch as fast as possible as that seemed to help a bit, at least judging by the naked eye watching the speaker cones pop (that made me wonder if the whole approach with adding a large cap after smps would have been wrong; maybe I need something across the switch?)
I did not try shorting the inputs for noise. i am reluctant to connect them to speakers until I have figured out the turn off.
turn on was seamless though, no issue whatsoever. only the turn off was bad.
I did not try shorting the inputs for noise. i am reluctant to connect them to speakers until I have figured out the turn off.
turn on was seamless though, no issue whatsoever. only the turn off was bad.
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ZM. Would you mind explaining the 1.7 amp bias mid???
Thanks so much for reading looking forward to your reply.
So if I changed the R15 2,21 to say 2,6 would that increase bias? To 1.7amps?
Thanks for guiding me, I'm a total newbie to DIYaudio projects
I used 2.67k because it's what I had on hand. Switched to 2.21k this past weekend and it's noticeably better.
Trying each one is best way to know, but that was my resent experience.
Vince
Ok one channel done with stock ACA kit from diystore...great sound quality...funny it works great with my floor standing Sony speakers 180W 8ohm, but pathetic with Sony bookshelf VX333 70W 6ohm...every one is just amazed with the treble mid base of this teeny 6W thingy...only bit of sound while startup...guess that are the capacitor's charging, but a very loud thump while switching it off...I read a lot of similar comments on thump issue, but no standard fix...the bleeding resistor at output was supposed to solve the power on thump...any know value of cap I can attach that will not change the audio signature...or any other suggestions
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