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Wow! Nice work, Doug! I think this is the most over-the-top implementation of an ACA that I've seen, both for the chassis and the power supply implementation. I built a second ACA just a short while ago using a cheapie switched mode power supply and discovered the reason why it was so cheap on ebay. Replacing it with a genuine Dell power supply made all of the power supply noise go away for me. The only oddity that I have now is that I get a brief "whistle" out of one of my speakers as it powers up. Not sure what is going on, my first ACA doesn't behave this way.
The only benefit to those generic SMPS bricks is that they're inexpensive...that's about it. Would not surprise me that the Dell is better simply because they have been put through emissions testing as required to sell in many markets, including the US and EU. We had a similar problem at work with the generic chinese brands...had to chuck the entire lot when they failed FCC testing.
Not sure why your amp is whistling exactly. For what it's worth, on my amp the speakers are connected directly to my PCBs (no speaker protection) and with the linear supply I built there is no turn on/off thump or other noises.
Whistle on power up / down is normal for switched-mode power supplies. Mine does the same, it is normal.
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Curious, my daughter and I built an ACA last summer that does not exhibit this behavior - both use Dell power supplies. The only two differences are that I used a different brand for the 3300uF cap and used IRFP 044 transistors instead of IRFP 240s.
Here is a picture of the completed amp that I posted over in the Pictures thread:
Eric
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Right side: Beyma TPL-150 (ESS Heil AMT-ish) together with a Saba Greencone 8" for everything above 200Hz, and a Meyer MS-12 12" ported midbass, all three on the same channel 1st order crossovers. Then an active sub, for movies and such.
Left side: Vintage yamaha horn drivers and supertweeters, and a Saba greencone. Does not play lower than 200hz.
Crossover: Digital XO to separate bass from sensitive speakers, and passive speaker level XO for everything else. 1st and 2nd to keep it simple.
I still can't decide what I like best.
BTW, no bias issue with the F-5 anymore. It just had to burn in to become more stable. It gave me some time to read How-To-Bias for dummies. Great book. Voltage across the resistors is the means and Offset=0 is the goal! Now I have offset=0.000V. Yeahi!
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Two pc power supplies and two aca amps in one chassie
I have choosen to build my amp camp amp dual mono. Two lap top power supplies and two pcb in one chassie. My question is..The minus on each pcb will be connected to ground when the pcb is mounted on the heat sink, with screws. There will be two minuses connected to ground now?
Is there any trouble with the minuses to ground?
I have choosen to build my amp camp amp dual mono. Two lap top power supplies and two pcb in one chassie. My question is..The minus on each pcb will be connected to ground when the pcb is mounted on the heat sink, with screws. There will be two minuses connected to ground now?
Is there any trouble with the minuses to ground?
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If your two sinks are connect to one another electrically, there is potential for a ground loop, though if both bricks get plugged into the same outlet, perhaps this is minimized.
If you two sinks are electrically isolated from one another (not using a metal chassis), there should be no problem at all as the two power supplies will never "mix."
If you two sinks are electrically isolated from one another (not using a metal chassis), there should be no problem at all as the two power supplies will never "mix."
Then I should isolate det pcb from the chassie with som nylon spacers...
Thanks for all the help!
In case the 2 boards are on the same heatsink but with only one common PSU non need for isolating from each other, right?
I could be wrong but I believe placing both PCBs on the same heatsink, assuming you use a large enough extrusion to handle the dissipation (stock ACA heatsinks are not big enough) will only reduce the loop area, not eliminate it. The best solution for the stock boards is to find a way to insulate the PCB mounting holes from the heatsink.
I worked around the problem by building a custom PCB for my dual mono application, but it's not a drop-in replacement for the stock boards. Check out my earlier post in this thread or go directly to Oshpark to see what I did...
https://www.oshpark.com/profiles/ottopilot
Yes the F5 is a fantastic amp and would probably be a better fit in most applications; the F5 is probably the best overall amp I've ever heard. But what if you don't need those things? That's where the ACA shines and that's how I use them to drive just a pair of 8ohm Fostex single drivers (I do augment with a small sealed sub). For me anything more than the ACA's is just overkill.
Enjoy both!
ACA build on the cheap with execellent results
Thanks for all the posts and work from everyone especially Nelson Pass that made this possible. I used an existing chassis from a scrapped industrial motor amplifier and built an integrated B1 and ACA set up in one chassis. The chassis has one heat sink on either side, so I stand it up on end when I use it. I used one 9amp Dell laptop power supply to power everything. It sounds great. I just had to add a surge protector to the B1 supply so that the Dell wouldn't shut down on power up. This thing sounds great better than any of the mid-priced Adcom, Denon, Mac and Caver stuff I have owned. I bought a pair of old DCM CX-17 for $50 to go along with it. The little Celestion 5 book shelf speakers didn't have enough bass for preamp with no tone control. Perfect system for my shop. I think better than my home system at this point.
Thanks for all the posts and work from everyone especially Nelson Pass that made this possible. I used an existing chassis from a scrapped industrial motor amplifier and built an integrated B1 and ACA set up in one chassis. The chassis has one heat sink on either side, so I stand it up on end when I use it. I used one 9amp Dell laptop power supply to power everything. It sounds great. I just had to add a surge protector to the B1 supply so that the Dell wouldn't shut down on power up. This thing sounds great better than any of the mid-priced Adcom, Denon, Mac and Caver stuff I have owned. I bought a pair of old DCM CX-17 for $50 to go along with it. The little Celestion 5 book shelf speakers didn't have enough bass for preamp with no tone control. Perfect system for my shop. I think better than my home system at this point.
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I was talking about the specific noise you get from grounding the rca with speaker outputs. It won't kill the speaker but scare the hell out of you. I was having trouble with a badly fitted rca connection. This is why I know this.
I have a problem I do not understand: one of my boards cannot be biased.
At some point I see 0.40V, and immedaitely after touching the pot I go to 14V. It is like switching on or off, no intermediate values (multimeter goes from 0.40 to 14V slowly but with no esitation).
Any idea of what is happening..?
At some point I see 0.40V, and immedaitely after touching the pot I go to 14V. It is like switching on or off, no intermediate values (multimeter goes from 0.40 to 14V slowly but with no esitation).
Any idea of what is happening..?