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Amp Camp Amp - ACA
Amp Camp Amp - ACA
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Old 10th August 2018, 03:18 AM   #5141
bloozestringer is offline bloozestringer  United States
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Got my parts kit today. I wish I wasn’t moving in several weeks. Gonna have to wait until we get settled in. Maybe by then some of the new surprise preamp designs may be out!
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Old 10th August 2018, 03:37 AM   #5142
Extreme_Boky is offline Extreme_Boky
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Originally Posted by kstagger View Post
Removed power supply lead to the two boards until I found the problem one. Once I unscrewed the PCB from the chassis, no more short problem. But once I bolted the power Mosfets back on, short. I replaced both Keratherm insulators since one looked as if it had a pinhole? I must have damaged it during installation?

Anyways - listening to the amp right now - gain is definitely lower than my Adcom 545, but nothing a twist of the volume can't fix. 6-7-8? Watts sounds pretty good, even on a pair of 86dB Wharfedale Denton mini-monitors.
Good that you got it working. You could also sand-off the heatsink surface with fine sandpaper, before installing the MOSFETs, and always check for shorts...

I also have 4 ohms / 86dB Dynaudios. They sound great (in general!); really nice even with 3W single-ended tube amps, due to their flat-ish impedance curve across the audio band.

The gain can be increased on ACA by replacing the feedback resistor with 68K or so... but distortions will go up, and damping factor will decrease.... It all really depends on your preferences; it may work with Dynaudio's....?
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Old 10th August 2018, 06:08 AM   #5143
Extreme_Boky is offline Extreme_Boky
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Originally Posted by Eric View Post
All of the testing I've done like this used only a resistive load. Is the cap added in series or parallel to the resistor? What are typical values of capacitance that should/should not cause trouble for the typical Pass clone?

Eric
In parallel.

Start with small values (.22uF) and check for stability and oscillations. You may miss the oscillations if your time base is set to "look-at" up to 20kHz only...

Connect the resistors and capacitors through a speaker cable you'd normally use with your speakers

No need to push the ACA to oscillations/destruction with the capacitive load, I mentioned it just as a precaution to ensure the amp is stable with let's say 0.22uF load... Some people use ribbon cables; these can introduce a fair amount of capacitive load.

What you want to ensure is that there are no oscillations at all during normal operation. The amp is missing the Zobel network, so... a bit of caution, testing and reassurance can't hurt.
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Old 10th August 2018, 06:45 AM   #5144
Nag is offline Nag  India
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Originally Posted by Mr_Zenith View Post
Hi Nag,

If this calculator is anywhere close to correct, then your experience sounds about right. I get a whopping 1 dB SPL increase with the following input:
  • 85 dB speaker sensitivity
  • 5 WPC amplifier power
  • 13 feet from speakers (~ 4m)
  • 2 speakers total
  • ...and speaker placement near to a wall
I'm getting similar results from the pair of speakers I mentioned in post #5132 above. Clearly this amp is best matched to a pair of high efficiency speakers, but what I've heard in the mere hours I've had it up and running has convinced me that it would take a cheap-a**ed pair of speakers indeed to make this amp sound truly bad. And remember: failing that you can always get a 24V power supply, jack up the bias to 12V, and prepare to party hearty - sort of.

YMMV...
Thank you Mr. Zenith.
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Old 10th August 2018, 03:16 PM   #5145
adason is offline adason  United States
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Originally Posted by bloozestringer View Post
Got my parts kit today. I wish I wasnít moving in several weeks. Gonna have to wait until we get settled in. Maybe by then some of the new surprise preamp designs may be out!
What are you talking about...if you got the full kit, you can built it in few hours. All is there. Soldering in 30 min. Putting box together, 30 minutes. Break for beer 30 min. Mounting power transistors, wiring the internals, 30 min. Powering it up, waiting for warm up, adjusting 10 volts on Q2, 30 min. Break for music, 30 min...all in few hours. I would not be able to wait few weeks, makes no sense. Believe me, I got 3 aca's.
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Old 10th August 2018, 03:17 PM   #5146
adason is offline adason  United States
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Originally Posted by bloozestringer View Post
Maybe by then some of the new surprise preamp designs may be out!
BA3 front end is good preamp.
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Old 10th August 2018, 03:49 PM   #5147
mpitogo is offline mpitogo  United States
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So with my pair of ML Motion 40's 92db at 4ohms, the bridged monoblocks are starting to open up. Seems it takes longer than a few hours to break them in. One minor concern the heat output measuring the heatsinks is steady at 135F in a 76F room once its up to temp. Normal?
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Old 10th August 2018, 05:09 PM   #5148
mpitogo is offline mpitogo  United States
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Originally Posted by Mr_Zenith View Post

Thanks again to all on the forum who worked so hard to make this possible!
Canít agree more thank you all. And Mr Zenith nice build!
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Old 10th August 2018, 05:17 PM   #5149
MEPER is offline MEPER  Denmark
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I can keep my fingers on the heatsink so think I am 10 degree lower. I also only have one ACA in each stereo chassis. So you are not far from normal. It could be normal. I will measure with a "temp gun" next time they are up and running. Room temp. is about same.
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Old 10th August 2018, 05:25 PM   #5150
WKCox is offline WKCox  United States
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Amp Camp Amp - ACA
Default ACA Kit Available

Ordered my ACA back in May, but couldn't wait, so I ordered the parts to build an F5. Have been so delighted with the F5, that I'm now building an M2x.

My ACA kit is being delivered on Monday, but I don't think I'm going to build it, now that I've stepped up to the First Watt amps.

Please PM me if you're interested in my ACA kit. Black front panel without power switch.
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