@motosapian, can you comment on your OB drivers and panel size. Do they require lot's of space?
Thanks,
MM
Thanks,
MM
Just finished my Mini. Less than ten minutes on it after dialing in the pots before dinner. Before that, I checked all the resistor values last weekend, then stuffed and soldered yesterday and today - about three hours(?) of stuffing and soldering. No blue smoke and the biasing seemed touchy but not difficult. This is my first build after building the Full Range Equalizer, which I’m not sure that I’ll need now that I’m hearing the Mini through my recently completed bipole microTowers (Mark Audio Pluvia 7.2 HD drivers in parallel) HT @planet10 .
My build includes the additional caps recommended by @ClaudeG by way of the kit offered by @birdbox . I have not yet built the SMPS filter with @ClaudeG recomended murata coil…maybe this weekend(?) and/or a wood plinth.
As for the jumpers J1, the dual pin is mounted, but not the cap…would this be considered “no jumper”?
I nearly installed the transistors backwards on one side. Thankfully just the first one just had a dab of solder in place when I realized my mistake.
My build includes the additional caps recommended by @ClaudeG by way of the kit offered by @birdbox . I have not yet built the SMPS filter with @ClaudeG recomended murata coil…maybe this weekend(?) and/or a wood plinth.
As for the jumpers J1, the dual pin is mounted, but not the cap…would this be considered “no jumper”?
I nearly installed the transistors backwards on one side. Thankfully just the first one just had a dab of solder in place when I realized my mistake.
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Well done JrKC, looks great!
Happy with the sound?
Yours is to my knowledge the 4th ACA Mini tweaked with the addition of some caps, congrats. Add the coil when you can, makes a massive difference ("somewhere" nearly as much as the caps you added), you won't be disapointed. But of course this is all IMHO, let us know please...
Second build only... well, I have a few more builds under my belt and mounted late at night 1 transistor backwards, luckily realising my mistake while at it... so well done again to you!
Last but not least, if nothing sits on J1, then indeed you are jumpers out / no jumper.
Have fun listening to music and thanks for posting
Claude
Happy with the sound?
Yours is to my knowledge the 4th ACA Mini tweaked with the addition of some caps, congrats. Add the coil when you can, makes a massive difference ("somewhere" nearly as much as the caps you added), you won't be disapointed. But of course this is all IMHO, let us know please...
Second build only... well, I have a few more builds under my belt and mounted late at night 1 transistor backwards, luckily realising my mistake while at it... so well done again to you!
Last but not least, if nothing sits on J1, then indeed you are jumpers out / no jumper.
Have fun listening to music and thanks for posting
Claude
Agree!! Mini is the greatest bargain in HIFI.
Stupid easy to build.
Sound is excellent. Wont play super loud, but it delivers at low volume levels. As a desk amp for near field, it is superb. I currently have mine in my work bench.
Even in my main system 14x14 room, it drives my Klipsch RP600II to satisfactory levels.
Hello
I’m seeking some help to repair my friend’s ACA mini.
During the bias stage there was a mishap and resistors R8, R9 on the left channel became extremely hot to the point that the solders melted away.
What is odd is that I’m able to bias both channels properly but once biased if I vary ever so slightly P1 on the left channel the bias increases to about 0.8V instead of 0.3V
One strange behaviour happens at higher power, when comparing my own ACA mini to his the distortion on his mini is much greater for the same settings.
One last nugget of info; when your mini is playing music and you power down by unplugging the power supply AC side, the sound is very low and distorted, I’m aware this is normal BUT on the defective mini this behaviour happens also on power on.
On my ACA mini, this doesn’t happen..
Should I replace the 4 JFET and the 4 MOSFET or is there something I could verify first.
Thanks in advance for any help
Eric
I’m seeking some help to repair my friend’s ACA mini.
During the bias stage there was a mishap and resistors R8, R9 on the left channel became extremely hot to the point that the solders melted away.
What is odd is that I’m able to bias both channels properly but once biased if I vary ever so slightly P1 on the left channel the bias increases to about 0.8V instead of 0.3V
One strange behaviour happens at higher power, when comparing my own ACA mini to his the distortion on his mini is much greater for the same settings.
One last nugget of info; when your mini is playing music and you power down by unplugging the power supply AC side, the sound is very low and distorted, I’m aware this is normal BUT on the defective mini this behaviour happens also on power on.
On my ACA mini, this doesn’t happen..
Should I replace the 4 JFET and the 4 MOSFET or is there something I could verify first.
Thanks in advance for any help
Eric
What was the mishap that caused the solder to melt?
The extreme heat and melted solder meant very high current through the output mosfets, so they could be damaged.
If this only happened to the left channel, then the right channel is likely not damaged.
I suggest replacing the left channel mosfets.
When the mosfets are off the board, measure the voltage at the mosfet gate pad relative to ground with the pot rotated to its extreme positions. This is to check the jfets.
The extreme heat and melted solder meant very high current through the output mosfets, so they could be damaged.
If this only happened to the left channel, then the right channel is likely not damaged.
I suggest replacing the left channel mosfets.
When the mosfets are off the board, measure the voltage at the mosfet gate pad relative to ground with the pot rotated to its extreme positions. This is to check the jfets.
Hi
I wasn’t there when the mishap happened 😩
Ok, I have removed the output MOSFET from the left channel.
Here are the voltages at the gates referring to gnd for Q3 and Q4 for the left channel.
As found:
Q3, Q4 respectively 18.9V , 5.14V
With the variation of P1, P2 voltages at Q3, Q4 respectively are varying from
Varying P1; 12.1V to 24V
Varying P2; 0V to 10.75V
Based on the above, are the JFET ok ?
Thanks
Eric
I wasn’t there when the mishap happened 😩
Ok, I have removed the output MOSFET from the left channel.
Here are the voltages at the gates referring to gnd for Q3 and Q4 for the left channel.
As found:
Q3, Q4 respectively 18.9V , 5.14V
With the variation of P1, P2 voltages at Q3, Q4 respectively are varying from
Varying P1; 12.1V to 24V
Varying P2; 0V to 10.75V
Based on the above, are the JFET ok ?
Thanks
Eric
The gate voltages appear reasonable so I would say the JFETs are ok.
Try replacing the mosfets.
Also check the overheated resistors.
Be sure to set the pots to the proper position (full counterclockwise) before powering up and biasing.
Try replacing the mosfets.
Also check the overheated resistors.
Be sure to set the pots to the proper position (full counterclockwise) before powering up and biasing.
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Ok, MOSFET changed but nothing has changed.
Just like before I was able to bias as per the recommended settings but I still have that very odd noise for the first 30 seconds after turning on the ACA mini.
Could this be the different power supply causing these artifacts?
You can have a listen but DIYaudio won’t accept the file type.(mp4)
Just like before I was able to bias as per the recommended settings but I still have that very odd noise for the first 30 seconds after turning on the ACA mini.
Could this be the different power supply causing these artifacts?
You can have a listen but DIYaudio won’t accept the file type.(mp4)
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I do not have an ACA Mini so I have no experience with turn-on and turn-off behavior. Perhaps members who have ACA Minis can comment.
Does the right channel which did not experience the overheating behave the same as the left channel?
Does the amplifier seem to work properly after the power-up period? Are operating point voltages correct and stable?
What is different about the power supply?
Does the right channel which did not experience the overheating behave the same as the left channel?
Does the amplifier seem to work properly after the power-up period? Are operating point voltages correct and stable?
What is different about the power supply?
Hi Ben
Once powered on, it takes about 30 seconds for the noise to stop and then the amp works properly.
Both power supply are switching type.
Tomorrow I’ll find a way to power the amp with the original power supply I have at home.
Thanks for the support.
Eric
Once powered on, it takes about 30 seconds for the noise to stop and then the amp works properly.
Both power supply are switching type.
Tomorrow I’ll find a way to power the amp with the original power supply I have at home.
Thanks for the support.
Eric
Quick question . . . should I bias the Mini with signal/music flowing or just "ON"?
AND I'm curious about recommended preamps . . . considering the Schiit route vs ACP+ or B1. Schiit Saga's dual preamp outputs would allow bi-amping, but that may be overkill for my nearfield office setup - low levels (+/- 60db is great) with Mark Audio Pluvia 7.2 HD bipole microTowers.
AND I'm curious about recommended preamps . . . considering the Schiit route vs ACP+ or B1. Schiit Saga's dual preamp outputs would allow bi-amping, but that may be overkill for my nearfield office setup - low levels (+/- 60db is great) with Mark Audio Pluvia 7.2 HD bipole microTowers.
Thank you. I was begining to think this were the case.
Should RCAs and speaker connections all be removed?
- John
Is there music playing on inputs when turning it on, or nothing plugged into RCA and you have some odd noise?
If I play music for the first 30-90 seconds after power on, there is very obvious distortion (I assume caps are still charging?). However, just turning it on with no input signal it's dead silent.
What size caps are being used? I "upgraded" to more capacitance (27,000uF caps) on my second ACA Mini and the distortion on power on was much more "jagged" and lasted well over a minute before subsiding, whereas the kit parts I got from the store for my first ACA Mini (15,000uF) the distortion on power up is softer and lasts less than 30 seconds.
Got to let it warm up longer than that anyway for sonic bliss.
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