@ronnieponsones : How long does it take after turning on the amp for the distortion to go away?
I don't recall ever turning on the ACA mini with the source already playing so I can't say if mine has the same issue. However, I've never noticed distorted output when I start the source after turning on the amp.
I don't recall ever turning on the ACA mini with the source already playing so I can't say if mine has the same issue. However, I've never noticed distorted output when I start the source after turning on the amp.
Are we perhaps looking at the switching supply protection?
Check for consistent 24V rail voltage in operation.
Check for consistent 24V rail voltage in operation.
I built two DIY ACA Mini amplifiers. Fun! Neither makes noise when it's turned on. However, I don't have music playing when I turn them on, since they take about an hour to fully warm up and sound their best.
Just today I measured the input voltage (at V+ and GND) while the amps were in use. Both are steady at around 24.02 V.
Interestingly, one power supply puts out 24.35 V and the other 24.15 V when measured directly at the jack. But they go down to just over 24 V when the PS is connected to the circuit board and powered on, and then to very close to 24 V when the bias is turned on. Playing music has no additional effect.
I set VO to around 11.6 V and VB to around 370 mV at 70 degrees F ambient temperature. I have a little fan aimed at the ACA Mini in my main system, for use when the room gets up to 78 degrees F or higher, as it did last week but seldom does here.
The ACA Mini sounds fantastic (agreeing with @6L6, who wrote the excellent build guide) when the bias is high. The heat sinks get pretty hot, to the point where it's painful to hold a finger on one for more than 3 - 5 seconds.
Incidentally, don't try to bias your amp when the ambient temperature is higher than usual. You'll probably set it too low, as I did at first.
Just today I measured the input voltage (at V+ and GND) while the amps were in use. Both are steady at around 24.02 V.
Interestingly, one power supply puts out 24.35 V and the other 24.15 V when measured directly at the jack. But they go down to just over 24 V when the PS is connected to the circuit board and powered on, and then to very close to 24 V when the bias is turned on. Playing music has no additional effect.
I set VO to around 11.6 V and VB to around 370 mV at 70 degrees F ambient temperature. I have a little fan aimed at the ACA Mini in my main system, for use when the room gets up to 78 degrees F or higher, as it did last week but seldom does here.
The ACA Mini sounds fantastic (agreeing with @6L6, who wrote the excellent build guide) when the bias is high. The heat sinks get pretty hot, to the point where it's painful to hold a finger on one for more than 3 - 5 seconds.
Incidentally, don't try to bias your amp when the ambient temperature is higher than usual. You'll probably set it too low, as I did at first.
Very nice! Have a picture or two? Now time to look into the Zenductor. 🙂
Hi, @Mikerodrig27.
Here is a photo of the ACA Mini amp I use in my main system. It sits on the lowest shelf of my "equipment rack," where I used to have my Schiit Aegir.
I mounted the amp to a bamboo cutting board I bought for $5.50, to keep it from tipping over. I installed female banana plug adaptors so I could connect my audio cables. The plastic thingies that keep the cables separated were made from an old coffee can lid.
Not a work of art like some, but it does the job and lets the amp breathe.
The amp in my bedroom is set up the same way.
Here is a photo of the ACA Mini amp I use in my main system. It sits on the lowest shelf of my "equipment rack," where I used to have my Schiit Aegir.
I mounted the amp to a bamboo cutting board I bought for $5.50, to keep it from tipping over. I installed female banana plug adaptors so I could connect my audio cables. The plastic thingies that keep the cables separated were made from an old coffee can lid.
Not a work of art like some, but it does the job and lets the amp breathe.
The amp in my bedroom is set up the same way.
@lastnamenelson - NEAT!
Gorgeous build all-around, but I'm most captivated by the widget you created from the coffee can lid. Nice hack!
Also, I don't want to change your words or misinterpret. When you say:
Gorgeous build all-around, but I'm most captivated by the widget you created from the coffee can lid. Nice hack!
Also, I don't want to change your words or misinterpret. When you say:
Are you saying that the mini 'replaced' the Aegir in the same system...? If so, that's pretty awesome, IMO.
Is this the one that Pass himself laid hands on? Very nice! The workmanship looks great! 👍
Yes, @ItsAllInMyHead, as I reported in my ACA Mini Listening Impressions thread, I much prefer the ACA Mini to the Aegir. So the Aegir is no longer in service.
I have 86 db sensitivity speakers, and I tend to listen with peaks at a maximum of 85 db, so the ACA Mini has plenty of power for me.
I was aware that the Aegir has a warm sound, with the treble slightly rolled off. When I put a properly biased ACA Mini in its place, I learned that the Aegir also rolls off the bass and has, in contrast with the clear and clean sound of the ACA Mini, a somewhat blurred or muddy sound.
I knew that amps designed by @Nelson Pass were famous for their clarity, but I'd never heard one before. I am really amazed by how good sounding this little kit amp he designed is. My hat is off to him!
I have 86 db sensitivity speakers, and I tend to listen with peaks at a maximum of 85 db, so the ACA Mini has plenty of power for me.
I was aware that the Aegir has a warm sound, with the treble slightly rolled off. When I put a properly biased ACA Mini in its place, I learned that the Aegir also rolls off the bass and has, in contrast with the clear and clean sound of the ACA Mini, a somewhat blurred or muddy sound.
I knew that amps designed by @Nelson Pass were famous for their clarity, but I'd never heard one before. I am really amazed by how good sounding this little kit amp he designed is. My hat is off to him!
Hi @Mikerodrig27.
The photo is of my second build. Nelson helped with the first, which I had biased way too low.
I put the second build into my main system in order to put some burn in time on it. I only occasionally listen in the bedroom.
The photo is of my second build. Nelson helped with the first, which I had biased way too low.
I put the second build into my main system in order to put some burn in time on it. I only occasionally listen in the bedroom.
And you know, Mike Moffat as a designer at Schiit is no slouch. The little ACA Mini is a little kung-fu killer.
@Mikerodrig27:
Here is a photo of my first ACA Mini build, the one that Nelson famously helped me with. It's sitting on top of an Emotiva amp in my bedroom.
Here is a photo of my first ACA Mini build, the one that Nelson famously helped me with. It's sitting on top of an Emotiva amp in my bedroom.
Every time you start a new amp project, rub that amp for good luck.
I think the Aegir was designed by Jason Stoddard, but I could be wrong.
In any case, it's a very good amp for $800. But it's not a Pass design.
In any case, it's a very good amp for $800. But it's not a Pass design.
I did not know that. I haven't heard the Aegir but can appreciate them. Pretty cool.
as I wrote several times (and somehow ppl are again and again surprised with fact):
Papa's
Kung
is
funniest
Fu
I just created a new thread for the ACA MinMax
It's the same circuit as the ACA mini but made to mount nicely in the store's ACA chassis, plus a few other goodies to tinker around with (voltage, bias, output devices)
Currently looking for feedback before I order a first prototype
It's the same circuit as the ACA mini but made to mount nicely in the store's ACA chassis, plus a few other goodies to tinker around with (voltage, bias, output devices)
Currently looking for feedback before I order a first prototype
