Small price to pay for lower noise. The longer you wait, the more time you get for warm-up anyway...
Amp has been fixed.
The 30 seconds delay with the noise is now down to a 2 sec. delay.
To resolve this, R4 was changed from 22k to 6k8 like in the original schematic.
MOSFET from left channel were replaced, all JFET were replaced and then the bias adjusted to 0.35V (Vb)
Thank you all for your help.
This is the beauty I was working on, my friend is very talented.
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I was wondering if anyone had tried a simple unregulated linear supply with the mini and what the pros/cons might be? I was thinking 24V single ended 2 amp supply from a bridge rectifier and a simple CRC filter. No regulator. Capacitors would be 10K uF and the R would be a 10 ohm 6 amp thermistor. Perhaps an additional thermistor in series with the transformer primary to reduce turn on surge. Basically Papa's F5M PS supply idea only single polarity.
I tried it with a CapMx plus CRC before and after the MOSFET (10mF-0.22r-10mF) and believe it or not went back to the 24v 5a SMPS plus Mark Johnson's filter.
Maybe if you employ some chokes in between you might have a better outcome.
Maybe if you employ some chokes in between you might have a better outcome.
Thanks, @Stanislav! Was that with jumpers "in" or "out"? I'm partial to "in". I was curious because I have a headphone amp I built that sounds better with a linear (regulated) supply than a MJ filtered SMPS. It's subtle but I find it less fatiguing during long listening sessions, i.e., smoother without loss of detail. But loudspeaker systems do seem more forgiving than headphones in that regard.
I've been using an inexpensive 4 amp SMPS with Mark's AmyAlice filter for my ACA mini and been pretty happy (and yes, the AA filter is rated at 3A but the ACA mini load is less than that). I was surprised to find that the DIY store kit SMPS is 2 amps because 3 or 4 amp supplies sound better to me and that's without touching the bias. Maybe I was overbiased for a 2A supply although I'm just a hair above the minimum at VB=0.32 V. Or maybe my elCheapo 2A supply is under spec compared to the higher quality DIY store supply. It is interesting that Papa's original power supply spec was a 3.75 amp Mean Well.
I've been using an inexpensive 4 amp SMPS with Mark's AmyAlice filter for my ACA mini and been pretty happy (and yes, the AA filter is rated at 3A but the ACA mini load is less than that). I was surprised to find that the DIY store kit SMPS is 2 amps because 3 or 4 amp supplies sound better to me and that's without touching the bias. Maybe I was overbiased for a 2A supply although I'm just a hair above the minimum at VB=0.32 V. Or maybe my elCheapo 2A supply is under spec compared to the higher quality DIY store supply. It is interesting that Papa's original power supply spec was a 3.75 amp Mean Well.
Ions ago, when I looked into the Mini, I read a post where people made SMPS comparisons for the Mini and it said the ACA 5A SMPS was better sounding than the then provided Ini 3.75A SMPS.
Yes, it seems odd, as long as the SMPS is a quality item (and once you filter it, it will be "anyway") and it doesn't run into hic cup, it should be fine,: a 2A SMPS is perfectly functional indeed... and yet...
Because of that doubt we decided on our Minis to go for high quality low ripple Meanwell 5A SMPS (see my posts for the reference). It sounded excellent once filtered with the Murata, but yet we had no comparison point. But we had also chosen that high current SMPS so it could potentialy drive 2 Minis... which is what we did.
So we compared 1 5A SMPS feeding 2 Minis (roughly each with a potential feed of 2.5A, far more than needed) and each of the 2 Minis being fed by the said 5A SMPS. For both configurations we fitted as many Murata coils as there were SMPS, so al were filtered the same way. The latter configuration with as many 5A SMPS as Minis sounded much better. I know this isn't exactly comparable (amp separation etc.) to a high A / lower A SMPS comparison , but the difference were quite great so I am inclined to believe that the Mini does sound better whith an overrated PS.
What is also quite clear is that in all cases the filtering Murata coil did (in that specific Mini case) a splendid job, even bettering MJ's little SMPS filter.
Bottom line: for us it is "Big low ripple quality SMPS + Murata" feeding each Mini,
I hope this helps
Claude
Yes, it seems odd, as long as the SMPS is a quality item (and once you filter it, it will be "anyway") and it doesn't run into hic cup, it should be fine,: a 2A SMPS is perfectly functional indeed... and yet...
Because of that doubt we decided on our Minis to go for high quality low ripple Meanwell 5A SMPS (see my posts for the reference). It sounded excellent once filtered with the Murata, but yet we had no comparison point. But we had also chosen that high current SMPS so it could potentialy drive 2 Minis... which is what we did.
So we compared 1 5A SMPS feeding 2 Minis (roughly each with a potential feed of 2.5A, far more than needed) and each of the 2 Minis being fed by the said 5A SMPS. For both configurations we fitted as many Murata coils as there were SMPS, so al were filtered the same way. The latter configuration with as many 5A SMPS as Minis sounded much better. I know this isn't exactly comparable (amp separation etc.) to a high A / lower A SMPS comparison , but the difference were quite great so I am inclined to believe that the Mini does sound better whith an overrated PS.
What is also quite clear is that in all cases the filtering Murata coil did (in that specific Mini case) a splendid job, even bettering MJ's little SMPS filter.
Bottom line: for us it is "Big low ripple quality SMPS + Murata" feeding each Mini,
I hope this helps
Claude
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It's with the jumper out. My mini is in a "proper" enclosure and it's a bit tricky to play with the jumpers. I'll have to one do it though and find out if I can hear any difference.
Head amps are a bit picky about their PSU as headphones are so sensitive you'll hear every bit of noise and hum.
My Zenlite headlamp uses a Vicor 48v SMPS which are used in satellite equipment and it's dead quiet.
Head amps are a bit picky about their PSU as headphones are so sensitive you'll hear every bit of noise and hum.
My Zenlite headlamp uses a Vicor 48v SMPS which are used in satellite equipment and it's dead quiet.
"I'll have to one do it though and find out if I can hear any difference."
I meant to write one day do it but somehow missed the word. Bloody mobile devices.
I meant to write one day do it but somehow missed the word. Bloody mobile devices.
Anyone know the input impedance on the mini? I'd like to run a parallel setup with them.
Here's my question from the Pass active xo thread: I want to split the low pass outputs into 4 channels from 2 and am wondering what is best practice here. can I simply split via wiring, or is some sort of buffer recommended? I've attached the datasheet for my pre/source and the general layout sketch -
Here's my question from the Pass active xo thread: I want to split the low pass outputs into 4 channels from 2 and am wondering what is best practice here. can I simply split via wiring, or is some sort of buffer recommended? I've attached the datasheet for my pre/source and the general layout sketch -
It will be 111500 ohms which is the equivalent value of parallel resistance of R2 and R3 plus the value of R1.
Whether or not to parallel the outputs all really depends on the output impedance of your active XO. Just looking at the output stage of that should give a good idea of output impedance or alternatively you just measure it by loading it resistively and looking if the output is affected in amplitude. In any case its not really an issue beyond reducing the amplitude... so you just turn the ACA gains up to compensate.
Most solid state line outputs are normally very low impedance, sometimes artificially increased a little by series feed resistors. Just measure it, play a constant tone and load the output with say a 1k and see if there is any drop in amplitude as a first step.
Most solid state line outputs are normally very low impedance, sometimes artificially increased a little by series feed resistors. Just measure it, play a constant tone and load the output with say a 1k and see if there is any drop in amplitude as a first step.
@ClaudeG I finally made the time to build the SMPS with the Coil yesterday after work. There is a subtle but IMPROVED sound. Maybe clarity and separation. THANK YOU.
EDIT: Music used for comparison: Ghosted & Tributaries 24 bit downloads
* added insulation between coil and box *
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Well done and... thanks for the kind feedback!
May I humbly suggest you keep just the coil and do without the SMPS filter?
It sounds even better that way to my ears: the SMPS filter robbed something, so you may notice a further improvement without (and that improvement plus the one you noticed already may start to become in total say less subtle 🙂
Note Mark's excellent SMPS can be used elsewhere, no doubt!
Coil alone in the PS... and now that you are there, what about trying the additional caps if you fancy? Dead easy and they are another improvement of similar magnitude than coil alone... IMHO.
Have a lot of fun with this fab little amp and thanks again for posting
Claude
May I humbly suggest you keep just the coil and do without the SMPS filter?
It sounds even better that way to my ears: the SMPS filter robbed something, so you may notice a further improvement without (and that improvement plus the one you noticed already may start to become in total say less subtle 🙂
Note Mark's excellent SMPS can be used elsewhere, no doubt!
Coil alone in the PS... and now that you are there, what about trying the additional caps if you fancy? Dead easy and they are another improvement of similar magnitude than coil alone... IMHO.
Have a lot of fun with this fab little amp and thanks again for posting
Claude
The caps have beeen on my Mini since I built it up; a very easy mod. @birdbox put together a mod-kit that included the caps, coil, and his 3d printed feet.
I'll see about including the coil alone and will let you know my thoughts.
John
OK, thanks?
Did you perhaps have a listen with and without the caps so you could post your findings on this mod... or did you go straigt for it?
Thanks for all your posts, for sure they will help other builders!
Birdbox offered indeed an incredible "enhencement" package for Aca Mini builders, at a very friendly price (a few coffees)!
Claude
Did you perhaps have a listen with and without the caps so you could post your findings on this mod... or did you go straigt for it?
Thanks for all your posts, for sure they will help other builders!
Birdbox offered indeed an incredible "enhencement" package for Aca Mini builders, at a very friendly price (a few coffees)!
Claude