Ah, sorry. Hope this is what you are referring to.
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Thank you all. I will order the parts and watch some vids on how to de-solder. Had to happen eventually and no doubt it will be a very useful learning experience 🙂.
Another thing before I order the pots, do I need to order a more powerful PSU as well? The build guide states 24v 90w (https://guides.diyaudio.com/Guide/ACA+Mini/21) and mine is 48w? Is 2 amps adequate?
smps charge a lot faster the caps vs 50/60hz and we have two 15000uf on board that are good for 50/70w in jap amp ....
Bass is really really good for 5w amp no hurry to try my old 24v 150w meanwell
I just finished aca mini assembly, bias and now doing musical testing. My Vb voltage bias are 307mV and 316mV and Vo voltage out are 11.18V and 11,22V for the LR channels. Appreciate any comments on these bias values? i bought the pcb kit and matched fets and used a 2k ohms trimpots (p1 and p1).
Thank you Papa Nelson and to all aca mini members logs that I constantly read, cheers!
Now planning a wooden case for the aca mini and acp + preamp build soon.
Thank you Papa Nelson and to all aca mini members logs that I constantly read, cheers!
Now planning a wooden case for the aca mini and acp + preamp build soon.
As I recall, all the jfets in the kits should run enough Idss for the 1K pot to work fine.
There was some thought to going to 1.5K or even 2K pots to allow slightly lower Idss
parts to work, but 1.5K seem to be unobtainium and the 2K were only in the wrong pin
pattern. If you are short on bias we can fix that.
If you don't initially get full bias, let the amp warm up - the bias will track upward with
temperature and then stabilize.
The DC Vo value is not critical - don't obsess over anything between 11V and 11.5V.
There was some thought to going to 1.5K or even 2K pots to allow slightly lower Idss
parts to work, but 1.5K seem to be unobtainium and the 2K were only in the wrong pin
pattern. If you are short on bias we can fix that.
If you don't initially get full bias, let the amp warm up - the bias will track upward with
temperature and then stabilize.
The DC Vo value is not critical - don't obsess over anything between 11V and 11.5V.
After reading this I thought I would have another crack at biasing before replacing the pots. After 10 min one channel was pretty stable at nominal values but the other was only around 250mv with both pots maxed. I left it for another 20min and it did indeed track up very very slowly and eventually did reach and hover around 300mv! I should have been more patient. I did find however that any air movement (such as my walking around nearby) caused it to drop so I am wondering if I should leave it as it is and make up a well ventilated enclosure to keep temps more stable and perhaps reduce the warmup time. I possibly wouldn't have had this problem at all if my house wasn't such an icebox at the moment (coldest winter in 10yrs).
What is the minimum VB for satisfactory operation? Will it sound OK after 10min @ 250-ish mv or would it require the long warmup period before use? Or perhaps it will stabilize more quickly while playing music? So many questions 🙂, I have no experience with these things.
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If it’s creeping to 300mV (or close) when up to temp, that’s quite close to perfect. Sound will be great (of course) during the warm-up.
Sit back and enjoy the music!
Sit back and enjoy the music!
I looked and I searched but clearly missed any discussion of the change of C6 to 1F, as per the 2022 BOM. Is this now the correct value? Thanks.
Yes, that's where I picked up that it had changed from the original 3.3F to 1F, but I couldn't find the reason.
Or you could omit that part of the circuit completely. It only makes sense that you think adding it makes the app sound better. I don't think it does. But other folks do think it makes it sound better. Either way, it's not a necessity.