I guess we probably don't need any more pictures of people's ACP+ builds, but here's mine anyway 
I didn't build it from the kit, as it didn't make much sense to buy it - I already had many of the parts on hand, including the all-important 2SJ74s and several of the resistors and capacitors. The big caps are 2200uf Nichicon Fine Golds, which is imo a more appropriate value in case you need to drive 16 ohm headphones, which I do. The input caps are 47uf Chemi-Con AWF audio bipolars, which I think are rare. I took them from a dead Toshiba SD-9200 DVD player; a living one serves as the source.
Also, I didn't want to bother measuring a bunch of J113s I'd likely never use again, so LM317s serve as the current sources for the input FETs. I don't know if they're noisier or worse in some other aspect, but they work just fine. They drop right in but must be placed "backwards" relative to the graphics on the PCB. A couple of tiny chokes in series in place of the 1 ohm resistors round out the mods - who knows, maybe they're better. Heh.
I did, unfortunately, get the dreaded power pulsing using the 24v SMPS I bought. Really stinks, I thought it'd be OK, as it's supposed to be stouter than the Triad unit. So, all I have on hand right now is a 12v linear supply by Jameco - and it works! I will order up another 24v Jameco unit and surely it will sound even better running at the correct voltage. Working fine for now, though, believe it or not!
Thanks to Nelson and the whole DIY community, of course. This thing is just awesome, and I really can't wait to get it running at 24v, as well as to try it as a preamp. Here's to more DIY projects!
I didn't build it from the kit, as it didn't make much sense to buy it - I already had many of the parts on hand, including the all-important 2SJ74s and several of the resistors and capacitors. The big caps are 2200uf Nichicon Fine Golds, which is imo a more appropriate value in case you need to drive 16 ohm headphones, which I do. The input caps are 47uf Chemi-Con AWF audio bipolars, which I think are rare. I took them from a dead Toshiba SD-9200 DVD player; a living one serves as the source.
Also, I didn't want to bother measuring a bunch of J113s I'd likely never use again, so LM317s serve as the current sources for the input FETs. I don't know if they're noisier or worse in some other aspect, but they work just fine. They drop right in but must be placed "backwards" relative to the graphics on the PCB. A couple of tiny chokes in series in place of the 1 ohm resistors round out the mods - who knows, maybe they're better. Heh.
I did, unfortunately, get the dreaded power pulsing using the 24v SMPS I bought. Really stinks, I thought it'd be OK, as it's supposed to be stouter than the Triad unit. So, all I have on hand right now is a 12v linear supply by Jameco - and it works! I will order up another 24v Jameco unit and surely it will sound even better running at the correct voltage. Working fine for now, though, believe it or not!
Thanks to Nelson and the whole DIY community, of course. This thing is just awesome, and I really can't wait to get it running at 24v, as well as to try it as a preamp. Here's to more DIY projects!
My limited experience suggests that AC-DC converters made by MeanWell, can tolerate lots of external bypass capacitors without entering "hiccup mode". It may be worth the effort to seek out and purchase a MeanWell wall wart, in addition to a Triad. Who knows, maybe replacing Nelson Pass's series resistors with your new idea (series inductors), accelerates the onset of hiccup mode. On all three: your no-name, the Triad, and also the MeanWell. Who knows?
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Thanks for your reply, Mark. At first I was thinking that it'd be silly to take the amp apart and try to modify it so my lousy wall wart supply would be happier, but I just remembered I have an extra CL-60 thermistor laying around from another project. Unless you give me a good reason not to, I think I may as well try putting it in the circuit near the DC input. By my estimation, it should start at around 10 ohms but drop down to around 2.5ish ohms once it warms up. I'm perfectly OK with losing a couple of volts, frankly -- I've already discovered the circuit functions well enough at 12v, so a 3 or 4 volts less than the intended 24 should be perfectly fine.
It's interesting to know that "hiccup mode" is an intended mode of operation and not a potentially dangerous failure. Whenever something mains-connected starts acting funny, it's good to first be sure you won't get yourself zapped or burn the place down. It also means, of course, that the PSU is still functioning properly and as long as we don't ask it to continually source a high current, it can recover and work normally again. It seems like hiccup mode kicks in when the SMPS is unable to charge the caps up and sees them as a dead short, so adding some start-up current limiting should be worth a shot. I'll bet you're right, the chokes in place of the resistors probably doesn't help things. I'll pop the CL-60 in and report back.
It's interesting to know that "hiccup mode" is an intended mode of operation and not a potentially dangerous failure. Whenever something mains-connected starts acting funny, it's good to first be sure you won't get yourself zapped or burn the place down. It also means, of course, that the PSU is still functioning properly and as long as we don't ask it to continually source a high current, it can recover and work normally again. It seems like hiccup mode kicks in when the SMPS is unable to charge the caps up and sees them as a dead short, so adding some start-up current limiting should be worth a shot. I'll bet you're right, the chokes in place of the resistors probably doesn't help things. I'll pop the CL-60 in and report back.
Is it normal for the amp to have a crackling (a fast one, more like a noise) sound in one of the channels (headphones) when turning off?
When turning on I get a dull "plop" left and right but when turning off the left channels fades out and the rigth one crackles.
And one more thing. I never used the amp as a preamp before. But when turning on and off the woofers move a lot (but no crackling).
Background: I used the amp some month before I put it aside. Today I put it back and resolderd two joints because they didn't looked as good as they could be from the top. After testing it I got the current behaviour and I can't remember if there always have been a crackling sound
When turning on I get a dull "plop" left and right but when turning off the left channels fades out and the rigth one crackles.
And one more thing. I never used the amp as a preamp before. But when turning on and off the woofers move a lot (but no crackling).
Background: I used the amp some month before I put it aside. Today I put it back and resolderd two joints because they didn't looked as good as they could be from the top. After testing it I got the current behaviour and I can't remember if there always have been a crackling sound
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https://diyaudiostore.com/collections/kits/products/acp-amp-camp-pre-amp?variant=40205532397641
Hopefully the price shown is a glitch!! Seems ALL prices have shot up!
Hopefully the price shown is a glitch!! Seems ALL prices have shot up!
I'm building my second ACP+ and looking to repurpose an adcom ACP555 (preamp) case. The input selector switch from the adcom is not reusable as its an ALPS that has a long tether that controls a sliding switch on the original pcb.
The Switch is a 20mm Shaft 18 spline alps, and I'm having a hard time locating a viable rotary switch for this project. I'd like to reuse the knob and have it sit at the same position. I've read through this thread and seems a SHORTING break before make connection is the way to go, but I'm at a loss with mouser as they don't seem to offer one.
appreciate any suggestions!.
The Switch is a 20mm Shaft 18 spline alps, and I'm having a hard time locating a viable rotary switch for this project. I'd like to reuse the knob and have it sit at the same position. I've read through this thread and seems a SHORTING break before make connection is the way to go, but I'm at a loss with mouser as they don't seem to offer one.
appreciate any suggestions!.
Use relays and microcontroller firmware instead of rotary switches. Now you can implement X BEFORE Y , X EXACTLY SIMULTANEOUS WITH Y, and X AFTER Y by simply diddling the firmware. Try every option you can think of, and select the one which pleases you the most / displeases you the least.
if selector, it must be shorting which is equal to make before break