Just got a "Lifetime Change Notification" from Mouser about those Panasonic 47Ohm resistors the ACA is using: they are now "Not recommended for new designs" 
Just got a "Lifetime Change Notification" from Mouser about those Panasonic 47Ohm resistors the ACA is using: they are now "Not recommended for new designs"
As 6L6 said, there are many that are suitable; try these:
https://www.mouser.com/ProductDetail/Vishay-Dale/CPF3R47000JNB14?qs=MJw/449BOx/BmHgUJauRtw==
It is easy to find alternatives at mouser. If you use the selector options at the link above, just select the R value, % tolerance and wattage rating (%3) but do not select the manufacturer you will see there is a whole host of options besides the above.
--Tom
I am seriously considering pre-ordering the ACA (Jan. 2021 shipping), and have a couple questions regarding preamp:
1. Anyone tried the ACP+ with the ACA? Any other recommendations for a preamp?
2. How about just adding a volume pot to the ACA? I do not need input selection... Just a volume control.
3. Is there a chassis for the ACA that would also accommodate the ACP+ or a simple added volume pot?
4. I would love to order the Korg B1 as a preamp, but those are sold out without future preorder... Can the Korg B1 b fitted in a single chassis with the ACA?
Thanks in advance for any recommendations or tips...
1. Anyone tried the ACP+ with the ACA? Any other recommendations for a preamp?
2. How about just adding a volume pot to the ACA? I do not need input selection... Just a volume control.
3. Is there a chassis for the ACA that would also accommodate the ACP+ or a simple added volume pot?
4. I would love to order the Korg B1 as a preamp, but those are sold out without future preorder... Can the Korg B1 b fitted in a single chassis with the ACA?
Thanks in advance for any recommendations or tips...
Need help ACA 1.6
Hi everybody. I need help with my ACA v1.6 (24 v Meanwell) build. Bought the kit 15 months ago, but just got around to building it. I'm a rookie, so probably did something stupid...
Was hyper focused, pre-checked resisters, took my time, watched soldering videos, etc. Kit fired up with no smoke, biased to 11.9 on each side, but sounds bad.
I thought my solder points looked pretty good, but followed forum advice to redo any connection that didn't look shiny and pristine. All troubleshooting values remained the same:
Should be Left channel right channel
Q1 0 ohms varies btw .1 to .4 varies btw .1 to .4
5.2 ohms 4.60 4.80
1k ohms .62 .62
R9 1k ohms .52 .52
R10 335k ohms 334 333
Q4 1k ohms .52 .52
R15 5.8k ohms 5.3 5.5
5.2k ohms 4.6 4.8
R5 10.9k ohms 10.5 10.5
Q2 11k ohms 10.62 10.62
1k ohms .52 .52
5.2k ohms 4.60 4.80
Q1 0v 20.8v 20.5v
11.8-12v 11.93 11.85
4.1-4.7v 4.66 4.70
R9 4.1-4.7v 4.66 4.71
R10 3.5-4.1v 4.28 4.30
Q4 24v 23.81 23.85
R15 12.3-12.6v 12.47 12.40
11.8-12v 11.96 11.87
R5 17.2-17.7v 17.42 17.32
Q2 17-17.2v 17.42 17.32
24v 23.8 23.83
12.7-12.9v 12.74 12.67
My pictures don't look very focused, buy will upload some if these troubleshooting results do not elicit some obvious error. Q1 is clearly screwed up...
Thank you for any/all help.
Craig in Seattle
Hi everybody. I need help with my ACA v1.6 (24 v Meanwell) build. Bought the kit 15 months ago, but just got around to building it. I'm a rookie, so probably did something stupid...
Was hyper focused, pre-checked resisters, took my time, watched soldering videos, etc. Kit fired up with no smoke, biased to 11.9 on each side, but sounds bad.
I thought my solder points looked pretty good, but followed forum advice to redo any connection that didn't look shiny and pristine. All troubleshooting values remained the same:
Should be Left channel right channel
Q1 0 ohms varies btw .1 to .4 varies btw .1 to .4
5.2 ohms 4.60 4.80
1k ohms .62 .62
R9 1k ohms .52 .52
R10 335k ohms 334 333
Q4 1k ohms .52 .52
R15 5.8k ohms 5.3 5.5
5.2k ohms 4.6 4.8
R5 10.9k ohms 10.5 10.5
Q2 11k ohms 10.62 10.62
1k ohms .52 .52
5.2k ohms 4.60 4.80
Q1 0v 20.8v 20.5v
11.8-12v 11.93 11.85
4.1-4.7v 4.66 4.70
R9 4.1-4.7v 4.66 4.71
R10 3.5-4.1v 4.28 4.30
Q4 24v 23.81 23.85
R15 12.3-12.6v 12.47 12.40
11.8-12v 11.96 11.87
R5 17.2-17.7v 17.42 17.32
Q2 17-17.2v 17.42 17.32
24v 23.8 23.83
12.7-12.9v 12.74 12.67
My pictures don't look very focused, buy will upload some if these troubleshooting results do not elicit some obvious error. Q1 is clearly screwed up...
Thank you for any/all help.
Craig in Seattle
Craig,
The numbers look good except for Q1 S (Source) volts as you say. But Q1 S is connected directly to the GND trace, so that could be a metering problem?
Then you say 'sounds bad' - so I assume you get some output from both sides and they sound the same.
Next check the resistance between the speaker terminals, power off of course. Red to Black should read from 500 ohms to 1k ohms after a few seconds.
If you get a low reading you have a short. Make sure the OUT - wire from the board goes to the Black terminal, and vice versa. Then check the terminal washers are correctly installed, they insulate the terminals and solder tags from the chassis - especially the Black terminal. See step 26 of the build guide. Let us know.
Alan
The numbers look good except for Q1 S (Source) volts as you say. But Q1 S is connected directly to the GND trace, so that could be a metering problem?
Then you say 'sounds bad' - so I assume you get some output from both sides and they sound the same.
Next check the resistance between the speaker terminals, power off of course. Red to Black should read from 500 ohms to 1k ohms after a few seconds.
If you get a low reading you have a short. Make sure the OUT - wire from the board goes to the Black terminal, and vice versa. Then check the terminal washers are correctly installed, they insulate the terminals and solder tags from the chassis - especially the Black terminal. See step 26 of the build guide. Let us know.
Alan
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Just got a "Lifetime Change Notification" from Mouser about those Panasonic 47Ohm resistors the ACA is using: they are now "Not recommended for new designs"
Please post clear pictures of the boards mounted. Can you also be specific about "sounds bad" (i.e.: hum, high distortion, etc...)?
ACA problems
Thank you Alan and Thomas. Your help is greatly appreciated.
Black to red is reading .997ohms from all combinations of the speaker terminals.
Terminal washers look good as well.
I think there is similar volume from each channel, but distortion particularly with higher frequencies.
Hope these pictures help.
Thank you Alan and Thomas. Your help is greatly appreciated.
Black to red is reading .997ohms from all combinations of the speaker terminals.
Terminal washers look good as well.
I think there is similar volume from each channel, but distortion particularly with higher frequencies.
Hope these pictures help.
Attachments
If you really read 0.997 ohms you have a short across the output / speaker terminals. Very low and distorted output is the normal symptom of shorted outputs...
First look behind the board and make sure the soldered wires are not too long and touching the chassis.
Next unsolder the OUT + and OUT - wires from the board.
Now check the resistance between Out + and Out - at the board. It should be 500 - 1000 ohms as before.
- If it is the 'short' is in the speaker wires and or terminals. You need to check the Black wire and terminal carefully. Use your meter to make sure there is no connection between the black wire/terminal and chassis.
- If the reading at the board is still 0.997 there is a short on the board. It will have to come out to examine it.
Just an nagging itch, 0.997 is very precise, are you sure it does not read 997 ohms?
First look behind the board and make sure the soldered wires are not too long and touching the chassis.
Next unsolder the OUT + and OUT - wires from the board.
Now check the resistance between Out + and Out - at the board. It should be 500 - 1000 ohms as before.
- If it is the 'short' is in the speaker wires and or terminals. You need to check the Black wire and terminal carefully. Use your meter to make sure there is no connection between the black wire/terminal and chassis.
- If the reading at the board is still 0.997 there is a short on the board. It will have to come out to examine it.
Just an nagging itch, 0.997 is very precise, are you sure it does not read 997 ohms?
1&3. The ACP+ was intended to be used with the ACA. It would work great, (plus:headphones). The PCB will fit in a Galaxy chassis the same size as the ACA chassis.
2.Yes you could just add a pot, and there's plenty of room inside the ACA chassis.
You could replace the on/off switch with it if you played around with washers inside and out, or carved something out of sheet aluminum- the knob would hide any uglyness..
I've considered this and from what I've heard a dual 10k or 20k audio taper pot on the input would work. I hope other thread participants will chime in!
So now you won't have an on/off switch, but there's room for one on the back panel (easy to drill aluminum) on one side or the other. It's quite common for amps to have an on-off switch on the back panel. I'm not even going to do that, I switch the entire system on and off with a power strip, so no need...
Drilling another hole somewhere else in the front panel is a bit complicated because the panel is so thick that the threaded part of most switches and pots isn't long enough to get the nut on. Probably you would need to "relieve" the back with a large hole partly through.
The ACA doesn't have a lot of gain so a preamp allows it to put out full power. Probably build it and temporarily wire in the pot. and see how loud it is without a pre. Probably fine for most uses, and if not, then it will at least work while you build the preamp.
4. I don't know, it might..
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For most applications, you really need a preamp. The ACA does not have very much gain. I tried driving my ACA direct from a DAC and it was hopeless with my speakers.
You can countersink the Aluminium plate of the ACA using a Forstener bit just bigger than the diameter of the knob you intend to use. Just wrap the whole plate in a couple of layers of masking tape to stop in getting scratched up then add oil and clamp it down on your drill press or bench. You could buy a blank plate so that the on off switch and volume knob are evenly spaced on the front or just make the whole front out of a nice piece of wood.
The Korg B1 fits easily into an ACA built into a Galaxy 2U 240 x 240 mm square chassis, with external power supplies....makes a really neat small integrated for speakers or headphones. If you use a small TKD pot in a tapered hole made with a step drill the thick front panel isnt a problem...alternatively a local machine shop can mill a 25mm dia hole into the rear face of the panel. Attached photos show the interior and the amp on the top of a stack
Attachments
While the ACAs "will work" you will be delighted if you drive them with a preamp with some sweetly done voltage gain like The Whammy.
Besides checking for those, make sure that the mode selector switch is in the right orientation (I can't tell from your pictures). I accidentally did this a while back (had it in bridged mode but was driving it in stereo. That did result in some oddly distorted output. Also besides the continuity tests suggested above, check that the RCAs are not shorted together or that the negatives on them have no continuity with the chassis.
Thanks guys for the overwhelming response and willing to help!!!
This one if also an inexpensive add-on. Thanks for confirming it fits easily into the standard ACA chassis.
As for the front panel - I am likely going to order a custom front panel from modushop, so it would NOT look ugly or like an after-thought
My DAC outputs 2.5V or 3V (I cannot remember). That is on the high side of things, and my speakers are very easy to drive, so I am not really worried.
Any thoughts from anyone on the ALPS RK09 with built-in off switch?
Hmmm... Never thought of the headphone out as a cool little extra feature added by the ACP+
This one if also an inexpensive add-on. Thanks for confirming it fits easily into the standard ACA chassis.
As for the front panel - I am likely going to order a custom front panel from modushop, so it would NOT look ugly or like an after-thought
I was always under the assumption that preamp LOWERS the line level, or keep it at max, but does not add voltage...
My DAC outputs 2.5V or 3V (I cannot remember). That is on the high side of things, and my speakers are very easy to drive, so I am not really worried.
As mentioned above in this post, I am going to order a custom front panel. I was going back and forth between moving the power switch a little down and place a hole-structure for volume pot (like in the Korg front panel) for ALPS RK27 above it, or maybe get an ALPS RK09 with built-in on-off switch (turns off when you turn all the way CCW). That would eliminate the separate physical power switch alltogether...
Any thoughts from anyone on the ALPS RK09 with built-in off switch?
My DAC is outputting over 2V (either 2.5V or 3V). My speakers are also easy to drive, so I seriously doubt I would run out of power ;-)
Nice build! This being my first amp build (done couple passive DIY projects thus far), and the fact that Korg is OOO - I think I would go with volume pot only or the ACP+ but I am not ruling out a future "upgrade" (or 2nd build) by adding the Korg
Thanks. I will go with volume pot only or ACP+ and will keep in mind voltage gain preamp in case I am not happy with the result. Thanks!