Pleased to hear it! I'm still a little worried about heatsink pins getting bent in shipping, though it is pretty easy to bend them back into place by hand.
Nelson - question concerning R13 and R16 on the Parts Check List you included in the kits:
R13 and R16 are listed under both the 10KΩ and the 2.2KΩ resistors
I tried to sort this out from available info:
-- On the silkscreen of the Ver 1.6 Rev 2 boards, R13 and R16 are labeled as "Rled", not the values like the other resistors are, so no help there.
-- R13 is on the Pass ACA 1.6 schematic as 10KΩ; R16 is not on that schematic.
-- Looking at the oblique photo of the stuffed board (several posts ago), I can't make out the color bands of R13 or R16 confidently enough (edit: they do look like 10K) to tell if they are 10K or 2.2K, and/or if they differ.
Realizing that you may have switched up the LEDs used in the kit, and the resistors may have changed, I am uncertain what goes where. Thanks for any clarification you can provide.
R13 and R16 are listed under both the 10KΩ and the 2.2KΩ resistors
I tried to sort this out from available info:
-- On the silkscreen of the Ver 1.6 Rev 2 boards, R13 and R16 are labeled as "Rled", not the values like the other resistors are, so no help there.
-- R13 is on the Pass ACA 1.6 schematic as 10KΩ; R16 is not on that schematic.
-- Looking at the oblique photo of the stuffed board (several posts ago), I can't make out the color bands of R13 or R16 confidently enough (edit: they do look like 10K) to tell if they are 10K or 2.2K, and/or if they differ.
Realizing that you may have switched up the LEDs used in the kit, and the resistors may have changed, I am uncertain what goes where. Thanks for any clarification you can provide.
I've just updated ampcampamp.com to host the temporary build guide.
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I finished the two boards in my kit on Monday morning, and have been listening since.
The kit was very easy to work with, especially with the guidance provided by the temporary build guild that Nelson Brock posted, plus the existing body of info available on the ACA generally, and Ver. 1.6 in particular.
Based on discussion over in the “ACA with premium parts” thread and that I had a some appropriate parts on hand, I decided to incorporate a few of ideas presented there, particularly those by TungstenAudio. I substituted a 2.2µF/450V Panasonic PP film cap into C3 (input coupling), and a 100µF UHW for C4 (filtering of the 24V PS). I also substituted a 2200µF UHW for the middle of the 3 paralleled 1000µF C1 caps (output), raising the total capacitance at C1 from 3000µF to 4200µF. If any of these prove problematical, they are easily reversible, but so far so good.
Below is a photo of the builds.
I’ve tried the ACA Redux with two different sets of speakers, both in 12’x12’x8’ rooms: Advent OLA and DCM Time Windows. In both cases, the speakers were driven to the top of my listening range with 12 o’clk on the preamp volume control, with no strain apparent.
The “no strain” deserves additional comment. There is something about the two Pass ACA amps I have made, the Mini and this Redux. I experience a calm, a serenity, when I listen to the music I love on them. I don’t know how to describe what it is; perhaps it is a feeling that the music played through them lacks any sense of compression and feels so natural. It is as if there is space around, for example, soloists, quiet space within the sound field. Much of the music I like seems to take on an ethereal quality when played on these amps, and I find it intoxicating.
Many thanks to Nelson P. for your designs and your generosity, and to Nelson B. for dreaming up this Redux implementation and all the work it took to make the kits available.
The kit was very easy to work with, especially with the guidance provided by the temporary build guild that Nelson Brock posted, plus the existing body of info available on the ACA generally, and Ver. 1.6 in particular.
Based on discussion over in the “ACA with premium parts” thread and that I had a some appropriate parts on hand, I decided to incorporate a few of ideas presented there, particularly those by TungstenAudio. I substituted a 2.2µF/450V Panasonic PP film cap into C3 (input coupling), and a 100µF UHW for C4 (filtering of the 24V PS). I also substituted a 2200µF UHW for the middle of the 3 paralleled 1000µF C1 caps (output), raising the total capacitance at C1 from 3000µF to 4200µF. If any of these prove problematical, they are easily reversible, but so far so good.
Below is a photo of the builds.
I’ve tried the ACA Redux with two different sets of speakers, both in 12’x12’x8’ rooms: Advent OLA and DCM Time Windows. In both cases, the speakers were driven to the top of my listening range with 12 o’clk on the preamp volume control, with no strain apparent.
The “no strain” deserves additional comment. There is something about the two Pass ACA amps I have made, the Mini and this Redux. I experience a calm, a serenity, when I listen to the music I love on them. I don’t know how to describe what it is; perhaps it is a feeling that the music played through them lacks any sense of compression and feels so natural. It is as if there is space around, for example, soloists, quiet space within the sound field. Much of the music I like seems to take on an ethereal quality when played on these amps, and I find it intoxicating.
Many thanks to Nelson P. for your designs and your generosity, and to Nelson B. for dreaming up this Redux implementation and all the work it took to make the kits available.
ACA Redux guide almost done... Need to take a few more photos and a short video or two, but it's 90% done and complete enough to be made visible now:
https://guides.diyaudio.com/Guide/ACA+Redux/22?lang=en
https://guides.diyaudio.com/Guide/ACA+Redux/22?lang=en
Unpacked the kit from Nelson B. and got a set built up over 3-4 hours, including a lunch break. The second board went a lot quicker 
. Really pleased with them, have them hooked up to a pair of Tannoy LGM's, using a Hagerman Clarinet as preamp. Comfortable listening level with pre around 10-11 o'clock. Thanks to all who made this possible.
. Really pleased with them, have them hooked up to a pair of Tannoy LGM's, using a Hagerman Clarinet as preamp. Comfortable listening level with pre around 10-11 o'clock. Thanks to all who made this possible.
It is! Caught me a bit off guard, didn't expect it to sound that much better than the Arcam Alpha it replaced.Isn't it a great little amp? I’ve always enjoyed the ACA, and the redux is a fantastic addition to the series. From a clever design standpoint, it’s the best, I absolutely love it.
I've been meaning to talk to Jason about this, haven't done it yet. I don't think I have the time to source and pack kits myself in the quantity needed to keep the store happy, and I don't have a supplier lined up that I'm confident in. You can buy kits direct from me until I get that together, or until I run out. ACA Redux Order Form
Those familiar with the ACA will know that two channels can be connected to make a single mono channel in a few different ways, each of which increase output power and lower distortion. My monoblock design makes this a bit more difficult compared to the store kit so I've attached a few images to show how the different connections can be made.
