Amp Camp Amp - ACA

May I ask why are you rolling off the low freqs?
The cut-off for 0.13uF and 10kOhm is around 120Hz.
Even if you double the Rin the cut-off will be 60Hz
Unless you are using the ACA to drive some MF or HF drivers in an bi-amp setup.
And even then there are better ways to do it.
Just curious...

I use the ACA to drive a pair of 4" full range drivers and pair that with a subwoofer to handle below 120Hz.
 
I am getting noise from the ACA through one channel. Originally I thought it was the pre but have changed everything but the ACA and speakers and still get the noise. Link to thread in analog line level. Note that the noise has gone from left channel to right and back to left as I try to trouble shoot it but for no reason I could figure out. User error in hookup maybe but I did not find anything.

Distortion from preamp

Original posting has a recording attached of the noise. I never notice it when I first turn the amp on, seems to happen after it warms up. I have tried re-flowing solder joints that looked at all questionable. Of course the normal poking to see if moving anything helps. Can't seem to find anything obvious to me but of course this was my first build. Amp is built to v1.6 spec with the exception of .13 uf worth of capacitors on the line in jack to roll off lower freq. It has been in the system for about 6 months and I have noticed the problem just over the last month. Looking for pointers on what to check next, it is driving me a bit nuts 🙁

I played your sound file and I have the same EXACT noise in the right channel of my amp. It's been there since the beginning, (almost a year now), but I haven't had the time time to fix it...until yesterday. :(

Mine would only rear it's ugly head once out of every 5 times or so and only on startup for a second or two. Well, it has gotten worse and was time to fix it. :yes:

I know this is a very long thread, but 98% of all the problems reported within, were solved by re-flowing solder joints. I was pretty sure that was going to solve my issue and it did! I touched up every solder joint and made sure I had good solid connections. :D

I also redid a couple of steps, (the build guide was changed during/after it was first completed and a few little changes were made), so mine is now done 100%.

Needless to say, my ACA is now performing perfectly and sounds GREAT. It actually always sounded fine, but now the scratchy, crackly noise is gone!!! :)
 
I replaced the input wires and redid the solder joints around the big resistors. I focused on these because I read a post about a similar problem and the issue being not getting connection on both sides of the PCB since it is double sided. The top connection around the big resistors looked consistently less than all other parts. So far after an hour of playing I have not had the problem resurface. I will let it play all day and hope this did it. Thanks all for the help. Only issue now is I should do a proper job cleaning up all the flux residue. I used IPA but it mostly just seems to smear the flux around.
 
That’s why I mentioned heat shrink. I had to search this thread to figure out what it was as well. Mine was a little loose as well so I used a little ring of heat shrink on mine near the outside cap. I didn’t heat shrink the whole barrel of the plug.

That was a good idea. Thanks for the suggestion! The Ace near me had a 1/4" black nylon plug that fit perfectly, so I just went with that.
 
Completed v1.6

Well, ACA’ers, I completed my ACA v1.6! This is the first HiFi kit I’ve completed since a Hafler preamp. I thinks it’s been better than 35 years. My 10 year old grandson helped me set the bias by calling out the volts. He thought it was so cool to do something “technical”! So grandson and I removed the Musical Fidelity 2si 60 watt integrated amp from my main system, connected the speaker wires, and used the audio output from a Project Pre Box S2 Digital (DAC with a digital volume control). Truthfully, I had my doubts if this tiny 8 watt amp could drive my Tekton Double Impact speakers even though I think the manufacturer rates them at an exaggeratedly high sensitivity. Risking that I perhaps am preaching to the “choir”, this little bitty amp is simply ******* amazing. It plays satisfyingly loud enough to fill my large listening space with width, depth, height and pace. Wow! I put on James Taylor’s Grammy winner, “Hourglass”. Bass? Again, I can’t believe this low powered Amp Camp Amp can reach deeper and with more authoritative slam than the 60 watt MF integrated. WTH? Does it run hot? Or should I say, H-O-T, HOT? I do have a slow turning 5” computer fan on top of the amp perched on soft silicone feet to bring the temp down a few degrees so my grandson cab touch it LOL. In closing, I wish to extend my gratitude to DIY Audio, everyone here on this forum and, of course, Nelson for offering this simply amazing kit, construction suggestions and brilliant design!
 
6-ohm, 97.5 db sensitivity speakers

build two stereo ACAs
use two channels in parallel (one stereo chassis per loudspeaker)

when you lack output voltage , bridging is the way

when you lack output current , paralleling is the way

or simply build bigger amp

I've searched the forums for some definitive answer... haven't found the right search terms yet I guess. I'm building an ACA 1.6 and I want to run it to speakers that are 6-ohms (Omega Super 3 HO). I've read (Google-know) that it's not a good idea (dangerous!) to run an amp that's designed for minimum 8-ohms (ACA right?) to speakers with a lower impedance (6-ohms)... That said, as a noob, it would appear that from a technical standpoint I can make the specs match up by running 2 ACAs in parallel mono mode, based on the operation modes doc I found for the ACA? And get more power—and more fun building time—I'm not entirely clear on exactly what this setup would look like in terms of making the actual connections? (I also plan on building a B1 buffer so I can have 2 sources—turntable and DAC) There are VERY clear pics of what the other setup modes look like in the build guide. And it's unclear to me if I need to make internal changes to run parallel mono (I was planning on building the version that uses the rear toggle as the bridge mono block switch). It seems the answer to this is yes, unless I use Y-cables. I'm trying to keep as many options open as possible—also haven't fully digested the technical part of the operation modes doc and the footnote about parallel mono...

Perhaps all of this doesn't matter for the specifics of this build? Stereo or bridged mono would be fine? I've read some conflicting posts on this....

Thanks!
 
@pfarrell
I had my old aca driving 4Ω speakers
you just get less power and higher distortion
no danger
A.

Thanks! Good to know.

However...."The" move would be to do as my instinct is telling me? 2x ACA in parallel mono?

If so, advantage over using the switch method vs Y cables? Presumably if I changed the switch function the other mono modes wouldn't work then later if I changed something... ... or I could add a switch....
 
Thanks! Good to know.

However...."The" move would be to do as my instinct is telling me? 2x ACA in parallel mono?

If so, advantage over using the switch method vs Y cables? Presumably if I changed the switch function the other mono modes wouldn't work then later if I changed something... ... or I could add a switch....

Hi All,

I also plan to set up my two ACAs as parallel monoblocks for my 6 ohm SAL 08C08. Would anyone be willing to publish a schematic? Amp Camp Amp 1.6 illustrated build guide still waiting for once Y-cables are made and photos taken.

Thank you
 
Hi All,

I also plan to set up my two ACAs as parallel monoblocks for my 6 ohm SAL 08C08. Would anyone be willing to publish a schematic? Amp Camp Amp 1.6 illustrated build guide still waiting for once Y-cables are made and photos taken.

Thank you

Hi Pavel,
Wiring for parallel mode has been covered a few times before (but it is a very long thread...).

Have a look back at post #6522 here; https://www.diyaudio.com/forums/pass-labs/215392-amp-camp-amp-aca-653.html#post5595943

It is all external and easily reversible too.

Link the two pins in the XLR socket with a suitable loop or wire as shown. That joins the left and right inputs together.
Link the two Black speaker connections with a wire. (The Red ones are already joined internally.)
If you have wired the rear switch from the build guide step 38, make sure it is Down as in the pictures.

For 6 ohm speakers you might want to try bridged mode first (as 6L6 suggests above) then try parallel mode and see which works best for you? Alan
 
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Hi Pavel,
Wiring for parallel mode has been covered a few times before (but it is a very long thread...).

Have a look back at post #6522 here; https://www.diyaudio.com/forums/pass-labs/215392-amp-camp-amp-aca-653.html#post5595943

It is all external and easily reversible too.

Link the two pins in the XLR socket with a suitable loop or wire as shown. That joins the left and right inputs together.
Link the two Black speaker connections with a wire. (The Red ones are already joined internally.)
If you have wired the rear switch from the build guide step 38, make sure it is Down as in the pictures.

For 6 ohm speakers you might want to try bridged mode first (as 6L6 suggests above) then try parallel mode and see which works best for you? Alan

Thanks for this—It's what I couldn't find for whatever reason when I did a search—then 6L6 chimed in..... I like to know what sounds like what to me in my space... so I have an obvious question about the images in the above linked thread related to parallel mono.

He's showing 1 ACA that's been connected. What does the other ACA (Right channel from the pics it seems) look like at the back where the connections are made to the inputs and speakers? Are they the same? I'm thinking that they are, based on how I'm understanding it all....but just confirming. Thanks!


-- Built the first 2 PCBs for one ACA last night with some help from my 9-yr-old. We had a blast and she sorted and identified resistors, tested each one for spec on the DMM, did some spacing bending and stuffing. AWESOME. Now she's asking about soldering... I will work that out with some test pieces. Next generation on the hook!
 
Thanks for this—It's what I couldn't find for whatever reason when I did a search—then 6L6 chimed in..... I like to know what sounds like what to me in my space... so I have an obvious question about the images in the above linked thread related to parallel mono.

He's showing 1 ACA that's been connected. What does the other ACA (Right channel from the pics it seems) look like at the back where the connections are made to the inputs and speakers? Are they the same? I'm thinking that they are, based on how I'm understanding it all....but just confirming. Thanks!


-- Built the first 2 PCBs for one ACA last night with some help from my 9-yr-old. We had a blast and she sorted and identified resistors, tested each one for spec on the DMM, did some spacing bending and stuffing. AWESOME. Now she's asking about soldering... I will work that out with some test pieces. Next generation on the hook!

Sensational. I was also 9 years old, 43 years ago when I started to learn to soldering.:up::up::up:
 
... He's showing 1 ACA that's been connected. What does the other ACA (Right channel from the pics it seems) look like at the back where the connections are made to the inputs and speakers? Are they the same? I'm thinking that they are, based on how I'm understanding it all....but just confirming. Thanks!

Yes you can do them the same.
But in 'parallel mode' it actually does not matter which RCA input you use or which red/black output terminals you use. (The link in the XLR socket and the wire between the 2 black speaker terminals 'joins' the 2 channels together.)
Hope that makes sense? Alan