According to the build guide (https://guides.diyaudio.com/Guide/Amp+Camp+Amp+V1.8+Change+Information/10?lang=en) the switch is this one:
https://www.parts-express.com/DPDT-Mini-Paddle-Switch-Center-Off-060-540?quantity=1
So any switch that matches the specifications should work.
https://www.parts-express.com/DPDT-Mini-Paddle-Switch-Center-Off-060-540?quantity=1
So any switch that matches the specifications should work.
There's this long hair, sort of look alike Jerry Garcia fellow in Northern California that once upon a time decided that a dynamic bias made some sense and he made some money off it. https://auralhifi.com/pages/thresho...QRlFa_2Msz-8ostHHVcDYR-sguGfwyFR83lRSAaTITKlQ
Since then, he decided that strange uber inefficient designs make sense... that pisses off the Julian Hirsch Audio Society and gets the ASR crowd's panties all in a bunch... Specially as he seems to maintain that Blue LEDs increase the negative 2nd order harmonic distortion.. you know, that "blue note sound"?
And, God Forbid, as a physicist he seems to believe that the current set of electronic measurements don't tell the whole story. Mon Dieu! What will Amir and the late David Ranada think of such?
Of course, he also came up with the Audio equivalent of the Borg: https://www.stereophile.com/content/pass-laboratories-aleph-0-monoblock-power-amplifier. A bunch of them indeed.
Anyhow there's a bunch of cantankerous old folks that somehow believe him and follow his design. Mostly because Nelson Pass sort of believes in sharing his Intellectual Property.... amazing, huh?
Now, not to be cantankerous myself, specially as I keep my hair short and shave on a daily basis, but I think this fellow Nelson is onto something. And I agree that the guy is nice as he is the Open Source Audio Design kind of guy. Pisses off the MBAs, I'm sure.
Next time... do a web search on "Nelson Pass"... I recommend you check your bank account before you check out https://www.passlabs.com/... although https://www.firstwatt.com/ is pushing $10K....
Seriously, you can't trust them long haired Physics fellows.... now us short haired Physics fellows... well...
So, it's not a "dedication" Forum, but a place to check out his work and his sharing. And the people there, are as funny as hell too. ( Nelson is funny too). Heck, they put up with me!
Caspisce?
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That is truly FUNNY > where do people come up with such things 🙂
^I'll let you on a secret... sshh.... my latest set of devices have CYAN LEDs... not blue.
Then I just got a pair of F4s, being used as monoblocks... the front LED switches are blue... of course, but I went to Amazon and got some RED (right) and WHITE (left) switches. Once of these days, when I have time to kill, I'll open them up and replace the lights.
Oh... the rumor I've heard is that Nelson Pass got a good deal on 100K blue LEDs a few years ago....
Then I just got a pair of F4s, being used as monoblocks... the front LED switches are blue... of course, but I went to Amazon and got some RED (right) and WHITE (left) switches. Once of these days, when I have time to kill, I'll open them up and replace the lights.
Oh... the rumor I've heard is that Nelson Pass got a good deal on 100K blue LEDs a few years ago....
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@anthony.chandler: if you are going to dedicate the amp to a single mode of operation, e.g only stereo or only balanced, then you can omit the switch and wire the inputs accordingly.
I think it's left is red and right is green.
If you approach an aircraft from its left side, then you see the red, so the other aircraft has the right of way. Conversely, if you approach it from its right side, you see green and you have the right of way.
The tail is white. So you can also discern its direction relative to you.
But, in audio, Right is Red and Left is usually White. I don't think the Right Of Way is important in audio.
Finally. Finished. ACA Amp is now working.
I would like to thank all of you who helped me along on this build and trying to find the error of my ways. I have to say that it was frustrating, but that, frankly, I learned FAR more about how the electronics actually work than if there were zero problems. I got to see how my multimeter is used, what transistors do, what voltage does, and how to mess everything up.
In the end, I think that my original issue was that I did not solder the Channel A output to the cup properly, which is why I had no sound on that channel.
Then, when I was starting the troubleshooting, I undoubtedly fried one or both of the Channel A mosfets, hence the power surges.
I ordered in replacement mosfets and some backup parts from Mouser and within a few days I had them in hand.
With the board out and disconnected, I pulled the two mosfets and added the new ones. Everything now runs and I biased the pots to approx 12v each.
Plugged into my system, I am using the AudioLab 6000a as the preamp into the ACA in stereo mode out to Heresy IV speakers. Out of the gate it definitely sounds different that the AudioLab as an integrated amp. Seems more crisp and separated than the AL, and I feel like the bass is less. The db level needs to go from -35db to about -19db to get the same volume.
I have a headache after the work, so I will need some time to see what I prefer, and maybe it is more about understanding the differences than saying one is "better".
Thanks again for all of the help and support.
A.
I would like to thank all of you who helped me along on this build and trying to find the error of my ways. I have to say that it was frustrating, but that, frankly, I learned FAR more about how the electronics actually work than if there were zero problems. I got to see how my multimeter is used, what transistors do, what voltage does, and how to mess everything up.
In the end, I think that my original issue was that I did not solder the Channel A output to the cup properly, which is why I had no sound on that channel.
Then, when I was starting the troubleshooting, I undoubtedly fried one or both of the Channel A mosfets, hence the power surges.
I ordered in replacement mosfets and some backup parts from Mouser and within a few days I had them in hand.
With the board out and disconnected, I pulled the two mosfets and added the new ones. Everything now runs and I biased the pots to approx 12v each.
Plugged into my system, I am using the AudioLab 6000a as the preamp into the ACA in stereo mode out to Heresy IV speakers. Out of the gate it definitely sounds different that the AudioLab as an integrated amp. Seems more crisp and separated than the AL, and I feel like the bass is less. The db level needs to go from -35db to about -19db to get the same volume.
I have a headache after the work, so I will need some time to see what I prefer, and maybe it is more about understanding the differences than saying one is "better".
Thanks again for all of the help and support.
A.
Congratulations!
Now, here is the sad part that no one explained... you're going to enjoy this for a while, then you're going to want to buy a second one so you can run them as mono-blocks. It took me about a year, I think. I now have two ACAs running in bridged mono and recently added the ACP+ preamp, all feeding my Forte IIIs. It sounds fantastic! I think the ACAs pair great with Klipsch.
Now, here is the sad part that no one explained... you're going to enjoy this for a while, then you're going to want to buy a second one so you can run them as mono-blocks. It took me about a year, I think. I now have two ACAs running in bridged mono and recently added the ACP+ preamp, all feeding my Forte IIIs. It sounds fantastic! I think the ACAs pair great with Klipsch.
Fortunately for my pocketbook the diy store is out of stock of the ACA for the moment!
With some quieter listening tonight, I think I now understand the sound of the amp a bit better: given the low output wattage it sounds best at a lower input from the preamp? When I dial back the db to a -30db (instead of the -19db to match what the AudioLab output as an integrated), the ACA takes on that silent darkness people write about where the music seems to leap out from a solid black. I could see how using it as a monoblock to increase the wattage would change things for a listener. It does make for more difficult listening with an 8 year old singing show tunes in those quiet background spaces, however. Ha ha ha.
Overall, this was a great build and I am happy with the ACA!
With some quieter listening tonight, I think I now understand the sound of the amp a bit better: given the low output wattage it sounds best at a lower input from the preamp? When I dial back the db to a -30db (instead of the -19db to match what the AudioLab output as an integrated), the ACA takes on that silent darkness people write about where the music seems to leap out from a solid black. I could see how using it as a monoblock to increase the wattage would change things for a listener. It does make for more difficult listening with an 8 year old singing show tunes in those quiet background spaces, however. Ha ha ha.
Overall, this was a great build and I am happy with the ACA!
A newbie question to ask the collective wisdom:
Am happily using a great sounding pair of Pass ACA that I run in a "one per channel" configuration, hooked to a Denafrips Ares 2 and playing through Goodmans Axiom 201 drivers in horn enclosures, without crossovers. I am currently using a passive pre stage: a Chinese ladder potentiometer like the one in the attachment.
The speakers are DIY and they are described in this thread:
Am very happy with the sound but... the upgrade bug!!!
Would like to add remote volume control and am thinking of one of the Khozmo attenuator (you can buy the innards from khozmo.com and create a box or you can buy the assembled component).
My question:
assuming
Denafrips Ares 2 -> passive pre -> two Pass ACA bridged -> 100+DB speakers
What resistance should I chose?
The options are:
10K, 25K, 50K, 100K.
Thank you.
Am happily using a great sounding pair of Pass ACA that I run in a "one per channel" configuration, hooked to a Denafrips Ares 2 and playing through Goodmans Axiom 201 drivers in horn enclosures, without crossovers. I am currently using a passive pre stage: a Chinese ladder potentiometer like the one in the attachment.
The speakers are DIY and they are described in this thread:
Am very happy with the sound but... the upgrade bug!!!
Would like to add remote volume control and am thinking of one of the Khozmo attenuator (you can buy the innards from khozmo.com and create a box or you can buy the assembled component).
My question:
assuming
Denafrips Ares 2 -> passive pre -> two Pass ACA bridged -> 100+DB speakers
What resistance should I chose?
The options are:
10K, 25K, 50K, 100K.
Thank you.
Attachments
For a “passive preamp” choose the 10K.
And look at active designs, will be a great next project.
And look at active designs, will be a great next project.
Thanks for the quick reply. I was under the impression that while 10k would work, it might load the Ares 2 unnecessarily, reducing dynamics slightly. This article mentions an output impedance of 2.4 balanced and lists 10k as the lower acceptable limit.
Is 25 not a safer choice?
6L6: I am too much of an ignorant to try active designs - might shop for one but don't have the knowledge to build one. The arrival of the passive pre I have now (a Chinese ready-made ladder thingee) has made my sound super transparent quite obviously. A very pleasant change. I assume active would mean more dynamic sound?
Is 25 not a safer choice?
6L6: I am too much of an ignorant to try active designs - might shop for one but don't have the knowledge to build one. The arrival of the passive pre I have now (a Chinese ready-made ladder thingee) has made my sound super transparent quite obviously. A very pleasant change. I assume active would mean more dynamic sound?
ok, as they claim
take 25K, as compromise between necessary loading of source, and loading of power amp
or ..... build Iron Pre, use 50K vol pot, set buffer stage for 330K Rin, recipe for bliss
take 25K, as compromise between necessary loading of source, and loading of power amp
or ..... build Iron Pre, use 50K vol pot, set buffer stage for 330K Rin, recipe for bliss
Reporting back... I ended up contacting the manufacturer of the Khozmo and he recommends 10K or even 5K. I went ahead and ordered a 10K - it's in the mail and eagerly awaited.
but... Small disaster while I wait! My upgrade bug got the best of me and I tried to experiment with a tweeter suplementation. Namely, I got Pyle Pro PDBT19 with a 3.3 µF capacitor that was factory installed to the tweeters. Before the khozmo arrives I had one of these chinese ladder thingees connected. So now this marvel of engineering is broken.
Symptoms:
I have set the passive pre at a very low level. wWen I turn the amps on there is a brooming noise from the main loudspeakers (15 Ohm 12 inches Goodmans Axiom 201) and their membranes suddenly protrude by about 1cm and stay like this until i (quickly) turn the amps off.
I eliminated the tweeters from the system and the symptom persists for as long as I have the pre connected.
Assuming the pre is dangerously passing some DC voltage to the speakers.
Now I eliminated the damaged pre and connected a different (supercheap) attenuator and all is fine albeit without tweeters.
However I do not have the courage to retry the tweeter connection of fear of ruining either my Pass ACAs or the Denafrips Ares 2 I'm using.
But mostly why I don't have the courage to experiment again, is that I love my axiom 201 drivers too much...
Might I had done a total mistake when calculating the capacitor value?
I thought the factory installed (by Pyle) 3.3 µF capacitor will give a cutoff at about 12.1 kHz.
Even have a pair of 3.9 µF capacitors ready to go (these should give me 10.2kHz cutoff).
Needless to say I am reluctant to even try, especially after the Khozmo arives. Perhaps someone has a suggestion? (almost feel like ditching this tweeter "upgrade" altogether). Thanks!
but... Small disaster while I wait! My upgrade bug got the best of me and I tried to experiment with a tweeter suplementation. Namely, I got Pyle Pro PDBT19 with a 3.3 µF capacitor that was factory installed to the tweeters. Before the khozmo arrives I had one of these chinese ladder thingees connected. So now this marvel of engineering is broken.
Symptoms:
I have set the passive pre at a very low level. wWen I turn the amps on there is a brooming noise from the main loudspeakers (15 Ohm 12 inches Goodmans Axiom 201) and their membranes suddenly protrude by about 1cm and stay like this until i (quickly) turn the amps off.
I eliminated the tweeters from the system and the symptom persists for as long as I have the pre connected.
Assuming the pre is dangerously passing some DC voltage to the speakers.
Now I eliminated the damaged pre and connected a different (supercheap) attenuator and all is fine albeit without tweeters.
However I do not have the courage to retry the tweeter connection of fear of ruining either my Pass ACAs or the Denafrips Ares 2 I'm using.
But mostly why I don't have the courage to experiment again, is that I love my axiom 201 drivers too much...
Might I had done a total mistake when calculating the capacitor value?
I thought the factory installed (by Pyle) 3.3 µF capacitor will give a cutoff at about 12.1 kHz.
Even have a pair of 3.9 µF capacitors ready to go (these should give me 10.2kHz cutoff).
Needless to say I am reluctant to even try, especially after the Khozmo arives. Perhaps someone has a suggestion? (almost feel like ditching this tweeter "upgrade" altogether). Thanks!