Converting from five wants 19 V to 24 V 8 W
I was looking for the information so I could copy and paste the link it’s in one of the amp camp amp build guides. Depending what version PCB you have 1.0 and then the later 1.1b
On the early version I remember seeing a picture of doing a jumper with a resistor that you add I’m trying to remember if it mentioned resistor placement on the later version R12 and this is going from a bad memory.
Which it sounds like you have the earlier version PCB because when I purchased the later version the circuitboard had the place for the resistor to be mounted.
Go search back into earlier build guides and I remember seeing the modification photo on how to do it I’m very sure somebody knows exactly what I’m talking about and I’ll provide a link in the next post.
I was looking for the information so I could copy and paste the link it’s in one of the amp camp amp build guides. Depending what version PCB you have 1.0 and then the later 1.1b
On the early version I remember seeing a picture of doing a jumper with a resistor that you add I’m trying to remember if it mentioned resistor placement on the later version R12 and this is going from a bad memory.
Which it sounds like you have the earlier version PCB because when I purchased the later version the circuitboard had the place for the resistor to be mounted.
Go search back into earlier build guides and I remember seeing the modification photo on how to do it I’m very sure somebody knows exactly what I’m talking about and I’ll provide a link in the next post.
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Post #2 of 6L6's original build guide shows the R15 mod:
https://www.diyaudio.com/forums/pass-labs/247361-aca-illustrated-build-guide.html#post3735742
https://www.diyaudio.com/forums/pass-labs/247361-aca-illustrated-build-guide.html#post3735742
Want to build a cool running ACA for near field use
There has been a lot of talk about higher power ACA's, but I want to do the opposite - build a low power ACA that runs a lot cooler than the one in my listening room. The reason is that it will be for near field listening when working on my PC and I really can't have all that heat in my small office.
I still have two unused v1.0 PCB's, but have no idea how to make it run cooler. Would lower voltage make less heat and how low voltage can I go and still make decent quality sound? I'll use high efficiency FR speakers: At least 90db, so I don't need the 5W of the original v1.0.
Any ideas would help. But please don't suggest using an AB amp. I'm used to the ACA sound and won't settle for anything less.
There has been a lot of talk about higher power ACA's, but I want to do the opposite - build a low power ACA that runs a lot cooler than the one in my listening room. The reason is that it will be for near field listening when working on my PC and I really can't have all that heat in my small office.
I still have two unused v1.0 PCB's, but have no idea how to make it run cooler. Would lower voltage make less heat and how low voltage can I go and still make decent quality sound? I'll use high efficiency FR speakers: At least 90db, so I don't need the 5W of the original v1.0.
Any ideas would help. But please don't suggest using an AB amp. I'm used to the ACA sound and won't settle for anything less.
There has been a lot of talk about higher power ACA's, but I want to do the opposite - build a low power ACA that runs a lot cooler than the one in my listening room. The reason is that it will be for near field listening when working on my PC and I really can't have all that heat in my small office.
I still have two unused v1.0 PCB's, but have no idea how to make it run cooler. Would lower voltage make less heat and how low voltage can I go and still make decent quality sound? I'll use high efficiency FR speakers: At least 90db, so I don't need the 5W of the original v1.0.
Any ideas would help. But please don't suggest using an AB amp. I'm used to the ACA sound and won't settle for anything less.
Your post made me look at ACA schematics...really closely for the first time ever. I have to say here how ingenious the whole design actually is! Amazing!!
You could replace the R7 with 20K trimpot, and R8 with 1K trimpot and play with their settings. That will control the current through Q2 and Q1 but will also take the amp out of class A mode of operation.... you might as well get a simple class AB, push-pull design, or even go class D.
I use fractal design 12V-super-quiet fans, powered up at 10V -> absolutely quiet... while doing a great job at keeping everything under control temperature-wise.
1 WATT CLASS A POWER, ACP+ , H2, LX mini
Get a pair of higher efficiency speakers full range 96-98 Or higher, run the ACP+ It is CLASS A. It already has a warm sound to. If you wanted to be anymore gooey like, Maybe adding the H2.
For all of us who were at Burning Amp This year we got to hear what that one WATT can do with those large 15 inch speakers I think it’ll be more than enough for near field. And I guess if somebody can chime in you had to have two way speakers you could get a very high efficiency Twitter and add in the LX mini instead of a crossover so you don’t eat up any power.
PS. You may have to add a resistor, talk to somebody with some experience to match your speaker to the ACP+ it likes 32 ohms or was it 38 ohms
There has been a lot of talk about higher power ACA's, but I want to do the opposite - build a low power ACA that runs a lot cooler than the one in my listening room. The reason is that it will be for near field listening when working on my PC and I really can't have all that heat in my small office.
I still have two unused v1.0 PCB's, but have no idea how to make it run cooler. Would lower voltage make less heat and how low voltage can I go and still make decent quality sound? I'll use high efficiency FR speakers: At least 90db, so I don't need the 5W of the original v1.0.
Any ideas would help. But please don't suggest using an AB amp. I'm used to the ACA sound and won't settle for anything less.
Get a pair of higher efficiency speakers full range 96-98 Or higher, run the ACP+ It is CLASS A. It already has a warm sound to. If you wanted to be anymore gooey like, Maybe adding the H2.
For all of us who were at Burning Amp This year we got to hear what that one WATT can do with those large 15 inch speakers I think it’ll be more than enough for near field. And I guess if somebody can chime in you had to have two way speakers you could get a very high efficiency Twitter and add in the LX mini instead of a crossover so you don’t eat up any power.
PS. You may have to add a resistor, talk to somebody with some experience to match your speaker to the ACP+ it likes 32 ohms or was it 38 ohms
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A twelve inch full range like this one from FANE is sensitive enough.
Budget priced driver. Can be ACA's friend in a 50-70 litres closed box.
Can sit with back near against the wall. Rising trend is taming off axis.
Shape it further with a simple electrical filter. A coil or LCR trap in series.
Salas “ Shape it further with a simple electrical filter. A coil or LCR trap in series.”
I’m just learning about crossovers By ready no hands on and only know enough to be dangerous and ,I don’t even know enough that I don’t even know. but I think with only one WATT power that LCR may devour some of the needed power.
That is why I recommended the LXmini. From reading Nelson’s published papers the way it works you can modify your signal before it gets to the amp not devouring any of the power that needs to get to the speaker the way passive crossovers do.
This sounds like a question that could be answered by Planet10
I’m just learning about crossovers By ready no hands on and only know enough to be dangerous and ,I don’t even know enough that I don’t even know. but I think with only one WATT power that LCR may devour some of the needed power.
That is why I recommended the LXmini. From reading Nelson’s published papers the way it works you can modify your signal before it gets to the amp not devouring any of the power that needs to get to the speaker the way passive crossovers do.
This sounds like a question that could be answered by Planet10
Changing the bias Voltage won't change the total heat, tweeking R7 or R8 won't do much of anything. Don't install the R15 mod.
Find a lower Voltage power supply, something like 12 or 14 Volt. Adjust the pot for roughly half the power supply Voltage. That will knock the heat down by 40% or so. To go lower, increase R1-R4, or just remove R2 and R4. That will lower the current and heat by half.
LCR trap like those three elements in parallel between them and the whole in series to the driver.
It will actually make the load impedance higher in the hump frequencies band it wants to attenuate.
Can do frequency shaping in the line level domain also no problem.
That's all about ironing it out though.
It will come out listenable enough with near wall placement and off axis listening i.e. drivers facing dead forward with you in the middle.
Acoustic filtering can also be done instead. Like utilizing a piece of foam behind grill cloth only at the area of the MID-HF coaxial cones.
Thanks for the heads up on the ACP+. It sounds very interesting and I might build it sometime, but I'll pursue the ACA route first. I just love it's sound and already have PCB's and original 2SK170's.
Thanks so much for your reply, Loudthud. It's exactly the type of info I was hoping to get.
I was already thinking about not doing the R15 mod. Without it, I'll start off with 5W and then apply your suggested mods.
Skylar,
I have the same problem here. That's why I'm still running my ACA with 19 v instead of 24v. It really makes a difference. So, using even lower voltages may help you.
Bigger heat sinks rock.
That's why I picked a 5U Deluxe for my Aleph J build.
If/when I do an ACA again, it will live in a chassis with an oversized heat sink.
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Theoretically lower B+ should do it, but you are entering a very non-linear region for the MosFet.
What astromo said is a very good suggestion, but comes at some cost.
You can build a Zen Lite with an input buffer, fed from 48VDC, with 300 - 500W (240V) light bulb, roughly 0.7 - 1A bias current, and take away half of the heat immediately. It will still need good heatsinks but not that big.
ACA and Zen Lite are sort of cousins, both simple, both unique, sound similar to my ears, both gorgeous in their presentation.
Worth a try.
If not follow astromo's advise.
Are you think of this sort of unit?
De-Lite Amplifier - diyAudio
In our wondrous land of green lighting (CFL, LED), enjoy tracking down some suitably sized incandescent bulbs. So, what? Looks like a fun build.