Theoretically using two ACA’s, each as a monoblock with the channels in parallel, will make it able to work well and deliver current to 4ohm impedance speakers
I wouldn’t be surprised if some people would prefer this configuration with their “6ohm” or even “8ohm” speakers because many speakers have a low impedance dip over a range of the frequency response,
Parallel monoblock is one of the 4 operating options the new model 1.8 wiring scheme allows one to choose with a switch. But even older ACAs are easy to hook up this way. Just combine both channels in parallel at the input with a “y” connector and run both positive outputs to the positive terminal of one speaker and both negative outputs to the negative terminal of the speaker. Then do the same to connect the second chassis to the second speaker.
I wouldn’t be surprised if some people would prefer this configuration with their “6ohm” or even “8ohm” speakers because many speakers have a low impedance dip over a range of the frequency response,
Parallel monoblock is one of the 4 operating options the new model 1.8 wiring scheme allows one to choose with a switch. But even older ACAs are easy to hook up this way. Just combine both channels in parallel at the input with a “y” connector and run both positive outputs to the positive terminal of one speaker and both negative outputs to the negative terminal of the speaker. Then do the same to connect the second chassis to the second speaker.
With no load all of the bias needs to be sunk by the CCS and thence into the heatsinks.
With a load some of the current goes into the speaker.
If you play a Class-A amp at max output, it will cool down a little.
Thank you! I have owned quite a few Class A amps over the years. I guess I never paid enough attention. I never knew that. Feel kinda stupid since I was in the high-end business for 40+ years and consider Class A amps the penultimate of amps, (just "my" opinion of course), but I wouldn't be caught without one...
class A is a fixed load for the psu, unlike class AB where the idle bias can be several times that at full power....not the same for class A, as far as biasing goes,it is full throttle from power on, whether or not music is playing thru your speakers...
so like any other class A amps, the amp actually cools a little bit with music....
in the case of the ACA, with both CCS and gain stage biased at half the b+, they both dissipate the same power, current thru them being the same...
so like any other class A amps, the amp actually cools a little bit with music....
in the case of the ACA, with both CCS and gain stage biased at half the b+, they both dissipate the same power, current thru them being the same...
thanks for the response- the friend is me
. I have some desoldering braid I can use. Funny that the LED is not that dim. I'm just trying to understand in good DIY fashion. I will swap them. I was going to build a second kit and was thinking, well if it works as is, why not just do the second one wrong as well.
. I have some desoldering braid I can use. Funny that the LED is not that dim. I'm just trying to understand in good DIY fashion. I will swap them. I was going to build a second kit and was thinking, well if it works as is, why not just do the second one wrong as well.
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Desoldering braid is a good way to remove old solder from the board. It sometimes leaves an unsightly residue behind, this can be cleaned with commercially available flux cleaner or isopropyl alcohol and an old tooth brush. Mop up excess with tissue paper.
If you are unsure about which resistor is which, you should measure them with a meter before you solder them into the PCB.
If you are unsure about which resistor is which, you should measure them with a meter before you solder them into the PCB.
it was actually the meter that caused the problem I think, the one that is recommended on the DIY website to get, when I read R10 it displays .332M ohm. (the cheap Radio Shack meter I've had in the tool box forever reads 332K Ohm) That's confusing isn't it? When I read R13 I get 33.1K ohm. So why it defaults to the higher range seems weird.
Different meters will operate to different rules if they are autoranging, however seeing 0.332M or 332k should not cause any confusion.
As you gain experience you just mentally juggle the figures, both are the same value.
Reading 33.1k for a 33.1k sounds like a nominally correct range. 0.033M wouldn't look correct and wouldn't allow for the resolution needed.
If that is what you mean
As you gain experience you just mentally juggle the figures, both are the same value.
Reading 33.1k for a 33.1k sounds like a nominally correct range. 0.033M wouldn't look correct and wouldn't allow for the resolution needed.
If that is what you mean
As well one has to keep in mind, that stereo ACA has an output impedance that is moderate, a parallel ACA will have half that so reasonable damping, but a bridged/balanced ACA has twice with an Rout in the range of typical SETs so one wants speakers with flattish impedance curve.
Parallel will be good into 4Ω not so good into 16Ω, Bridged/balanced not good into 4Ω good into 16Ω.
dave
If the midpoint volts is correct and to within 0.5 a volt or so then you would not reliably detect a difference in temperature.
If there is a real difference and the setting is correct then it can only be because of different thermal characteristics of the enclosure and heatsinks i.e. one device gets its heat removed better than the other.
Work it out...
The current is constant and the voltage across each device is the same when set up correctly. So the power dissipated in each is the same. Just multiply them out.
Vary the midpoint volts by '1' and you get something like 20.8 watts in one device and 17.6 watts in the other device for an Iq of 1.6 amp.
A couple of years ago I posted these two posts:
Amp Camp Amp - ACA
Amp Camp Amp - ACA
Since then I have used these nice IPP600N25N devices in all of my class A PLH / JLH type projects.
I am very impressed with the subjective results and have experienced no reliability problems.
I recently emailed Nelson to seek his opinion on this device. His reply was as follows:
I haven’t tried it, but seems like a nice enough part. The other slight
drawback is the lower dissipation rating, but I don’t see that as much
of an issue for the ACA.
Maybe you would like to post your results on diyAudio.
np
So I am reposting here for now.
What I do not have yet are real world FFT results and I'm not sure how much we can trust the dramatic SPICE FFT comparison in my previous post. But very soon I will be designing a PCB for a JLH project I have been working on which will be able to take both devices which will enable an AB comparison.
Will post again when I have more concrete data. All I would say for now is that they really shine with a simple input snubber network.
Best
mike mears
Amp Camp Amp - ACA
Amp Camp Amp - ACA
Since then I have used these nice IPP600N25N devices in all of my class A PLH / JLH type projects.
I am very impressed with the subjective results and have experienced no reliability problems.
I recently emailed Nelson to seek his opinion on this device. His reply was as follows:
I haven’t tried it, but seems like a nice enough part. The other slight
drawback is the lower dissipation rating, but I don’t see that as much
of an issue for the ACA.
Maybe you would like to post your results on diyAudio.
np
So I am reposting here for now.
What I do not have yet are real world FFT results and I'm not sure how much we can trust the dramatic SPICE FFT comparison in my previous post. But very soon I will be designing a PCB for a JLH project I have been working on which will be able to take both devices which will enable an AB comparison.
Will post again when I have more concrete data. All I would say for now is that they really shine with a simple input snubber network.
Best
mike mears