Amp Camp Amp - ACA

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Yves845

Member
Joined 2020
Thank you both for your explicit and simple enough answers, specifically concerning the output capacitor.

It's so different here than in French forums ....

I think I will opt for 2 stereo Amp Camps : these are easy to assemble, and then only, I will try my hand on a second pair of mono Nemesis amps : the hardest part will be to find a CNC machined chassis.
 
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peterpaan89

Member
Joined 2020
Hi there! I am completely new in DIY audio business and just discovered Nelson and his work a while ago. I'm already super stoked! Today I received a fully built ACA with another kit to build a second one myself. After heating up for an hour this 8wpc thingy really blew my mind. Now I am already thinking about how to move one. So I would like to build a second ACA and use them in mono mode. Thing is as I noticed, then I have to connect it via XLR which limits the choice of preamps quite a bit and as I am a beginner, I would like to start with the ACP+. SO, my question is:

Can I also use a RCA socket as mono input for the ACA or not? I am also building cables myself so I could also just make some XLR to RCA cables right? Am I missing something? Please enlighten me :)

Thanks in advance.

Cheers,

Johannes
 
Mooly

Mooly

Administrator
Joined 2007
Paid Member
There is not much to test tbh.

If you have the bias current of the ACA set at around 1.6 amps then it draws approx 39 watts per channel or around 78 watts in total from the PSU. So that is your figure of how much 'power' goes to the ACA.

How much the SMPS consumes from the mains depends on its efficiency (which might given in the data sheet for it) but that figure could be in the 90%+ region for a good quality PSU.
 
Alan4411

Alan4411

Member
Joined 2011
It works the other way round.
Each ACA board takes 36 watts, so an 'ACA' takes 72 watts.
The Meanwell is not 100% efficient so expect it to take about 80 watts from your mains.

Another way to look at it each ACA draws 3 Amps, the Meanwell can deliver 5 Amps, so has a 'reserve' of 2 Amps. The power used does not alter with volume/how loud you play it.
 
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Mikem53

Member
Joined 2020
Alan4411 said:
It works the other way round.
Each ACA board takes 36 watts, so an 'ACA' takes 72 watts.
The Meanwell is not 100% efficient so expect it to take about 80 watts from your mains.

Another way to look at it each ACA draws 3 Amps, the Meanwell can deliver 5 Amps, so has a 'reserve' of 2 Amps. The power used does not alter with volume/how loud you play it.
Click to expand...

That’s right on ! I measured 81 watt consumption after building and biasing the amp.
 
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wcwc

Member
Joined 2011
I was looking at my ACA 1.1B mono blocks construction. It looks like I could add another heatsink to the other side with some minor enclosure modifications. From now on all my preamps and amps will be XLR input only, so I was thinking about doing this modification. I still only have the 19V SMPS, so I would also buy the 24V SMPS. Has anyone done this?

So is there any issue combining an ACA 1.1 and a ACA 1.6/1.8 board in the same amp to run them as XLR monos or would it be better to make one amp ACA 1.1 and the other ACA 1.8?
 
thomasnadeau

thomasnadeau

Member
Joined 2010
Mooly said:
Hi Yves. My thoughts for what they are worth :)

Tbe SMPS specified for the project is absolutely ideal and is both cost effective and efficient.

A linear supply built to equal the performance of this would be bulky and heavy and also much less efficient... something you are concerned over.

There are no stability concerns at all with the ACA. If you don't need go under 800Hz then a smaller cap could be used however there is something to be aware of... something that stops it working as you expect.

The feedback for the ACA is taken from after the coupling cap and so this means that the amplifier will try and maintain the output level regardless of a smaller cap. It is an important point.

So in practice what this means is that as the frequency falls, the amplifier increases the level before the cap such that the level at the output (where the feedback is taken from) remains constant.

Even a 100uF coupling cap will still see the response extend down to 20Hz but the amplifier output before the cap will be very large and probably running into clipping.

So the answer here is that it is much better to compromise and perhaps look at reducing the input value coupling cap as well as the output coupling cap.

Only you can answer that... and remember the SMPS goes some way to offsetting the inefficiency.

The heat of the ACA will add to room heating in colder weather and so you gain there as well.
Click to expand...

I am using both high quality SMPSs (meanwell 24vs) as well as some linears I (over)built based on the AMB.org sigma 22 (regulated) supply and both produce excellent results with these little guys. If you have the room, built yourself a linear in an ACA-sized chassis and stack it underneath. Use a blue LED indicator on the front to match. :)

--Tom
 
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monotube2

Member
Joined 2012
I'm interested in trying an input transformer on aca camp in order to use the xlr connection with my preamp. Is there any value to change (capacitors and resistors)? The amplifier will work in a high efficiency (107db) active multi-way system from 700 to 4000hz (I have already seen Mooly's suggestions regarding input and output capacitors )
Many thanks to all
 
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