Its probably fine. You have to account for the voltage lost across R1,2,3 and 4.
24 volts less 22.6 leaves 1.4 volts lost across these resistors. That sounds a bit high but could be accounted for by drift of the transistor voltages as you measure them and you also need total accuracy of all values when measuring.
24 volts less 22.6 leaves 1.4 volts lost across these resistors. That sounds a bit high but could be accounted for by drift of the transistor voltages as you measure them and you also need total accuracy of all values when measuring.
The V+ wire to the right channel is too short to reach the left channel pad.
I tried flipping the speaker connections as well as the inputs. No change. Now that I pay more attention it’s doing it without music once warmed up good. I measured the voltages going into the LED resistors and they are a solid 23.9V. But, on the left channel the LED stays at a constant 2.78V. The right channel fluctuates between 2.64 to 2.72V. I wonder if I just have a bad resistor? The solder joints look good and I’ve chopsticked it to see, but no effect.
Here’s a short video of it with nothing but power attached.
ACA LED Flicker
edit. Reflowed the solder joints on the LED resistor to no change.
As a quick check I desoldered the negative leg of the LED. Connected a temp blue LED with clips and no flicker. Has to be the LED I think.
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That is a vital difference... flickering when no music playing. The devil is in the detail when fault finding.
It would seem so. LED's are quite heat sensitive. I always use a croc clip as a heat shunt when soldering them if possible.
Yep. I just never let it sit there very long without music playing 😁
This is the first LED I’ve ever had so that. Should have been the first thing I checked. At least everything has been gone over!
Thanks for the help!
Up and running. zero issues apart from it seems to be a very low gain amp .do I have things correct.?
Running irfp140n/24v and from a Salas DCG3 at 1.5x gain . I have it all flat out for a 'decent' level. Not mega loud by any means and I have no headroom.
Speakers for this are B-W DM 14. UK living room .2.5/3m listening distance
Running irfp140n/24v and from a Salas DCG3 at 1.5x gain . I have it all flat out for a 'decent' level. Not mega loud by any means and I have no headroom.
Speakers for this are B-W DM 14. UK living room .2.5/3m listening distance
Here is a simple test to establish if the ACAs are amplifying correctly. I suspect you do not have enough output voltage, from your source, but the test will prove or disprove that.
https://www.diyaudio.com/community/threads/amp-camp-amp-aca.215392/page-298#post-5547999
https://www.diyaudio.com/community/threads/amp-camp-amp-aca.215392/page-298#post-5547999
If you do need more gain then you can experiment with increasing R12 (the 39k feedback resistor). A 68k would give almost 14.5db overall gain with 8 ohm loading and 100k almost 17db. I don't know what the official thinking is on doing this but it seems very workable. The DC conditions are totally unaffected doing this.
Perhaps a modest gain increase on both the ACA and also on the DCG3 would get you where you need to be.
Perhaps a modest gain increase on both the ACA and also on the DCG3 would get you where you need to be.
I looked up the specs on your speakers and found that they are 8 ohm, but with a sensitivity of only 86db. Not an ideal match for the ACA. I tried numerous speakers with my ACA and only a few worked very well.
I doubt it's the gain that it's the problem. I have not followed DCG3, but I guess that it can output 2V which should be more than enough to clip ACA.
It's the low watts that are the constraint. You can add all the gain in the world, but in the end you are just going to clip the amp at a lower volume setting
B&W speakers are generally hard to drive. 86dBs are difficult. But even so, with 8 watts you should be getting enough volume to get complaints and start affecting the sensitivity of your hearing. The distortion should be high though. ACA is an amp that shines with sensitive speakers.
Please share your thoughts for Dali 6006 - 4 ohm, 91 db sensitive floorstanding speakers, would two ACA in parallel would be able to drive them fine. I listen around 9'o clock volume level. Thanks.
The Dali's should work fine. Afraid the 9'Oclock position will be more around noon or later
Volume/clockface settings are always different for each amp/preamp/source/speakers/room set.I spent the evening with mine last night and the 86db B&Ws. I think for 75pc of the time it would be fine. Volume about 3 o'clock and it goes to 5 so it is quite wicked up.
Sounds lovely though. It is maybe the quietest (background) amp I have. With a signal but no music and volume on full they are as good as dead silent. ....winner!
I'm using traco power 100w SMPS, open frame things. They're running quite warm. I got them cheap to use as easy test PSUs and I'm more a trafo/cap bank guy but I am quite surprised by them.
I measure sub mV ripple which I'm not sure is correct but having measured AC ripple successfully before there's not much I can get wrong.?! It does make me think twice about building a traditional (crc?) PSU but I guess I shall try .
My ACAs are Mark Johnson's circular things with the SMPS filter on board. I'm running 2 X 1500uf on the output .
I have a semi completed.Aleph 30 and so this is a nice way for me to keep the class A goodness without me having to deal so much with heat and the energy bills.
Sounds lovely though. It is maybe the quietest (background) amp I have. With a signal but no music and volume on full they are as good as dead silent. ....winner!
I'm using traco power 100w SMPS, open frame things. They're running quite warm. I got them cheap to use as easy test PSUs and I'm more a trafo/cap bank guy but I am quite surprised by them.
I measure sub mV ripple which I'm not sure is correct but having measured AC ripple successfully before there's not much I can get wrong.?! It does make me think twice about building a traditional (crc?) PSU but I guess I shall try .
My ACAs are Mark Johnson's circular things with the SMPS filter on board. I'm running 2 X 1500uf on the output .
I have a semi completed.Aleph 30 and so this is a nice way for me to keep the class A goodness without me having to deal so much with heat and the energy bills.
If you're a severely demented lunatic you can insert a Ship Of Theseus PSFILT in series between the SMPS and the "RACAM" / "Nelson Brock Hedgehog with Filter" . That board includes LC filtering, plus RC filtering, plus ferrite bead filtering -- to get rid of both SMPS high frequency noise, and 100/120 Hz mains hum, which it may surprise you to learn, often appears on the output of a switcher: MeanWell 100Hz noise plot from their own test report attached below.
Each of the two PSFILT DC outputs can supply about 2 amps, which is enough for a pair of stock unmodified RACAMs that draw ~1.7 amps each.
If that's not crazy enough you can upgrade to "Tuba" which is even greater overkill.
_
Each of the two PSFILT DC outputs can supply about 2 amps, which is enough for a pair of stock unmodified RACAMs that draw ~1.7 amps each.
If that's not crazy enough you can upgrade to "Tuba" which is even greater overkill.
_
