Hi Mooly
ok the sine wav is H2 harmonic - lets say that is the sound character.
yes the Rchannel is strange -i tried it several times...every 10mVrms input more i can see on scope that the upper sine wave is groing higher and higher and the lower part just "reacts" every 3rd or 4th time and rise a bit.
Supply clean?
i use my LRS150-24V supply its able to support 6A easy...for both channels at the same time so when something happened then it acts for both channel at the same time.
What do you mean with clean? the voltage is sagging during max power?
chris
ok the sine wav is H2 harmonic - lets say that is the sound character.
yes the Rchannel is strange -i tried it several times...every 10mVrms input more i can see on scope that the upper sine wave is groing higher and higher and the lower part just "reacts" every 3rd or 4th time and rise a bit.
Supply clean?
i use my LRS150-24V supply its able to support 6A easy...for both channels at the same time so when something happened then it acts for both channel at the same time.
What do you mean with clean? the voltage is sagging during max power?
chris
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ok i used the 220 test tone:
i listened some titles with my chip amp some funky title...so loud...and then i use the mp3 file for 220hz. i got 2,803 Volts --> its about 7,85 for 8R ......so double that is about 16Watt for 4R.
right?
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You played the music really loud, then played the test tone without touching the volume controls anywhere in the chain.
You must also use the same device for playing the music as playing the files.
So you measured 2.8 volts (rms voltage) which equates to needing a 7.84 watts rms from the amplifier.
Lets work back from that and see if the ACA can do this...
7.84 watts rms is a shade under 8 volts rms needed at the speaker terminals. 8 volts rms is 11.3 volts peak or 22.6 volts peak to peak. As you can see 22.6 volts is nearly equal to the supply voltage.
So the ACA will not provide this level (that the test provided based on your chosen listening level says you need) I'm afraid, even on 24 volt rails
The ACA realistically is going to deliver around 18 to 20 volts peak to peak which is 5 to 6 watts into 8 ohms.
hmm...my new speakers are 85dB..
attached the DIY magazine K+T....sorry its german
85db/metre @ 1watt is low efficiency. I used to have some Celestion SL6's that were just 82db
put they were partnered with a Pioneer A80 amp which was 150 watts rms capable.Numbers again.
You need to double the power to get just a 3db increase in level and 3db isn't particularly noticeable, it is not twice as loud.
So if you have a speaker of 90db efficiency and one of 84db you can see that you are starting from a place that needs 1 watt vs 4watts to achieve similar levels.
Drive the 90db speaker to say a level of 99db and it needs 4 watts.
Do the same for the 84db speaker and that one needs 32 watts.
The numbers start to get big very quickly as you edge that volume control up.
You played the music really loud, then played the test tone without touching the volume controls anywhere in the chain.
You must also use the same device for playing the music as playing the files.
So you measured 2.8 volts (rms voltage) which equates to needing a 7.84 watts rms from the amplifier.
Lets work back from that and see if the ACA can do this...
7.84 watts rms is a shade under 8 volts rms needed at the speaker terminals. 8 volts rms is 11.3 volts peak or 22.6 volts peak to peak. As you can see 22.6 volts is nearly equal to the supply voltage.
So the ACA will not provide this level (that the test provided based on your chosen listening level says you need) I'm afraid, even on 24 volt rails
The ACA realistically is going to deliver around 18 to 20 volts peak to peak which is 5 to 6 watts into 8 ohms.
Hi Mooly
thank you for supporting me.
as i read the test correctly is stated that i should search for a title and make it loud...i did this
....yes this is the max enjoyable levelmy chain is Tidal-laptop-USB-DAC ....so i note the max volume setting it was 42. ...so i have for endurance listening level a bit of buffer
thx for your calculation...that is exactly what i got.... so i will tomorrow go up with the supply to 24V...lets grill some IRFP240
...today i got some spare IRFP240thank you
chris
85db/metre @ 1watt is low efficiency. I used to have some Celestion SL6's that were just 82db
Numbers again.
You need to double the power to get just a 3db increase in level and 3db isn't particularly noticeable, it is not twice as loud.
So if you have a speaker of 90db efficiency and one of 84db you can see that you are starting from a place that needs 1 watt vs 4watts to achieve similar levels.
Drive the 90db speaker to say a level of 99db and it needs 4 watts.
Do the same for the 84db speaker and that one needs 32 watts.
The numbers start to get big very quickly as you edge that volume control up.
yes small low efficiency speakers can hurt an amp.
one year ago some firends (mostly speaker builders) organized a meeting to compare some 4" and more. i but my DAC and my hand baked TPA3255 amp with me.
during testing some use the speaker called "Bon Bon" 81dB ---some amps got strange sound effects..mean highs were not really nice the amp sound really stressed. room was about 30m2 and very high top...
with my amp (28V supply) it was fine
The temperatures you are seeing on the FET's are OK but it is important to understand that the repeated heating and cooling of the devices can sometimes cause other issues such as the fixing bolts to gradually loosen... if they are inappropriate for the use and aren't using the correct washers and so on, and also things like solder joints to crack. All long term issues that happen over months and years.
Also make sure the devices are tightened to approximately the correct torque which is given in the data sheets. I'm seeing around 10lbf/in or 1.1Nm given.
The basic temperatures on the devices themselves are fine though.
Also make sure the devices are tightened to approximately the correct torque which is given in the data sheets. I'm seeing around 10lbf/in or 1.1Nm given.
The basic temperatures on the devices themselves are fine though.
at R channel :
at the scope i see it as lower sine wave which is not ok....but its an inverted amp so its in real the positive voltage at the Q1 that is not work well.
correct?
any idea how i can fix this...? maybe the IRFP240 is not really open?
If it is just one channel doing this then you should see if the distortion disappears when you remove the load.
If it does then consider the possibility that you may have a grounding issue... that can contribute to this effect. To prove that you would have to wire just the one channel to the power supply and have just this channels input connected.
That means disconnecting any possible loops formed via the other channel. In effect you are running the one channel in total isolation as a test.
I would really doubt there are any issues with the FET's tbh.
If it does then consider the possibility that you may have a grounding issue... that can contribute to this effect. To prove that you would have to wire just the one channel to the power supply and have just this channels input connected.
That means disconnecting any possible loops formed via the other channel. In effect you are running the one channel in total isolation as a test.
I would really doubt there are any issues with the FET's tbh.
This might sound slightly odd but do you have any measurable DC voltage across the speaker terminals when the load is disconnected
The only voltage present should be leakage in the output coupling cap. If there is voltage present then it might show you have ground wiring issue and the being caused by the speaker return not going to the correct point.
The only voltage present should be leakage in the output coupling cap. If there is voltage present then it might show you have ground wiring issue and the being caused by the speaker return not going to the correct point.
Hi Mooly
thanks for your help. i will go again through the GND loop issue. not clear for me why one channel is ok and the other not. because i go directly from the power terminal with each wiring to the amp boards.
but maybe a have a leakage at the caps....and re check the DC voltage.
... i will do so...
I wish you and other members a Happy new year !
chris
thanks for your help. i will go again through the GND loop issue. not clear for me why one channel is ok and the other not. because i go directly from the power terminal with each wiring to the amp boards.
but maybe a have a leakage at the caps....and re check the DC voltage.
... i will do so...
I wish you and other members a Happy new year !
chris
Happy New Year 
(the caps won't be leaky but any DC voltage showing across the speaker terminals (which might be just millivolts) might suggest a grounding issue because there would be the ACA's high bias current flowing in the ground system and that will develop volt drop along those conductors. Its a bit tenuous but needs checking)
(the caps won't be leaky but any DC voltage showing across the speaker terminals (which might be just millivolts) might suggest a grounding issue because there would be the ACA's high bias current flowing in the ground system and that will develop volt drop along those conductors. Its a bit tenuous but needs checking)
Amp switched on. no load connected, RCA connected to my DAC. DAC is off.
both channels show me -3,9mV. looks fine
during playing card and other games to wait for the count down.
..i am thinking about the "floating" SMPS:my LRS150-24V is earth GND at the housing, but the output terminals not...for sure. connection is: with the cable i go to the amp and there is the GND at the +output terminal by the amp housing. but the real earth GND comes by my DAC with earth at the RCA connectors.
is that the loop?
but why at the Rchannel and not at the L channel
WOW Tony
thats an ACA MONSTER
yes, two two channels were bridged hence just 2 pairs of speaker terminals...
earlier, i did the same with 24 volts, a balanced type from input to output...
single 47k resistor did the trick..
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no, i did not.....but bridging 48vdc ACA is like having an amp with +-48vdc rails, power is estimated at 70 watts...
to be honest, i am not an 845 fan, more like 2a3 for me...
my 48vdc ACA pulls 230 watts from the wall.....
here is a video clip.....Tony Tecson
my 48vdc ACA pulls 230 watts from the wall.....
here is a video clip.....Tony Tecson
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