Re: noise output
That's of course a lot lower than 1800µV.
I can live with that because from the moment on the music
is playing it's absolutely inaudible to me.
IMO, the best way to lower that noise is even better filtering.
Look at post#89 here. After every R the noise diminishes a lot.
Others like Till and Edwin also report some output noise but very inaudible.
Of course, a lot depends on the sensitivity of your speakers.
Did you build the AlephX?
From what point of view are you not happy with +/- 2mV?
A practical or a theoretical point?
Greetings
/Hugo
The XA200 specs tell us the output noise is about 300µV.john-china said:
That's of course a lot lower than 1800µV.
I can live with that because from the moment on the music
is playing it's absolutely inaudible to me.
IMO, the best way to lower that noise is even better filtering.
Look at post#89 here. After every R the noise diminishes a lot.
Others like Till and Edwin also report some output noise but very inaudible.
Of course, a lot depends on the sensitivity of your speakers.
Did you build the AlephX?
From what point of view are you not happy with +/- 2mV?
A practical or a theoretical point?
Greetings
/Hugo
Hi,
since I tried building my amp in a enclosure one channel has a slight 50hz humm... You can only hear it within 10-20cm of the speaker but it is there and it was not there before. I get this humm even with the other channel disconnected completely from the mains, power supply and pre-amp. This one channel evens humms without the pre-amp connected. As both channels have the same grounding scheme and wire gauge and wire length and one channel humms and the other does not I do not think I have a ground loop... But...
I will swap powersupply maybe one of my rectifier diodes are bad. hmm...
any ideas?
Edwin
since I tried building my amp in a enclosure one channel has a slight 50hz humm...
You can only hear it within 10-20cm of the speaker but it is there and it was not there before. I get this humm even with the other channel disconnected completely from the mains, power supply and pre-amp. This one channel evens humms without the pre-amp connected. As both channels have the same grounding scheme and wire gauge and wire length and one channel humms and the other does not I do not think I have a ground loop... But... I will swap powersupply maybe one of my rectifier diodes are bad. hmm...
any ideas?
Edwin
I have just been looking at your pics.
Is the driver board still mounted on the heatsink?
If this is the case I doubt if it is the bridge or capacitors and sounds like you have some induced hum into the driver board.
The postion of the high current wiring from the bridge to the capacitors relative the driver board will effect you local hum and also any earth wiring near the power supply.
I had this problem with the Baby X until I move the driver board and hope this is a cure for your slight hum.
regards,
macka
Is the driver board still mounted on the heatsink?
If this is the case I doubt if it is the bridge or capacitors and sounds like you have some induced hum into the driver board.
The postion of the high current wiring from the bridge to the capacitors relative the driver board will effect you local hum and also any earth wiring near the power supply.
I had this problem with the Baby X until I move the driver board and hope this is a cure for your slight hum.
regards,
macka
it is because xa200 specs said only 300uv noise, i am unhappy with 2mv , i did not build aleph-x but aleph-4, my aleph-4 outputs
2mv hum noise , i am so sensitive to hum noise that when my ears close to speaker, i feel the hum will be louder and louder. of cause i can not hear any hum when i am listening some music.
maybe i am a completist, so i want to reach the spec of pass comercial xa200 amp . how should i do?
ps : does anyone 's amp reach this specs ?
2mv hum noise , i am so sensitive to hum noise that when my ears close to speaker, i feel the hum will be louder and louder. of cause i can not hear any hum when i am listening some music.
maybe i am a completist, so i want to reach the spec of pass comercial xa200 amp . how should i do?
ps : does anyone 's amp reach this specs ?
macka said:
My boards are still on the heatsinks at a distance of about 2cm from the heatsinks. I will remove the heatsink from the chassis and move it away from the wires and transformers to see if the hum level will get lower. The strange thing is still why one channel hums and one does not with the same wiring layout.
Edwin
macka said:
The box is has a width of 50cm by 60cm deep and is 22cm in height! It weighs? I dunno!
You can see pictures in my 'How to connect the blue led' thread here on diyaudio!
Edwin
http://www.diyaudio.com/forums/showthread.php?s=&threadid=18818
Re: tl431
The original sim I made was done at the time someone came up with the TL431. (Can't remember who)
The 81 ohm is 82 ohm in real life and the pot was trimmed until the differential DC was OK.
Oops, just looked at the posted schematic and it has indeed 82 ohm on the 82 ohm resistor.
The picture could have been a bit better though.
Sorry for that.
/Hugo -
No particular reason to use TL431. I never tried something else.lieven said:
The original sim I made was done at the time someone came up with the TL431. (Can't remember who)
The 81 ohm is 82 ohm in real life and the pot was trimmed until the differential DC was OK.
Oops, just looked at the posted schematic and it has indeed 82 ohm on the 82 ohm resistor.
The picture could have been a bit better though.
Sorry for that.
/Hugo -
Instead of sitting in front on the Internet I did some measurement on the AlephX today.
Being able to make the distortion analyser work and behave like it should
and not loosing my notes, here are the unpolished results of a measurement.
While the AlephX was warming up for more than an hour, the distortion of the signal generator
was measured so I could deduct them from the
AlephX figures. After all, they are pretty well ignorable.
The generator at 0.775mV output:
100Hz: 0.14%
1Khz: 0.03%
10Khz: 0.042%
50Khz: 0.084%
Since the AlephX is a bridged amp, I could only measure half of the amp at the time.
(Outputs can’t be ground referenced) Correct me if I’m wrong here.
With the 0.775mV SE in, I had about 7.9V RMS out on half a channel. (+Out to ground)
The other channel only gives 6.9V RMS out. (-Out to ground)
100Hz: 0.14% being very low as the generator gives the same figures.
1Khz: 0.25% - 0.03% = 0.22%
10Khz: 2.22% - 0.042% = 2.178%
50Khz: 9.3% - 0.084% = 9.216%
Other channel:
100Hz: 0.14%
1Khz: 0.23% - 0.03% = 0.2%
10Khz: 2.4% - 0.042% = 2.358%
50Khz: 8.8% - 0.084% = 8.716%
As you can see, the commas are rather unimportant with such high numbers and
in high contrast with Grey’s measurements.
No need to tell you that a few comments will be appreciated.
/Hugo
I did some measurement on the AlephX today.Being able to make the distortion analyser work and behave like it should
and not loosing my notes
, here are the unpolished results of a measurement.While the AlephX was warming up for more than an hour, the distortion of the signal generator
was measured so I could deduct them from the
AlephX figures. After all, they are pretty well ignorable.
The generator at 0.775mV output:
100Hz: 0.14%
1Khz: 0.03%
10Khz: 0.042%
50Khz: 0.084%
Since the AlephX is a bridged amp, I could only measure half of the amp at the time.
(Outputs can’t be ground referenced) Correct me if I’m wrong here.
With the 0.775mV SE in, I had about 7.9V RMS out on half a channel. (+Out to ground)
The other channel only gives 6.9V RMS out. (-Out to ground)
100Hz: 0.14% being very low as the generator gives the same figures.
1Khz: 0.25% - 0.03% = 0.22%
10Khz: 2.22% - 0.042% = 2.178%
50Khz: 9.3% - 0.084% = 9.216%
Other channel:
100Hz: 0.14%
1Khz: 0.23% - 0.03% = 0.2%
10Khz: 2.4% - 0.042% = 2.358%
50Khz: 8.8% - 0.084% = 8.716%
As you can see, the commas are rather unimportant with such high numbers and
in high contrast with Grey’s measurements.
No need to tell you that a few comments will be appreciated.
/Hugo
Hugo,
I think you need to use a differential amplifier between the amp OPs and the distortion analyser. This amp is designed to make the error signal common mode - your set-up will not reject this component.
I have run into this problem myself (also testing a bridge load amp) and need to figure out a simple way round it I was thinking of an AD623 and a battery (as i have some already) to do differential to single-ended prior to my ADC ...
Dave
I think you need to use a differential amplifier between the amp OPs and the distortion analyser. This amp is designed to make the error signal common mode - your set-up will not reject this component.
I have run into this problem myself (also testing a bridge load amp) and need to figure out a simple way round it I was thinking of an AD623 and a battery (as i have some already) to do differential to single-ended prior to my ADC ...
Dave
Grataku,
The input is single ended.
Henrik, Dave,
My guess was also the X-effect being cancelled.
How could this problem be solved? An AD623 and a battery???
Please explain.
Could a second distortion meter solve the problem?
Another option could be the feedback. Don't know but I might try
a lower resistor than the 220k now.
/Hugo
The input is single ended.
Henrik, Dave,
My guess was also the X-effect being cancelled.
How could this problem be solved? An AD623 and a battery???
Please explain.
Could a second distortion meter solve the problem?
Another option could be the feedback. Don't know but I might try
a lower resistor than the 220k now.
/Hugo
Hi Hugo!
I don´t have an distortion analyser my self, so I have no practical expierience in this, but what´s wrong about connecting -out to the analyser´s gnd and +out to the other input? I do that in my simulator without problems, I know sim´s aren´t real, but anyway.
By the way, you have done some realy nice job!!!!!
I don´t have an distortion analyser my self, so I have no practical expierience in this, but what´s wrong about connecting -out to the analyser´s gnd and +out to the other input? I do that in my simulator without problems, I know sim´s aren´t real, but anyway.
By the way, you have done some realy nice job!!!!!
Hugo,
Any OPamp can be wired to provide differential inputs / single ended output.
You would also need a potential divider (to stay within the limits of the OPamp inputs) to connect the differential inputs of the OPamp to the differential output of the X amp. Of course, also connect the distortion instrument to the single ended output of the OP-amp. Assuming the OPamp distortion is somewhat lower than the amp you should be able to make good measurements.
My idea of using AD623 (actually an instrumentation amplifier) was simplicity (and the fact I already have some !) - it will run from 6-12V single ended PSU at microscopic current drains. I also have some 5534's if the distortion / bandwidth prove to be a problem but I would then need a proper PSU
I have not got any further than the idea ....
Dave
PS Henrik's idea would require you to float the earth of the distortion analyser
Any OPamp can be wired to provide differential inputs / single ended output.
You would also need a potential divider (to stay within the limits of the OPamp inputs) to connect the differential inputs of the OPamp to the differential output of the X amp. Of course, also connect the distortion instrument to the single ended output of the OP-amp. Assuming the OPamp distortion is somewhat lower than the amp you should be able to make good measurements.
My idea of using AD623 (actually an instrumentation amplifier) was simplicity (and the fact I already have some !) - it will run from 6-12V single ended PSU at microscopic current drains. I also have some 5534's if the distortion / bandwidth prove to be a problem but I would then need a proper PSU
I have not got any further than the idea ....
Dave
PS Henrik's idea would require you to float the earth of the distortion analyser
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