I have a very big problem with my just finished Aleph 3.
In my speakers I hear a noise who is doing something like: twiiiIIIIIiiIIIiiiiiiiiiIIiiiit. It seems to be a high frequency parasite noise.
And what is curious is that when I move some wires, particulary the inputs wires and the power wires, the noise increase or decrease.
I forgot to say that it is the same when i disconnect the CD player and that the noise is loud.
I am sad, because the sound seems to be very good.
Am i the first who have this problem, do you have an idea of the origin of my problem?
In my speakers I hear a noise who is doing something like: twiiiIIIIIiiIIIiiiiiiiiiIIiiiit. It seems to be a high frequency parasite noise.
And what is curious is that when I move some wires, particulary the inputs wires and the power wires, the noise increase or decrease.
I forgot to say that it is the same when i disconnect the CD player and that the noise is loud.
I am sad, because the sound seems to be very good.
Am i the first who have this problem, do you have an idea of the origin of my problem?
I'm posting here beaucse I'm working on email with Jekyll.
I hope he will manage to correct his problem.
So, i've got a little question. On the enter of Aleph 3 what is the voltage level needed.
Because I'm using a kit preamp giving 40dB controled gain. So i've got a signal about 100mV --> 1,5V. This is not too much?
I hope he will manage to correct his problem.
So, i've got a little question. On the enter of Aleph 3 what is the voltage level needed.
Because I'm using a kit preamp giving 40dB controled gain. So i've got a signal about 100mV --> 1,5V. This is not too much?
Miles Teg,
>>On the enter of Aleph 3 what is the voltage level needed.
>>Because I'm using a kit preamp giving 40dB controled gain.
>> So i've got a signal about 100mV --> 1,5V. This is not too much?
Your preamp output is correct , less than 2 volts is perfect ;
and the Aleph gain is 20 Db.
You just have to check for the output impedance to match with the input impedance of the Aleph 3 which is 23 Kohms.
Regards.
Alain.
>>On the enter of Aleph 3 what is the voltage level needed.
>>Because I'm using a kit preamp giving 40dB controled gain.
>> So i've got a signal about 100mV --> 1,5V. This is not too much?
Your preamp output is correct , less than 2 volts is perfect ;
and the Aleph gain is 20 Db.
You just have to check for the output impedance to match with the input impedance of the Aleph 3 which is 23 Kohms.
Regards.
Alain.
I've tried before your answer. It works !!!
My 1 voice aleph have emit his first sounds !
But my preamp is too much. The sound is a little bit loud for the minimum setting of the preamp.
And the sound quality is really poor. I guess a lot of cut in the signal. I need an oscilloscope...!
This is my first prototype of Aleph, mounted spread on the bench. Now i know I can create my chassis and start a better one with all the improvements I know.
My 1 voice aleph have emit his first sounds !
But my preamp is too much. The sound is a little bit loud for the minimum setting of the preamp.
And the sound quality is really poor. I guess a lot of cut in the signal. I need an oscilloscope...!
This is my first prototype of Aleph, mounted spread on the bench. Now i know I can create my chassis and start a better one with all the improvements I know.
A lot of things could be the reason, starting with grounding routing (usually that leads to just hum though), interference pickup, missing/dropped ground reference of some component etc.
So... you could try to re-rout your grounding, and before that at least make sure that everything that is supposed to be connected to ground actually IS on ground (slder joints, forgotten connections). Also, both the signal ground/PCB ground , and the power ground (return from speaker), should come together only at the PSU, and not directy between the PSU caps but at some distance from the filter caps. A few mm can make a big difference in noise here, as I found out with my own Mini-Aleph.
So... you could try to re-rout your grounding, and before that at least make sure that everything that is supposed to be connected to ground actually IS on ground (slder joints, forgotten connections). Also, both the signal ground/PCB ground , and the power ground (return from speaker), should come together only at the PSU, and not directy between the PSU caps but at some distance from the filter caps. A few mm can make a big difference in noise here, as I found out with my own Mini-Aleph.
MBK, I controlled with an ohmmeter, and all seems ok.
All the grounds are connected on one screw isolated from the chassis, and there is only one wire who go to the ground of the power supply.
What I don't understand is that both level and frequency of that noise change when I move some wires inside the amp.
It is like if there was a transmitter and a receiver, and the wires were working like an antenna. And when I move the wires, I only change the orientation of "THE" antenna.
IS IT POSSIBLE???
All the grounds are connected on one screw isolated from the chassis, and there is only one wire who go to the ground of the power supply.
What I don't understand is that both level and frequency of that noise change when I move some wires inside the amp.
It is like if there was a transmitter and a receiver, and the wires were working like an antenna. And when I move the wires, I only change the orientation of "THE" antenna.
IS IT POSSIBLE???
Jekyll,
Check out post #26 of this thread http://www.diyaudio.com/forums/showthread.php?s=&threadid=32856&perpage=15&pagenumber=2
Who knows, you might be having the same problem.
Check out post #26 of this thread http://www.diyaudio.com/forums/showthread.php?s=&threadid=32856&perpage=15&pagenumber=2
Who knows, you might be having the same problem.
I second that... much has been discussed on that thread and the solution was simple 
As in the other thread though I'd recommend to first earth the chassis directly, and to put the star ground somewhere else (not on the chassis, but connected with one connection, either direct, or through a low power resistir, or two diodes wired parallel with opposite polarity.
As in the other thread though I'd recommend to first earth the chassis directly, and to put the star ground somewhere else (not on the chassis, but connected with one connection, either direct, or through a low power resistir, or two diodes wired parallel with opposite polarity.
Frank, the chassis is connected to ground through a wire going from it to the star ground.
Fcel, thank you, but I don't understand how replacing a wire by a wire can solve a problem.
MBK, i tried to connect the chassis directly to earth, no difference.
But, as I repeat, my problem is very special: "THE NOISE" changes of level and frequency when I move the wires inside the amp.
And when I disconnect the chassis from ground, I have the famous "HUM". But it is very different from my "Twiiiiiiiiiiiiiit".
Fcel, thank you, but I don't understand how replacing a wire by a wire can solve a problem.
MBK, i tried to connect the chassis directly to earth, no difference.
But, as I repeat, my problem is very special: "THE NOISE" changes of level and frequency when I move the wires inside the amp.
And when I disconnect the chassis from ground, I have the famous "HUM". But it is very different from my "Twiiiiiiiiiiiiiit".
JEKYLL,
What you describe is typical of radio frequency instability, when even moving your hand near to the active circuit can have an effect. Moving wires around can also have the same effect.
Possible causes (as the aleph designs are know to be sound) :
[1] Poor PCB layout
[2] Faulty component / wrong type or value
[3] Load problem (too reactive ?)
Things to try (assuming std aleph circuit) :
[1] Twist the power supply wires togeather
[2] Fit a ferite bead to the PS wires
PS
I would not fit the small electrolytic caps to the PS lines, these will likely be working well outside their max ripple current rating - I have seen this done in commercial amps, however the caps often end up exploding when the amp is worked hard
Dave (not a aleph expert !)
What you describe is typical of radio frequency instability, when even moving your hand near to the active circuit can have an effect. Moving wires around can also have the same effect.
Possible causes (as the aleph designs are know to be sound) :
[1] Poor PCB layout
[2] Faulty component / wrong type or value
[3] Load problem (too reactive ?)
Things to try (assuming std aleph circuit) :
[1] Twist the power supply wires togeather
[2] Fit a ferite bead to the PS wires
PS
I would not fit the small electrolytic caps to the PS lines, these will likely be working well outside their max ripple current rating - I have seen this done in commercial amps, however the caps often end up exploding when the amp is worked hard
Dave (not a aleph expert !)
hi JEKYLL, I was refering to the layout of tracks / components on the PCB and if the layout you are using is 'proven'. For example, if lots of other people have used the same PCB layout and their alephs work correctly then layout problems can be eliminated.
Did you build a 2-channel (stereo) amp ? Do both channels behave the same way ?
good luck,
dave
JEKYLL,
Could you please make some detailed pictures of the inside of your Aleph 3
That could help, at this point I cannot tell anything more to say.
Regards.
PS: And "Dupont" is my real name, I was born in Nîmes - Gard - France.
For the history
City founded by Emperor Augustus 2nd century BC ; famous for his Roman Amphitheater, the Crocodyle and for sure: the Denim fabric gets its name also
from this city ("de Nîmes")
Alain.
Could you please make some detailed pictures of the inside of your Aleph 3
That could help, at this point I cannot tell anything more to say.
Regards.
PS: And "Dupont" is my real name, I was born in Nîmes - Gard - France.
For the history
City founded by Emperor Augustus 2nd century BC ; famous for his Roman Amphitheater, the Crocodyle and for sure: the Denim fabric gets its name also
from this city ("de Nîmes")
Alain.
Are you using snubber resistors in series with the gates of the FETs? If not this could cause the amp to oscillate. Values of 220 to 1K can be used, it's not critical. The resistor should be as close to the gate lead as possible.
Just something to try and a known cause of this type of problem.
Later BZ
Just something to try and a known cause of this type of problem.
Later BZ
DRC, the layout is not proven, I designed it on the base of one found on the forum.
The layout is in attached file. The components are drawn by hand because I lost the EAGLE file. Everybody can give me his opinion, because I'm beginning to believe that it is the origin of my problem but I don't found any fault.
The amp is a 2 channel with a common power supply, and I hear the noise on both channels.
Alain DUPONT, sorry for the pictures, I don't own a digital camera.
HDTVman, the circuit is exactly the same than in the Service Manual excepted for the power supply: I use 2 bridges. The IRFP240 are connected to the circuit whith shorts wires (5cm/2in).
The layout is in attached file. The components are drawn by hand because I lost the EAGLE file. Everybody can give me his opinion, because I'm beginning to believe that it is the origin of my problem but I don't found any fault.
The amp is a 2 channel with a common power supply, and I hear the noise on both channels.
Alain DUPONT, sorry for the pictures, I don't own a digital camera.
HDTVman, the circuit is exactly the same than in the Service Manual excepted for the power supply: I use 2 bridges. The IRFP240 are connected to the circuit whith shorts wires (5cm/2in).
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