So after two years I rebuild my aleph5 with a new psu and more easy to access layout, see my earlier problems at:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=52936
The amp is working fine but now I have a humm problem.
When all inputs are empty there is nearly no audible hum. If I connect a shorted inputcable to the right channel (or left) the hum starts (no preamp just cable). When I attach my preamp to 1 channel it gets louder, it doesn't mather if the preamp is turned on.
Please help me to find the ground problem
Groundschematic, chassis is not grounded since it is glued together
The pcb's are the origanal ones I bought about 5 years ago: http://www.kk-pcb.com/aleph-4.html, the fets are hard wired.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=52936
The amp is working fine but now I have a humm problem.
When all inputs are empty there is nearly no audible hum. If I connect a shorted inputcable to the right channel (or left) the hum starts (no preamp just cable). When I attach my preamp to 1 channel it gets louder, it doesn't mather if the preamp is turned on.
Please help me to find the ground problem
Groundschematic, chassis is not grounded since it is glued together
The pcb's are the origanal ones I bought about 5 years ago: http://www.kk-pcb.com/aleph-4.html, the fets are hard wired.
Attachments
Assuming that I'm reading your diagram correctly and that it accurately reflects what you have in your circuit, you'll need to make sure that the inputs (both RCA & XLR) attach to ground in some manner. Also, why are the RCA jacks connected to both the XLR and the circuit board? One or the other I can understand, but not both.
Depending on how close your amp is to other things that might induce hum, you might need a chassis that shields the circuit. I've got some Aleph 2s that function just fine naked, but you may have something nearby that's causing problems.
As far as support for the kk boards, I would suggest that you contact the fellow who sold you the boards. I've never seen a set and have no idea how they're laid out. He should support his boards.
Grey
Depending on how close your amp is to other things that might induce hum, you might need a chassis that shields the circuit. I've got some Aleph 2s that function just fine naked, but you may have something nearby that's causing problems.
As far as support for the kk boards, I would suggest that you contact the fellow who sold you the boards. I've never seen a set and have no idea how they're laid out. He should support his boards.
Grey
You want to have a star ground which brings together all the input,
0utput, chassis and AC grounds together and then attach that via a
single fat wire to the main power supply ground. Also, you should
allow for isolation of earth (AC) ground to the wall through a
power thermistor or resistor to help break ground loops.
0utput, chassis and AC grounds together and then attach that via a
single fat wire to the main power supply ground. Also, you should
allow for isolation of earth (AC) ground to the wall through a
power thermistor or resistor to help break ground loops.
My quickly drawn schematic was, as it seems, not very clear. But after some changes I wilt try to describe the fenomenon a little bit in more detail for 1 channel (the other one acts the same.)
Input:
XLR + --> pcb+
XLR - --> pcb-
rca + --> pcb unbalanced
rca ground and XLR ground --> star ground
Output:
speaker - -->star ground
Other:
pcb ground --> star ground
psu ground --> star ground
star ground --> ntc --> ac ground
chassis --> not grounded (corners are glued and have
no baremetalconnections between each other)
these are all single wires. But here it comes. After turning the amp on dc offset goes to about 13mV when connecting the preamp and the humm gets louder dc offset doesn't gets higher and my multimeter tells me that is exactly 100Hz.
PSUschematic:
Input:
XLR + --> pcb+
XLR - --> pcb-
rca + --> pcb unbalanced
rca ground and XLR ground --> star ground
Output:
speaker - -->star ground
Other:
pcb ground --> star ground
psu ground --> star ground
star ground --> ntc --> ac ground
chassis --> not grounded (corners are glued and have
no baremetalconnections between each other)
these are all single wires. But here it comes. After turning the amp on dc offset goes to about 13mV when connecting the preamp and the humm gets louder dc offset doesn't gets higher and my multimeter tells me that is exactly 100Hz.
PSUschematic:
Code:
bridge+ ----------------------------------V+
| |
C 68Mf MKP 4,7uF
| |
bridge- -----------------------------------
|
|----star ground
|
bridge+ ----------------------------------
| |
C 68Mf MKP 4,7uF
| |
bridge- -----------------------------------V-What I just found out today is not a groundloop although it seemed one but parasitic hum (the 100Hz give it away) from the trannies. When moving the wires around I could make the noise nearly go away but since I used some lang wires I'm going to rewire the amp first and move all wires away from the magnateic field of the trannies
Ralph
Ralph
Small update
I inserted the bottom of the amplifier backwards so that the trannies were on the same side als the inputs/outputs. I coorected this so that the magnetic interference is minimal and I made all the wires as short as possible.
Salas:
I found the wiring schematic that came with the pcb and connected it accordingly. The pcb does have it's own grounding but it concerns not input/output
Here's the part I'm cuurently concerned with. When connecting the aleph to the pre amp out of my sudgen amp I get an increase of humm, when I connect I to the "tape out" (which is unfortunately not controled by any means of attenuation so I cannot use it) there is no increase of hum. Where do I start seaching now.
I inserted the bottom of the amplifier backwards so that the trannies were on the same side als the inputs/outputs. I coorected this so that the magnetic interference is minimal and I made all the wires as short as possible.
Salas:
I found the wiring schematic that came with the pcb and connected it accordingly. The pcb does have it's own grounding but it concerns not input/output
Here's the part I'm cuurently concerned with. When connecting the aleph to the pre amp out of my sudgen amp I get an increase of humm, when I connect I to the "tape out" (which is unfortunately not controled by any means of attenuation so I cannot use it) there is no increase of hum. Where do I start seaching now.
Attachments
Sorry,
but it seems I'm in a mary-go-around (or whatever the correct name is)
The humm increases the I short the input, it doesn't matter if it is connected to any device. Not connected: very low 50Hzhumm, shorted RCA definite increas, higher frequency in both channnels.
Is it an idea to separate the star ground for the channels ?
but it seems I'm in a mary-go-around (or whatever the correct name is)
The humm increases the I short the input, it doesn't matter if it is connected to any device. Not connected: very low 50Hzhumm, shorted RCA definite increas, higher frequency in both channnels.
Is it an idea to separate the star ground for the channels ?
Exactly, a visous circle.
So I seperated the common star to get a seperate ground for each seperatechannel (real dual mono). Now my left channel humms very very slightly without any input connections and when shorting the rca input it the humm completely disappearce, it so quit, it's almost eerie,. I'm a happy man with the left channel.
Now the right channel...., damn, here lies the problem. Whith no connection, slight humm, when shorting input, humm (like a andgry bug) !
I'm getting closer and closer. Because the separation of the ground there is now no connection from both stars to the mainsground, how can I connect both grounds to mains ground and still keep both ground seperate (my gutfeeling says a diodenetwork should do the trick)
Ralph
So I seperated the common star to get a seperate ground for each seperatechannel (real dual mono). Now my left channel humms very very slightly without any input connections and when shorting the rca input it the humm completely disappearce, it so quit, it's almost eerie,. I'm a happy man with the left channel.
Now the right channel...., damn, here lies the problem. Whith no connection, slight humm, when shorting input, humm (like a andgry bug) !
I'm getting closer and closer. Because the separation of the ground there is now no connection from both stars to the mainsground, how can I connect both grounds to mains ground and still keep both ground seperate (my gutfeeling says a diodenetwork should do the trick)
Ralph
Aleph 5 Hum
I also got a hum problem.
I put two PCB in one case (stereo...), one transformer (750KVA), one capacitor bank (12 X 22,000mfd), star ground and 5 ohm thermistor.
But I have hum! When I disconect one input cable, hum disappears...
So, would it be better to connect the two RCA grounds together and then to the star ground?
Would it help to connect the two output grounds together and then to the star ground?
But it plays wonderfully...
Thanks.
I also got a hum problem.
I put two PCB in one case (stereo...), one transformer (750KVA), one capacitor bank (12 X 22,000mfd), star ground and 5 ohm thermistor.
But I have hum! When I disconect one input cable, hum disappears...
So, would it be better to connect the two RCA grounds together and then to the star ground?
Would it help to connect the two output grounds together and then to the star ground?
But it plays wonderfully...
Thanks.
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