My aleph P1.7 is more or less finished and sound marvellous but I have a humm with this.
I use a attenuator boards made using relays and precision resistors in balanced mode and when I increase the volume the hum increase.
I use board from PCB design and dantimax attenuator.
I have connected 1 ground to each channel to the chassis from the main board of Aleph p1.7 and only one ground goes between the 1.7 to the board attenuator. I think that I can’t have a ground loop with this configuration.
Do you have any suggestion?
Best regard’s
I use a attenuator boards made using relays and precision resistors in balanced mode and when I increase the volume the hum increase.
I use board from PCB design and dantimax attenuator.
I have connected 1 ground to each channel to the chassis from the main board of Aleph p1.7 and only one ground goes between the 1.7 to the board attenuator. I think that I can’t have a ground loop with this configuration.
Do you have any suggestion?
Best regard’s
Hi,
mains powered equipment with exposed conductive parts must have a safety earth. This safety earth connects the conductive parts back to the electrical distribution board.
A fault current to safety earth will blow the fuse and isolate the faulty equipment from the mains Live input.
If this is new to you, then give up building mains powered equipment until you have been trained to stop killing yourself.
mains powered equipment with exposed conductive parts must have a safety earth. This safety earth connects the conductive parts back to the electrical distribution board.
A fault current to safety earth will blow the fuse and isolate the faulty equipment from the mains Live input.
If this is new to you, then give up building mains powered equipment until you have been trained to stop killing yourself.
Andrew
Sorry for my bad english but I know what is a safety earth and for proof you I can always reply to you
You have not understand my question and it's normal because sometime I speek like a spanish cow.
Meanwhile I have finded a part of the problem.
I continue but I feel that i will have maybe some help from you.
Best regards.
Sorry for my bad english but I know what is a safety earth and for proof you I can always reply to you
You have not understand my question and it's normal because sometime I speek like a spanish cow.
Meanwhile I have finded a part of the problem.
I continue but I feel that i will have maybe some help from you.
Best regards.
OK OK enough joking around. Lets see. You have a lot of hum and
it gets louder when the pre volume is turned up.
Do you have any hum from the power amps alone with no input
connected? It should be very quiet even when you put your ear
right by the speaker cone. Or at least you should be able to hear
nothing if your ear is a foot away from the speaker cones.
If the hum is only when preamp connected, try to disconnect all inputs
to the preamp. Do you still have hum? If not, then there is a ground
loop between the pre and the source component. If there is hum with
the pre inputs disconnected, then there is a ground problem between
the pre and the power amp.
I had a similar thing... on my power amps I had the + and G connections
reversed. Not good. I'd say look for the same sort of thing. Either the
pre output has an error or the cable has an error (are they DIY cables??)
or the power amp input has an error in the connections. THey are
all balanced connections, no?
If they are balanced, it should be so quiet it's spooky. Don't give up
til you find your problem.
One more thing - you did separate your signal ground from chassis
ground with a thermistor as in the schematics didn't you?
W.
it gets louder when the pre volume is turned up.
Do you have any hum from the power amps alone with no input
connected? It should be very quiet even when you put your ear
right by the speaker cone. Or at least you should be able to hear
nothing if your ear is a foot away from the speaker cones.
If the hum is only when preamp connected, try to disconnect all inputs
to the preamp. Do you still have hum? If not, then there is a ground
loop between the pre and the source component. If there is hum with
the pre inputs disconnected, then there is a ground problem between
the pre and the power amp.
I had a similar thing... on my power amps I had the + and G connections
reversed. Not good. I'd say look for the same sort of thing. Either the
pre output has an error or the cable has an error (are they DIY cables??)
or the power amp input has an error in the connections. THey are
all balanced connections, no?
If they are balanced, it should be so quiet it's spooky. Don't give up
til you find your problem.
One more thing - you did separate your signal ground from chassis
ground with a thermistor as in the schematics didn't you?
W.
Oh and BTW nice work - very professional looking.
Also. Having the pre above the power amp is hindering the air
circulation and losing cooling of the power amp. Putting the power
amp above the preamp will give the same problem. There is supposed
to be unimpeded air flow up the fins of the heatsinks. But it's probably
not that big of a problem.
Also. Having the pre above the power amp is hindering the air
circulation and losing cooling of the power amp. Putting the power
amp above the preamp will give the same problem. There is supposed
to be unimpeded air flow up the fins of the heatsinks. But it's probably
not that big of a problem.
andrew and wayne325
Thank's for your reply.
Concerning my aleph 5, he is totaly quiet when he is connected alone. When the aleph P1.7 is connected I have the famous Humm, doenst matter if a source is connected or not. For the both (amp and preamp) I use a thermistor for separate my signal ground from chassis ground.
I use only Balanced connection between Amp/preamp.
Doesn't matter what kind of cable I use, the problem stay the same.
If I can reformuled my first question was.
I Use for cable my preamp two conductor shielded wire. I only connect the shield (the ground) in one of the cable : for example Input side I connect both signal/ground and in the other side I only connect the signal. Then I use one cable to connected the audio ground to the chassis. In this case It is important to isolate chassis ground from signal groud. But because there is always a but I use a Balanced mode with my famous two conductor shielded wire, not three conductor and I use the same configuration for connect. Example Input side (cabel 1) I connect both positive/ground and in the other side I only connect the positive (cabel 2) I connect both inverted/ground and in the other side I only connect the inverted then I use a one conductor wire to put the board on chassis.
I think in this case everything must be good.
Thank's for your reply.
Concerning my aleph 5, he is totaly quiet when he is connected alone. When the aleph P1.7 is connected I have the famous Humm, doenst matter if a source is connected or not. For the both (amp and preamp) I use a thermistor for separate my signal ground from chassis ground.
I use only Balanced connection between Amp/preamp.
Doesn't matter what kind of cable I use, the problem stay the same.
If I can reformuled my first question was.
I Use for cable my preamp two conductor shielded wire. I only connect the shield (the ground) in one of the cable : for example Input side I connect both signal/ground and in the other side I only connect the signal. Then I use one cable to connected the audio ground to the chassis. In this case It is important to isolate chassis ground from signal groud. But because there is always a but I use a Balanced mode with my famous two conductor shielded wire, not three conductor and I use the same configuration for connect. Example Input side (cabel 1) I connect both positive/ground and in the other side I only connect the positive (cabel 2) I connect both inverted/ground and in the other side I only connect the inverted then I use a one conductor wire to put the board on chassis.
I think in this case everything must be good.
Hi Wayne,
how safely can you work?
Can I tentatively suggest you temporarily disconnect the Thermistor from safety earth to audio ground. With the unit removed from the mains check that you have an open circuit between safety earth and audio ground.
With the interconnect plugged into the power amp, check again.
Now plug in the interconnect at both ends (both units still disconnected from the mains) and recheck.
Now carefully repeat these checks with the units plugged into the mains but both switched OFF.
Now switch on just the amplifier and measure the DC and AC voltages on the the audio ground to safety earth and at the speaker terminals. Switch on the source and check these voltages again.
This may isolate the problem or at least eliminate a ground loop as the culprit.
how safely can you work?
Can I tentatively suggest you temporarily disconnect the Thermistor from safety earth to audio ground. With the unit removed from the mains check that you have an open circuit between safety earth and audio ground.
With the interconnect plugged into the power amp, check again.
Now plug in the interconnect at both ends (both units still disconnected from the mains) and recheck.
Now carefully repeat these checks with the units plugged into the mains but both switched OFF.
Now switch on just the amplifier and measure the DC and AC voltages on the the audio ground to safety earth and at the speaker terminals. Switch on the source and check these voltages again.
This may isolate the problem or at least eliminate a ground loop as the culprit.
OK Andrew,
I have disconnected the thermistor from the safety earth to audio ground and the circuit it's now open.
I switch on the amp and preamp but the humm still the same.
At low level (-63db) you must put your ear close the cone speaker for hear something. At high volume (-5db) if I'm at 1 meter I can't hear the noise but with the max volume (-0db)I can hear the noise at 2 meters.
Now I will start your check process but what do you mean with this sentensce :With the interconnect plugged into the power amp
Best regards
I have disconnected the thermistor from the safety earth to audio ground and the circuit it's now open.
I switch on the amp and preamp but the humm still the same.
At low level (-63db) you must put your ear close the cone speaker for hear something. At high volume (-5db) if I'm at 1 meter I can't hear the noise but with the max volume (-0db)I can hear the noise at 2 meters.
Now I will start your check process but what do you mean with this sentensce :With the interconnect plugged into the power amp
Best regards
Gents,
Measuring voltages for ground loops doesn't work. THe voltages are
too small and they are not DC voltages.
Is you power amp balanced? I know the pre is balanced. If you have hum
it means you have a wrong connection somewhere. Check your signal
connections. Make sure you don't have - swapped with G or + swapped
with G. Are all your components connected to the same outlet?
Measuring voltages for ground loops doesn't work. THe voltages are
too small and they are not DC voltages.
Is you power amp balanced? I know the pre is balanced. If you have hum
it means you have a wrong connection somewhere. Check your signal
connections. Make sure you don't have - swapped with G or + swapped
with G. Are all your components connected to the same outlet?
Hi,
the reason for checking the audio ground to safety earth is to check for dangerous voltages in the amplifier.
There may be mains that would be earthed by the Thermistor that I suggested he remove.
The interconnect is the lead from source to amplifier. XLR plug?
Sorry for quoting the wrong name, hope it didn't confuse you.
the reason for checking the audio ground to safety earth is to check for dangerous voltages in the amplifier.
There may be mains that would be earthed by the Thermistor that I suggested he remove.
The interconnect is the lead from source to amplifier. XLR plug?
Sorry for quoting the wrong name, hope it didn't confuse you.
rbe43164 said:
With no signal in, if there is hum and it increases when volume increases, it means that input ground path would be picking up a small hum and ordering amplifiers to make it big. I guess so . . . I would try to make layout of all paralleled ground path instead of any serial path so that I could see the symmetry of left-right sides and left-right channels from the star ground point of view. Good luck.
I also have a problem with hum from the dantimax kit. I have connected the input card directly to the attenuator. I am quite sure that we're talking about some sort of ground loop on the relvol3 card (no sure).
Are there any means to find out if there is a ground loop?
From the input card to the attenuator card there are at least 3 connections to ground. Through the serial connection (5 ground pins), from the output of one channel on the input card (confusing) and from the PSU ground (the attenuator draws power from the input card).
This is before the preamp card is connected.
The humm in my cases has the 50Hz hum, and something more similar to white noise - or higher order noise.
thanks for any help
F
Are there any means to find out if there is a ground loop?
From the input card to the attenuator card there are at least 3 connections to ground. Through the serial connection (5 ground pins), from the output of one channel on the input card (confusing) and from the PSU ground (the attenuator draws power from the input card).
This is before the preamp card is connected.
The humm in my cases has the 50Hz hum, and something more similar to white noise - or higher order noise.
thanks for any help
F
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