Glad to hear you worked it out Dean 
I hadn't seen this and was just about to post you this link as I thought it might help. http://www.diyaudio.com/forums/pass-labs/121228-f5-power-amplifier-298.html#post2923127
Since you have sorted the problem it's probably irrelevant but it might help someone else who reads this thread
Tony.
I hadn't seen this and was just about to post you this link as I thought it might help. http://www.diyaudio.com/forums/pass-labs/121228-f5-power-amplifier-298.html#post2923127 Since you have sorted the problem it's probably irrelevant but it might help someone else who reads this thread
Tony.
Hey Tony.
Thanks for that last link, I could not make exact sense of it though. Is there something I should be trying with my setup?
As i mentioned, the hum doesn't come from the amp or the miniDSP when either is used with other devices, only when they are connected together.
Could this be an impedance matching issue?
Does anybody have any suggestions of what I might try next?
Cheers
Dean
Thanks for that last link, I could not make exact sense of it though. Is there something I should be trying with my setup?
As i mentioned, the hum doesn't come from the amp or the miniDSP when either is used with other devices, only when they are connected together.
Could this be an impedance matching issue?
Does anybody have any suggestions of what I might try next?
Cheers
Dean
Hi Dean, is the problem with the MiniDsp present when only one channel is connected to it? If not (but it is there when more than one channel is connected) then the problem may be similar to the problem that dvb-projekt had.
I'm not versed enough in impedance matching problems to know whether that may be an issue. Does the minidsp run off a powersupply that has a safety earth connection or is it a wall-wart type supply? If it has safety earth, you *may* need an earthloop breaker.
Tony.
I'm not versed enough in impedance matching problems to know whether that may be an issue. Does the minidsp run off a powersupply that has a safety earth connection or is it a wall-wart type supply? If it has safety earth, you *may* need an earthloop breaker.
Tony.
The issue is constant under all conditions. So when i run 1 channel from the dsp to the amp with the matching channel shorted on the amp I still get the hum.
The dsp runs from a wall-wart style 12v1a supply with no safety earth. I have tried many different supplies including a regulated bench top supply and still have the same issue. I have been able to lessen the amount of noise using different supplies and a miniDC but the buzz is still clearly audible in all cases.
Cheers
Dean
The dsp runs from a wall-wart style 12v1a supply with no safety earth. I have tried many different supplies including a regulated bench top supply and still have the same issue. I have been able to lessen the amount of noise using different supplies and a miniDC but the buzz is still clearly audible in all cases.
Cheers
Dean
I have been reading the thread you suggested Tony and have had a chance to try some different star earthing config's. Still have the buzz but learning more.
One thing I know for sure is that with only 1 channel connected to a single trafo I have no hum, when I connect the second channel (psu+amp) I get the hum back. I am still trying some more star earth options and will report back.
From the thread i found ESP's site and copied the diagram attached.
Will the values stated for the 'Ground Loop Breaker' be appropriate for my setup?
I have 3 x 400vA Taroidal's running 2 x Audiosector LM4780 PSU/AMP kits each.
Cheers
Dean
One thing I know for sure is that with only 1 channel connected to a single trafo I have no hum, when I connect the second channel (psu+amp) I get the hum back. I am still trying some more star earth options and will report back.
From the thread i found ESP's site and copied the diagram attached.
Will the values stated for the 'Ground Loop Breaker' be appropriate for my setup?
I have 3 x 400vA Taroidal's running 2 x Audiosector LM4780 PSU/AMP kits each.
Cheers
Dean
Attachments
Hi Dean, I don't think that the earth loop breaker is going to help (unless one of the other components you are connecxting to is also earthed to safety earth. The loop occurs through the interconnects and out through the mains wiring.
The bridge should be fine, 400V 35A is much more than the mains can deliver, and it is mains level faults you are concerned about with safety earth. I found that I had to go to an 18 ohm resistor instead of 10 ohms to get a reasonable amount of attenuation (my earth loop was between my PC and my Amp.
A quick question, If you only use one channel of each amp connected to separate transformers do you still get the hum? ie turn on say two of the traffo's but only use one channel of each amp connected to that traffo.
Tony.
The bridge should be fine, 400V 35A is much more than the mains can deliver, and it is mains level faults you are concerned about with safety earth. I found that I had to go to an 18 ohm resistor instead of 10 ohms to get a reasonable amount of attenuation (my earth loop was between my PC and my Amp.
A quick question, If you only use one channel of each amp connected to separate transformers do you still get the hum? ie turn on say two of the traffo's but only use one channel of each amp connected to that traffo.
Tony.
Hey Tony.
Good question and that's the point shedding the most light at the moment. If I disconnect the second psu/amp combo from the transformer the buzzing stops. But when I add the second channel to the trafo, the noise is back.
Just working on a drawing of current wiring and will post asap for clarity.
Dean
Good question and that's the point shedding the most light at the moment. If I disconnect the second psu/amp combo from the transformer the buzzing stops. But when I add the second channel to the trafo, the noise is back.
Just working on a drawing of current wiring and will post asap for clarity.
Dean
Here's the drawing of the current wiring. As you can see I have followed others advice and redone 'some' of the star earthing.
Can anybody suggest others things that need changing?
Also note that the 2 PSU's on each transformer are wired in parallel.
Its when I disconnect one of these psu/amp combo's that the buzzing stops.
Is it OK to wire two of these PSU's in parallel?
Have I somehow created an earth loop by doing this?
PS. Cant hurt to install the 'Loop Breaker' to avoid any issues with other 'earthed equipment' I might use later so I may go ahead with that anyway.
Can anybody suggest others things that need changing?
Also note that the 2 PSU's on each transformer are wired in parallel.
Its when I disconnect one of these psu/amp combo's that the buzzing stops.
Is it OK to wire two of these PSU's in parallel?
Have I somehow created an earth loop by doing this?
PS. Cant hurt to install the 'Loop Breaker' to avoid any issues with other 'earthed equipment' I might use later so I may go ahead with that anyway.
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I see 8 secondary tappings coming from each transformer.
Are these transformers, quad secondaries? I.e. all channels are isolated from each other.
If these are dual secondary transformers then the two channels supplied by each transformer are not isolated. A dual transformer feeding two PSUs and two amplifier creates a potentially enormous loop in the grounding wiring. Three dual sec transformers could have three big loops.
The two channels of amplification must be laid out (adjacent or on top of each other) to minimise the loop area.
Even doing this will not eliminate the hum at the output. This hum will vary with the various interconnections you adopt.
A monoblock is much easier to build hum free. A stereo is difficult to get hum free.
A 6channel is a challenge I will never rise to.
Are these transformers, quad secondaries? I.e. all channels are isolated from each other.
If these are dual secondary transformers then the two channels supplied by each transformer are not isolated. A dual transformer feeding two PSUs and two amplifier creates a potentially enormous loop in the grounding wiring. Three dual sec transformers could have three big loops.
The two channels of amplification must be laid out (adjacent or on top of each other) to minimise the loop area.
Even doing this will not eliminate the hum at the output. This hum will vary with the various interconnections you adopt.
A monoblock is much easier to build hum free. A stereo is difficult to get hum free.
A 6channel is a challenge I will never rise to.
Good Question.
a) 1 channel, shorted input = no buzz
b) 1 channel, dsp input = no buzz + small hiss
c) 2 channel, shorted input = buzz
d) 2 channel, dsp input = buzz + small hiss
The hiss when connecting the dsp is very low level and requires my ear right next the the tweeter.
More importantly the buzz starts as soon as two channels are connected to the same transformer.
a) 1 channel, shorted input = no buzz
b) 1 channel, dsp input = no buzz + small hiss
c) 2 channel, shorted input = buzz
d) 2 channel, dsp input = buzz + small hiss
The hiss when connecting the dsp is very low level and requires my ear right next the the tweeter.
More importantly the buzz starts as soon as two channels are connected to the same transformer.
Posted just before I saw your post Andrew.
Here is a new drawing showing the Antek AS-4222 Dual Secondary Trany.
Each PSU/AMP board is simply paralleled with the other.
With only 1 transformer turned on would this not act like a simple stereo amp?
Should I be using only 1 PSU board with two AMP boards?
Cheers
Dean
Here is a new drawing showing the Antek AS-4222 Dual Secondary Trany.
Each PSU/AMP board is simply paralleled with the other.
With only 1 transformer turned on would this not act like a simple stereo amp?
Should I be using only 1 PSU board with two AMP boards?
Cheers
Dean
I have not found any way to get 2channel hum free operation using dual PSUs from a dual secondary transformer.
Either quad secondaries or single PSU in a two channel amplifier is the only recommendation I can give.
If anyone can give better advice then please do shout out.
I need the answer.
Either quad secondaries or single PSU in a two channel amplifier is the only recommendation I can give.
If anyone can give better advice then please do shout out.
I need the answer.
Its nice to hear you still get challenged by this bobby too Andrew.
I definitely considered 6 mono-blocks but the cost was way too high, my f5 build will be but with only 2 its much more probable.
Peter Daniel suggested turning the gain down. Just looking for his post now. Is this an option and would anybody suggest how to try it?
I definitely considered 6 mono-blocks but the cost was way too high, my f5 build will be but with only 2 its much more probable.
Peter Daniel suggested turning the gain down. Just looking for his post now. Is this an option and would anybody suggest how to try it?
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