What frequency does the humming have?
In your drawing you have connected just one power supply ground to star ground. In reality you connected both grounds (from upper and lower half) of the power supply to the sg, right?
Try to connect all metal parts to safety ground, even if this helps just a bit against hf noise. But it's security wise more than nice to have.
Try to rotate the toroid, if you get lesser humming.
Try to separate low signal wires from power signal wires. Try not to run them in parallel, crossing is OK.
Get all party with high magnetic fields away from those with gentler signals, e.g. toroid and coils from input wires, input transformers,...
Good luck!
PS: Take your time and look at the original First Watt Amps pictures at 6moons, not just the M2's. Try to learn how Nelson connected everything, until you know every wire's beginning and end.
Zen Mod also has many pictures for inspiration and meditation.
Regards,
Matthias
In your drawing you have connected just one power supply ground to star ground. In reality you connected both grounds (from upper and lower half) of the power supply to the sg, right?
Try to connect all metal parts to safety ground, even if this helps just a bit against hf noise. But it's security wise more than nice to have.
Try to rotate the toroid, if you get lesser humming.
Try to separate low signal wires from power signal wires. Try not to run them in parallel, crossing is OK.
Get all party with high magnetic fields away from those with gentler signals, e.g. toroid and coils from input wires, input transformers,...
Good luck!
PS: Take your time and look at the original First Watt Amps pictures at 6moons, not just the M2's. Try to learn how Nelson connected everything, until you know every wire's beginning and end.
Zen Mod also has many pictures for inspiration and meditation.
Regards,
Matthias
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Thanks for the input Matthias
I have had an F5 and F6 in the past
The grounding method used on those amps was different
Those methods were also employed in the M2 as well ( bus style ) and a few other earthing methods trialled - and no difference in hum resulted
It's always the same ( constant )
So I'm leaning towards the JFets for now and as time allows I will also enclose the torodial in an enclosing can and follow up with the MuMetal for the Edcore transformers
Fingers crossed
I will keep all updated as they are implemented
------------
A quick post regarding the hum frequency in Hertz
Downloaded a new App for the iPad called " Frequency " just to test and report back - so I don't know how accurate it will be
Basically stuck the iPad into the horn and tested the frequency with the App - and the results are
Midrange Horn - Hertz frequency reading fluctuates from 107 Hz to 250 Hz
Bass Horn - Hertz frequency is a constant level of 250 Hz
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Based on my recent experience with my Aleph-X monoblock amp, I would recommend AGAINST a CL60 between PSU ground to AC mains ground, unless you are solving a very specific problem. This is how mine was arranged and then one of my psu caps died from a short. This drove voltage onto the psu ground plane, which then drove the opposite psu rail to higher than normal voltage.
The CL60 lit up and flamed 
and it took FAR too long for the AC fuse to blow because the CL60 slowed everything down. Luckily, no damage was done to the pcb components. It sure smelled bad for a while, though. My wife wasn't happy with the fireworks or the lasting smell. I let the magic smoke out for sure! I would have much preferred for the voltage on the ground plane to have popped the fuse immediately and shut the whole thing down!
Based on my recent experience with my Aleph-X monoblock amp, I would recommend AGAINST a CL60 between PSU ground to AC mains ground, unless you are solving a very specific problem. This is how mine was arranged and then one of my psu caps died from a short. This drove voltage onto the psu ground plane, which then drove the opposite psu rail to higher than normal voltage.
In my M2 build I never had a CL60 connected to the PSU in any variation only installed one from the IEC input switch to Safety Earth ( now removed from the safety earth line as per Zen Mods tip on an earlier post )
And of course a CL60 is connected on the active power line to act as a soft start
Eric,
This is not normal. There should not be any leakage current flowing throw the CL60 to lite it up. It is just a ground lift.
There was another member having the similar issue with his F5 Turbo. He tracked it down to a shorted turn from the toroid to the chassis. The leakage was not enough to blow the fuse but strong enough to burn for excessive time. You may want to investigate regardless to whether you keep the CL60 or not.
This is not normal. There should not be any leakage current flowing throw the CL60 to lite it up. It is just a ground lift.
There was another member having the similar issue with his F5 Turbo. He tracked it down to a shorted turn from the toroid to the chassis. The leakage was not enough to blow the fuse but strong enough to burn for excessive time. You may want to investigate regardless to whether you keep the CL60 or not.
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Exactly! When the CL60 sits between PSU ground (zero volts) and AC Mains ground (also zero volts), there is usually no voltage at all across the CL60. BUT, when one of my caps died, it shorted, thus the PSU ground was no longer at zero volts - it started climbing (up to about 10v). NOW there is a problem between AC Mains ground (always zero volts) and the PSU ground (which was now reading +10v DC). Thus, the CL60 sitting in the middle of these two voltages started to behave like a light bulb - and it wasn't very happy with this situation.
Additionally, my PSU rails are designed for +22v and -22v rails. It was the positive rail that had the failed cap, so it drove the PSU ground point from zero to near +10v. Thus, my negative PSU rail now had -32v potential on it! I guess I got lucky, as the potential could have gone as high as -44v which would have started to toast components on the PCB.
My advice is for a heavy gauge direct connection from PSU ground to AC mains ground with a "just big enough" fuse on your transformer primary. If you use a CL60 to remove ground loop/ac hum, my advice is to use the CL60 between PSU ground and signal ground.
Additionally, my PSU rails are designed for +22v and -22v rails. It was the positive rail that had the failed cap, so it drove the PSU ground point from zero to near +10v. Thus, my negative PSU rail now had -32v potential on it! I guess I got lucky, as the potential could have gone as high as -44v which would have started to toast components on the PCB.
My advice is for a heavy gauge direct connection from PSU ground to AC mains ground with a "just big enough" fuse on your transformer primary. If you use a CL60 to remove ground loop/ac hum, my advice is to use the CL60 between PSU ground and signal ground.
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CL60 between PSU and signal ground is probably not an option either. imagine all the return amperes going through the CL60 continuously.
In both cases (Eric's and Luvdunhill's), the fuse wasn't blown due to the the leakage not big enough. Perhaps the 2 diodes and one resistor is still the preferred way to prevent ground loops.
In both cases (Eric's and Luvdunhill's), the fuse wasn't blown due to the the leakage not big enough. Perhaps the 2 diodes and one resistor is still the preferred way to prevent ground loops.
Eventually got the amp running, got a bit of a hum (speakers are 100db efficiency) and running through a Pass B1 buffer. I'll start tracking the hum down tomorrow but am a little worried by a lack of volume. Using an AT OC9ml/ii through a Salas phono stage set to 82 or so db gain I'm having to use 2 to 3 o clock on the volume control to get a reasonable level in a 5.5m by 3.3m room. From my Rega Apollo cd player the volume setting is nearer 12 o clock.
Any thoughts, do I need a pre with some gain or do I need to check the M2 again? It biased to zero DC offset with a couple of turns on the variable resistor after 30 minutes of warm up.
Any thoughts, do I need a pre with some gain or do I need to check the M2 again? It biased to zero DC offset with a couple of turns on the variable resistor after 30 minutes of warm up.
have you any way of producing then measuring simple sine signal ?
say that you feed 400-500Hz in M2 , measure it ,set to (say) 1V input then measure what's coming out ?
PC with simple proggie will do for sine , while plain DMM (set to Vac) will do for measuring ...... no need for absolute accuracy , we need just relative one
no need for load on output for that
say that you feed 400-500Hz in M2 , measure it ,set to (say) 1V input then measure what's coming out ?
PC with simple proggie will do for sine , while plain DMM (set to Vac) will do for measuring ...... no need for absolute accuracy , we need just relative one
no need for load on output for that
let's say that this one will do for ya
http://www.diyaudio.com/forums/pass-labs/244106-lsk-pre-baf-2013-a.html#post3665608
http://www.diyaudio.com/forums/pass-labs/244106-lsk-pre-baf-2013-a.html#post3665608