I isolated the tabs on the regulators on the protection board. The hum is barely audible on the test bench but it's still there. Now I'm seeing some 60hZ garbage when I connect the scope (USB POS). I connected the amp with a power cord with no ground pin. The 60hZ garbage is gone on the scope but the hum is still there when hooked to a PC.
PS. It's dead silent with no input connected.
PS. It's dead silent with no input connected.
I found that the speaker return is best sent to chassis/main cap return point.
But , even using the OPS speaker ground return produced no errata.
PS - but it would actually produce measurable AC at high levels.
Better for G1/G2 to just have the OP switching "garbage" minus the
much larger speaker current pulses.
OS
I twisted the speaker return wire in with the rail feeds. I remember seeing AndrewT recommend that for noise cancellation. I think he recommends running the return back through the rail feed grounds too.
Yes I'm running single supply and single bridge. I was running dual bridges up until I had my first supply fizzle from a bad bridge.
Time for a test drive at home! Hopefully my preamp will keep the hum from my PC down.
You just passed "mile marker one". 🙂
-Dead silent with nothing connected. All you should hear is the input pair junction
noise out of a tweeter (real low- you need to have your ear right to it).
The PC issue I have explored (and solved). My OEM's actually did worse in
this area.Tried 2 PC's , one with onboard sound and one with a creative - same
"shat".
Same ground reference (same power strip) was the best non- isolated power
configuration - but a little hum was still there.
I have radio shacks isolator now , hook the PC to a separate house circuit ,
audio on it's own power strip .... unreal sound.
Still , a non-optimal setup ( Toslink optical IS optimal - NO electrical).
OS
I'm getting 60hZ noise with just my Nad preamp hooked up. I forgot to bring a meter home. I'm not sure if the signal grounds are earth grounded in it or not. If we can get this noise issue resolved this will be an amazing amp. It's exactly like Valery's CFA-CFPX2 at low volumes(other than the noise). It leaves it behind at high volume.
Not just because I designed /built it , But mine "leaves behind" just about
everything I have repaired or owned. 😱
I'm actually cutting <40hz out of my listening to be able to push my daytons
to 150W+... at this level , this amp doesn't even reach 40C ("break a sweat")
Need " a shelving HPF" to break 150 (below).
Sound card just puts out 2v p-p , the amp has another 6-9db more headroom
(or more).
OS
Attachments
My Klipcsh' are so sensitive I can't be in the same room as them at half volume. Sounds excellent but I can hear my mouse scroll wheel through the speakers. Any idea why these are so sensitive? Another odd thing I've noticed, I get noise with RCA cables connected to the amp but the other end open. If I touch the case it goes silent.
And Nad V1.3 '' accuphase update'' function with double op amp servo.or perhaps a super Nad
with 'Accuphase' coming?
with 'Accuphase' coming?
You have a grounding issue. I have a stand alone CDROM that I use for testing. Whenever I have a grounding issue I can hear the little indicator light cycling on on off. Fix the grounding issue and the sound goes away. I see you have a ground lift utilizing a 35A bridge. Do you have a resistor in that circuit? If so, try removing the resistor and see that changes anything.
I have a 10 ohm resistor on it. I'll unhook it and see what happens. This reminds me of a car amp when the RCA connector has been smashed off the circuit board. The sound the same when they loose audio ground.
Please don't torch me....my slew masters and val's tubsumo have been running without a connection to the power plug ground. I did need to jumper the ground lift on the slew master front end boards. My speaker return is to the output board. These amps are dead silent with sensitive speakers.
Almost every time I put something together I think I have the grounding worked out perfectly only to find I need to do something that is not intuitive to make the system quiet. I am sure this is due to my ineptitude but Oh well....live and learn
Almost every time I put something together I think I have the grounding worked out perfectly only to find I need to do something that is not intuitive to make the system quiet. I am sure this is due to my ineptitude but Oh well....live and learn
I just tried your experiment.
Real cheap 1$ store stereo RCA cable -
I do get a barely noticeable buzz .
I have to actually pass over a wall switch or lamp cord to hear it ,
this cable is picking up radiated AC fields.
Better thick 10$ RCA stereo cord-
NO hum at all - silence .... even with it right over the top of my trafo
(biggest radiated field I could think of).
Wrapped this better RCA cable right around another active toriod -
- I could hear a faint hum. But , I was actually making a turn
around a trafo core !! 😱 Not too bad ??
Hummm - I wish I had some type of graphical way besides photo's
or a long-winded description to help you copy my earthing scheme.
It's better than my HK or pioneer (radiated field sensitive - hum).
As far as the PC as source -
I've had cheaper PC's/soundcards that exhibited HDD/peripheral audio
noise. None of my homebuilt Antec SMPS's are that bad - but they are
not perfect.
My CD player has an analog PS , quietest of all the sources.
OS
I've got an APC ups beside the computer. That's likely the AC I'm picking up with open cables. I can hear 60hZ if a speaker wire gets too close to it with the amp off. I've got an Antek supply in my PC too.
I didn't mean that my example was one to follow just that often grounding for least noise is not what I expect it to be.
Yes grounding can be a nightmare. I keep a tester cable around with the ground pin broken off. That's my first test when I suspect ground issues.😀 Trying to get things to work in a vehicle with all the stray magnetic fields and multiple grounds have taught me that.
Experiments ....
I just tried a heavier , thicker "audiophile" mini stereo plug to
my sound card A real short one , too.
I had no hum/buzz , but a slight "harshness" that would come and go.
Gone ! Very noticeable SQ improvement. Screw this ... OPTICAL !!
Dirty ol' digital , messin' with my super clean amp. 😀
edit - I still have exceptional ears at 51. Objective background "ghost noises"
would come and go - now they are even more pronounced.
OS
I just tried a heavier , thicker "audiophile" mini stereo plug to
my sound card A real short one , too.
I had no hum/buzz , but a slight "harshness" that would come and go.
Gone ! Very noticeable SQ improvement. Screw this ... OPTICAL !!
Dirty ol' digital , messin' with my super clean amp. 😀
edit - I still have exceptional ears at 51. Objective background "ghost noises"
would come and go - now they are even more pronounced.
OS
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I'd like to go coaxial digital but that likely wouldn't help with the hum. Eventually I'd like to figure out how to decode HDMI and do room correction.
coax still has an electrical ground , some buffer it .... but it is still electrical.
Cables have shielding 🙁 trying to keep something OUT.
Light don't need no (electrical) shielding. 🙂
OS
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