Author Topic: Please advice! Hum issues!  (Read 1140 times)

Offline wizardofoz

  • Trade Count: (+23)
  • Full Member
  • Posts: 12712
  • Dont take life so seriously, nobody gets out alive
Re: Please advice! Hum issues!
« Reply #15 on: October 09, 2019, 10:47 »
Please DON'T use TAPE to lift a ground permanently as you are asking for trouble. Get your power cable modified or do it internally in the equipment but only if it is safe to do so based on manufacturer confirmation.


WARNING lifting grounds of equipment designed to have them should really only be used for problem determination by competent technicians. The ground is there for SAFETY RESONS...dont risk your life.
I have a pile of stuff that pushes out squiggly waveforms from smaller squiggly waveforms that sometimes come from 1's and 0's.
It's wonderful to behold as long as you don't let the magic smoke out.

Life is short! Enjoy the music while it plays, when it stops, there might be a chair for you...or  maybe not.

Offline Boxerfan88

  • Trade Count: (+1)
  • Full Member
  • Posts: 1517
  • Life begins at 7000rpm
Re: Please advice! Hum issues!
« Reply #16 on: October 09, 2019, 13:25 »
WARNING lifting grounds of equipment designed to have them should really only be used for problem determination by competent technicians. The ground is there for SAFETY RESONS...dont risk your life.

Agree 100%, be careful !

Very interesting scenario, interested to know root cause...watching this thread...
Soekris dac1541 | DA&T A38  | Usher MD2+X616 | Orisun DD12 | Samsung PS50B850 | Elementa BAC 2500 |
Yammy RXA3030 | RPi3+Kodi | BDP-S5100 | PC+foobar2000 | Chromecast

Offline aero88

  • Trade Count: (0)
  • Jr. Member
  • Posts: 12
Re: Please advice! Hum issues!
« Reply #17 on: October 09, 2019, 14:28 »
Terfyo, i have pm you his contact.
Please let him check.

Offline jaffrie

  • Trade Count: (0)
  • Full Member
  • Posts: 235
Re: Please advice! Hum issues!
« Reply #18 on: October 09, 2019, 15:53 »
Lifting ground is a no no especially for power amps. If you've been using the same set up without issues before why is it happening now ?
It is clear now that you've got a ground loop issue somewhere along the chain.

Offline terfyo

  • Trade Count: (0)
  • Full Member
  • Posts: 321
    • Facebook Profile
Re: Please advice! Hum issues!
« Reply #19 on: October 09, 2019, 16:19 »
Lifting ground is a no no especially for power amps. If you've been using the same set up without issues before why is it happening now ?
It is clear now that you've got a ground loop issue somewhere along the chain.

Understand that it is very dangerous to do that.
So the puzzling thing is that when i lift the ground of the preamp, the hum still persists.
When i lift the ground of the power amp with the preamp grounded, the hum disappears.

This is especially weird when only the pre and the power amp is connected together.
If i just power on the power amp without any inputs, there is no hum (just some slight hissing).
Just when i plug in the interconnects, starts to hum, even when the preamp is not turned on.

Oh btw, did i mention? if i just connect the interconnects, and the interconnects are not connected to the preamp, there is no hum.
I tried another preamp, there's hum as well.
Stereo:
CEC TL-51XR + Pro-Ject Xpression 3 + MusicHall USB 1 (AudioNote PH1)
Eastern Electric MiniMax DAC / Beresford T7510 (Self Modded)
Audio Research LS8
Krell KSA200s / Krell KSA150 / AudioSpace AS8i / Emotiva UPA-200
Vienna Acoustics Baby Beethoven Grand / Thiel CS2.4 / Aurum Cantus Leisure 2

Offline aero88

  • Trade Count: (0)
  • Jr. Member
  • Posts: 12
Re: Please advice! Hum issues!
« Reply #20 on: October 09, 2019, 17:15 »
Terfyo, there is nothing wrong with your preamp.
Is your power amp problem.
Maybe transistors shorted.
Don't let it power on for too long, or else more damages may happen.

Offline jaffrie

  • Trade Count: (0)
  • Full Member
  • Posts: 235
Re: Please advice! Hum issues!
« Reply #21 on: October 09, 2019, 18:38 »
You brought up a good point aero 88. My initial thoughts wasto check loose solder joins etc then the caps first there after transistors.
Being a class A amp the next culprit could be the vas transistors. In any case thing it's better to get it service if you not diy competant.

Cheers

Offline terfyo

  • Trade Count: (0)
  • Full Member
  • Posts: 321
    • Facebook Profile
Re: Please advice! Hum issues!
« Reply #22 on: October 09, 2019, 19:26 »
You brought up a good point aero 88. My initial thoughts wasto check loose solder joins etc then the caps first there after transistors.
Being a class A amp the next culprit could be the vas transistors. In any case thing it's better to get it service if you not diy competant.

Cheers
I've actually had it checked by a tech who gave it a clean bill of health.
Zero hum when tested at his place.
But the hums came back when I brought the amp back home and plugged it into my setup.

Sent from my SM-N975F using Tapatalk

Stereo:
CEC TL-51XR + Pro-Ject Xpression 3 + MusicHall USB 1 (AudioNote PH1)
Eastern Electric MiniMax DAC / Beresford T7510 (Self Modded)
Audio Research LS8
Krell KSA200s / Krell KSA150 / AudioSpace AS8i / Emotiva UPA-200
Vienna Acoustics Baby Beethoven Grand / Thiel CS2.4 / Aurum Cantus Leisure 2

Offline jaffrie

  • Trade Count: (0)
  • Full Member
  • Posts: 235
Re: Please advice! Hum issues!
« Reply #23 on: October 09, 2019, 22:14 »
Are you able to check your wall socket if the earth is properly grounded ?
The other option is to get the tech to drop by your house to assist in checking.
Yep chasing down hum can be a real pain. On my system There's only 2 sockets
& the wires are individually runned from the breaker just to this sockets.










Offline terfyo

  • Trade Count: (0)
  • Full Member
  • Posts: 321
    • Facebook Profile
Re: Please advice! Hum issues!
« Reply #24 on: October 09, 2019, 22:29 »
Are you able to check your wall socket if the earth is properly grounded ?
The other option is to get the tech to drop by your house to assist in checking.
Yep chasing down hum can be a real pain. On my system There's only 2 sockets
& the wires are individually runned from the breaker just to this sockets.
Yes. The sockets are grounded properly.
I've checked this.
I'm now checking with Krell US for then to confirm that cheating the earth at the amp is safe.
If they confirm it's safe, then I'll leave it that way. Since all the hum is gone.

Sent from my SM-N975F using Tapatalk

Stereo:
CEC TL-51XR + Pro-Ject Xpression 3 + MusicHall USB 1 (AudioNote PH1)
Eastern Electric MiniMax DAC / Beresford T7510 (Self Modded)
Audio Research LS8
Krell KSA200s / Krell KSA150 / AudioSpace AS8i / Emotiva UPA-200
Vienna Acoustics Baby Beethoven Grand / Thiel CS2.4 / Aurum Cantus Leisure 2

Offline jaffrie

  • Trade Count: (0)
  • Full Member
  • Posts: 235
Re: Please advice! Hum issues!
« Reply #25 on: October 09, 2019, 23:59 »
If that's the case to be safe never touch the chassis of the amp when powered up.

Cheers

Offline wizardofoz

  • Trade Count: (+23)
  • Full Member
  • Posts: 12712
  • Dont take life so seriously, nobody gets out alive
Re: Please advice! Hum issues!
« Reply #26 on: October 10, 2019, 00:24 »
I assume you have changed the IC's between the amp and pre and ruled out any issue there. Are you using balanced XLR or RCA?
I have a pile of stuff that pushes out squiggly waveforms from smaller squiggly waveforms that sometimes come from 1's and 0's.
It's wonderful to behold as long as you don't let the magic smoke out.

Life is short! Enjoy the music while it plays, when it stops, there might be a chair for you...or  maybe not.

Offline terfyo

  • Trade Count: (0)
  • Full Member
  • Posts: 321
    • Facebook Profile
Re: Please advice! Hum issues!
« Reply #27 on: October 10, 2019, 07:21 »
Yes, have switched out the ICs between pre and amp.
Tried both SE and XLR.
Stereo:
CEC TL-51XR + Pro-Ject Xpression 3 + MusicHall USB 1 (AudioNote PH1)
Eastern Electric MiniMax DAC / Beresford T7510 (Self Modded)
Audio Research LS8
Krell KSA200s / Krell KSA150 / AudioSpace AS8i / Emotiva UPA-200
Vienna Acoustics Baby Beethoven Grand / Thiel CS2.4 / Aurum Cantus Leisure 2

Offline aero88

  • Trade Count: (0)
  • Jr. Member
  • Posts: 12
Re: Please advice! Hum issues!
« Reply #28 on: October 18, 2019, 13:27 »
So what is their reply from US?

Offline terfyo

  • Trade Count: (0)
  • Full Member
  • Posts: 321
    • Facebook Profile
Re: Please advice! Hum issues!
« Reply #29 on: October 18, 2019, 23:00 »
favorable.
as long as there is an IC connected to another equipment that is ground, it is safe to lift the ground from the power amp.

oh btw, i have recently bought the EMI Power Line Tester from an MO and realized that when my airconditioner is not turned on, the reading shows 450mV there about. However, when my AC is turned on, with the compressor cut in, the reading is 1,500mV.
That is some real noise there. I have tested almost every other socket in the house and am getting about the same reading.
I'm using the Starmex Inverter system.

Anybody got any ideas on how to reduce the noise injection into the power line when the AC is running?

Stereo:
CEC TL-51XR + Pro-Ject Xpression 3 + MusicHall USB 1 (AudioNote PH1)
Eastern Electric MiniMax DAC / Beresford T7510 (Self Modded)
Audio Research LS8
Krell KSA200s / Krell KSA150 / AudioSpace AS8i / Emotiva UPA-200
Vienna Acoustics Baby Beethoven Grand / Thiel CS2.4 / Aurum Cantus Leisure 2