Author Topic: Please advice! Hum issues!  (Read 1137 times)

Offline terfyo

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Please advice! Hum issues!
« on: October 08, 2019, 07:55 »
Would like to seek advice from all the gurus out there!

Introduction of equipment;
Krell KSA200s [Krell]
Audio Research LS8 [ARC]
Vienna Acoustics Baby Beethoven Grand [VA]

So there is the hum problem.
when i have the Krell, without any inputs, only connected to the VAs, turn it on, a little buzzing here and there, probably some transistor rush, etc. not really audible from a distance.

so now, i connect the ARC outputs (unbalanced) to the Krell (unbalanced), dang, the hum starts. The ARC does not have any inputs connected to it at all. this is basically a preamp to power amp test. of course, when i am using unbalanced inputs on the krell, i will need to put in the shorting pins to the XLR inputs as stated in the owner's manual.

Both ARC and Krell are connected to the same power strip, so i think that kills the ground loop issues.
I've checked continuity between the ARC chassis and the Krell chassis, there is no issue.

Any thoughts?
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

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Re: Please advice! Hum issues!
« Reply #1 on: October 08, 2019, 10:41 »
The KSA is already an oldie but regardless you should not hear buzz or what so ever when power on.
Suggest that you open up to check for loose joints first.

Offline jaffrie

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Re: Please advice! Hum issues!
« Reply #2 on: October 08, 2019, 10:46 »
Btw have you tried powering the KSA directly from the wall socket ?

Offline terfyo

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Re: Please advice! Hum issues!
« Reply #3 on: October 08, 2019, 12:16 »
Yes. Have tried direct UK to IEC from wall socket.
The amp by itself without any inputs doesn't have any hums.

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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

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Re: Please advice! Hum issues!
« Reply #4 on: October 08, 2019, 13:13 »
Wait let's start all over again. Has the preamp & amp been with you for a long time or ?

Offline terfyo

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Re: Please advice! Hum issues!
« Reply #5 on: October 08, 2019, 13:18 »
Wait let's start all over again. Has the preamp & amp been with you for a long time or ?
Has always been with me. For many years already.
Until recently when I moved place to Hougang...

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

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Re: Please advice! Hum issues!
« Reply #6 on: October 08, 2019, 13:38 »
OK let's start with the simplest first. Open up the inter connect to check on soldering also confirm that ground is not touching signal pin of rca. At times nuts happens where the ground wire comes detached. If all ok then open up your ARC preamp to check the same at the rca socket & ground wire to the pcb.

Cheers

Offline terfyo

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Re: Please advice! Hum issues!
« Reply #7 on: October 08, 2019, 13:51 »
I've checked the RCA interconnects last night. Switched out the Interconnects as well. The ICs are fine.

I'll probably head on to check the preamp.
I do have an Easter electric MINIMAX dac with preamp function as well. So I connected it directly to the power amp and the result was the same humming. Just louder than the ARC.

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

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Re: Please advice! Hum issues!
« Reply #8 on: October 08, 2019, 14:19 »
Just to be sure use another IC & if the same then problem is in the amp.
Capacitors drying up can also cause hum but you can only check condition via ESR meter.
Whose it might just be a loose wire or solder in the amp.

Offline aero88

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Re: Please advice! Hum issues!
« Reply #9 on: October 08, 2019, 15:16 »
Hi, if your equipments need repair, can pm me.
I know a few good technicians.

Offline terfyo

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Re: Please advice! Hum issues!
« Reply #10 on: October 09, 2019, 08:47 »
Hello to all,
I have solved the hum issue but i need some explanation as to why this solution works.
Perhaps somebody can explain to me the logic behind it.

I was recommended by a technician to lift the ground for the preamp, which should solve the problem.
by lifting the ground, i would tape ground pin at the iec inlet of the preamp so that when the power cord is plugged in, the ground is not connected.
Well, this does not solve the issue and as soon as the amp is powered on, even when the preamp is not powered on, the hum sets in.

However, when i "lifted the ground" for the power amp, (of course with the preamp grounded), the hum is totally gone!
I made sure to check that the power amp chassis is grounded to the preamp chassis, also made sure that the power amp chassis is grounded to earth using a multi-meter, before turning the power amp on.

Any possible explanation as to why this can work?

Cheers. ??? ???
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

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Re: Please advice! Hum issues!
« Reply #11 on: October 09, 2019, 09:23 »
Hi Terfyo, you mean the earth ground from the poweramp is lifted and the hum issue gone?

Offline terfyo

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Re: Please advice! Hum issues!
« Reply #12 on: October 09, 2019, 09:26 »
Hi Terfyo, you mean the earth ground from the poweramp is lifted and the hum issue gone?
Yup. That's exactly what I did.
Only at the IEC power cord there. of course, the picture shows the preamp, but i did it for the power amp, couldn't take a photo because it was a hell lot of weight.


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« Last Edit: October 09, 2019, 09:28 by terfyo »
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

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Re: Please advice! Hum issues!
« Reply #13 on: October 09, 2019, 09:33 »
Terfyo, so you lifted the ground for both preamp and poweramp right?

Offline terfyo

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Re: Please advice! Hum issues!
« Reply #14 on: October 09, 2019, 09:35 »
Terfyo, so you lifted the ground for both preamp and poweramp right?
Nope, at the end of the day, the preamp is grounded, but the power amp is lifted.
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