speaker hum and power conditioner

[pyonc]

Hi guys,

I'm driving my vintage 4343 with two power amps in a bi-amp mode, with JBL preamp.
What I hear first after turning on the amp switches is this audible hum from the speakers before I playing the music.
Basically I have no problem lisening to music once they're turned on.
Still I wonder if this power conditioner can reduce hum or buzzing from the speakers.
I know some sort of speaker hum is inevitable, but is there any way you can reduce or "remove" it by using a power conditioner?
Some say power conditioner is just waste of money, citing no big difference.
What do you think? Do you want to recomend a power conditioner to address this "hum" issue?
What is the best power conditioner on the market, if you want to recommend?
Thanks for your feedbacks or comments based on actual use.

[Odd]

I do not think you need a power conditioner, if you have old pre and power amps, they need recap. New capacitors.
Can also be bad cables or connectors.

[hjames]

Tell us more about your current amps and stack of gear ...
What crossover are you using to biamp with?
What about the Audio sources you use in that system-
Is it connected in any way to CableTV or television signals?


Hi guys,

I'm driving my vintage 4343 with two power amps in a bi-amp mode, with JBL preamp.
What I hear first after turning on the amp switches is this audible hum from the speakers before I playing the music.
Basically I have no problem lisening to music once they're turned on.
Still I wonder if this power conditioner can reduce hum or buzzing from the speakers.
I know some sort of speaker hum is inevitable, but is there any way you can reduce or "remove" it by using a power conditioner?
Some say power conditioner is just waste of money, citing no big difference.
What do you think? Do you want to recomend a power conditioner to address this "hum" issue?
What is the best power conditioner on the market, if you want to recommend?
Thanks for your feedbacks or comments based on actual use.

[JuniorJBL]

Wall power is typically one of the last places to look (unless you are using a ground lift somewhere in the system or your outlets are not grounded). The other suggestions above are good places to start. It is of course is not the speakers, they just play what they get.

Try to turn on just the amps and see if there is any noise, if not move to the next component in line with them and turn it on and listen for the hum. This can help you get a handle on where the problem can be.

[Mr. Widget]

It could be the equipment, but is very likely a ground loop. As others have said, I doubt a power conditioner will help. Ground loop issues are quite common with bi-ampped systems, especially if you are mixing pro-audio active crossovers with consumer electronics.

You should plug all equipment into the same AC circuit so that all equipment is at the same ground potential. You may need to lift the ground of one or more pieces of gear or you may need to use isolation transformers in the audio chain.


Widget

[pyonc]

Thanks for your kind replies.:)
Okay, this is my finding, based on your feedbacks and comments:

1. I first turned on the power switch of almost new Crown DC300A for LF, and heard just a little audible hum from the speakers.
The hum was a bit louder when I turned the volume up to its maximum.
2. Next I turned on almost new Crown IC150A for M/HF, and heard almost the same amount of audible hum as DC300A.
The hum was a bit louder when I turned the volume up to its maximum.
3. The hum was overall just a little more audible when I turned up the volumes of DC300A and DC150A all the way down to their maximum.
4. Now comes this interesting discovery.:blink: I turn on the vintage preamp JBL SG520, with the active crossover Ashly XR1001.
The hum grew more audible when I slowly turned up the volumes of both power amps, but with the preamp volume at its maximum low.
When I turned up the preamp volume, I didn't hear any change in the audible level of the hum, though.

So, do you think this audible hum is more or less related with this vintage preamp?
Thanks much for your diagnostics in advance.

[BMWCCA]

Okay, this is my finding, based on your feedbacks and comments:

1. I first turned on the power switch of almost new Crown DC300A for LF, and heard just a little audible hum from the speakers.
The hum was a bit louder when I turned the volume up to its maximum.
2. Next I turned on almost new Crown IC150A for M/HF, and heard almost the same amount of audible hum as DC300A.
The hum was a bit louder when I turned the volume up to its maximum.
3. The hum was overall just a little more audible when I turned up the volumes of DC300A and DC150A all the way down to their maximum.
4. Now comes this interesting discovery.:blink: I turn on the vintage preamp JBL SG520, with the active crossover Ashly XR1001.
The hum grew more audible when I slowly turned up the volumes of both power amps, but with the preamp volume at its maximum low.
When I turned up the preamp volume, I didn't hear any change in the audible level of the hum, though.

So, do you think this audible hum is more or less related with this vintage preamp?
Thanks much for your diagnostics in advance.

First, I assume you mean D150A and not IC150A. We are talking power-amps, right? And the JBL is the only pre-amp, right?

The "volume" controls on the Crown amps are actually input attenuators so if the hum increases as you rotate these controls clockwise, the hum is likely from your sources upstream of the amps.

I have no idea what you mean by "almost new" twenty-year-old amps. Have they been re-certified by Crown?

You might also check that the sleeve (ring) of your amp input-cable connectors fit tightly in the 1/4-inch jacks on the amps. Many cables or adapters are undersized these days and don't fit well. They make a ground connection for the amp, too. Try wiggling the plugs in the jacks and see if that changes the hum at all.

That's just my experience from using similar amps for years.

[JuniorJBL]

Do you have other gear that you can swap in for testing?
How are you going from RCA to XLR/TRS Balanced?
Are you staying balanced to the amps?
Try lifting the ground to the Ashly......

[hjames]

Again, what are your SOURCES?
Are there any Cable TV or Satellite TV sources in the system?
Are you using XLR connectors or Phone connectors on the ASHLY crossover?
Do you have a ground line connecting your preamps and power amps together?

[pyonc]

Again, what are your SOURCES?
Are there any Cable TV or Satellite TV sources in the system?
Are you using XLR connectors or Phone connectors on the ASHLY crossover?
Do you have a ground line connecting your preamps and power amps together?


Thanks, hjames. No cable TV or sat. TV sources. Only audio sources.
As for Ashly connectors, they're XLR with 1/4 TRS male cables.
And I use the ordinary power outlets with surge protector.
Regarding your question on "ground line", I'm not sure what you mean exactly. :blink:
Except for preamp and CD player, all power cords of source gear are three-pronged plugs with ground pin.

[hjames]

Thanks, hjames. No cable TV or sat. TV sources. Only audio sources.
As for Ashly connectors, they're XLR with 1/4 TRS male cables.
And I use the ordinary power outlets with surge protector.
Regarding your question on "ground line", I'm not sure what you mean exactly. :blink:
Except for preamp and CD player, all power cords of source gear are three-pronged plugs with ground pin.

Okay - when I built my 4341 biamp system a few years ago, I actually rack mounted the amps and crossover, and used some heavy copper single-strand wire to connect the chassis of that gear together. The wire was from a 4 foot piece of copper household wiring - heavy single gauge copper grounding. In the picture below, the heavy copper wire has a white plastic jacket so it doesn't short anything out.

To fully remove hum from my gear, at one point I used a power adapter to connect the 3 prong power cord to 2 prong and lift the ground.

At the very bottom of the rack I used an Adcom ACE power conditioner (it also did a controlled power down when I shut the system off) - and you can see the device on the very far left plugged into the rack had the 3 prong adapter. I "believe" that was the Ashly, but its been 2 years so I'm not absolutely sure. I used a pair of Adcom GF-555 Power amps.



60490

[pyonc]

That looks impressive. So, what's the outcome? No hum or noise from your 4341s?

[JuniorJBL]

Thanks, hjames. No cable TV or sat. TV sources. Only audio sources.
As for Ashly connectors, they're XLR with 1/4 TRS male cables.
And I use the ordinary power outlets with surge protector.
Regarding your question on "ground line", I'm not sure what you mean exactly. :blink:
Except for preamp and CD player, all power cords of source gear are three-pronged plugs with ground pin.

Lift the ground to the Ashly. Use a 2 prong (wall side) to 3 prong adaptor.

How are the cables made that go from the preamp to the ashly?

The pre is RCA only correct?

[pyonc]

Lift the ground to the Ashly. Use a 2 prong (wall side) to 3 prong adaptor.

How are the cables made that go from the preamp to the ashly?

The pre is RCA only correct?

Thanks. Yes, RCA only.
I'm going to try a ground lifter for this preamp 2-prong power plug with no ground pin.

[hjames]

That looks impressive. So, what's the outcome? No hum or noise from your 4341s?
Notice I ran the inputs on the right side of the rack, power amp outputs went down the left.

I would occasionally get some hum, usually cured by reseating the connectors!
It was old gear and connectors get dirty from time to time.

Of course, after 7 years of the system, I broke it all down, sold the speakers as is, and parted out the rack about 2 years ago,
tho I did keep a spare Ashly for possible use.
Even the adcoms are now gone - replace with B&K amps ...

Yes, get a 3 to 2 power connector and lift ground for the Ashly!

[JuniorJBL]

Thanks. Yes, RCA only.
I'm going to try a ground lifter for this preamp 2-prong power plug with no ground pin.


Do you have the connector made per Ashly specs and tie Negitive to Ground or use a mono phone jack to run it in an unbalanced input?

http://www.ashly.com/products/manuals/xr-1001-r10.pdf

[pyonc]

Well, like you mentioned, I found out the major cause of this hum was the 'ground loop', after all.
When I used ground lift plugs for the power amps, Ashy crossover and the Linn turntable, all with three-pronged plugs with ground pins,
I was pleasantly surprised to find about 90% of the hum was gone!:)
What little hum was from the amps, but I could not hear the bothersome hum from the speakers anymore.
Thanks so much for your great feedback and advice on this hum issue.:applaud: