speaker noise

[pyonc]

Hi friends, How do you remove your speaker hum and buzz, if any? I hear very audible noise not only from the woofers but from mi/high drivers of my 4343 speakers when I turn up the volume of Crown amps: Crown DC-300 Series II for woofers, Crown D150A II for M/HF. Active crossover Ashly XR001 for this bi-amp set-up.
Is this simply ground loop issue or any other problem? Just curious. Any feedback and comment on the possible fix are welcome.

[Ruediger]

You may have a "pin 1 problem". There is plenty of information about it, it even has its own website.

All your consumer gear which is connected to the preamp should not be connected to mains ground. It will float at some potential. Cinch cable shield should pull all of these boxes to the same potential. A thick shield has a small resistance, which is good here.

Disconnect the preamp and all the gear connected to it from the crossover. Connect the crossover with open inputs to the amps and see what happens. What happens when you short-circuit the crossover's inputs? You should get the pro gear (crossover and amps) clean (noise-free).

From here on it depends on your particular setup. Do some educated experiments and let us know.

Ruediger

[BMWCCA]

You may have a "pin 1 problem". There is plenty of information about it, it even has its own website.

I'm guessing that would assume you're using XLR connectors. Regardless, at the end you have to be unbalanced TS 1/4-inch into the Crowns. What I've found is that there's a wide degree of variance between diameters of 1/4-inch plugs and often the sleeve/ring isn't making good contact inside the jack on the Crown. Wiggle your input cables while in position and see if it helps the hum. If it does you can either go inside the Crown and tighten the contacts on the jack, or find plugs that fit tighter.

Another issue could be your pre-amp or sources. You didn't mention what you're using there or if you tested those for the source of the hum. You could also be magnifying the noise with improper matching of the amps to the pre-amp. The Crown input attenuators should be set so that your pre-amp operates around mid-range on its volume control at your normal listening level. With volume control at 12-o'clock then adjust the Crown attenuators to where the SPL is about as loud as you'd ever run the system. This will help keep the noise floor of the system as low as possible.

[pyonc]

I'm guessing that would assume you're using XLR connectors. Regardless, at the end you have to be unbalanced TS 1/4-inch into the Crowns. What I've found is that there's a wide degree of variance between diameters of 1/4-inch plugs and often the sleeve/ring isn't making good contact inside the jack on the Crown. Wiggle your input cables while in position and see if it helps the hum. If it does you can either go inside the Crown and tighten the contacts on the jack, or find plugs that fit tighter.

Another issue could be your pre-amp or sources. You didn't mention what you're using there or if you tested those for the source of the hum. You could also be magnifying the noise with improper matching of the amps to the pre-amp. The Crown input attenuators should be set so that your pre-amp operates around mid-range on its volume control at your normal listening level. With volume control at 12-o'clock then adjust the Crown attenuators to where the SPL is about as loud as you'd ever run the system. This will help keep the noise floor of the system as low as possible.

Thanks a lot for your practical guide. Let me try and report back. Preamp is JBL SG520, and this excellent preamp (yes, excellent!) is definitely not the source of the hum. So, let me try your first suggestion.

[Mr. Widget]

To sleuth the source of your hum, disconnect everything in the system. Hook up the speakers to the amps and listen for hum... it should be silent. Next add the interconnects and the crossover... if you now have hum, investigate the signal wiring scheme and the power grounding. If/when this is quiet add your preamp and finally the sources.

The most common problem is due to the use of balanced pro audio gear with unbalanced home gear... but it could be something else.


Widget

[pyonc]

To sleuth the source of your hum, disconnect everything in the system. Hook up the speakers to the amps and listen for hum... it should be silent.

Widget

Well, I did as suggested, and I hear this audible hum from the Crown amps even the volume all the way down (yes, both of them (DC300 II, DC150A)!
Nothing from the preamp. Then, is this the amp issue? They are in fairly good condition, though.

[pyonc]

The most common problem is due to the use of balanced pro audio gear with unbalanced home gear... but it could be something else.

Widget

Well, I switched the active crossover from Ashly XR1001 (balanced XLR) to 5234A (unbalanced RCA). And the amps are the same Crowns with unbalanced TS 1/4. So, all unbalanced from the source (5234A) to preamp SG520 (unbalanced) to power amps Crowns (again unbalanced). And the outcome? Much reduced hum not only from the amps but from the speakers. Maybe thanks to synchronized "unbalanced" from the source to the amps?

[Mr. Widget]

Well, I switched the active crossover from Ashly XR1001 (balanced XLR) to 5234A (unbalanced RCA). And the amps are the same Crowns with unbalanced TS 1/4. So, all unbalanced from the source (5234A) to preamp SG520 (unbalanced) to power amps Crowns (again unbalanced). And the outcome? Much reduced hum not only from the amps but from the speakers. Maybe thanks to synchronized "unbalanced" from the source to the amps?

It shouldn't be reduced, it should be silent. The fact that your amps have hum by themselves is an indication of "issues"... I have found that vintage equipment is frequently problematic... in some cases it is simply poor design but usually it is an indication that your equipment needs a little tech love.


Widget

[pyonc]

It shouldn't be reduced, it should be silent. The fact that your amps have hum by themselves is an indication of "issues"... I have found that vintage equipment is frequently problematic... in some cases it is simply poor design but usually it is an indication that your equipment needs a little tech love.
Widget

I think so, and I'm tempted to upgrade the amps. Well, frankly speaking, I have avoided doing so, partly because of our forum member 4313b's comment in another thread that JBL used Crown amps exclusively for its 43xx series studio monitor series... By the way, I mainly listen to jazz records on Linn LP12 turntable and there is no hum whatsoever from the turntable thanks to its well-managed earth lead.

[BMWCCA]

Well, I switched the active crossover from Ashly XR1001 (balanced XLR) to 5234A (unbalanced RCA). And the amps are the same Crowns with unbalanced TS 1/4. So, all unbalanced from the source (5234A) to preamp SG520 (unbalanced) to power amps Crowns (again unbalanced). And the outcome? Much reduced hum not only from the amps but from the speakers. Maybe thanks to synchronized "unbalanced" from the source to the amps?

There's no reason to use the XLR jacks on the Ashly if the rest of your system is unbalanced. Just run cables terminated in 1/4-inch plugs into the Ashly and run 1/4-inch out to 1/4-inch into the Crowns. I've been doing it that way for years and my PS400/200 are dead quiet at the speakers. My DC300A-II and D150A-II would sometimes transmit a hum but once I found cables that fit tightly into the 1/4-inch jacks, the hum disappeared.

Here's the Ashly manual if you need guidance for connection or wiring. If you use simple mono phone plugs you won't need to do anything beyond just plugging them in. http://www.ashly.com/products/manuals/xr-1001-r10.pdf

[pyonc]

There's no reason to use the XLR jacks on the Ashly if the rest of your system is unbalanced. Just run cables terminated in 1/4-inch plugs into the Ashly and run 1/4-inch out to 1/4-inch into the Crowns. I've been doing it that way for years and my PS400/200 are dead quiet at the speakers. My DC300A-II and D150A-II would sometimes transmit a hum but once I found cables that fit tightly into the 1/4-inch jacks, the hum disappeared.

Here's the Ashly manual if you need guidance for connection or wiring. If you use simple mono phone plugs you won't need to do anything beyond just plugging them in. http://www.ashly.com/products/manuals/xr-1001-r10.pdf

That's great! If you don't mind, could you upload the picture of the back panel of your Ashley and the cable connections? Seeing is believing!

[BMWCCA]

That's great! If you don't mind, could you upload the picture of the back panel of your Ashley and the cable connections? Seeing is believing!

Hah! That's not really possible right now but here's a shot from the Ashly web site showing the 1/4-inch inputs and outputs right next to the XLRs:

[pyonc]

Hah! That's not really possible right now but here's a shot from the Ashly web site showing the 1/4-inch inputs and outputs right next to the XLRs:

Got it! I've just tried, and hear much reduced hum just like 5234A, but not "silent" as Widget suggested. I guess some degree of such hum is inevitable from the old amps like Crown DC300.

[Mr. Widget]

Got it! I've just tried, and hear much reduced hum just like 5234A, but not "silent" as Widget suggested. I guess some degree of such hum is inevitable from the old amps like Crown DC300.

Older designs and less refined designs will have some degree of noise (hiss), but should not hum. That said it is rare to find vintage gear that is truly operating to spec.

You may still want to play with your system grounding. I've found that higher quality "hospital grade" outlets can offer a more solid ground and improve system grounding. I would also try plugging everything into the same outlet to make sure everything that is grounded us at the same potential. There is also the temporary test of lifting grounds on some equipment. If this helps you can install isolation transformers on the gear that requires lifting and then ground them for safety.


Widget

[pyonc]

Older designs and less refined designs will have some degree of noise (hiss), but should not hum. That said it is rare to find vintage gear that is truly operating to spec.

You may still want to play with your system grounding. I've found that higher quality "hospital grade" outlets can offer a more solid ground and improve system grounding. I would also try plugging everything into the same outlet to make sure everything that is grounded us at the same potential. There is also the temporary test of lifting grounds on some equipment. If this helps you can install isolation transformers on the gear that requires lifting and then ground them for safety.


Widget

Thanks a lot for your insight on this issue. Actually I've got all the power cords plugged in the APC outlet, as you suggested. Compared with the very audible hum at the time of posting this issue initially, I now see the hum about 50% reduced. Sooner or later I'm planning to find the kind of amps that match well with 4343s, such as Mcintosh 2255.