I think I fried ANOTHER speaker amp?

[Ross H]

OK...hoping there is an electrical guru out there who can help me out.

I have owned a pair of NS-10s for several years. In that time I have had lots of trouble with amps powering them.

I first bought an Alesis RA300 (or something like that) which worked great for a while and then all of a sudden I started getting sizzing egg frying sounds in the left channel. This behavior was intermittent at first but eventually became constant and rendered the set up useless.

I then bought a new Alesis RA300 to replace the old one and within a week, THE SAME BEHAVIOUR started in the LEFT channel again. I immediately took the amp back and was told that the Alesis amp is fairly "low grade" (which I kinda knew already)and that it was not out of the question that I got a second defective amp...I had a hard time buying into this but "sh*t happens". I was guided that the right amp for the job was a Hafler P3000. This amp has performed great for about a year.

Low and behold the LEFT channel recently started acting up. When I shut the amp down, the LEFT speaker would release a "shhhhhh" sound similar to a tire being deflated. After 10 seconds or so it would go away. Then, randomly I started getting cracks and pops when I turned the amp switch on.

Now as of today...when I fire up the amp the LEFT speaker sucks in rapidly and creates a loud noise and the amp is turned all the way down. So it looks like once again I have fried another LEFT channel.

What is going on here????? Can anyone tell me what I am doing wrong? This is starting to get quite expensive!!!!

Here are the specs:
-Yamaha NS-10M Studio - speakers 8 ohms program 60 watts max 120
-Hafler P3000 400 watt - amp inputs on back of amp are labeled 4-8ohms
-Prolink by Monster Cable - Standard 100 Compact High Resolution Speaker cable with magnetic flux tube. These are banana style plugs.

Originally I would have the amp power all the way up and the power switch on, plugged into a power strip, and would turn on the amp by flipping the power strip switch. When I stared getting the erratic behavior I started turning the volume down and shutting off the amp manually, then the power strip. This did not seem to correct any further damage as it got worse.

The amp is located in an Argosy desk and has plenty of ventilation.

I switched the right speaker cable with the left speaker cable and the problem still existed.

I switched the right speaker with the left and the behavior is the same.

So I believe I have ruled out a damaged cable? I believe I have ruled out something within the speaker "electronics"? It looks like it is coming down to another toasted amp?

Could it be an OHM thing I don't understand that eventually gets the best of an amp?

Could it be the speaker cables themselves allowing for some eventual failure?

If ANYONE has any suggestions, I am all ears????

Thanks,

Ross

[Matt Syson]

Hi
Probably your mixer putting out HF (greater than 20KHz) or your 'fancy' speaker cables are encouraging your amps to oscillate. I had this with an ADCOM amp and short speaker cables (they weren't fancy just short.) A longer pair of cables worked fine.
You need a good 'scope on the output to find out what is going on.
Matt S

Tried some wire instead of monster stuff? I'm not being a wise guy but don't trust monster - what the heck is a flux tube? You want some nice stranded 12 gauge wires!

The HF suggestion is also good, check your output with a scope.

[dementedchord]

looking at the inputs to the amp is a good place to start as was suggested... i noticed though that you dont say you're eating tweeters... which if it were strictly speaking an oscillation problem you would be doing and probably long before roaching an amp... dc on the input could be a problem though again eating speakers (woofer this time) could be expected... strange problem... keep us posted...

[Geoff_T]

Originally Posted by Lou Judson

Tried some wire instead of monster stuff? I'm not being a wise guy but don't trust monster - what the heck is a flux tube? You want some nice stranded 12 gauge wires!

The HF suggestion is also good, check your output with a scope.

Hi

As a matter of principle I won't buy Monster products as I frequently find them monopolising racks of cables and minimising my choice. I think that they are overpriced and, as suggested, regular cable works just as well or the difference is so darn minute you'd have a job hearing it.

It's not commonly known that interference and instability causing issues can enter the amplifier via its output. It'll race around the negative feedback loop and come out again, refreshed and with a vengeance.

I use a Hafler P3000 on my test area (driving NS10's like yours) and have had no issues with it for all the years it's been there. I'm deeply suspicious of your cabling, especially as the same fault reoccurs with three different amps and suggest changing the speaker leads for something less exotic.

You may find the problem goes away.

[Wavebourn]

May be that "flux tube" is a magnetic core that makes a transformer from wires, like in the EM filter? In such case RF presented on input of the amp (or generated by the amp because of the complex load impedance) will fry output transistors, but will not go to tweeters.

[tINY]

You might try an impedance sweep on your NS10s. There might be a component in the crossover gone bad....



-tINY

[Matt Syson]

Hi
The theme of 'left channel going faulty' is kind of interesting. How long are the speaker cables (are they the same?). Is one routed near the amp input cables or a source of RF (computer/ UPS or whatever)?
Where has Ross gone (he hasn't replied to the posts yet)?
Has the monster cable eaten him as well?
Matt S

[Ross H]

OK...

I have replaced speakers in these NS-10s. It's been frustrating, but I always thought is was coming from an occassional loud spike, which could be the case or it could be related to this amp issue.

Could my soldering job create some internal speaker short effecting crossover etc. which would eventually burn up the amp?

I will replace my "fancy" speaker cables as they have been involved in the "chain" since the day I bought the speakers. In thinking back...It would be probable that the speaker cables at some point and time could have been mixed up and used on either the right or left speaker (studio moves, maintenance, new desks, etc.) so the fact that the left channel is always the channel that goes bad makes me think it is not a cable issue, but it is inexpensive to replace to rule that out.

The main stereo signal from my DA goes into a Mackie Big Knob that it used for speaker A/Bing. I have had no problems with the other speakers. Something new to add...
I also have Monster brand cables going from the speaker management outputs to the input of the amp. The output of the speaker management is 1/4" to 1/4" inputs on the amp. The cable however are 1/4" on one end and RCA on the other. Therefore I have been using cheap Radio Shack RCA to 1/4" adaptors. Could the adaptors be creating a dynamic getting into the amp causing failure?

Last advice needed...I now need to have this amp repaired. Rumor is Hafler is out of business? Other than going to a local electronics shop, is there a recommendation for getting the amp repaired back to "quality" working condition? Also, it might make sense to have the speakers evaluated and resoldered...any recommendations on who to send them to for evaluation and possible repair?

Ross
Baltimore MD

[Ross H]

Matt,

Speaker cables are the same length about 12' long each. The amp is mounted in Argosy desk on the right side. I have dual monitors on top of the desk so the left channel of the amp is just below the right edge of the speaker. The amp is mounted at a 45 degree angle (desk design).

The NS-10s flank the dual monitors. Just far enough away that the magnets in the NS10s dont discolor the screens. No UPS or computer near the amp. The additional length of cable is loosly rolled and laying inside of the argosy desk.

Ross

[Matt Syson]

Hi Ross
Sorry I can't help with 'stateside' fix it recommendations.
Go for 'ordinary' cable when the amp and speakers have been checked out and if you can, get someone with an oscilloscope to come by and check it over for any oscillations. Or measure the length of cable you need and get the repairer to check amp, cable and speakers together, although this won't rule out some wierdness from the controller. I don't know if any of your kit has a switchmode power supply but a good dose of HF could be getting around although as posted earlier I would expect it to fry your tweeters first.
Good luck
Matt

[Ross H]

Thanks to all...delighted with the "frequency" in which people respond in this forum. I will post back with my results in the future.

Ross