HELP! 250TI distortion/feedback...

[Storm]

Argh. Don't know where to turn, so I will ask a question here.

I have my 250TI's setup and they were all good and running until I could hear feedback/distortion when all music is turned off through the tweeters.

I removed the audio cable that was connected to the amp to the preamp and the distortion was removed. I then replaced the cable with a different one, but the feedback is still there, loud and clear.

What the heck am I doing wrong?

:banghead:

Thanks, guys.

-Storm.

[johnaec]

By feedback, so you mean a loud squeal? If removing the cable between preamp and amp deletes it, then obviously, the problem is ahead of the speakers and amp, and should have nothng to do with the 250's... Is it possibly microphonics from a turntable cartridge?

John

[Storm]

Not a squel - a tiny buzzing sound...

No turntable in the system.

Just the amp, preamp, and the power conditioner, along with a CD player and a DirecTv tivo system.

Argh.

-Storm.

[SMKSoundPro]

is it coming from the tivo device? I have a horrible time with the catv converters at the bar. They induce all sorts of noisy stuff, ground hums...etc.

I have used 1:1 transformers with good luck.

Now if only the music service on the cable tv system was good quality! It is so compressed and thin and the sound of it drives the customers right out the door. The bartenders dont seem to mind as less customers mean less work...ARGH!

Seriously Storm, unplug any video stuff from your preamp to see if that chases down the offending noise.

I am SURE someone else will chime in to help. They always do.

Good luck.
Scott.

[sourceoneaudio]

The buzzing is A/C related. Did you just add the TiVo/Direct box? If so that could be the issue. Same as b4 with that Mac preamp, you have an A/C hum and it is being picked up by something. Is the TiVo box sitting on top of your TV, or close to it? Your TV is a noisy issue remember b4.

Another check, does it still do it with the TV off?

I helped another person with the same issue, and it was TV/Video related. He also had a CRT tube TV. (RADIATING NOISE FROM TUBE)

One other fix. You can try tying the gold ground tab/lug on the back of the Monster to the gold phono ground on the CA-5AII. Use a no: 10 wire with crimped on eyelets.

Time for a flat panel..............:blink:

Jeff
J/S-S1A :)

[Titanium Dome]

I don't run any external video cables into my system anymore, as they always introduce unwanted noise, whether one can hear it or not. It was impossible to avoid line noise unless I lifted the ground, risking death and destruction, or ran the cable through a Monster unit. (Yes, I'm writing that there was an audible AND visible difference.)

In any event, when I went HD, I bought a lowly Zenith Silver Sensor antenna and a Samsung SIR451 OTA Terresrtral HD receiver. I ran the analog RGB signal straight through to the CRT PJ and the optical audio out to the FAP T1+. With the passive, unamplified antenna, there's no grounding or other issues. The picture is crystal clear and the audio is much, much improved over cable or satellite. And I still have more channels than I can watch.

[boputnam]

When troubleshooting -
Look at the system as a stream ( or as a line) - Assume NOTHING.

Start in the middle...Almost perfect...

Start with ONLY the amp. Disconnect everything.
Turn the amp on, no inputs from anywhere - any noise?

Power down.

Connect the pre-amp, with nothing connected to it.
Power-up the amp and pre-amp - any noise?

Now, one by one, connect your input devices - try one at a time, and disconnect it if it is not the noise source.

Also, is everything on the same AC edison plug? If not, run an extension cord from the TV pile-of-crap to the audio racks - see if this remedies the symptom(s). If so, you will need to run everything to the same AC outlet. Been there, doing this... ;)

[WDJ]

What was the last thing you added/changed/did to the system before the offending noise showed up?

If your electrical plugs are not polarized, try flipping them over and reinserting them.

[Storm]

It must be the TV.

There is a slight buzz, but when I am 10 feet back -- cannot hear a thing.

Oh well, guess I need to save up for a plasma?

;)

-Storm.

[boputnam]

It must be the TV.

There is a slight buzz, but when I am 10 feet back -- cannot hear a thing.

TRY this...


Also, is everything on the same AC edison plug? If not, run an extension cord from the TV pile-of-crap to the audio racks - see if this remedies the symptom(s). If so, you will need to run everything to the same AC outlet. Been there, doing this... ;)

[opimax]

also try it w and w/o the surge/power supply

[sourceoneaudio]

Another 2 cents:

Storm,
You had the noise with the Mac preamp, and Nak. amp combo, and this was when the Mac preamp was very close to the Tube TV. You moved the Mac up a shelf and still had the noise. Then you swapped out the Mac for a Nak. preamp, and the noise was gone.

You still did not answer the question, is the
Direct Box a new addition?

Have you tried removing it from the system to see if the noise goes away if it is a new addition?

Have you shut the TV off, and did it go away?

If you have tried all of the above then I would say the TV is heading further south for the winter. :blink:

[Storm]

Nope, the directv box is not a new addition.

What TV do I get that won't interfere with the speakers?

Thanks.

-Storm.


Another 2 cents:

Storm,
You had the noise with the Mac preamp, and Nak. amp combo, and this was when the Mac preamp was very close to the Tube TV. You moved the Mac up a shelf and still had the noise. Then you swapped out the Mac for a Nak. preamp, and the noise was gone.

You still did not answer the question, is the
Direct Box a new addition?

Have you tried removing it from the system to see if the noise goes away if it is a new addition?

Have you shut the TV off, and did it go away?

If you have tried all of the above then I would say the TV is heading further south for the winter. :blink:

[hjames]

Nope, the directv box is not a new addition.

What TV do I get that won't interfere with the speakers?

Thanks.

-Storm.

TV doesn't interfere with speakers - but a picture tube can have a large magnetic field that can be picked up by other things.

But before you buy a New TV you might want to follow the tests Bo and I posted and be sure its the TV picture tube. If its a ground problem from Satellite or cable and you buy a new TV you will still have the noise, but be out the $$

[opimax]

If you did any of the suggestions could you post results of the individual tests?

Mark

[edgewound]

Move the pre-amp as far away from the TV as practical and below the top.

I could be the TV itself that you hear the buzz from...since you can't hear it from 10 feet away.

[sourceoneaudio]

TV doesn't interfere with speakers - but a picture tube can have a large magnetic field that can be picked up by other things.
Like equipment........:blink:

Dude, your driving me nutz. You only answered one of the questions I posted prior. Second like Heather said, TV's do not interfere with speakers. But speakers can interfere with a tube TV when speakers are not shielded, or speakers without Bucking Magnets applied, and tube TV's can cause issues with gear with the fields they produce. (IT IS NOT THE SPEAKERS)

Your speakers are not shielded so watch moving them close to that TV or you will be turning the tube to purple and green.

Back to the questions. Does the noise go away when the TV is OFF? It is easier to help you when you answer questions. ???

Your noise issues are very simple, it is either an A/C radiated hum, or a ground loop.

Have you tried my grounding suggestion? Second time asking.

If the noise is gone with the TV off there lies the problem. Also remember you did not have the noise when you switched too the Nak from the Mac, so something has changed, or you changed something ??

[edgewound]

Argh. Don't know where to turn, so I will ask a question here.

I have my 250TI's setup and they were all good and running until I could hear feedback/distortion when all music is turned off through the tweeters.
What the heck am I doing wrong?

:banghead:

Thanks, guys.

-Storm.


Hey Storm....

Is this buzzing unique to your newly acquired vintage 250ti's and wasn't present with your Altec's.

If so...maybe you have a rotten foam damping pad that lives inside the 044ti tweeters. When the foam pad rots it kind of turns to goo and runs into the voice coil gap making the tweeters sound distorted. If that's the case the 044ti's need to be carefully disassembled, cleaned and new damping pads installed.

Worth a look, because it can present itself as an electronics problem when in fact it's a speaker problem.

Hope that helps rule out other demons. Good luck:)

[Robh3606]

TV's do not interfere with speakers.

Well actually they can. It depends on how close the speakers are and how much of a stay field the TV put's out. I had to move my crossover in my center channel and re orient the board so the coils were 90 degrees to the stay field. I could turn on the TV and get a buzz from the speakers with the system off.

Rob:)

[edgewound]

Well actually they can. It depends on how close the speakers are and how much of a stay field the TV put's out. I had to move my crossover in my center channel and re orient the board so the coils were 90 degrees to the stay field. I could turn on the TV and get a buzz from the speakers with the system off.

Rob:)

Hey Rob...

You've just described a kind of Westlake Audio "PE Distortion":applaud:

[Storm]

Hey guys.

Sorry for the lack of response. I am in the middle of a move and it was laundry day today -- 8 loads of laundry.

;)

Here are some pictures of the current setup.

Thanks.

-Storm.

[Robh3606]

Hello Storm

Hey they look great!!

Rob:)

[hjames]

Hey guys.

Sorry for the lack of response. I am in the middle of a move and it was laundry day today -- 8 loads of laundry.

;)

Here are some pictures of the current setup.

Thanks.

-Storm.

Man - get the preamp the heck away from the TV - really - its the high gain point most susceptable to stray magnetic fields ... You really need a small rack or cabinet or something away from that TV. What's the black box on the Altec to the right of the TV?
Honest - a number of folks here have worked with equipment racks - you have to keep high gain devices like preamps away from hi noise devices like TVs (unless they are special magnetically sheilded TVs, and I'm guessing that one isn't).

[Storm]

Man - get the preamp the heck away from the TV - really - its the high gain point most susceptable to stray magnetic fields ... You really need a small rack or cabinet or something away from that TV. What's the black box on the Altec to the right of the TV?
Honest - a number of folks here have worked with equipment racks - you have to keep high gain devices like preamps away from hi noise devices like TVs (unless they are special magnetically sheilded TVs, and I'm guessing that one isn't).

That is the Nakamichi Amplifier.

Am I doing the preamp damage if I leave it the way it is?

Where should I put it?

;)

Thanks.

-Storm.

[edgewound]

That is the Nakamichi Amplifier.

Am I doing the preamp damage if I leave it the way it is?

Where should I put it?

;)

Thanks.

-Storm.

Nope...just move it far enough away to stop the maddening noise. Try underneath the TV...there might be sufficient shielding from the TV chassis.

Also...try moving that iPod.

[sourceoneaudio]

Hey Storm....

Is this buzzing unique to your newly acquired vintage 250ti's and wasn't present with your Altec's.

If so...maybe you have a rotten foam damping pad that lives inside the 044ti tweeters. When the foam pad rots it kind of turns to goo and runs into the voice coil gap making the tweeters sound distorted. If that's the case the 044ti's need to be carefully disassembled, cleaned and new damping pads installed.

Worth a look, because it can present itself as an electronics problem when in fact it's a speaker problem.

Hope that helps rule out other demons. Good luck:)

They did not have the noise when I had them. Tweets worked fine. Also if the VC assembly is glued down from what I understand they will get destroyed when taken apart. I could be wrong but I understand also most of them came this way. That is why JBL Japan never pulled mine apart.

It's that damn TV causing the issue. He still has not answered if the noise is gone when the TV is off. ??????????? Hello STORM>


What's the black box on the Altec to the right of the TV?
NAKAMICHI PA-5

Come on Heather, you know what a power amp l@@ks like.

[Storm]

They did not have the noise when I had them. Tweets worked fine. Also if the VC assembly is glued down from what I understand they will get destroyed when taken apart. I could be wrong but I understand also most of them came this way. That is why JBL Japan never pulled mine apart.

It's that damn TV causing the issue. He still has not answered if the noise is gone when the TV is off. ??????????? Hello STORM>

Yes, the hum goes away when the TV is off.

So, should I move the preamp?

Jeff -- email always works...but, good think I am an LH Junkie!

;)

-Storm.

[sourceoneaudio]

There it is in a nutshell, was that so hard?

TV is the issue just like b4.

Try moving the pre under the TV as suggested, and move the Direct box or the DVD player out to make room. Or the best fix Dump the tube time for Plasma, or LCOS LCD.

What are the Altecs hooked up to, or are they equipment stands?

[Storm]

There it is in a nutshell, was that so hard?

TV is the issue just like b4.

Try moving the pre under the TV as suggested, and move the Direct box or the DVD player out to make room. Or the best fix Dump the tube time for Plasma, or LCOS LCD.

What's so hard in sending a direct email, Jeff?

Why all the hostility?

Wowza!

;)

Going to try to move things around...will post results shortly.

-Storm.

[Storm]

Dont have good news to report.

Tried putting the preamp under the TV to no avail. Then, I moved the TV 15 feet away, but the buzzing was still in the tweeter (the one on the top).

I then tried to remove the power conditioner, thinking it was that -- nope. I did remove the Tivo, but that was not it either.

However, when I play with the HF attenuators on the back of the speaker, I can remove the buzzing -- but the HF goes away.

I have no clue what this could be. I also tried to change out cables running from the amp to the preamp, but that does not help either.

If anything -- at low volumes and on the quietest of songs, the humm can barely be heard.

Maybe I will put back my system the way it was and just leave it alone.

Any thoughts?

Thanks.

:biting:

-Storm.

[edgewound]

Dont have good news to report.


However, when I play with the HF attenuators on the back of the speaker, I can remove the buzzing -- but the HF goes away....


...If anything -- at low volumes and on the quietest of songs, the humm can barely be heard.

...Maybe I will put back my system the way it was and just leave it alone....

Any thoughts?

Thanks.

:biting:

-Storm.

Storm,

Sounds to me like the tweeters need to be cleaned out.

I guess you and sourceone had a transaction on these 250ti's that were fitted with NOS 044ti tweeters from Harman Japan? Those tweeters are probably 20 years old and the foam damping pad has deteriorated and seeped into the voice coil gap causing a buzzing distortion with greatly reduced output. It's a common problem with all older JBL tweeters with foam pads under the dome.

They can be cleaned...trust me. Playing them in their current state is a risk to burning up the voice coils....plus it sounds like crap, right? Why leave it alone when there is a remedy?

PM me if you'd like more info.

[sourceoneaudio]

Yes, the hum goes away when the TV is off.

-Storm.

Edgewound,
The tweeters in those 250Ti's are stock. The noise he is experiencing is a AC noise/hum generated by the TV. If you did not see his reply in a previous post the noise goes away when the TV is off. There is nothing wrong with the tweeters. They are, and were performing correct when I had the speakers over here, and I plugged many an hour of music through them. I'm working on the AC noise with him. ;)

I would also say that the effect on the noise by moving the buss bars is at the given frequency of the hum/buzz, that is why it is affected/removed.

P.S. JBL Japan went through the 044Ti's and they swept fine, they still met factory spec.

[edgewound]

Edgewound,
The tweeters in those 250Ti's are stock. The noise he is experiencing is a AC hum generated by the TV. If you did not see his reply in a previous post the noise goes away when the TV is OFF! There is nothing wrong with the tweeters. They are, and were performing correct when I had the speakers over here, and I plugged many an hour of music through them. I'm working on the AC noise with him. ;)


Hey Source,

Cool your jets, please. I read his last reply and he said when the tweeters are shut off the noise goes away.

AC hum is typically 60hz and would come through all the drivers, not just the tweeter....the tweeters are crossed over just a little higher than that.

Why don't you go over to his place and trouble shoot it in person rathar than freak out at everyone who is responding.

Ball's in your court....I'll butt out....good luck.

[boputnam]

Yes, the hum goes away when the TV is off.Critical point. The rest here, is noise... :rotfl:

Have you tried an isolation transformer on the RCA cables between the TV and pre-amp? The TV/cable audio signal interconnect to your HiFi is corrupting your otherwise ostensibly clean signal. This is common...

You need to break the physical connections between:
- the signal ground of the stereo and AC ground of the TV/cable
- and the poor grounding of the cable cable. Often, there is potential (a bad thing) between the cable signal wire and it's shield which cannot be resolved even with a good solid ground outside your home. :dont-know

This is what the version from Radio Shack looks like (Part No. 240-054 (http://www.radioshack.com/product/index.jsp?productId=2062214&cp=&sr=1&origkw=ground+loop&kw=ground+loop&parentPage=search)) Wish I had a nickel for every time I've posted this...:p . This should work wonders.

Go get one... :scoot:

[sourceoneaudio]

Bo,
Yes, I have used them in car audio applications as a last resort. (Ground Loop Isolator)

Storm, if the strap I send you does not work try one of the above mentioned, and make sure to only use it the TV signal output on the Direct box, or TV which ever you are using to control TV volume.

You should get your ground strap by Saturday.

I had noise on a HT system once, and it was only coming through the Center Channel, and the Center was on top of the TV, well guess what the noise was a goner after installing the same filter. So they do work for that dreaded TV A/C Hum/Buzz radiating issue

Thanx for the tip Bo.

[JBLRaiser]

And the hum is from them all. TV/preamp juxtaposition, ground loop cabling thing and a gooey tweeter.;)

[jim campbell]

i had that and the quick test was to plug your audio gear in using an ungrounded plug adaptor or (cheater)...just cut the ground off an old unwanted extension and try ............

[Storm]

Thanks for all of the help, guys.

Do all radio shacks carry these, or are they online order only?

Do I just need the one?

-Storm.

;)

[boputnam]

...I have used them in car audio applications as a last resort. (Ground Loop Isolator)Actually they have many useful applications. Cost relates to the quality of the transformer. In pro audio (SR) we live by putting DI's into the signal path to break this same ground-loop problem. DI's also provide line-level output, but their greatest "save the gig" application is to relieve GL 60Hz hum induced when an artist's rig on-stage has a ground path different from the PA (and these are inter-connected by way of the signal snake). Anyway, enough on that...


Do all radio shacks carry these, or are they online order only?Most outlets have at-least one on their racks. Give them a call. Use the part no. And do report back!


Do I just need the one?Now there is an interesting question.

It seems now, that the TV is the culprit. Quite possibly, due to the vagaries of interconnects, once you remedy this GL, you'll find that another either develops, or was there all along but buried deeper in the noise floor.

Start with one.

[SMKSoundPro]

I use these same 1:1 matching transformers at the bar to isolate the video cable tv converters from the Sony hifi receiver in the main bar sound system.

Then I use more of these little jewels to run a 2nd audio output from the Sony to each of the two dancefloor control booths.

This way, I always have the "barfeed" (codenamed - "barf") coming into each of the mackie mixers in each booth.

Bottom Line: I learned about these little transformers when doing car stereo installs back in the day, and have always carried a couple in my gig bag, with a bunch of adapters.

Some "vidiot" would always come to me at a gig looking for an audio line out to go to his video world and induce a buzz in my gear, or complain that my audio sucked because of the buzz in his phones. Finally told them to use their own shotgun mic and go away!

(Storm: Pride parade this weekend. Lisa and I built BIG float with floating spinning triangle with JBLs inside covered in pink fuzzy fabric. Many, many JBL's aboard to hump and bump the parade route. Another modern marvel. May post pics.)

Heed Bo's advice. Heed Sourceone's advice. They definately have your back-side!

Carry on.

Scott.

[Storm]

Nice avatar, Source!

Reckon' I have seen that b4.

:p

I am not currently controlling the volume with the remote -- I control it using the preamp volume knob.

Is there a way I can use the TV's volume to control the volume coming out of the preamp?

Thanks.

-Storm.


Bo,
Yes, I have used them in car audio applications as a last resort. (Ground Loop Isolator)

Storm, if the strap I send you does not work try one of the above mentioned, and make sure to only use it the TV signal output on the Direct box, or TV which ever you are using to control TV volume.


Thanx for the tip Bo.

[sourceoneaudio]

Yes, come out of the Direct box two channel outputs on the rear, it should be variable, go into the AUX in on the preamp. Then leave the preamp on one set volume while listening to TV, probably around 11:00. That will give you a variable out while watching TV. :bouncy:


(You will probably have to go into the Direct box set up menu to change the output to variable.)

[Storm]

Yes, come out of the Direct box two channel outputs on the rear, it should be variable, go into the AUX in on the preamp. Then leave the preamp on one set volume while listening to TV, probably around 11:00. That will give you a variable out while watching TV. :bouncy:

Doing it this way -- I will be able to adjust the volume on my remote instead of readjusting on the preamp?

Going to Radio Shack now to get ONE isolator.

Source - call me if I need to purchase more than one.

Thanks.

-Storm.

[sourceoneaudio]

Don't open it until you try the strap first that I made you. You might not even need it. ;) Grounding strap was mailed today.

[Storm]

Okay. I am fuming.

Got back from radio shack and installed the ground loop -- with no success. Still a faint buzzing from both the top tweeter and the tweeter underneath.

I removed the TV from the room including the DirecTv and so now the only thing that is hooked up is the preamp and amp. I hooked the ground loop into the amp to the preamp with no success.

Nothing is hooked up to the preamp except for my Ipod.

When the ground loop is near the cord on the amp - there is real buzzing in the speakers. What is it?

I am very frustrated.

The faint buzz in the tweeter can only be heard when my ear is pressed up against it.

Would it be OK to run the speakers like they are or should I continue to try and remedy the problem?

Thanks.

:banghead:

-Storm.

[Robh3606]

The faint buzz in the tweeter can only be heard when my ear is pressed up against it.

If you can't hear it from where you sit declare a victory and be happy you can't. There is always some residual noise that close to a speaker through any system.

Rob:)

[boputnam]

Yea, I'm with Rob - this may be down in your particular noise floor and not able to be remedied, but...

Can we try one more swing?

1. Hook only the amp to the speakers. Nothing connected to the amp. Any noise?

2. Add the preamp to #1. Any noise?

3. Add the iPod to #2. Any noise?

4. Keep going until you isolate the specific device or unique configuration with the noise.

Also, the Radio Shack device is not a "ground loop" - it is an isolation transformer which will remove the opportunity for ground loops to develop. Since it didn't help, you may not have a ground loop in the first place. I'm beginning to think you have a noisy something-or-other and a high noise floor...

[JBL 4645]

Placing a small piece a wire that is insulated on one end of an audio device and the other to the amplifier 9/10 it clears it for me from buzzing to humming in most cases.

Other than that I’d start from scratch. Disconnect all the equipment power up the amplifier to the JBL with a CD player and see if the offending ground loop Gremlin is still there if it isn’t connect the next piece of audio equipment and so on until you hear the little Gremlin!

I’ve been scanning though the comments, disconnect the RCA phones that go to the amplifier can you still hear the buzzing sound?

By the way nice catch those JBL are around 18 years old I think, I think they where going for around near to £2.000.00pounds new when I first saw them at the Christchurch Hi-Fi store.:p

[Titan100]

1. Your direct tv converter box has an RF input. The RF input comes either from an external dish antenna or an external cable service. In both cases, the cable or the antenna is grounded somewhere outside your home in your area. It is a good practice to isolate that RF input by an RF isolating transformer. This is needed because a lot of ground loop cases happen because of that RF input. The tricky thing is that this ground loop caused by the RF input can be variable with time according to local electricity consumption. Sometimes it can be present and sometimes it can disappear. I give you this information because sooner or later the tv is probably going to come back into your audio system. When the TV returns be sure not to pass interconnects along it.

2. Since for the time being you have already moved out of the equation the TV and the direct tv converter, you have to be sure that there is no ground loop between your audio system components. The best thing to do is to plug all the power cords on the same power bar (use a standard non sophisticated one). This should eliminate any potential ground loop problems between your audio system components.

3. The use of some high end interconnects can sometimes introduce some buzz because their ground conducting wire doesn't have a close to 0 ohm resistance, hence deteriorating the ground connection and the shielding effect of the cable. Try using more standard interconnects if you are using high end ones.

4. Some interconnects don't have a high shielding capacity percentage. Such cables are prone to pick-up of 60 Hertz ac hum or buzz. Try using higher quality interconnects if you are using cheap ones.

5. If you have dimmers in your house for lights or electronically controlled heaters, the dimming or controlling circuits might in some cases generate excessive AC spikes rich in high frequency which can be easily picked up by poorly shielded interconnects or by the audio components. If applicable, try turning off the dimmers and/or the heaters to see if the buzz disappears.

6. You can have audio components with dried out capacitors in the power supply sections, hence diminishing the filtering capacity of the power supply. In this case capacitors should be updated.

7. Finally you can have bad power transformer/s in your amp or preamp having excessive leakage between the primary and secondary windings causing a buzz in the audio circuits by creating a path with the ground. To verify this, a leakage test must be done at a respected repair shop having the necessary equipment.

One or more of these cases might apply in this situation. I hope the information will help resolving your and similar problems one way or another. ;)