Radio Interference With RT3000p Subwoofer?

Gatecrasher

I recently purchased a complete RT5000 system and noticed that I can hear a radio station playing on the RT3000p subs. These speakers are the older models with the power indicator light that shuts off automatically.

Has anyone else had this issue?

Is this inherent to the older amp design?

I thought I was going nuts hearing things until I got up close to one of the subs last night and could hear the radio station in the background on it.

TennMan

If you think that's bad, I'm starting to think I hear the sound of a TV playing coming out of gas pumps. :razz: Are you using shielded cables for the connections?

George Grand

If you have excess speaker cable going to one of the speakers, and it is "looped" at all, it can be an outstanding AM antenna.

Gatecrasher

It's weird because I don't get this with my other two RT3000p speakers which are the newer design with the indicator lamp on all the time. I'll have to check and make sure there is no AM radio "loop" or anything different from the others. I did a search on Google and see others have had the same problem with RT3000p too. I never experienced any of it prior to getting these older units.

rebuy

Places I've lived had monitors built right into the pump. Good thing there is no electric charges floating around to ignite fumes.

[Deleted User]

Hello GC,
One of the changes between the older series of RT3000p bass amps and the newer was the overall circuit's grounding scheme. You can contact Polk's CS department about replacing the amps with the newer versions. Be sure to mention your CP membership for the reduced price.
Regards, Ken

newrival

I'm glad you chimed in here, Ken. I knew that there was a revision done to the amps and I couldn't remember what the fix was. But I do remember Polk asking RT3000p members to send in their amps to get them updated from long ago threads.

[Deleted User]

No problem, I used to do some mods to the original amp before the new design arrived. I probably have the paperwork around somewhere. NAP and I flew to Seattle to help diagnose a problem a customer had with an RT5000p system. The guy lived in an area that had lots of radio masts and was having problems.

Gatecrasher

I thought it might be related to the older amp design because I've never noticed any radio interference in the 9 years I've owned my other RT3000p pair. I would be very interested in any modifications that may eliminate the problem Kenneth and appreciate anything you can help me with.

I will contact Polk service on this too and see what they say but a few weeks ago when I asked about replacement feet for the Rt3000p, they replied that they didn't have any parts for them anymore. I don't know if that means they no longer offer the modification though.

George Grand

rebuy wrote: »

Places I've lived had monitors built right into the pump. Good thing there is no electric charges floating around to ignite fumes.

Can I buy a combination dvd/vcr/gas pump? I don't need the monitor, I already have one.

[Deleted User]

Hello GC,
I believe Polk has the second generation bass amplifiers available, they won't have any ability to do modifications to your current amps. That was a stopgap measure to help owners while the revised amp was being produced.
Cheers, Ken

Gatecrasher

I'll give Polk a call tomorrow and see what they say. Any idea what the revised amps cost? Sounds like it might be expensive.

[Deleted User]

Kenneth Swauger wrote: »

No problem, I used to do some mods to the original amp before the new design arrived. I probably have the paperwork around somewhere. NAP and I flew to Seattle to help diagnose a problem a customer had with an RT5000p system. The guy lived in an area that had lots of radio masts and was having problems.

Glad you chimed in here. What happens in Seattle stays......, well you know the rest. I thought we had heard the last of this problem (no pun intended). :cool:

cataritas

Places I've lived had monitors built right into the pump. Good thing there is no electric charges floating around to ignite fumes.

Gatecrasher

nap wrote: »

Glad you chimed in here. What happens in Seattle stays......, well you know the rest. I thought we had heard the last of this problem (no pun intended). :cool:

I never knew Polk had issues with the RT3000p until I purchased an older pair. The guy I bought them from said he purchased them direct from Polk back when the first came out which I think was around 1998 or so. The pair I bought brand-new in 2004 or so are the newer amp design and I've never had the problem with any interference.

One thing I do notice about the older RT3000p is that the wood veneer is nicer than the later models. Beautiful grain to it. It appears as time went on, Polk may have switched to a less expensive veneer. Not that my newer ones look bad or anything. The grain and quality of the veneer seems a little less expensive than the older models.

Gatecrasher

Kenneth Swauger wrote: »

Hello GC,
I believe Polk has the second generation bass amplifiers available, they won't have any ability to do modifications to your current amps. That was a stopgap measure to help owners while the revised amp was being produced.
Cheers, Ken

Well after speaking to a Polk rep, he told me that there was a modification and he would get back to me. He said there was a retired Polk engineer on the forum who should know how to do the modification and he would contact him for me. But when I didn't hear anything and e-mailed him again, the rep never responded.

What are my options? I've been told by others that the RT3000p amps are no longer available. Are they actually available?

It's weird because another Polk rep told me flat-out that there were no replacement parts available at all for the RT3000p but then I was able to purchase new potentiometers for them last week. It seems that there are some parts still available even though some Polk customer service reps claim there aren't.

You wouldn't happen to be the retired Polk engineer would you? Is there any way to find out for sure if the newer version of the RT3000p amps are still available?

Thanks for any help you guys can give here.

[Deleted User]

Hello Gate,
Probably the best person to contact is Kim Jasper, the CS manager at kjasper@polkaudio.com or via telephone at 1-800-377-7655 and ask for him. I found the original notes that described the amp modification, made a copy and mailed them to Kim. He was probably thinking of NAP as the person who would be in the best position to contact the original engineer if needed.
I hope this is helpful.
Regards, Ken

transmaster

Nice to see a forum that has been around for awhile.

http://www.polkaudio.com/forums/search.php?searchid=724528

[Deleted User]

Kenneth Swauger wrote: »

Hello Gate,
Probably the best person to contact is Kim Jasper, the CS manager at kjasper@polkaudio.com or via telephone at 1-800-377-7655 and ask for him. I found the original notes that described the amp modification, made a copy and mailed them to Kim. He was probably thinking of NAP as the person who would be in the best position to contact the original engineer if needed.
I hope this is helpful.
Regards, Ken

I have not received any inquiries in regard to this. I do not have any of the information regarding the mod. From what I can remember it involved re-routing the ground trace from input to output to try and eliminate the problem. A lot of cutting traces and re-wiring. In some instances it helped and it didn't work in all cases. Now, I am still friends with the engineers at the vendor where Polk purchased these amplifiers. I can try and contact them if you still want to give this a try. If so, please let me know and I will see what I can do for you but I can't promise anything. :cool:

cincycat13

I have 2 older towers that had the old amps as confirmed by the power light that would go off in standby mode. I found that if I switched from normal to reverse phase that the radio reception would go away. Not sure what that will do for your sound. It worked until my amps went to buzz and I replaced them with the newer style.

+1 for the veneer on these. Mine had a hard life before I got them but the grain pattern is very nice. How do these compare to yours? And I actually wanted black.

transmaster

I was reading up on this problem and apparently the revision that Polk made to end this problem was a different design on the circuit board, this board is no longer available. Hopefully whatever the mod's to this amp was that fixed it will be found; meanwhile:idea:

In Amateur Radio we deal with this sort of problem all of the time what is needed here is RF chokes that are positioned on wire runs to break resonate RF loops, and RF shielding. A suggestion I have for the Amp itself is if there is room to do it is build a copper mesh shield around the amp properly fabricated copper screen of this type will keep the RF out of the Amp it self while permitting air flow for cooling. Constructed with care these copper shields can be very attractive to look at. after this you are left with the RFI introduced by the various feed lines and interconnects.

go here for copper mesh
http://www.twpinc.com/wire-mesh/TWPCAT_3?gclid=CI7ZiPTxoq8CFYi6KgodAmoGbA.

Here is a nice tutorial about what we call RFI once you understand what is going on you can usually fix it
http://audiosystemsgroup.com/RFI-Ham.pdf

Here is a good source of various devices to help stop RFI.
http://www.mouser.com/Passive-Components/Inductors/RF-Inductors/_/N-wpdb?SAP=true?cm_mmc=google-_-ppc-_-americas-_-Passives&gclid=CPrztI7voq8CFe4DQAod8g0fXQ

I have an idea that could be very useful in future years. As I said above the circuit board for RT3000p amps were revised to end the RFI problem, and that board is apparently no longer available. I wonder if Polk could post a sticky with printable actual sized layouts of circuit boards they no longer supply, these can be used to photo etch copies. Photo Etching a circuit board is fairly easy, the equipment and chemicals to do it are very reasonably priced, and you don't have to dress up in a space suit to use them. With photo etching you chemically place a photo copy layout to the circuit board material. You end up with an exact copy of the original board.

transmaster

This is about the sized copper mesh we used to shield pre-1955 HF transmitters to prevent Television interference (TVI) it really doesn't have to be this fine a mesh but this was easy to work with and attractive to look at when completed

http://www.twpinc.com/control/productDetail.pdf?productCategoryId=TWPCAT_3&product_id=018X018C0170W36T

Here is a tutorial for the use and placement of RF beads, snap on chokes etc.
http://www.k0bg.com/beads.html


The link to the Mouser source pages for RF chokes I realized belatedly is way to much for this forum. I know what I am looking for in advance and enter that into the search engine you see at the top. What you want is in this section but there is nearly 1400 pages of them so unless you know exactly what you are looking for don't bother

Gatecrasher

Hi transmaster,
I am an amateur radio operator too (or at least used to be) and am familiar with RFI but before I tried experimenting with various devices or shielding, I wanted to make sure there wasn't an easy modification or the chance to purchase the upgraded boards for these speakers. I wish I would have known about the evolution of these amplifiers because I might have passed on this second set of RT3000p's I got a couple months ago. My original RT5000 system that I purchased new several years ago have the later amp design.

I'm just trying to find out as much as possible about the design change and wouldn't rule out etching my own circuit boards as I have done a few in the past for other Ham radio projects and even for some solid state pinball machines (one of my other hobbies) but I'd rather not if I can help it.

I guess I could always remove one of the amps from one of my newer RT3000's and compare them to these older units and possibly reverse engineer them but that's a last resort. Another option would be to purchase a couple blown amps from someone with the later design and rebuild them using their boards. I do see some people post from time to time with blown amps.

Anyone know what version of the amp design the schematics posted on this forum link are? Did I hear now that there were actually three different designs?

http://www.polkaudio.com/forums/attachment.php?attachmentid=48432&d=1272430795

Gatecrasher

cincycat13 wrote: »

I have 2 older towers that had the old amps as confirmed by the power light that would go off in standby mode. I found that if I switched from normal to reverse phase that the radio reception would go away. Not sure what that will do for your sound. It worked until my amps went to buzz and I replaced them with the newer style.

+1 for the veneer on these. Mine had a hard life before I got them but the grain pattern is very nice. How do these compare to yours? And I actually wanted black.

I tried the reverse phase and the radio interference does seem to go away cincycat13. The sound is a little different though but it still sounds good. I wonder why this affects the noise issue? What exactly does the "phase" switch accomplish?

Here's what the manual says;

"PHASE SWITCH
If the satellites are positioned on top of the
subwoofers, set this switch to "Normal". If
the satellites and subwoofers are physically
separated, experiment with the Phase switch
and crossover frequency control to achieve
overall bass "fullness" and impact."

My satellites are on top of the subs. Does the phase switch change something in the crossover or what?

You know it's kind of interesting. Both of my RT5000 sets are black but the older speakers have nicer veneer & grain than the newer ones do. I've seen the Rosewood models before and they have a smoother finish while the black ones are more raised. I think they both look good but always favored the black ones myself. It matches the rest of my equipment and I use the Can-Am modular cabinetry in black also.

Gatecrasher

It looks like the phase switch is "SW2" in the schematic. It's hard to tell what exactly it accomplishes though.

Gatecrasher

Well I decided to try a fairly bass-heavy CD and see how it sounded in reverse phase. I used the latest release from Los Plantronics "Organic Voodoo Soup" for the experiment.



As expected, the bass sounded a little out of phase for my setup. Definitely has more punch and sounds better when set to normal.

Still can't see why the RFI is eliminated when set to reverse though.

transmaster

Gatecrasher wrote: »

Still can't see why the RFI is eliminated when set to reverse though.

It is a mystery, and it is mysteries like this that sell stuff like CrystalConnect Dreamline Phono
tone arm cables for $8,100. Not pulling your leg, see the link below.

http://www.thecableco.com/Product/CrystalConnect-Dreamline-Phono