Subsonic Rumble Solutions

I received a reply from Rod Elliott on my questions about his filter (see below):

My question about using a lead acid battery or a laptop power supply: "The circuit is specifically designed to operate from a split (+/-) supply. While a single 12V supply could be used, I don't recommend it."

Op-amp related questions: "All the signal runs though the opamp all the time - there's no other way to do it. You can use any dual opamp that you like - despite its age, the NE5532 is a good choice, as is the OPA2134."

Gain related question: "The circuit is unity gain."

Thanks Rod. I will have to reassess after the holidays are over. I may try a few other things in the meantime. Maybe an experiment with resonance damping in the headshell just to make sure it's not a mechanical issue I'm having.

Thanks for everyone's replies,
Bob

Hi Bob#1, Keep us informed. Many times, people report a increased clarity to the music, as a result of removing unwanted cone movement (equals noise, wasted power from you amp and loss of control of the driver). And your amp will be happier.

You appear to have only one sub, so you are in mono at your crossover point. That would be your "rumble filter".
You now need to try a 20hz filter for the subsonics.

Albert had kindly offered to speak to me over the phone regarding this issue, but I think we should keep it in this thread so everyone can benefit. Albert if you have any suggestions or comments please post them here.

Bob#1, you are probably limiting your system if this is a problem in your system. It needs to be eliminated for your system to shine (if it is disturbing/loud enough). How you do it is up to you. Whether you can find a mechanical solution, adding a filter or roll off of your speakers low freq extension. All of these have benefit in not hearing rumble or subsonics. If you can live with a little "rumble" that is an option that is up to you.
My guess is it is not rumble (since you have a mono sub, OR it may be rumble that is above your crossover point!) so it is probably subsonics ie: below 20hz. And filters work very well for this.

You never did mention when you have this problem, is it at certain volume levels, LPs with low bass, certain records that otherwise appear quiet?

Of course there is one other problem that is not system related which I mentiond above, which is rumble pressed into the record. Some of this rumble can even be above 100hz. This you just have to live with, knowing that it is in the lp and not your system. But even this can be eliminated, with a filter. The problem with this is that you want to keep it stereo down to as low as you can. I think this means stereo down to at least 50hz or better yet 40hz. And these freq will do a very good job of elimininating most rumble.

Bob#2
We are not men , we are Devo

Hey Buddy-Bob 2,

I can say with some certainty that the woofer pumping is there on most LP's to one extent of the other. But my ears feel like they are popping on some, but not all, LP's. If I turn the sub off on these I don't get that annoyance (my regular speakers probably drop down to about 30hZ). It is most noticeable on the lead-in groove and 1st song or two, and less at the end of the record, but still there.

You are correct about the amp - less low frequency need means a more efficient presentation overall, helping both speakers and amp.

I don't have time for a new project right now, but I will probably get itchy after New Years and look at this possibility again. It also means adding another interconnect into the mix, since there's no room to incorporate this into an existing box.

Bob #1

I've seen or been able to feel (to the touch) unwanted low end woofer excursions in smaller bookshelf/monitor speaks I've owned in the past during record playback that on paper could not produce subsonic frequencies.

This tells me that the unwanted signal was not subsonic, yet still undesirable in terms of reproducing unwanted low frequency noise often associated with record playback that one would ideally prefer to not exist.

Despite having access to low in addition to subsonic filters available, my choice was most always to not apply low (high pass) filters that would also negatively impact the real music signal in that range of the audio spectrum.

Effective isolation, clamps, etc. are probably more effective ways of dealing with low end noise introduced during playback of warped records, etc. without impacting the music.

If your record is warped or cut too poorly to deliver satisfactory sound, even with filters, clamps, etc., then you have two practical options:

1) get a better pressing of the record
2) buy the CD or digital equivalent if possible.

Unless the tt is not operating properly, that is seldom the cause IMHO.

Low end noise, audible or not, is one of the inherent banes of vinyl.

That's just the way it is.