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  • Interesting hiccup with turntable

    So I'm really digging my new Project Carbon Debut Turntable (how could I resist it with a name like that!!). I did come across an interesting hiccup however.

    First, the set-up: Turn-table through a project phono stage to a UMC-200 (analogue inputs) and powered by a UPA-700 to my ONS 5.1 (TMM towers, MTM centre and TM surrounds and swope sub). Pretty straight forward.

    I usually listen to my vinyl using 2-channel (stereo) setting on the UMC-200 but one day it was accidentally on a multi-channel setting (doesn't really matter which, I've tested all now). All of a sudden, my sub-woofer kicked in and started freaking out. That's the best description I can give. Started pumping low frequency waves at a crazy rate.

    I'm not too bothered as I prefer 2-channel with the vinyl but sometimes I don't mind running all channels if I have a full house of people. So anyone have any insights into this? I would have thought the UMC could process the analogue signal to multiple channels without too much problems (yes, I recognize it's a bit of an illusion but I didn't expect the sub to freak out). Just trying to understand the effect.

    Carbon
    Carbon13

  • #2
    When on two channel is it a true 2 channel meaning no lfe output? It could be that in multi channel mode it turns the lfe output on. There are a lot of subsonic frequencies that can come through a tonearm.

    My only guess really.

    Dan

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    • #3
      We listen to music on a stereo system with a sub woofer, although we have a 5.1 system in the workshop.

      I don't know why your sub will do what it did, but I find that when playing many LPs I have to turn off the sub to avoid low frequency rumble and noise from the LP. It's not turntable rumble, but maybe poor quality pressing or vinyl , off centre LPs or poor EQ. But it sounds awful, so I just turn off the sub.

      Geoff

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      • #4
        You're hearing one of two things: Feedback and/or Resonance.

        All turntables have a ultra low-frequency rumble. That's why you'll find many phono preamps have a cutoff switch around 19Hz to help alleviate this exact issue. Alternatively, it can be feedback from the speakers that is transmitting through the tonearm/cart, then back to the preamp, out the speakers, in a loop.

        Solutions:

        -isolate the turntable better. Use sorbothane feet or the commercially available 'vibrapods'
        and/or
        -get a phono preamp that has a LF cutoff built in (UTurnPluto) or one that has a switchable LF cutoff (Cambridge Audio 651). Those are just the first that come to mind.

        Hope this helps!

        Comment


        • #5
          Thanks for the replies. The phono box I have is the lower end model, not the "s" with the LF cutoff so I suspect that may be part of the issue. Yes, the stereo setting is true 2-channel (no lfe) so that's probably why it's OK in that mode and not others. No biggie but now I have an excuse to upgrade my phono preamp!!!
          Carbon13

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          • #6
            Originally posted by ScenesFromAHat View Post
            You're hearing one of two things: Feedback and/or Resonance.

            All turntables have a ultra low-frequency rumble. That's why you'll find many phono preamps have a cutoff switch around 19Hz to help alleviate this exact issue. Alternatively, it can be feedback from the speakers that is transmitting through the tonearm/cart, then back to the preamp, out the speakers, in a loop.

            Solutions:

            -isolate the turntable better. Use sorbothane feet or the commercially available 'vibrapods'
            and/or
            -get a phono preamp that has a LF cutoff built in (UTurnPluto) or one that has a switchable LF cutoff (Cambridge Audio 651). Those are just the first that come to mind.

            Hope this helps!

            +1, I had the same issue until I put sorbothane isolation pads under my turntable. Now I can crank it up with no probelm at all.
            -Kerry

            www.pursuitofperfectsound.com

            Comment


            • #7
              Originally posted by ScenesFromAHat View Post
              All turntables have a ultra low-frequency rumble. That's why you'll find many phono preamps have a cutoff switch around 19Hz to help alleviate this exact issue.
              In the old days, they actually called it a "Rumble Filter"

              .
              Click image for larger version

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              • #8
                Any additional thoughts on phono preamps?

                A local place had a refurb cambridge 651p for "40% off" ($250USD). Then I looked around and saw a brand new CP2 (the 651 replacement) is going for $250 brand new!

                I don't really want to spend a ton of dough but wouldn't mind an upgrade on the preamp if it's going to give me good bang for the buck; and this rumble does appear to be a bit of an issue.

                So what's your pick on best bang for your buck phono preamps?
                Carbon13

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                • #9
                  Look at Music Hall and Schitt. Both very nice units.
                  craigk

                  " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

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                  • #10
                    The Schiit Mani and the UTurn Pluto are great budget options

                    Comment


                    • #11
                      Does the Schiit have a LF filter?

                      I looked at the Music Hall and I don't think they have one (at least that I can see).

                      UTurn seems like a great budget option. I could afford to step up to the CP2 but would it be worth it?

                      Carbon13

                      Comment


                      • #12
                        I just want to add a x3 to what ScenesFromAHat said... definitely need a rumble filter. You probably just don't see it on the OS speakers because they're rolling off too high (just a guess?).

                        As far as which phono pre... consider if you think you'll ever upgrade your cartridge later down the road. If you think you might, try to find a phono pre that is good for both MM and MC carts. As far as a rumble filter goes... what I did on my system was added an external EQ that has a rumble filter (IIRC mine is a BSR EQ-3000, you can find them on eBay for around $50). But, I'm not sure how you would incorporate that on a 5.1 system? Maybe run your phono preamp RCA through the EQ, then into the stereo? Adding the EQ is an inexpensive option that opens a lot of doors to various phono preamps, because you're no longer looking for one that also comes with a rumble filter. Plus, having an EQ in your system is handy at times for building speakers, sometimes I use mine to hear whether or not a peak in my response is something I need to fix.

                        So based on that^, if I were you I would just add the EQ for now and use what you have. Save some money and later down the road get yourself a Peachtree or a Budgie phono preamp. A lot of places that sell them offer 30 day satisfaction guarantees, which is nice because you can get it and A/B with what you already have, and if you don't hear the difference just return it. If you think you'll move into the world of MC cartridges, you'll want a stepup transformer as well (but only if you're going to use a MC cart). Just some food for thought (IMO). Good luck!
                        "The ability of any system to produce exceptional sound will be limited mainly by the capability of the speakers" Jim Salk
                        "Audio is surely a journey full of revelations as you go" JasonP

                        Comment


                        • #13
                          Originally posted by mattsk8 View Post
                          .... definitely need a rumble filter. ...
                          Saw that earlier and brought back memories of dealing with the infra-sonics; As the speakers became more capable of extended bass response, up popped the problem.
                          The first circuit board ( for an op amp audio filter ) I assembled in the 70s was an FMJ board that was a "rumble filter"
                          "Not a Speaker Designer - Not even on the Internet"
                          "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                          • #14
                            An old article on "Rumble Filters"
                            one of many designs on-line
                            http://bestengineeringprojects.com/h...rumble-filter/
                            http://sound.whsites.net/project99.htm
                            "Not a Speaker Designer - Not even on the Internet"
                            "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

                            Comment


                            • #15
                              So low frequency rumble is definitely the issue. Interestingly, it's most noticeable if I turn the processor to a theatre setting (Like PL II movie), I guess cause that setting emphasizes the bass. Now I know I won't be listening to my vinyl with a theatre setting on but if it does happen accidentally I can tell you that my heart palpitates about as fast as the drivers!! So better safe than sorry.

                              I looked at the upgrade feet from Project Audio and they're $250CAD!! For feet!!

                              So I found these at the local homedepot: https://www.homedepot.ca/en/home/p.f...000672766.html

                              They look like crap when you take them out of the box, kinda grey and dirty looking. I washed them and then rubbed them with a bit of mineral oil to get them to a decent flat black.

                              Tried them out and they did make a HUGE difference. I have to play the music pretty loud to trigger the rumble whereas before it would happen even at low volumes.

                              I'm still thinking about an upgraded phono preamp or an equalizer with subsonic filter but this was a nice quick fix for time being.
                              Carbon13

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