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Thread: Subsonics with new phono stage. Is this a comms issue?

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  1. #1
    Join Date: Sep 2013

    Location: Wilts

    Posts: 130
    I'm Richard.

    Default Subsonics with new phono stage. Is this a comms issue?

    I wonder if anyone can advise? I've had a Inspire Rega turntable for years. It's got the full Groovtracer package, lots of SRM Tech stuff, and a J7 re-wired 303 arm. External speed drive PSU and Swagman PS to that PSU. I'm using a 2m Black. It's on a dedicated and well-isolated wall shelf.

    Until recently and for many years I have been alternating between a Haden Boardman 33.3 v3 valve phono stage and a SS Edwards MC3. But recently I moved house and in my new rather dreadful room my TT wasn't sounding right at all. I then acquired a Robert Airey Worx modded Jolida F159 (Black Ice Audio). Frankly, the improvement in sound repro was astonishing. A remarkable bit of kit, but I have also started suffering from marked subsonic speaker oscillations on any LP. I have tried modifying the VTF and azimuth and anti-skate and it doesn't make any difference. VTA is a cruder mod with the Rega arm but it is set on the middle shim position which is what everyone recommends. Moreover it is the position that has worked well before.

    I'm told that Ortofon developed the 2M range specifically with the Rega arms in mind. They have always worked well together for me.

    Is it possible that the phono-stage is just not compatible for the arm/cart combo, or is there another trick I'm missing? I have marked motor rumble, too.

    I certainly l don't want to get into subsonic filters... That would be awful.

    In my limited experience of swopping decent phono stages, there is often little between them, or if there is it's more a change of flavour that better or worse (which is why I kept both my other stages - I could never decide which I preferred!), by the Airey Worx F159 is a major step-up. Can these things simply be incompatible? I know it worked well in Robert's rig.

    In short, what, all things considered, could be the cause? Any help greatly appreciated. I sure don't want to chop in the F159. It's absolutely wonderful.

    Cheers, Richard

  2. #2
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 10,157
    I'm Oliver.

    Default

    Quote Originally Posted by Kneesup View Post
    I wonder if anyone can advise? I've had a Inspire Rega turntable for years. It's got the full Groovtracer package, lots of SRM Tech stuff, and a J7 re-wired 303 arm. External speed drive PSU and Swagman PS to that PSU. I'm using a 2m Black. It's on a dedicated and well-isolated wall shelf.

    Until recently and for many years I have been alternating between a Haden Boardman 33.3 v3 valve phono stage and a SS Edwards MC3. But recently I moved house and in my new rather dreadful room my TT wasn't sounding right at all. I then acquired a Robert Airey Worx modded Jolida F159 (Black Ice Audio). Frankly, the improvement in sound repro was astonishing. A remarkable bit of kit, but I have also started suffering from marked subsonic speaker oscillations on any LP. I have tried modifying the VTF and azimuth and anti-skate and it doesn't make any difference. VTA is a cruder mod with the Rega arm but it is set on the middle shim position which is what everyone recommends. Moreover it is the position that has worked well before.

    I'm told that Ortofon developed the 2M range specifically with the Rega arms in mind. They have always worked well together for me.

    Is it possible that the phono-stage is just not compatible for the arm/cart combo, or is there another trick I'm missing? I have marked motor rumble, too.

    I certainly l don't want to get into subsonic filters... That would be awful.

    In my limited experience of swopping decent phono stages, there is often little between them, or if there is it's more a change of flavour that better or worse (which is why I kept both my other stages - I could never decide which I preferred!), by the Airey Worx F159 is a major step-up. Can these things simply be incompatible? I know it worked well in Robert's rig.

    In short, what, all things considered, could be the cause? Any help greatly appreciated. I sure don't want to chop in the F159. It's absolutely wonderful.

    Cheers, Richard
    I don't know if this is the same thing but i just changed my preamp and noticed that the left speaker cones were moving quite noticeably, especially the bass cones. They were quite violent actually, when the cart was in the lead in groove.

    I asked a friend who suggested that my bias weight may not set correctly so I checked and he was right.

    Bias adjusted and everything went back to normal.

  3. #3
    Join Date: Sep 2013

    Location: Wilts

    Posts: 130
    I'm Richard.

    Default

    Exactly that Oliver. Thanks for flagging it. But the bias weight adjustment hasn't helped in my case.

    I was wanting to move to a new Audiomods arm in any case. Although not just yet. I'd change the arm before the phono stage.

  4. #4
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 10,157
    I'm Oliver.

    Default

    Quote Originally Posted by Kneesup View Post
    Exactly that Oliver. Thanks for flagging it. But the bias weight adjustment hasn't helped in my case.

    I was wanting to move to a new Audiomods arm in any case. Although not just yet. I'd change the arm before the phono stage.
    Ah, sorry. I didn't know if it was that but it struck me due to the change in preamp. The phonostage was the same. Mad.

    Anyway, hope it.

  5. #5
    Join Date: Feb 2010

    Posts: 4,173
    I'm Tom.

    Default

    The RIAA standard eq curve does not include a subsonic filter, however many phono stages out there use the IEC version of RIAA which does have a rolloff below 20hz. My guess is that the new phono stage doesn't have this rolloff.

    Clearly though there is an issue somewhere that's causing very low frequency rumble and that may be equipment related, or possibly room related, or both. Just a thought (only one of many possibilities) but by any chance have you moved from concrete floor to suspended, or some other change in the way the table is mechanically coupled to the stand/floor/room?

    It could be a combination of room issues + kit problems on the tunrtable, plus the fact that subsonics were filtered on your old kit. Do you still get rumble when you use one of the old phono stages? When was the last time you oiled the bearing and changed the belt?

  6. #6
    Join Date: Sep 2013

    Location: Wilts

    Posts: 130
    I'm Richard.

    Default

    Thank you, Tom, for taking such a time to reply so painstakingly. The TT is on a high quality wall shelf, so no issues with the floor or table. The room generally is smaller and more 'intense' sonically, whereas my old room was airy and glorious, so there could be some interaction with speaker proximity, but it happens even at the lowest volumes. So I think probably not. The only thing that's changed kit-wise is the phono stage. Dual belts and oil are perhaps three years old. But relatively low hours. The roll-off RIAA issue certainly deserves attention. I'll ask the ever-excellent Robert Airey. Thank you again.

  7. #7
    Join Date: Feb 2010

    Posts: 4,173
    I'm Tom.

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    Just looking at the specs of the original Jolida, it has what it describes as a bass boost of 3db at 20hz, which is quite a lot in terms of deviation from RIAA, and could be causing or at a minimum exacerbating your problems. Not sure if the modding work would have addressed that.


    Basic Specifications:
    1- Gain @ 1KHZ in low gain position 40DB with 47K input.
    2- Gain @ 1KHZ in high gain position 60DB with 47K input.
    3- Noise floor in high gain position approx -70 DB with input load set to 10 ohms, noise floor will be lower with gain set in low position.
    4- Frequency response with RIAA EQ is Plus/Minus 1/4 DB from 250 HZ to 20KHZ, + 3DB at 20 HZ (Bass Boost)
    5- Distortion .05% @ 1 KHZ 1V RMS out.
    6- Plate voltages APPROX 90V on input stage, 70V on second stage.
    7- The calibrate meters work the same way as the XTR.
    8- Rear panel adjustable loading
    9- uses 2 6922/6DJ8 tubes and comes with 2 sets of tubes, one 6922 and one 6DJ8

  8. #8
    Join Date: Sep 2013

    Location: Wilts

    Posts: 130
    I'm Richard.

    Default

    Great detective work, Tom. That sounds well worth investigating. I’ll get on to Robert (Open Door) who did the fabulous mods. I have copious bass in my rig so will happily do without that ‘boost’ if it helps. Really appreciate your help. Thank you. R

  9. #9
    Join Date: Sep 2013

    Location: Wilts

    Posts: 130
    I'm Richard.

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    Tom. Meant to mention that Ive old both my other stages to pay for the 159. So I can’t compare. But I will borrow another.

  10. #10
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 42,230
    I'm Geoff.

    Default

    If subsonic record warps and ripples are being reproduced by the deck, i.e. bass cones oscillating, it suggests the arm/cartridge mass is overcoming the cantilever suspension. This happens when the arm/cart resonance is too low. It occurs if a cartridge is too compliant for the combined mass with the arm it's mounted on.
    "when common sense, logic and plausibility are excluded. All that remain are foolishness and lies"

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