New phono pre is ringing like a bell. What's the problem?

Discussion in 'Audio Hardware' started by Jeffreylee, Oct 25, 2020.

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  1. Jeffreylee

    Jeffreylee Rock 'n' Roll Typist Thread Starter

    Location:
    Louisville
    Hi, and thanks for any advice/insight.

    I recently fulfilled a longtime goal of buying a Fosgate Signature Phono V1, but it's behaving in ways that can't be right.

    While trying to get rid of some hum, I noticed that whenever I tapped the ground lug with a fingernail there was a dull thudding noise in the speakers. Then I tapped on one of the storage capacitors and got an even louder noise, along with a light ringing sound. Then I tapped on the chassis top and got a thud accompanied by a loud ringing sound and a buzz, both of which slowly faded within a few seconds.

    I've had several pieces of all-tube gear, including an Eastern Electric phono stage, and have never experienced anything like this. Can anyone shed some light?
     
  2. oregonalex

    oregonalex Forum Resident

    The tubes are picking up the knocking. It may be that one (or more) of the tubes is more microphonic than optimal, especially the input tubes. Unless the unit goes into a howling rage when you knock on it, I'd say it is not a problem. My Tavish Vintage Phono does the same thing, especially with vintage tubes.
     
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  3. Jeffreylee

    Jeffreylee Rock 'n' Roll Typist Thread Starter

    Location:
    Louisville
    It was a tube. Can't believe I've dodged that bullet for so many years. In my lame defense, the trouble tube was not causing the same problem in my other phono stage, an Eastern Electric. Thanks for the heads up.
     
  4. Dillydipper

    Dillydipper Space-Age luddite

    Location:
    Central PA
    :idea: Have you considering just answering it...? :D
     
  5. TarnishedEars

    TarnishedEars Forum Resident

    Location:
    The Seattle area
    Its definitely a microphonic tube. These are most audible in phono stages.
     
  6. John Buchanan

    John Buchanan I'm just a headphone kind of fellow. Stax Sigma

    Try replacing the 6DJ8s with 6922s or the very expensive 7038s. Special Quality. I had trouble with 6DJ8 microphony in an Audio Research SP10 preamp, the solution for which was to select the first two phono stage valves very carefully. That preamp had 10 of them :yikes:
     
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  7. Jeffreylee

    Jeffreylee Rock 'n' Roll Typist Thread Starter

    Location:
    Louisville
    Apparently it already has a pair of 6922. I say apparently because I can't completely narrow them down. Siemens, gold pin, labeled Made In Germany with CCa on one side and 07051 on the other. A tiny metal tab is stamped A2 J6. I can find plenty of CCa and A2 stampers referenced online but the 07051 is nowhere to be found so far.

    I thought I had it solved but after further warming up I'm still getting a fair amount of noise. I'm going to have to try systematically changing every tube.
     
  8. Davey

    Davey NP: Portishead ~ Portishead (1997)

    Location:
    SF Bay Area, USA
    Do you have it on high gain? It's one of the few tube preamps with that much gain, most designers use solid state or transformers to get 60dB gain from a tube preamp, so it is bound to be a little noisy and more susceptible to microphonics with that much gain. You can always use inexpensive tube dampers to quiet it down some.
     
  9. Bill Hart

    Bill Hart Forum Resident

    Location:
    Austin
    The SP-10 was notorious-- I had one for years- fabulous preamp in its day, truly a classic, but microphonic as hell. I even went to the length of sourcing some gel type tube sockets-- which were novel at the time-- and had ARC factory install them in the hope those would minimize the problem. It didn't, so they uninstalled them.
    That unit was the high point of ARC's tube preamps. The SP-11 had how many tubes?
     
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  10. Mike from NYC

    Mike from NYC Senior Member

    Location:
    Surprise, AZ
    The SP-10 was the high point? I doubt that - ARC products are updated to show new insights they have learned with every model. I haven't heard the SP10 but I think my ARC REF 3 pre is its equal if not better - no microphonics.
     
  11. John Buchanan

    John Buchanan I'm just a headphone kind of fellow. Stax Sigma

    Y
    You haven't heard one and you're comparing a complete (M/C phono included) preamp with a line level preamp? WOW!
     
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  12. John Buchanan

    John Buchanan I'm just a headphone kind of fellow. Stax Sigma

    The SP11 had only 6 x 6DJ8 with a S/S power supply (a total of 6 tubes). The SP10 had a total of 15 valves. The SP15 had only 3 x 6DJ8s. I was incorrect above - the SP10 had 12 x 6DJ8s, 2 x 6L6WGCs and 1 x 12AT7
     
  13. Bill Hart

    Bill Hart Forum Resident

    Location:
    Austin
    Sorry I meant high point in the sense of tube heavy, not necessarily better. It is probably dated by comparison to the current Reference line or whatever. But, in its era, it was a jewel, microphony notwithstanding. I know that a bunch of people jumped from the 10 to the 11 as soon as the model changed and there was a little bit of a backlash at the time- that the 11 sounded a bit clinical and arid by comparison to the 10, which was "juicy." Just by noise standards alone, I couldn't use my SP10 when I switched to horns-- it wasn't quiet enough.
    PS: in its day, the phono stage was very highly regarded. I have no idea how it would stand up to a modern state of the art phono section, but at the time the 10 was made, as you likely know, preamps still had phono sections. What's also interesting is that the SP3, which I had when it was the cat's meow, sounded very dated to me when I last heard it in the late 80s or early 90s, but apparently they are fetching big money now. I liked the ARC stuff but its sound did change a couple times over the years.
     
  14. BillWojo

    BillWojo Forum Resident

    Location:
    Burlington, NJ
    I'm using a Audio Research SP8ver5 in my system and love it. I think it was the last one before the big switch to 6DJ8 tubes. I had a LS15 with the 6DJ8 tubes but I found it a bit sterile, had to go backwards to get the sound I wanted.

    Billwojo
     
  15. Jeffreylee

    Jeffreylee Rock 'n' Roll Typist Thread Starter

    Location:
    Louisville
    After lots of interruptions, I was finally able to change out tubes pair by pair. One or both of the Siemens 6922 tubes were badly microphonic. I replaced them with some old Amperex 6DJ8s I had and everything is cooking. Thanks for all of the help, folks!
     
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  16. Mike from NYC

    Mike from NYC Senior Member

    Location:
    Surprise, AZ
    Why, what's the difference if it has a phono pre installed - it's a preamp.

    There's a reason why ARC changed the type of tubes it uses and I highly doubt that newer ARC components sound worse than the older components. If it sounded worse ARC would not be in business anymore or just basking in its 'glory days' like so many other audio companies of the past that are just a name and that's it.

    I've heard 'tubey' pre's and receivers from the past - including my late Dad's Fisher 500C and other older components that just had too much tube sound and ill defined bass and a reticent treble but a glorious midrange. Most current tube equipment sound vastly different from those of 20 or 30+ years ago - as tastes change and people want tubes but w/o the downsides while still using tubes and ARC and others have managed to do that.

    Almost every piece of equipment I installed in my main system has tubes in it and they sound nothing like my Dad's 500C - the response of SS but the liquid sound of tubes without over-doing it.
     
  17. John Buchanan

    John Buchanan I'm just a headphone kind of fellow. Stax Sigma

    The fact remains that you have never heard an SP10 and said your Reference 3 is better because it's newer. WOW.
     
  18. slovell

    slovell Retired Mudshark

    Location:
    Chesnee, SC, USA
    Your tubes and maybe the case are microphonic. Get a couple of sheets of Lightweight Sonic Barrier Sound Damping sheets from Parts Express and line the inside and top of the case with it. It's cheap from Parts Express (crazy expensive from Music Direct) and will stop the case from ringing. If your tubes/tube are microphonic either live with it of change them out. I just did the case on a Jolida Fusion preamp I just bought used, it was ringing like a bell. I bought three sheets (10" X 13") for $25.50 shipped via UPS and had a sheet and a half left over. I also changed tubes, two were microphonic, and now it's quiet as a mouse. I tried the o-ring tube dampers on the tubes but didn't like what they did to the sound. It helped with the ringing but sucked the life out of the sound. I'm going to do my JD9 phono pre and my CD100 with it next.
     
  19. Jeffreylee

    Jeffreylee Rock 'n' Roll Typist Thread Starter

    Location:
    Louisville
    @slovell Thanks but it's been settled. See post #16.
     
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  20. slovell

    slovell Retired Mudshark

    Location:
    Chesnee, SC, USA
    No problem, just trying to help. :)
     
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