What next for lower noise floor?

Discussion in 'Audio Hardware' started by SpiritMachine, Oct 20, 2016.

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  1. SpiritMachine

    SpiritMachine Active Member Thread Starter

    Location:
    Richmond, VA
    This question primarily concerns my analog system but the issue is present to a lesser extend in my digital playback.

    My analog system consists of:
    Music hall 5.1 turntable with music hall magic 3 MM cartridge
    Lehmann audio black cube SE II phono stage
    Line magnetic 518ia amplifier with gold lion 12ax7 tubes
    Rega Rx5 speakers
    Wireworld mid level cables

    While listen to LPs (and to a lesser extend digital) there is a faint but bothersome hiss. This is not a hum like when I disconnect my grounding. It is an ever present hiss which becomes louder proportionally with increasing volume.

    My thoughts to improve would be... better turntable, better phono stage, better (NOS?) preamp tubes in the line magnetic or power conditioning (current have none).

    What would your approach be?

    Thanks!
     
    Jeb likes this.
  2. russk

    russk Forum Resident

    Location:
    Syracuse NY
    Buy an RCM. They go a long way toward quieter playback. I've heard and been impressed by Torus. The one I tried made my system noticeably quieter in quiet spots.
     
  3. chervokas

    chervokas Senior Member

    Unplug the phono pre from the Line Magnetic integrated. Do you have more or less hiss? then plug in the phono pre but with the turntable not plugged into the phono pre inputs. Do you have more or less hiss? Then plug the turntable into the phono pre. Do you have more or less hiss? ID where the max hiss is coming from. My guess is it's the phono pre gain -- that phono cart has I think a 3 mV output, which is lowish for a MM and probably means you're using more gain that you would with a 5 mV cart and probably have more hiss as a result. That and the integrated (you said the hiss is there with digital sources too ). From the Stereophile measurements section of a review of the amp: "Even after the hum-balancer adjustment, the Line Magnetic's noise floor was higher than is typical for a tubed design. Measured with the inputs shorted but the volume control set to its maximum—the worst-case condition—the unweighted, wideband signal/noise ratios, ref. 2.83V into 8 ohms, were: 57.4dB (16 ohm tap), 59.7dB (8 ohm tap), and 61.5dB (4 ohm tap). Switching an A-weighting filter into circuit improved these ratios to, respectively, 65.6, 67.4, and 68.8dB, which will be barely adequate with high-sensitivity loudspeakers. " Not that those Rega speakers are particularly high-sensitivity. What impedance tap are you using on the integrated? Those are 6 ohm nominal impedance speakers, yes?

    Higher output cart, quieter amp are probably my guesses at the two places where a change would most improve hiss. Tubes? Maybe. A lot of older tubes are noisier than new tubes (though they may sound better and certainly will last longer); and probably most of the thermal tube noise is coming from those hot running output tubes which will cost you a mint to replace with quality NOS stuff.
     
    beowulf likes this.
  4. IanL

    IanL Senior Member

    Location:
    Oneonta, NY USA
    If you can do it, I recommend a dedicated line. If not, then a power conditioner may help. I have the same integrated amp and I don't have any problems with noise. In fact, even with my turntable running, you have to have your ear right up to a tweeter to hear anything. BUT, I had a dedicated line installed a couple years ago and I am sure that is contributing to these results. I also use a fancy outlet and some fancy power cords. While I don't think these other items make a huge difference, I do think they make a cumulative difference. Careful grounding of your phono components and ideal placement are important too, although it sounds like you have that part covered.

    As far as your preamp tubes, you should be able to test them for noise. You can certainly improve the sound quality of your system by swapping in some NOS tubes, but you need to buy from somebody wh0 has tested them and can verify that they are quiet. Otherwise you could just swap one set of noisy tubes for another.
     
  5. Sharp 1080

    Sharp 1080 Well-Known Member

    Location:
    Dallas,TX
    You might want to try what chervokas recommended. From what you describe it is indeed a gain issue. I thought along the same as the above poster as soon as you mentioned the "hiss". Not understanding how listening to the digital side gives you the same problem but less than the phono stage. The digital should be dead quiet in your system. Is it both channels or one channel? Try the stock tubes if you have them around. There might be an issue with the tubes perhaps? Just taking a SWAG.
     
  6. SpiritMachine

    SpiritMachine Active Member Thread Starter

    Location:
    Richmond, VA
    OK. Switching the amp to the input with my DAC and turning the volume all the way up results in essentially zero noise. Turning the volume up on the amp with input selected to my turntable results in audible hiss once I hit 10 o'clock and continues to get louder. If I disconnect the input at the amp, turntable or phono stage the sound goes to zero at full volume. If I turn the gain of my phono stage up the hum is louder...so I am guessing the primary source is my phono stage.

    I have looked at the torus and think I will make the jump at some point but wonder if maybe the first thing to do to get a better phono stage? I am surprised by the noise coming from the Lehmann given it is an $1100 phono stage...is to be expected? If I switch to a MC and therefore need higher gain I wonder if the noise would be even worse?

    Also, thanks for the tip on the dedicated power line. I have asked my electrician for a quote.
     
    IanL likes this.
  7. chervokas

    chervokas Senior Member

    You're always going to have more hiss from using more phono stage gain and more hiss from a phono rig than from typical digital sources. There are phono stages with lower noise specs than the Lehmann, but given that the specs are often measured and/or reported differently it can be hard to make apples to apples comparisons based on the specs. And yes, if you use a low output moving coil and more phono stage gain, you'll likely have more hiss too. You can use a step up transformer and then the lower level of active again from the phono pre and you should have less hiss than you'd have with more active gain. Also, like I said, if that cart's a 3 mV output cart, you could move to a 5 mV output cart, which is a pretty common MM output level, and then probably you can use the lowest gain setting on the Lehmann and probably have less hiss.
     
  8. jupiterboy

    jupiterboy Forum Residue

    Location:
    Buffalo, NY
    When I'm looking at ground hum I sometimes hook the ICs out from the phono pre into my laptop and I can see real-time using free Vonexgo VST software.
     
  9. blakep

    blakep Senior Member

    Unless the issue is very bothersome to the OP while he's playing music I would consider leaving well enough alone. Do you hear the hiss during playback and is it obtrusive on all records while music is playing?

    I have a similar issue (almost the reverse) at play in my system using a very low output MC into a high gain phono stage into a hybrid integrated with ok, but just ok S/N spec of 85 (I see the Line Magnetic is 87) and highish input sensitivity of 375 mV. It really only becomes a noticeable issue when I am playing records that have been cut at pretty low levels and require jacking of the volume in a pretty big way, and even then it's not really an issue when music is playing; it's more that the noise levels generated by the system become noticeable between tracks or when music is not playing and my volume control is close to being maxed out.

    The OP's Lehmann is a gain monster in both MM and MC mode (46 dB in MM and 66 dB in MC), more than enough-some would argue too much-even for a 3 mV moving magnet cartridge. Input sensitivity on the Line Magnetic is also a lowish 220 mV which means you do not have to get far into the volume pot before you're really increasing volume and SPL's. And then there's the 87 dB S/N spec on the Line Magnetic. So it's not surprising there is a fair bit of hiss being amplified on the analog side of things here.

    OP could improve things by doing some serious gain matching with cartridge and phono stage (that would involve replacing one or the other, or both); that would probably quiet things down considerably but even then the LM might well continue to inject some noise into the signal because of its sensitivity and S/N, abeit to a lesser extent.

    Unless it's really annoying while actually listening to music, relaxing and forgetting about it might be a consideration.
     
  10. SpiritMachine

    SpiritMachine Active Member Thread Starter

    Location:
    Richmond, VA
    It does annoy me. It is subtle but distracting in quieter passages when listening to music. I feel like with a 10K system it shouldn't be there. Maybe my expectations are unrealistic.
     
  11. blakep

    blakep Senior Member

    Then buy a good low output M/C cartridge with an output between .15mV and .2 mV that mates well with your tonearm. That should eliminate quite a bit of the noise and also give you a major upgrade in sound quality. That's what I would do if I was you.

    Doesn't make sense to me to start dumping the Line Magnetic or the Lehmann as the cartridge is probably the weak link in your system to start off with.

    But analog is inherently a bit noisier than digital. I actually have a bit more noise as a result of the last upgrade I did (I was pretty much dead quiet before, so it can be achieved) but, as I said, I do not find it to be bothersome, especially in light of the major improvements in overall sound quality it brought about.

    EDIT:

    Whoops, just noticed that your Lehmann has MM settings of 36 dB and 46 dB for MM!

    I initially saw only the 46 dB setting. Not sure which you are using but I would experiment with both of these settings before doing anything. Neither are optimal for your cartridge but I would expect that one would sound quite different than the other with respect to the noise you are experiencing. Unfortunately the "noisier" input might also be the better sounding but there is only one way to find out what your ears prefer. Under the circumstances, my bet would be on the 36 dB of gain but you should definitely try out those two different gain settings if you have not already.
     
    Last edited: Oct 21, 2016
    SpiritMachine likes this.
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