Question Amp too loud?

Discussion in 'Hi-Fi Stereo Systems & Separates' started by davenice, Nov 8, 2018 at 10:55 PM.

  1. davenice

    davenice
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    I have been attempting to build my 2-channel hifi setup over the last couple of years and I have ended up with the system detailed below. However, whenever I play music, I can't get the volume dial on the preamp past 2 (on a scale of 0 to 11) before the music gets too loud. What do I need to tweak/changes in my setup? Is there is mismatch between my preamp and power amp? Is my amp too powerful for the speakers?

    Source: Oppo 205 (I play CD and Flac via Roon)
    PreAmp: ModWright LS 36.5 (one box version)
    Power Amp: Cyrus Mono X 300 Signature (rated at 319W into 6 Ohms)
    Speakers: B&W CM9 S2 (recommended power: 30W-200W into 8 Ohms)
    Cables: source to preamp(chord chameleon plus RCA), preamp to power amp(chord anthem reference XLR), speaker(chord rumour).
    Room: 16' by 12'

    Please help review. Thanks
     
  2. BlueWizard

    BlueWizard
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    Too Powerful and Too Loud are not the same thing. Huge jumps in power only create small jumps in volume level.

    Your amps are rated at 320w at 6 ohms, converting that to 8 ohms you lose a bit. The estimated 8 ohm power would be 240w/ch (best guess).

    It is not uncommon to have amps rated at more power than the speakers on the assumption that you are never really going to reach full power, especially with a considerable 240w/ch. But, with powerful amps you do have to apply common sense. Any amp can blow any speaker, if you fail to apply it ... common sense that is.

    It is never Over-Powered amps or Under-Powered amps that blow speakers; it is always the guy running the volume control. Don't be that guy.


    In general assuming you are not some drunken irresponsible stoned teenager, I don't see a problem.

    Steve/bluewizard
     
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  3. gibbsy

    gibbsy
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    Great answer Steve. Brilliantly put.:thumbsup:
     
  4. MikeFaulkner

    MikeFaulkner
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  5. RBZ5416

    RBZ5416
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    Attenuators as suggested above is the answer. But probably best between the Oppo & pre-amp as it's usually the high output of CD/DVD/BD that cause this issue. The Oppo being no different at 2.1V output.

    If the Oppo is the only source then it doesn't matter where they go. Just that if you do use other sources, either now or in the future, attenuating the pre-amp may render them too quiet. Of course you can always move them around to suit.

    A quick look at the pre-amp didn't show the sensitivity of the inputs. So before buying attenuators, it may be worth trying alternative inputs in case one has a lower sensitivity for this exact scenario. But obviously not the HTBP as with that activated, you'll send full power to the speakers & that will likely kill them & deafen you!
     
  6. davenice

    davenice
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    Thanks all for the the replies. There is plenty here for me to work through.

    The Oppo is currently my only source which prior to me acquiring the preamp was plugged directly into my power amps. With this configuration (oppo into power amp), I had the same problem and had to limit the oppo’s volume to about 20 (out of 100) when using the analogue out resulting in loss of headroom. I thought introducing a preamp would solve that.

    Reading my preamp’s spec I see that it has a gain of 12dB - does this mean the preamp adds 12dB to the input signal?
     
  7. Timmy C

    Timmy C
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    Attenuators seem the obvious and sensible solution so please forgive me when I tell you the first thing that sprang to mind when seeing your thread title, followed by you comment about a scale of 0-11, was that your problem is your amp is one louder!

    Spinal Tap - "These go to eleven...."
     
  8. BlueWizard

    BlueWizard
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    Ah... I misread the question ...or... part of the question.

    The ModWright 36.5 is about a £4750 Pre-Amp that puts it up on the higher end.

    ModWright LS 36.5 Pre Amplifier

    So, as to the volume control, I had the same problem using a DVD-Universal Player as a CD Player, the volume level was just too high. I used Harrison Attenuators, but in the UK Rothwell are easier to come by.

    These are RCA connectors that have attenuator built in and have worked out excellent for me. Though I thought the slightly long attenuators put too much stress on the Amp's RCA connectors, so I spliced mine in-line. They don't normally sit on top of the DVD/CD, that was just for the photo. Normally they are behind the equipment out of sight. -

    [​IMG]

    I tested the output using an SPL Meter and compared my turntable which I consider the standard level with the output of the DVD/CD player and determined that -12db attenuators would be about right.

    You can read about my process of reaching that conclusion here. That combined with a few more also interesting tests. -

    For What It's Worth - LP vs CD SPL

    Here are some further links to the Rothwell Products -

    ROTHWELL - Attenuators

    Those and others are available on Amazon-UK -

    https://www.amazon.co.uk/Rothwell-RCA-In-Line-Attenuators/dp/B00B7383F8

    It is just a matter of making a best guess on the Attenuation size of the Attenuators.

    I normally played in the 10 o'clock to 11 o'clock position on the volume dial. Without the Attenuators, I played at 9 o'clock or a bit less, and that equalled a roughly 10db need for attenuations. So I choose -12db. Though I think the Rothwell come in -10db.

    https://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias=electronics&field-keywords=Rothwell+RCA+in+line+attenuators

    Steve/bluewizard
     
    Last edited: Nov 9, 2018 at 6:39 PM
  9. davenice

    davenice
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    This is great stuff. Thanks. I will order the -10db attenuators this weekend.
     
  10. BlueWizard

    BlueWizard
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    Just so we are clear, the problem is very most likely your Signal Source, and not your Pre-Amp or Amp. If the incoming signal is too loud (from the source) it can actually overdrive the input stages and cause the early stage equivalent of Clipping.

    So, the Attenuators should go between the Source and the Pre-Amp.

    If you plan to splice the Attenuators In-Line the way I did, you will either need one RCA Cable that has RCA Female on one end and RCA Male on the other, or you will need an RCA coupler as shown in the link below -

    https://www.amazon.co.uk/s/ref=nb_sb_noss_2?url=search-alias=aps&field-keywords=RCA+coupler

    OR -

    https://www.amazon.co.uk/d/RCA-Cables/JuicEBitz-Premium-Shielded-Female-Extension-Red/B01MTAXBP6/

    https://www.amazon.co.uk/deleyCON-Cinch-Extension-Stereo-Gold-Plated/dp/B00HJUH4A8/

    https://www.amazon.co.uk/kenable-Phono-Extension-Socket-Audio-Dark-Blue/dp/B00NCSTEDQ/

    The RCA Male to RCA Female cables are relatively rare.

    Let us know how it works out.

    Steve/bluewizard
     
    Last edited: Nov 10, 2018 at 7:15 PM
  11. Paul7777x

    Paul7777x
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    I’d say attenuators are mandatory from what you describe. And as your usable volume control is so tiny I’d be tempted to opt for a larger attenuation than the nominal 10dB.
     
  12. davenice

    davenice
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    I agree. I will get both the -10dB and -20dB attenuators and see which one works better.
     
  13. Paul7777x

    Paul7777x
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    Can you find out from the preamps manual what the input value is?
     
  14. davenice

    davenice
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    According to the Modwright preamp's manual, input impendance is 50Kohm. And I believe its input sensitivity is 1V, although that is not directly stated in the manual.

    The Oppo output Level is: (RCA) 2.1±0.2Vrms. (XLR) 4.2±0.4Vrms. I'm currently using an RCA cable from source to preamp.

    @BlueWizard, rather than splicing the attenuator inline etc., I think for now I will just get the Rothwells and plug it at the end of my existing cable.
     
  15. MikeFaulkner

    MikeFaulkner
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    I'd experiment with both, between source and Pre and Pre and Power. I initially bought mine to tame my CDP, which it did but left me with an imbalance in volume settings. Once i put them between Pre and Power I can play CD and Vinyl at the same volume level.

    Don't forget, I am talking about MY system, yours may be the opposite.
     
  16. Paul7777x

    Paul7777x
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    2.1V is about par for a CD player analogue output, and if the preamp really is 1V then it shouldn’t have the tiny volume movement you describe. Small, but not minuscule.

    I can only suggest that the gain of the power amp is rather large as well.

    If so it may suit you to have -10dB from the player, and -10dB from the preamp to the power amp too.

    Also, in case you didn’t know already, it’s best to put the attenuators at the end of the cables, ie, going into the power amp connectors and into the preamps.
     

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