1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Where does clipping/distortion occur ?

Discussion in 'AV Pre-Amp/Processors & Power Amps' started by Toyboy, May 14, 2005.

  1. Toyboy

    Toyboy
    Standard Member

    Joined:
    Sep 10, 2004
    Messages:
    65
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +0
    I know it happens between amp and speaker, when an amp is overloaded, but can this type of distortion occur in the processor if the volume is set too high? My Chord 3005 amp is clipping (blue led's on) at -3db volume on my MC12B with 2 channel music. Dealer said I shouldn't have the MC12B volume that high as it can output a distorted signal to the amp. Is this true ? Source is Pioneer 868i DVD player or Marantz 63SE CD player, same results, both using digital coax input to the MC12B. Output to amp is XLR, speakers are PMCIB1's 4 ohms, 500 watts rating.
     
  2. alexs2

    alexs2
    Well-known Member

    Joined:
    Nov 13, 2002
    Messages:
    13,896
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,674
    It's true to say that any piece of equipment containing active components can be driven into clipping,and thus if the volume control on your MC12 is set to pretty near maximum,it's a possibility.

    Another point is,that even with the fairly compressed dynamic range of a lot of music and DVD material,whilst the average level may be well below clipping,the peak level may transiently be much higher(by 10-20dB or more in some cases),thus putting your amp close to,or at it's clip point.

    Given that your Chord is rated at 4x300W into 8 ohms,to clip it,you could well be listening at levels which won't do your hearing any good in the long term,but in backing off the input level by a few dB,you may be able to stop either it clipping,or damaging your ears.
     
  3. Toyboy

    Toyboy
    Standard Member

    Joined:
    Sep 10, 2004
    Messages:
    65
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +0
    Maximum volume on MC12B is +12db, but I wouldn't dare go anywhere near that. When it clips, it's quite loud, but not loud enough to hurt the ears. It's the bass that drawing the current, as proven if I bi-amp.
     
  4. alexs2

    alexs2
    Well-known Member

    Joined:
    Nov 13, 2002
    Messages:
    13,896
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,674
    Ok...then at that level it's very unlikely to be the MC12 clipping,and the Chord is the source of that in this case,but as I said,given the transient nature of music in terms of peak levels,the amp is being driven to near it's maximum for very short periods.

    Your speakers are relatively efficient at 89dB/W,but are also 4 ohm speakers,which in effect can be said to raise the efficiency to a degree,but at the expense of loading the amp harder,and the Chord doesnt double it's output into a decreasing load.

    All that I'm saying really is that at high volumes,a 4 ohm load is hard work for many amps,even ones as well built as the Chords,and the fact that the clip indicators light at times is simply a reflection of you getting near to their limits.

    Bass always is the heaviest current/power draw on an amp's capabilities.
     
  5. Toyboy

    Toyboy
    Standard Member

    Joined:
    Sep 10, 2004
    Messages:
    65
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +0
    I think you're right, which means I need a bigger amp, like an SPM 4000 or even a pair of 1400E monblocks.
     
  6. alexs2

    alexs2
    Well-known Member

    Joined:
    Nov 13, 2002
    Messages:
    13,896
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,674
    LOL...isn't it always the case!....you can always make a good reason to upgrade,but do bear in mind that to significantly increase the headroom on your current amps you really are entering the realms of high cost and decreasing gains,because doubling the power output of the amp will only raise the maximum SPL by 3dB,and will exceed your speaker's maximum input rapidly.

    I do think that the fact that the clip indicator comes on occasionally isn't a big problem,so much as an indication of you getting near to maximum output on the amp....it's a multichannel amp,and if the other channels are also going at or near full tilt,may explain things to an extent.

    Thankfully(or perhaps not from the upgrade bug view),I've not managed to audibly clip my old Krells,but I'm sure the speakers would give out long before they do,as even very inefficient designs like Linn Keltiks got uncomfortably loud with them before any signs of distress from the KMA's.
     
  7. Toyboy

    Toyboy
    Standard Member

    Joined:
    Sep 10, 2004
    Messages:
    65
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +0
    Chord say that in 2 channel mode, with no output to the other 3 channels, the unused power from those channels is available to the 2 channels in use, as all the outputs loadshare available current. This means that, although it's still 300w per channel, there is more current available from the unused channels, so the 4KWatt PSU in this amp should deliver loads of current in 2 channel mode. Doesn't seem to be working that way.
     
  8. alexs2

    alexs2
    Well-known Member

    Joined:
    Nov 13, 2002
    Messages:
    13,896
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,674
    In theory,the power supply should do what you say,but the output devices will likely not deliver more than their rated maxima,which may explain why the rated power delivery isnt being exceeded....it simply means that the power supply with 2 channels driven is very unlikely to drop line voltage,as a lot of multichannel amps do.

    That's not in any way a criticism of the Chords,which I think are sonically very good indeed,and in many respects similar to Krell.
     
  9. Toyboy

    Toyboy
    Standard Member

    Joined:
    Sep 10, 2004
    Messages:
    65
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +0
    Sounds right to me, the limit has to be the output devices, regardless of how much current is sitting behind them. This amp is fine in surround mode, but it would be, as the front L/R output levels are lower for a given volume in non 2 channel mode. I might just live with it, if it breaks, it breaks. If it can be broken, it's me that will break it. I aslo have a Chord 1200E, which also suffers when driving the fronts in 2 channel mode. Don't know if it's clipping under load, no indicators to show that, but the pretty blue and purple led's under the top grill go dim in time with the bass at -3db, as the power gets sucked away from them. They are wired across the outputs.
     
  10. alexs2

    alexs2
    Well-known Member

    Joined:
    Nov 13, 2002
    Messages:
    13,896
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,674
    I think you'll have a hard job breaking a Chord,but I do see what you're saying,as you evidently enjoy music at reasonably high levels!

    It's quite interesting to see the differences between similarly specc'd amps,as some run out of grunt way before others,even those with lower rated power outputs,and obviously some is down to aggressive protection circuits,but there are a lot of other factors there.....what you describe about the led's dimming may well be the line voltage sagging a bit.

    One of the main reasons I stick with my ancient Krells is that I've yet to find a set of speakers that gives them any trouble at all,at any volume level I can reasonably tolerate....they aren't in many ways the most subtle amps in the world,but virtually bomb-proof.
     
  11. Toyboy

    Toyboy
    Standard Member

    Joined:
    Sep 10, 2004
    Messages:
    65
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +0
    Krell's were on my shortlist, but I wasn't that keen on their sound, but they are bombproof. I prefer the Chord sound myself, but each to his/her own. I'd just rather not be pushing the amp to it's limits on a regular basis. This may not be a problem, but it's like anything that runs at cruise speed, lasts longer.
     
  12. alexs2

    alexs2
    Well-known Member

    Joined:
    Nov 13, 2002
    Messages:
    13,896
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,674
    Very true....the sound of the older Krells(KMA and KSA series) is actually very similar to the current Chords,but I wouldnt recommend looking for old amps unless you get good ones,and things like those arent easy to come by.

    If you did go down that route,the KSA 200 is worth looking for,as is the Levinson 20.5,but both of those will make your Chords rather small(no offence intended) in terms of weight and power consumption!

    In the end,the sound you like is an entirely personal thing,and the bigger CHords will offer that as well....good luck with the upgrades!
     
  13. Toyboy

    Toyboy
    Standard Member

    Joined:
    Sep 10, 2004
    Messages:
    65
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +0
    Chord found the problem with the PSU, said the voltage was set to 27v instead of 48v. At least they owned up.
     
  14. alexs2

    alexs2
    Well-known Member

    Joined:
    Nov 13, 2002
    Messages:
    13,896
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,674
    Interesting....and would mean your amp was delivering about half the power it should have been.

    Certainly enough to explain things....how does it perform now?
     
  15. alexs2

    alexs2
    Well-known Member

    Joined:
    Nov 13, 2002
    Messages:
    13,896
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,674
    This little gem has always reassured me with respect to my amps....

    Resistance RMS watts Current RMS Peak watts Voltage peak
    8 ohms.........132w..........4.06 A .........264w...............46v
    4 ohms.........236w..........7.69 A..........473w...............43.5v
    2 ohms.........420w..........14.5 A..........841w...............41v
    1 ohms.........800W..........28.28 A........1600w..............40V
    0.6 ohms......1140W.........43.6 A..........2281w..............37v


    It actually relates to a Krell KSA 100S,which isn't as grunty into low loads as the earlier series Krells,but still gives an idea of how little the line voltage drops down to 2 ohms,and still continues to deliver some serious power into a load down to 0.6 ohms.

    This explains why at one time,they were the only things properly capable of working with Apogee Scintillas.
     
  16. Toyboy

    Toyboy
    Standard Member

    Joined:
    Sep 10, 2004
    Messages:
    65
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +0
    Only heard from Chord today, sales manager himself bringing "repaired" amp round next week. He'll be getting an ear bashing (from my amp when I thrash it to the limit).
     

Share This Page

Loading...