Attenuators effect SQ?

Discussion in 'Hi-Fi Stereo Systems & Separates' started by sebbyp, Jan 4, 2012.

  1. sebbyp

    sebbyp
    Active Member

    Joined:
    May 23, 2011
    Messages:
    520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Surbiton
    Ratings:
    +27
    Hi Guys

    I have a bit to much Gain in my system at the moment. I wanted to gain more volume control and reduce noise.

    I bought a cheap pair of Attenuators - Monacor ILA-1020 Passive Level Attenuator (Pair), 212840

    Wanted to test with a cheap basic pair before I looked at the likes of Rothwell...

    Got them plugged in and working, to be honest - I feel like they have made low level listening very thin.

    Is that my imagination or can it affect SQ?

    Seb
     
  2. noiseboy72

    noiseboy72
    Well-known Member

    Joined:
    Apr 24, 2011
    Messages:
    5,419
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,457
    Attenuators can reduce the input impedance of the amp and that could affect sound quality. However, a signal that is too loud could also have been overloading the input to the amp and that might have thickened the sound up a bit...

    TBH I think the drop in volume is probably making you perceive a change in quality rather than anything else.
     
  3. steveledzep

    steveledzep
    Active Member

    Joined:
    Aug 3, 2009
    Messages:
    485
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Swansea
    Ratings:
    +56
    Yes, I'm sure attenuators affect sound quality. That's why I use a pair between my cdp and amp. Without attenuation, I can't get the volume past 9 o'clock when using my cdp, it's too painful. That suggests to me that the cdp output is too high for the pre-amp on my MF to cope with. I use -10dB Goldenjacks and am very pleased with them. My cdp sounds a lot smoother and is not shouting at me any more. The overload of the input circuitry is introducing distortion which is intolerable at high volume levels. Maybe this distortion is having the effect of the old loudness button when listened to at low levels ? I have a dedicated listening room, so don't listen at low/background levels. Maybe that's why your music sounds "thin" at low levels ?

    Just a thought ?
     
  4. BlueWizard

    BlueWizard
    Distinguished Member

    Joined:
    Jun 19, 2007
    Messages:
    21,556
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +4,024
    The impedance using an Attenuator should be stable. I suspect they assume a 47k Ohm impedance for the amp, and with the attenuation, the driving source will still see 47k Ohms. The only potential problem is if the input impedance is NOT 47k Ohms, though that is rare, and the amount of attenuation will shift only slightly.

    I've got a couple of them coming in the mail, I'm hoping they will be here tomorrow. Then I'll see if there is any change in sound quality or noise. There really shouldn't be as the attenuator is only a couple of resistors, and you amp is filled with other resistors, so there shouldn't be a problem.

    The problem is determining how much attenuation you need. I did an analysis of my system here -

    http://www.avforums.com/forums/hi-fi-systems-separates/1561542-what-its-worth-lp-vs-cd-spl.html

    In my case, using an SPL Meter, I determined I needed about 10dB of attenuation. The closest value we 12dB, we'll see how well that works.

    Steve/bluewizard
     
  5. Mark.Yudkin

    Mark.Yudkin
    Well-known Member

    Joined:
    Sep 19, 2007
    Messages:
    9,909
    Products Owned:
    0
    Products Wanted:
    1
    Trophy Points:
    136
    Location:
    Zurich, CH
    Ratings:
    +1,505
    Maybe it's just the specific attenuator (I can't find technical details)? I'd have said to go with a Rothwell if you need to attenuate.

    Incidentally, an attenuator will increase noise, inserting an attenuator in order to reduce noise is counterproductive.
     
    Last edited: Jan 6, 2012
  6. alexs2

    alexs2
    Well-known Member

    Joined:
    Nov 13, 2002
    Messages:
    13,959
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,671
    The Rothwells are good but expensive.

    There is no doubt in most people's opinions that attentuators can affect sound quality,both beneficially(as in the case of an input overloaded by high output from typically a CD player),and sometimes adversely,in terms of flattening the apparent dynamic range and so on.

    As with so many things,it's a trade off between the benefits and downsides.

    I used both Rothwell fixed attenuators,and also an Audio Synthesis passive pre,when I had input stages on a couple of amps which were unable to deal with peak levels from a CD player.
     
  7. Alan Mac

    Alan Mac
    Active Member

    Joined:
    Feb 13, 2007
    Messages:
    1,459
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Location:
    Highlands of Scotland
    Ratings:
    +248
    The Rothwell “10 dB” attenuator consists of a 22 kΩ series resistor and a 10 kΩ parallel resistor. The assumption in this case is that the amplifier input impedance is infinite.

    If the input impedance of the amplifier is actually 47 kΩ then:

    the attenuation will be 11.3 dB

    the driving source will see 30.2 kΩ


    Alan
     
  8. alexs2

    alexs2
    Well-known Member

    Joined:
    Nov 13, 2002
    Messages:
    13,959
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,671
    Nicely explained.

    Input and output impedance can have quite significant effects on the ability of (particularly some op-amps)the source component to drive the input stage of the amplifier.

    Not all are very good at dealing with relatively low input impedances.
     
  9. sebbyp

    sebbyp
    Active Member

    Joined:
    May 23, 2011
    Messages:
    520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Surbiton
    Ratings:
    +27
    After a solid day of blind testing, with a few friends... (spl meter in hand)

    The attenuators were having a negative effect on the dynamics of the system. I don't think this would happen in everyone's system.. However my pre-amp I'm temporarily using has an obscenely high output impedance.. With the attenuators in place the impedance was clearly becoming to high for the power amp.
     
  10. BlueWizard

    BlueWizard
    Distinguished Member

    Joined:
    Jun 19, 2007
    Messages:
    21,556
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +4,024
    I just installed the 12dB Attenuators on my system, so far I've only played one CD but I'm seeing very positive improvements, though my volume control is only slightly higher than before. Originally it was at about 9 o'clock, now it is between 9 o'clock and 10 o'clock, still below what I'm used to, but the sound is now more mellow.

    It is hard to describe how the sound was before the attenuators. It is not that it sounded bad, but it came across as aggressive and grinding. I guess one could say the music had something of a sharp edge. Now that edge has softened, and as I said, is far more listenable.

    Again, I haven't had much time to play with it. Once I have more time, I'll make some measurements and post them in my other thread, as linked to above.

    Right now I'm in the middle of a small woodworking project, and have to get the finish coat on some wood, but after that, I'll test the same CDs as before, and see if I'm really getting the attenuation stated in the specifications of the attenuators.

    Referring to what Mark.Yudkin said about noise -

    "Incidentally, an attenuator will increase noise, inserting an attenuator in order to reduce noise is counterproductive."

    Yes, all resistors are noisy, but the noise is atomic level noise, and is very small. However, when amplified it can be noticed ... in some cases. Keep in mind that your amp is filled with resistors, they can't be adding all that much noise or it would be a lot more prominent.

    As in most cases, the signal swamps these minor 'atomic level' noises.

    Steve/bluewizard
     
  11. noiseboy72

    noiseboy72
    Well-known Member

    Joined:
    Apr 24, 2011
    Messages:
    5,419
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,457
    Although I understand what you are trying to say, you are incorrect in saying the impredance is becoming too high for the power amp. When you ay your pre-amp has a high output impedance, how are you measuring it ? Anything with either a pre-amp or transistor buffer stage as it's output will have a an output impedance of better than 600 ohms, and probably more like a few ohms. Is your connected via a high impedance transformer or something ?

    There are very few resistors in the direct signal path of a well designed amp. Most will be used for biasing and for negative feedback loops that stabilise the amplifer.

    If you are handy with a multimeter and a soldering iron, you could always look at changing the voltage gain of the power amp by modifying the input stage gain. I have done this on my AV amp so that I can drive a pair of tactile transducers off an unused Centre channel. I effectively added 6dB of gain by changing a resistor in the feedback loop on the input buffer.
     
  12. sebbyp

    sebbyp
    Active Member

    Joined:
    May 23, 2011
    Messages:
    520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Surbiton
    Ratings:
    +27
    I havent measured but taken the information from the spec sheet for each item:

    Pre: Output / Impedance 1V / 470 Ohms

    Power amp:
    Input impedance 10k.
    Output impedance 0.01
    ...

    The Pre is a tempoary fix, a budget Rotel integrated - hence the poor stats. 460 is WAY to high! The power amp is a DIY build with Hypex modules and HUGE transformers.

    Naim amps are under 50!

    I dont want to mess with the power amp, the pre that will be replacing it is close to 0 ohms as possible.

    Which should allow me to use attenuators if required.

    We have all the tools between us to measure, however we wanted to take an opinion from listening. Will be interesting to see what happens with the new pre.

    Seb
     
  13. noiseboy72

    noiseboy72
    Well-known Member

    Joined:
    Apr 24, 2011
    Messages:
    5,419
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,457
    Errmm, why would you need attenuators between the pre and power amp ? Surely you can just turn the pre-amp down ? Then any issues with the loading of the attenuators is neagted. There will only be at most a buffer between the volume control and the output.

    Attenuators are normally only required to drop the level of "fixed" outputs - IE CD players etc. I can see why you would need them between the sources and the input to the preamp.
     
  14. sebbyp

    sebbyp
    Active Member

    Joined:
    May 23, 2011
    Messages:
    520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Surbiton
    Ratings:
    +27
    The same reason anyone buys attenuators.

    To gain more volume control on the pre-amp.

    "Although the attenuators can be used on the inputs of the pre-amp in exactly the same way as they would be used on an integrated amp (with the same benefits), alternatively they can be used between the pre-amp and the power amp to even greater effect. When used this way, not only is system gain reduced by 10dB, but the signal to noise ratio is improved by 10dB. This pushes the noise floor down enough to create an inky black silent background from which the music can emerge with better resolved fine detail and transparency. This applies to even very high-end and very expensive pre/power amps."
     
  15. Alan Mac

    Alan Mac
    Active Member

    Joined:
    Feb 13, 2007
    Messages:
    1,459
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Location:
    Highlands of Scotland
    Ratings:
    +248


    Adding an attenuator anywhere in the chain can only reduce (degrade) the signal to noise ratio.


    Alan
     
  16. sebbyp

    sebbyp
    Active Member

    Joined:
    May 23, 2011
    Messages:
    520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Surbiton
    Ratings:
    +27
    True, but if between Pre+power will affect all sources not just one.

    Edit in my system it was more of a degrade.
     
  17. ozzzy189

    ozzzy189
    Well-known Member

    Joined:
    Jun 1, 2006
    Messages:
    7,600
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    North Lincolnshire
    Ratings:
    +1,134
    Don't confuse 'dynamics' with harshness, edginess and hard sound that's too forward.
    With correct attenuation your music should be more musical, easier to follow, more enjoyable and less tiring. You should also be able to listen at a higher volume and have an increase in the scale of the music without the harsh 'grab you by the throat' sound favoured by the likes of what hifi.
     
  18. sebbyp

    sebbyp
    Active Member

    Joined:
    May 23, 2011
    Messages:
    520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Surbiton
    Ratings:
    +27
    I hear what everyone is saying, however I think without the attenuators... I did not really have that harsh/edgy sound. However - I do a lot of low level listening, so I was looking for some more control on the first 25% of the volume knob that is all. As someone pointed out earlier, maybe I just had it playing too quiet with the attenuators in hence calling in my friends to help assess and test multiple volume levels.

    At the moment I am very happy with the latter end of my chain (Power amp -> speakers). To give a bit of history over the last two months I have done a variety of home trials that generally lasted a week. I have tried a: Bryston BP-60, Bryston 3bstt2, Naim Supernait, Naim 202/200 and a Linn Akurate Pre/Power..

    The Hypex produced the most enjoyable sound to ME. It doesnt matter how loud it gets, it is still airy and spacious. No wall of sound effect/harshness, they just seem to keep driving and driving. Soundstage remains perfect, the space around instruments doesn't disappear!

    I think it depends on your system and how you enjoy your music. I am happy with mine without the attentuators, was just looking for a small benefit of having more lower end volume control. The reason for the post was to ascertain if people had come to the same conclusion I had within their system.

    :)
     
  19. noiseboy72

    noiseboy72
    Well-known Member

    Joined:
    Apr 24, 2011
    Messages:
    5,419
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,457
    Can't fault you on wanting to improve the S/N ratio of your system. It will improve quiescent noise, but I would argue against the S/N claim, as you will need to increase the gain on the pre to compensate, and the gain control will be after most of the gain (Noise adding) stages. Normally, one adds as much gain into a signal chain as early as possible and does not reduce gain half way through, certainly not just before the current gain stage.

    Looking at the Hypex modules, do they not have have input gain trim ? I spied a variable resistor and assumed that it was for that purpose.

    My comments on modding the power amp would also apply to the pre. You might find you can even knock out a whole gain stage and run it as almost a passive pre. Probably worth a play if you are into DIY!

    I would also ditch the big transformers and no doubt matching caps on the power amp PSU and stick in a meaty swtich mode. The bass attack and bottom end will improve significantly.
     
  20. sebbyp

    sebbyp
    Active Member

    Joined:
    May 23, 2011
    Messages:
    520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Surbiton
    Ratings:
    +27
    To be honest I hadn't looked for an input gain trim.... Will have to check that out..

    I have been planning on building a passive pre, in a separate box however time is at a limit this early into the new year! Waiting for my M-dac to come back to see how it works using that as a pre.

    Interesting note on the transformers..... The power supplies are my friends design. What is the reasoning behing using a SMPS? Hypex do sell them and I had been considering going from Dual mono to Mono blocks with SMPS..

    The amp is close on 20 kilos at the moment... Would be nice to lighten it..

    Pictures to show...

    [​IMG]

    [​IMG]
     
  21. ozzzy189

    ozzzy189
    Well-known Member

    Joined:
    Jun 1, 2006
    Messages:
    7,600
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    North Lincolnshire
    Ratings:
    +1,134
    What did you think of the akurate pre /power? I'm thinking of ak amps in the future. They need a long time running in to sound their best though.
     
  22. sebbyp

    sebbyp
    Active Member

    Joined:
    May 23, 2011
    Messages:
    520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Surbiton
    Ratings:
    +27
    They're really very good, as you would expect from a brand like Linn. I am not great at reviewing, hence why I didn't post any of my findings last year. I always guesed Linn's house sound was rather more laid-back and rather coloured, hadnt heard any of their gear until then. Especially compared to some of the more neutral offerings on the market.

    But.... The Akurate were clean, crisp, fast on dynamics and extremely neutral... albeit slightly bass light. The dealer said there was something on the back that could allow for my bass depth... Didnt bother to explore it.

    At 7 odd thousand VFM wasn't there for me, there was no huge jump between the Bryston pairings at half the price. This probably had a large factor into what I washearing. Bryston and Hypex are known for the same clean and revealing sound hence there success in the mastering industry.

    Hypex took it a step above the Linn in my opinion, when it came to the sound staging, tonal balance and realism.

    I looked at the Linn, for more of a sanity check. I dont want to be changing my amp again for a while. Used it as a benchmark.
     
  23. noiseboy72

    noiseboy72
    Well-known Member

    Joined:
    Apr 24, 2011
    Messages:
    5,419
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,457
    Nice and clean amp design. the only thing I might have done differently would be to rotate the toriodals around so that the connections were away from the amps as this tends to be where any interference stems from. Probably not an issue on a power only amp.

    Setting aside the possible electromagnetic interference, the advantage of switch mode is simple. A linear power supply with a transformer, bridge rectifier and capacitors refreshes each power supply rail 100 times a second. Therefore, if the music content depletes the power supply rail, it must wait until the next half cycle to re-charge. A switch mode PSU recharges the rail thousands of times a second (Depends on the invertor speed, could be millions), therefore, the supply has less ripple.


    The common approach to overcome ripple on linear supplies is to fit bigger capacitors, which leads to bigger in-rush current, which leads to bigger transformers...

    Older Switch mode designs had noise and stability issues, but this is all in the past.

    Looking at the hypex design, it accepts balanced line signals. This will further improve signal to noise and should give you enhanced dynamic range as well. This does increase the demands on the pre, but might be worth the effort.
     
    Last edited: Jan 7, 2012
  24. sebbyp

    sebbyp
    Active Member

    Joined:
    May 23, 2011
    Messages:
    520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Surbiton
    Ratings:
    +27
    Thanks Noiseboy, I think you are right to switch over to a SMPS.

    I have also been looking at going Balanced funnily enough. I think this is the kick up the ass I needed. Time to get ordering some good looking mono cases, balanced inputs and a couple of Hypex SMPS.
     
  25. ozzzy189

    ozzzy189
    Well-known Member

    Joined:
    Jun 1, 2006
    Messages:
    7,600
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    North Lincolnshire
    Ratings:
    +1,134
    Cheers for the input noiseboy, there's no thank you button on the avforums app, and even when I open up the browser, still now there, so I'll say thank you here! I'm looking at second hand. Linn's new stuff is far removed from the 90's black boxes. My exotik is an akurate Kontrol generation one in all but name, i paid 800GBP for it. I hopefully to be in a position to buy a couple of 3200's in a year or two, chakra ones will be fine, don't have to be latest model. They should come in about 3k, with a bit back for my gear, it should be a great upgrade.
     
  26. sebbyp

    sebbyp
    Active Member

    Joined:
    May 23, 2011
    Messages:
    520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Surbiton
    Ratings:
    +27
    Did you mean Noiseboy or me lol?

    Secondhand is the best way forward in any Hi-Fi purchase! End of Year bonus only reason I was even considering something new.

    Good luck with the upgrade!
     
  27. ozzzy189

    ozzzy189
    Well-known Member

    Joined:
    Jun 1, 2006
    Messages:
    7,600
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    North Lincolnshire
    Ratings:
    +1,134
    LOL, you're correct sebbyp, sorry dude, bloody phone app! Not as good as the desktop site by a mile.
     
  28. zorrofox

    zorrofox
    Active Member

    Joined:
    Jan 20, 2008
    Messages:
    222
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Location:
    Dundee
    Ratings:
    +13
    I've been following this thread with interest and have a question. My system is shown in my sig and I'm wondering if lowering the output level of my soundcard would have a similar effect to using attenuators. Any thoughts?
     
  29. noiseboy72

    noiseboy72
    Well-known Member

    Joined:
    Apr 24, 2011
    Messages:
    5,419
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +1,457
    It depends how you reduce the level from your sound card.

    Digital reduction reduces the level of the signal in the digital domain, so effectively you end up with a lower resolution signal. Not a big issue with 24 bit cards, but on 16 bits, the effect is noticable. Reduction should be analogue - post the DACs for best resolution. In this case attenuators are your friend!
     
  30. zorrofox

    zorrofox
    Active Member

    Joined:
    Jan 20, 2008
    Messages:
    222
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Location:
    Dundee
    Ratings:
    +13
    Ah ok, that clears that up. I actually went ahead and tried it but other than the volume decreasing I couldn't hear any positive change.
     

Share This Page

Loading...
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice