1. Join Now

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

Do all THX approved amp’s have the same gain?

Discussion in 'AV Receivers & Amplifiers' started by pwiles1968, Oct 5, 2003.

  1. pwiles1968

    pwiles1968
    Active Member

    Joined:
    May 15, 2003
    Messages:
    773
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Location:
    Leicestershire - England
    Ratings:
    +10
    I can not remember where I read that all THX approved Amplifiers have the same gain it was probably on these forums somewhere, but I have never confirmed it, can anyone confirm :confused: .

    The reason I ask is that eventually I will upgrade my kit, but I would like to keep the mono-blocks (you may have guessed from other threads I am very keen on them). If the above statement is true I can match them up with other THX kit not just Marantz and they should have the same gain. I know there could be tonality differences but I will cross that bridge whenever. It is looking like it will be a very long time before I can afford to upgrade to something that will give enough performance difference to warrant the change.
     
  2. avanzato

    avanzato
    Active Member

    Joined:
    Jan 21, 2003
    Messages:
    1,874
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    51
    Location:
    Norfolk
    Ratings:
    +60
    From what I remember THX amps do have the same gain or a variable trim control marked with a THX reference level.

    What are you thinking of getting? Going the whole way with THX speakers, DVD etc. or not?
     
  3. pwiles1968

    pwiles1968
    Active Member

    Joined:
    May 15, 2003
    Messages:
    773
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Location:
    Leicestershire - England
    Ratings:
    +10
    That is what I heard, thanks for the reply, it was more a curiosity question for the moment.

    Currently I cant even afford to buy myself films, I am quite happy with the system as is, but that will not last forever, I will probably go processor and power amp route (possibly THX) and as far as speakers you know what they say about first love, I do not think I will ever go away from B&W.

    In the short term I am looking to reduce the amount of Kit I have, either replace my CD & DVD with a universal player (DV6400 looks nice) or replace DVD and Video with a DVD recorder, have not decided which yet. :confused:
     
  4. John Dawson

    John Dawson
    Member

    Joined:
    Jan 16, 2001
    Messages:
    852
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    43
    Location:
    Cambridge, UK
    Ratings:
    +112
    The THX power amp gain is standard and is 28.3 times - i.e. 1 volt input gives 100W rms into 8 ohms.

    Even if the gains of your various power amps were different, you would be able to correct for this in the processor on a per channel basis, in 1 or perhaps 0.5 dB steps.

    HTH.

    John Dawson (Arcam)
     
  5. pwiles1968

    pwiles1968
    Active Member

    Joined:
    May 15, 2003
    Messages:
    773
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Location:
    Leicestershire - England
    Ratings:
    +10
    I believe this is only totally correct at a fixed volume as the correction is a dB offset rather than a gain adjustment (high end processors may be different), admittedly most people probably would not notice the difference at other volumes anyway.

    What gain will the AVR300 have? Will it be possible to re route some of the internal amplification in order to Bi Amplify the Front Pair? or will this require an extra amp And will it have any multi room capability?
     
  6. John Dawson

    John Dawson
    Member

    Joined:
    Jan 16, 2001
    Messages:
    852
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    43
    Location:
    Cambridge, UK
    Ratings:
    +112
    Paul - unless you are trying to biamp one channel with two different amplifiers this type of gain correction (on the processor) will work at all volume settings. It is no different from compensating for loudspeaker sensitivity.

    As to the upcoming AVR 300 I would like to thank you for your interest in its feature set and your comments are noted. However I am not in a position to release its specification into the public domain at this time. All I can say it that it is pretty comprehensively equipped.

    Sincerely,

    John Dawson (Arcam)
     
  7. pwiles1968

    pwiles1968
    Active Member

    Joined:
    May 15, 2003
    Messages:
    773
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Location:
    Leicestershire - England
    Ratings:
    +10
    If you used an amp with a different gain for one of the sets of speakers (i.e a gain of 25 on front L/R and 28.3 on all others) and you adjusted the levels in the processor so the SPL was the same on all speakers (I have always assumed the adjustment is a fixed offset and not a gain change) then when you change master volume surely the speakers would then be out of level, or am I missing something. :confused: Are you saying that the amp applies a gain compensation? Is this just Arcam or are most processors like this?


    I appreciate your comments on revealing spec details, I did not know how much info was in the public domain already, I look forward to seeing the specification. :smashin:
     
  8. John Dawson

    John Dawson
    Member

    Joined:
    Jan 16, 2001
    Messages:
    852
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    43
    Location:
    Cambridge, UK
    Ratings:
    +112
    Paul - a fixed offset in dB (which is a logarithmic scale) is exactly the same as a gain change! FYI 1dB represents appoximately 12% gain change in terms of amplitude. So a change in gain of 25 to 28.3 is 20log(28.3/25) = 1.08dB.

    AFAIK all processors work in this way.

    John Dawson (Arcam)
     
  9. Paul Reading

    Paul Reading
    Member

    Joined:
    Feb 2, 2003
    Messages:
    92
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +0
    Dear John,

    I know you don't want to say anything about the product, but are you able to give an indication as to timing of release?
     
  10. pwiles1968

    pwiles1968
    Active Member

    Joined:
    May 15, 2003
    Messages:
    773
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Location:
    Leicestershire - England
    Ratings:
    +10
    That makes sense, thank you for your time and for bearing with me. :)
     
  11. John Dawson

    John Dawson
    Member

    Joined:
    Jan 16, 2001
    Messages:
    852
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    43
    Location:
    Cambridge, UK
    Ratings:
    +112
    Hi Paul,

    If the project continues to proceed to plan then you can expect to be able to buy AVR300s from retailers in the UK very early in the New Year. This I believe to be a realistic timescale, i.e. not overoptimistic.

    HTH.

    John Dawson (Arcam)
     
  12. Miron

    Miron
    Active Member

    Joined:
    Sep 26, 2002
    Messages:
    1,408
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    51
    Location:
    Vienna, Austria
    Ratings:
    +49
    John, I understand you do not want to comment AV300 yet because of political reasons, but is it really smart/fair to show it to public and advertize it (usa distributor at least) and to keep quiet about the features?
     

Share This Page

Loading...