1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

interesting article about "transistors vs tubes" in audio

Discussion in 'General Electronics Chat' started by unclejed613, Nov 28, 2011.

  1. unclejed613

    unclejed613 Well-Known Member

    Joined:
    Apr 3, 2009
    Messages:
    1,828
    Likes:
    99
    there are such DSP devices for home systems. in fact they are built in on many home theater A/V receivers. and they can do some amazing things. Yamaha makes a line of sound bars that use DSP to create "virtual" surround speakers using room reflections and phased array techniques. when our repair shop went through Yamaha training, we set one up and let it go through it's "learning" routine. if you were anywhere in the center area of the room, the effect was very convincing. all there was in the room was the sound bar and subwoofer at the front of the room, but you could hear sounds from the back corners of the room as if there actually were speakers there. Denon receivers have Tom Holman's Audyessy automatic room EQ system in their DSP, and it works quite well.
     
    Last edited: Dec 3, 2011
  2. Sceadwian

    Sceadwian Banned

    Joined:
    Oct 27, 2006
    Messages:
    14,047
    Likes:
    141
    Location:
    Rochester, US
    The space where those kinds of effects are distinguishable are very small though unclejed, and moving your head in relation to the speaker arrangement's destroys the effect, might as well wear headphones.
     
  3. unclejed613

    unclejed613 Well-Known Member

    Joined:
    Apr 3, 2009
    Messages:
    1,828
    Likes:
    99
    actually, the effect persists over a wide area of the room, except for within 2 feet of any wall, where you begin hearing the directed sound from the sound bar. i fully expected it to only be effective in the spot where the setup mic was, but it's effective over a much wider area.
     
    Last edited: Dec 3, 2011
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. Mr RB

    Mr RB Well-Known Member

    Joined:
    Jul 22, 2008
    Messages:
    4,716
    Likes:
    194
    Location:
    Out there

    Well i don't own one and don't care that much either way, but for $350 in most loungerooms with a decent enough amp and speakers it would probably do more for HiFi sound than a purchase of an "audiophile" $2000 amp and $2000 speakers...

    You can't really mention "surround system" in a discussion about music HiFi quality!

    You do know what a surround system does to those two perfectly mastered stereo 16bit audio channels? :eek: It's not nice.
     
  6. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,331
    Likes:
    653
    Location:
    Derbyshire, UK
    You're not supposed to play stereo through a surround system, you should set it to stereo (plus sub) only.

    But I agree, surround isn't as good a quality as a decent stereo.
     
  7. Sceadwian

    Sceadwian Banned

    Joined:
    Oct 27, 2006
    Messages:
    14,047
    Likes:
    141
    Location:
    Rochester, US
    I had a sound card that had decent software setup that used a 4.1 surround system that had an option that phase shifted the rear channels somehow, stereo sounded great from four speakers.
     
  8. tvtech

    tvtech Well-Known Member Most Helpful Member

    Joined:
    Mar 27, 2010
    Messages:
    3,167
    Likes:
    348
    Location:
    South Africa
    Really good Audio equipment is designed to be used without any interference/modifications from any form of equalizer/signal modification.

    I have heard the best. Those that say valve amps are always distortion monsters are talking out of their backsides. There are valve amps that are purposely designed for stage amplification for live guitarists performances. See here http://en.wikipedia.org/wiki/Peavey_Electronics

    Then there are others that deliver absolute accuracy for Audiophile reproduction of a musical performance. See here http://www.audioresearch.com/products.html

    Now what are you ignoramuses going to say about valve amps in general again??

    Thank You
    TV Tech
     
  9. Sceadwian

    Sceadwian Banned

    Joined:
    Oct 27, 2006
    Messages:
    14,047
    Likes:
    141
    Location:
    Rochester, US
    tvtech.. yer funny =)
    The quoted distortion of one of those tube pre-amps is .01%

    Just one random chip I found The LM4562 from National Semiconductor has a THD+N of 0.00003%

    It is a simple and absolute fact that no tube amp regardless of how well designed can do better than a well designed solid state amp at signal reproduction.
     
    Last edited: Dec 4, 2011
  10. tvtech

    tvtech Well-Known Member Most Helpful Member

    Joined:
    Mar 27, 2010
    Messages:
    3,167
    Likes:
    348
    Location:
    South Africa
    You are not listening for distortion...it's a music thing...right??
     
    Last edited: Dec 4, 2011
  11. Blueteeth

    Blueteeth Well-Known Member

    Joined:
    Oct 15, 2003
    Messages:
    1,168
    Likes:
    34
    Location:
    Hertfordshire, UK
    I would like to point out that 'guitar amps' and 'hifi amps' are two different beasts. Hifi, for reproducing 'music' or sound accurately are designed for the lowest distortion possible, with flat response. Guitar amps (be they valve, or solid state) are designed to purposefully colour the sound - significantly. The area of guitar amps appears to be the bulk of the 'valves vs solidstate' debates all over the internet.

    We're not talking 'distortion' as an added effect for metal/rock, or overdrive although that is designed into the amp and speakers. Even when a guitar amp is 'clean', it exhibits much greater signal distortion over hifi amps. You can try this yourself - plug your guitar into a buffer (for impedance) then A/B it into a guitar amp and speaker, and hifi amp with its speaker. The hifi amp will sounds teribly stale, cold, and generally unpleasant when compared to the guitar amp - thats because that is what the guitar signal is :) A guitar amp/speaker will amplify harmonics, even when well below the 'overdrive' threshold - sounding perfectly clean. Also note: guitar amp speakers are designed to enhance this - limited frequency respose in the mid-range.

    Whilst most of us electric guitarists love distortion/overdrive (there's a massive culture/debate/discussion/religion about it on the web) many forget about a clean tone, and somehow assume its just the guitar signal 'but louder'. It really isn't. Otherwise all guitar amps would sound the same when clean, and there wouldn't be countless digital effect processors all with hundreds of 'clean amp modelling' (otherwise, the clean tone wouldn't require any processing!).

    So, not trying to get off track here, after all this is all 'valves vs solid state' - but for electric guitars or basses, they serve to change the sound as well as amplify, so they have the opposite goals of a true 'amplifier'. tvtech, its easy to get confused when words like 'distortion' is used. In guitar amps, it generally means crunch/grind where the amp is designed to have high distortion, with a low clipping threshold, and distort 'musically'. In true electronic amplifiers, that is something which is to be avoided, at all costs. I have probably over-simplified it, after all many have gone into great detail, but essentially, thats what I understand, and agree with.

    I haven't even touched on 'why' what with modern processing guitarists still use unreliable, heavy, expensive valve amps - its just because historically, electric guitars have been used with them, because at the begining, they were the only amps available, and we've all grow up listening to guitar music made with valve amps (or music influenced by music made with valves)
     
    Last edited: Dec 4, 2011
    • Like Like x 1
  12. unclejed613

    unclejed613 Well-Known Member

    Joined:
    Apr 3, 2009
    Messages:
    1,828
    Likes:
    99
    one of the major differences between tube amps and solid state amps is in their output impedance. this has an effect on how the speakers interact with the amplifier. this is another reason why a "clean" guitar tube amplifier and a solid state home audio amplifier sound so much different. the higher output impedance of the tube amp (typically 8 ohms) allows the speaker cones to "do their own thing", so that cabinet and driver resonances are more pronounced. this is mentioned in the article i linked in post #1 of this thread. i also have done some study of the subject, and it's described in the pdf linked to the blog article here http://www.electro-tech-online.com/blogs/unclejed613/121-ac-ohmmeter-revisited.html
     
  13. bountyhunter

    bountyhunter Well-Known Member

    Joined:
    Jul 17, 2009
    Messages:
    1,560
    Likes:
    81
    Some years back, a buddy of mine showed me a sub woofer that had a second "control" winding on the voice coil paired up with a special amp that used the "position" information from the winding on the voice coil to apply corrective signals to force it to track the desired (input) signal...... as opposed to just letting it "do it's thing". Sounded really tight.
     
  14. bountyhunter

    bountyhunter Well-Known Member

    Joined:
    Jul 17, 2009
    Messages:
    1,560
    Likes:
    81
    I maintain there is a peculiar pleasure to be derived from watching something glow.... like a fireplace or a tube filament.
     
  15. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,590
    Likes:
    951
    Location:
    Canada, of course!
    ONLINE
    Modern speakers are designed to have their resonances damped by the extremely low output impedance of a modern solid state amplifier.
    Speakers made 50 years ago were allowed to "do their own thing" because a vacuum tubes amplifier had a high output impedance that did not damp anything.

    A modern amplifier driving an old speaker damps it too much then there is little bass and other problems.
     
  16. unclejed613

    unclejed613 Well-Known Member

    Joined:
    Apr 3, 2009
    Messages:
    1,828
    Likes:
    99
    that's called a "servo" amp, where the second voice coil signal is summed into the amplifier feedback loop. this makes for a very "tight" control of the cone motion, and compensates for some of the mechanical distortion mechanisms of a speaker. unfortunately, the amp must be in the enclosure, as the wiring between amplifier and speaker need to be short. long wires and their stray inductances and capacitances would cause errors in the feedback.
     
  17. bountyhunter

    bountyhunter Well-Known Member

    Joined:
    Jul 17, 2009
    Messages:
    1,560
    Likes:
    81
    That's surprising since the impedance of the feedback coil would be ralatively low and the current through it not much.

    Or maybe you mean the amp driving the sub power coil needs to be close to minimize length to the voice coild doing the driving. That line could have high peak currents.
     
  18. unclejed613

    unclejed613 Well-Known Member

    Joined:
    Apr 3, 2009
    Messages:
    1,828
    Likes:
    99
    feedback loops must be kept short to minimize errors. and to avoid capacitive and inductive coupling that might cause oscillation. the sense coil since it is experiencing the same motion induced induction that causes the back-emf on the actual voice coil, creates a copy of the back-emf, without the signal applied to the voice coil itself. the copy of the back-emf contains the slight errors caused by nonlinearities in the cone motion (so does the back-emf of the voice coil itself, but many of the nonlinearities may be masked by the voltage drop through the high current wiring to the voice coil) and since it is voltage feedback, the current is somewhat irrelevant, as it is feeding a higher impedance input than the actual back-emf from the driven voice coil. it works well when done right. too much feedback from the second voice coil can cause the output impedance to move into the negative impedance twilight zone, causing the system to become unstable. there really aren't too many things to go wrong with less than optimal feedback from the second coil, except that those cone nonlinearities show up as the distortion we wanted to cancel out in the first place, after all the amp itself does have it's main feedback loop intact.
     
    Last edited: Dec 5, 2011
  19. unclejed613

    unclejed613 Well-Known Member

    Joined:
    Apr 3, 2009
    Messages:
    1,828
    Likes:
    99
  20. Sceadwian

    Sceadwian Banned

    Joined:
    Oct 27, 2006
    Messages:
    14,047
    Likes:
    141
    Location:
    Rochester, US
    I think I'll have to drop a few decent sized resistors inline with a few small speakers to see how they sound, very interesting.
     
  21. unclejed613

    unclejed613 Well-Known Member

    Joined:
    Apr 3, 2009
    Messages:
    1,828
    Likes:
    99
    only as to b 8 ohms at half your amp wattage to reduce the damping factor to 1 as a tube amp would have.
     

Share This Page