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Thread: Amplifiers are more significant than you may think!

  1. #16
    Charley Rummel
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    I'm a tube head (sounds better than vacuum head) and I've built a number of projects over the years.

    I have a stereo power amp I built a few years ago, mostly out of surplus. The whole of the circuit is a hybrid utilizing pieces of other circuits I've felt were good designs: the power stage (not the power supply) is push-pull parallel beam-powered tetrodes, biased pure class A, which drives an output transformer (secondary impedances are typical 4, 8 and 16 ohms); the phase inverter and driver stages were styled after an obscure 50 year old circuit I came across once, which I forget the name of (not like the type commonly found in guitar amps or ultralinear circuits); no elaborate coupling of the stages, though there are stabilization circuits in the power amp section; completely open loop (no negative feedback circuits); and an otherwise relatively common voltage divider network design for the power supply (with two large power transformers wired in paralell, and oversized capacitors). I have a provision on it which allows for adjusting the contour by introducing a tuning circuit in the input triode plate supply.

    It has a nice even frequency response from 25 Hz, develops incredible dynamics, and is CLEAN and FLUID at all levels! This amp will crank like hell and not break up at all. Overall sound is amazing. I have had numerous and intense praizes from individuals, sound pros and audiofiles alike.

    Who cares about the numbers. Some of the numbers I get when I've bench tested this thing would make anyone the laughing stock of the AES. The only data I will share here is that It will develop 80 watts per channel before clipping on a 1000 Hz sinewave.

    Regards,
    Charley

  2. #17
    Senior Señor boputnam's Avatar
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    Yea, interesting, Scott...

    I've not had the opportunity to A/B too many set-ups yet, but to my ears, these QSC's would be very hard to beat. When I think I hear harshness in the highs, I swap sources and find it mix-related. Many producers, simply shouldn't be...

    The LF and ULF is extremely tight, and responsive, full. No smearing here (hear...?). I'd used four of these bad-boys in my FOH rack and they were lauded by all not too drunk to still critique. And, they simply use no current - never once blew a "20amp" circuit, with Soundcraft 24-channel board, 4 QSC's, 3 dbx 1231's, gates and comp/limiters. They run cool, and reliable. And, as Mike Caldwell posted, they are real easy on the back - they are virtually weightless. I used to set the PA up and park a chair in the sweet spot and just roll the CD's until Set time. Phenomenal imaging. (EV Eliminator mains).

    So, I'll watch this Thread for other's experiences, but in the meanwhile, this 1,000 watt configuration has riveted my attention.

    And, hey - Mr. Rummel! Next time through Chi-town, what say I taxi over and get an audition, hey? I would love to hear that creation. Wow.

    Thanks,
    Last edited by boputnam; 08-20-2003 at 08:24 PM.
    bo

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  3. #18
    RIP 2010 scott fitlin's Avatar
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    Bo

    QSC isnt to highly damped! When I talk about overdamping Im speaking of Crowns new products like the CTs series which has damping of >3000 and the Macro Reference, 20,000 to 1.

    Tight bass, and too tight are very different things! My BGW,s give very taut low end, but dont sound hard! I have heard various models of QSC and they are pretty good!

    It also depends on the speakers you have! Ported boxes will like a somewhat higher damping factor! But how much is the question! As has already been stated, anything above 17 and your in the game! To me >500 works. If your using an amp thats a little higher, thats cool too. But Ive heard some amps that are so tight they sound hard! Thats what I dont like!

    And of course, everythings a matter of preference!
    Last edited by scott fitlin; 08-20-2003 at 10:50 PM.

  4. #19
    PSS AUDIO
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    Damping factor, what a nonsense...

    I always thought, said and wrote that this number is one of the fakest numbers invented by sellers with the approval of audio “engineers”!

    More this number is gigantic; more the sound is squeezed and not natural. There is so much control that the speakers cannot move as free as they should do, you are loosing all the warmness of the signal and this makes a horn sound hard and aggressive.

    The damping factor must be over 20 and 100 is already a very good number!

    No one can imagine, unless using a bulb amplifier, how smooth a horn can sound.

    A transistor amplifier can sound as smooth as a bulb amplifier in the mids and offer a better dynamic than a bulb amplifier.

    Because big names are unable to build something new and really innovative in the amplifier industry, they are just launching each year new amplifiers with better numbers and they force “ignorant” persons to think that if the numbers are good the amplifier will be!

    I personally think that in the last 30 years or more there were NO major improvement made in the quality of amplifiers (and other audio items too) and that a non complementary (using only NPN output bipolar devices) AB amplifier is the best compromise for a sound reinforcement system and why not in an audiophile use too.

    But one must work very hard to make it sound clean!

    The only improvements made in the last decades were in reliability, size and cost of amplifiers.

    Remember Phase Linear amplifiers. They sounded quite well, were big and were smoking for no reasons.

    I do not agree white some of you using big name of PA amplifiers as I do think that they are just good to make some noise even if they claim being the king of the audio industry …

    Some of our customers think that our latest 9D amplifier is sexy as a queen!

    Since years now the only credo is how many watts can an amplifier deliver?

    1 000, 1 500, 2 000, 5 000 or perhaps 10 000 watts on a short circuited load of 0.1 ohm?

    Using speakers with a 2 ohm load is one of the biggest nonsense I ever heard, it is so close to the ground that you cannot have any dynamic, in such a case the only thing one must do is to increase the power and so on.

    Lots of amplifier manufacturers have just forgotten that making noise with what they call powerful amplifiers is just made to cover the weakness of something else (why does a dog shouts when you are facing him? Not to scare you, as in fact the dog is scared, so that is why he is shouting).

    Lots of manufacturers are claiming to have designed an amplifier with the lowest of the lowest distortion this apparatus ever had. This means, in their mind, that it is a good apparatus. This makes me laugh out loud. One must know that an excellent speaker has about 1% distortion, a very good ear has the same and that the room will also deliver the same amount of distortion! This makes a total of at least 3% of distortion. They are just fooling you, and themselves by the same way.

    All the benefit from ALTEC and JBL went into smoke, as it is not on the power of an amplifier that one must play with to increase the SPL of a sound system but on the quality and the SPL of a speaker.

    But this is by far more difficult to achieve than playing with the power of an amplifier and it was done 50 years ago.

    As one must create something new to sell it otherwise what is the use buying something that exists before we were born!

    That is why I claim that we, at PSS AUDIO, sound different!

  5. #20
    Senior Señor boputnam's Avatar
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    I think that's all of 'em. Whew! Tough sledding out here!

    I may (make that: "are") indeed be ignorant about lots of stuff, but not about what sounds good. I dragged the QSC's into the home on a lark, and was stunned by their clarity, depth and imaging. It's as if the listener is in the room with the performer - certainly much of the credit goes to the 4345's, but they cannot do their part alone.

    Oh, and numbers don't wow me at all - but do provide a useful starting point, IMMHO.

    I disagree completely on it being "wrong" to employ "big name" PA amplifiers" in home rigs. MY ears tell me you're just not correct on that, but then these are only my ears. I thought this a crazy notion and didn't do it for years, but when I finally gave these QSC's a try, I was most impressed.

    The "1,000 watts" I threw-in for reaction - guess it worked! I find it laughable myself that I've got 1,000 watts in the dang family room! Ha! That's nuts! But, I don't run these at high SPL's (now that would have the dogs shouting... ), and surely don't exceed 20-25watts per channel output, ever.

    If I ever get a chance to A/B one of your wonderful creations, Yuri, I will enjoy it. Until then, I'm quite blissful, and all who come 'round are wowed too, and they are even less swayed by numbers than I might be.

    As a sage once posted:
    Obviously we're on different pages though. I have zero interest in what the Marketing folks are churning out of their propaganda machines. Damping factor, or even better, output impedence, is real, and is valid, but I personally couldn't care less what some Marketing person is doing with the numbers.
    Keep the reports coming in!
    Last edited by boputnam; 08-21-2003 at 07:42 AM.
    bo

    "Indeed, not!!"

  6. #21
    Senior Señor boputnam's Avatar
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    1,000 watt addendum...

    I omitted that in my bi-amp set-up I'm using, the QSC's are 200 watts per channel for the MF/HF/UHF, and 300 watts per channel for the LF. That is a surprisingly and fortuitously nice match for the 4345's.

    Just because it aggregates to 1,000 watts, doesn't mean that it's "too much". It seems "ample".

    That's enough outa me...
    bo

    "Indeed, not!!"

  7. #22
    PSS AUDIO
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    Re: 1,000 watt addendum...

    Originally posted by boputnam
    I omitted that in my bi-amp set-up I'm using, the QSC's are ...
    I was reported from several customers that they do not sound, this brand and the other one, the king, as good as other “small” brands....

    I do not say that those big names are crap, but for the money and the name they carry, they should be the best of what can be done, but it is not...

  8. #23
    PSS AUDIO
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    Originally posted by boputnam
    I disagree completely on it being "wrong" to employ "big name" PA amplifiers" in home rigs. MY ears tell me you're just not correct on that, but then these are only my ears. I thought this a crazy notion and didn't do it for years, but when I finally gave these QSC's a try, I was most impressed.
    The problem is what is compared to what with, in the middle a good speaker.

    If you had a crappy amplifier, the QSC will sound great and you will think that the band performs in front of you.

    Turn your QSC for a GAMUT amplifier and you will think that the band is behind the speakers far away but extremely close to you, that you have silk in your ears, that the bass are coming down on your feet.

  9. #24
    Senior Señor boputnam's Avatar
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    "If you had a crappy amplifier"


    Regardless, I am not adverse to trying a GAMUT, but the QSC's aren't going anywhere. "Turn 'em in"...? What 're you, nuts!? Ha! But you are VERY passionate about your brand! Cool...



    Hell, I was just thinking: if you lived nearby - even near Toledo, maybe - I ship you a QSC CX502 and trust you to return it, even after you realize there truly is merit to both their engineering, and the reported performance.

    Oh well, never mind...
    Last edited by boputnam; 08-22-2003 at 08:24 PM.
    bo

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  10. #25
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    Hmm...I love this sort of topic and in the end think power counts in itself.

    My experience is that bigger amps certainly pay dividends with the large format JBLs because they are so clean and linear you can actually hear lesser amps mis behave.

    Power seems to give depth and you can actually see right down the throat of a Sax with a nice big amp on monitors like the 4343 , 4345 & 4355. The micro dymanics that skate along the leading edge appear to hold the clues to spatial details that create the life excitment we live for.

    On the subject of damping factor the jury is still out here fo me.

    Recently I switched to a 100 watt pure class A design that is fully balanced ie there is only hot and cold output , no earth.

    The damping factor is only 30 or so but its delivers the tightest most dyamic and life like bass I've ever heard. The amp performs equally well in every other respect.

    This could be because there is only a touch of global negative feedback and the power supply is not in series with the current going the the speakers, but this is only a theory.

    The amp is a diy Passlabs effort based on merging the best the aclaimed X Series and Aleph.

    Ian
    Last edited by Ian Mackenzie; 08-23-2003 at 12:17 AM.

  11. #26
    PSS AUDIO
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    Originally posted by Ian Mackenzie
    Power seems to give depth and you can actually see right down the throat of a Sax with a nice big amp on monitors like the 4343 , 4345 & 4355. The micro dymanics that skate along the leading edge appear to hold the clues to spatial details that create the life excitment we live for.
    From my own experience, I must say that I always preferred listening my favourite tunes with an amplifier able to deliver 1000W while I only asked for 10!

    Since several months now I am listening my 4350 with a 300W amplifier modified with a bigger transformer (in fact the amplifier delivers 300 W + 300 W as it is a double mono as all the amplifiers I am working on, but is built with two 800 Watts transformers and 2x60 000 MF in the mains).

    At the time being it is quite hard answering witch one sounds better than the other (it is the same schematic, same PCB, all components are from the same origin and so on, only some resistors do change).

    What is certain is that the amount of capacitors and their quality, the presence of polypropylene capacitors wired in parallel with the mains capacitors, the power of the transformer and its quality, the type of the bridge makes half of the quality of an amplifier.

  12. #27
    Charley Rummel
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    Hi, Bo:

    Sorry I didn't reply earlier. Let me know when you plan to be in this neck of the woods again.

    Regards,
    Charley

  13. #28
    Senior Member Steve Schell's Avatar
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    Another thought to add to this damping factor (damnping factor?) discussion:

    In some older article I have somewhere in the files, the author states that the ideal amplifier damping factor for a particular speaker is that which will return the speaker's moving element to rest in minimum time after it has been displaced from its position of rest. He uses the analogy of a swinging pendulum, with a tail swinging in a trough of viscous fluid. If there is no fluid (no damping), the pendulum will oscillate for a long time before coming to rest. If the fluid in the trough is too thick, the pendulum will take an excessive time to find its way back to center. Somewhere between these extremes would be a fluid with the correct viscosity to allow the pendulum to come to rest in minimum time.

    Perhaps this is why a super duper high damping factor transistor amp can make the bass sound overdamped, even strangled and anemic, with a high sensitivity speaker. Again, referring to the Lansing - Hilliard article, maybe an amplifier with a higher output impedance (lower damping factor) will allow reproduction with greater fidelity to the waveform in a particular circumstance.

    One other thought- Hal Cox knew Jim Lansing in the late 1940s. Hal told me that Jim mentioned to him that keeping a few one and two ohm resistors in one's pocket was a good idea, that adding them in series with the speaker lead would allow for the adjustment of damping factor for the best overall sound.

  14. #29
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    "One other thought- Hal Cox knew Jim Lansing in the late 1940s. Hal told me that Jim mentioned to him that keeping a few one and two ohm resistors in one's pocket was a good idea, that adding them in series with the speaker lead would allow for the adjustment of damping factor for the best overall sound."

    Hi Steve,

    We used to do that very thing with the 124/2203 with it's ultra-low Q. There are mathematical formulas which one can use to figure out just how much series resistance is needed to achieve a specific LF response curve. Of course, computer aided design has come a long way in that it allows one to figure out how to control damping via enclosure size, tuning, and fiber fill so that series resistors aren't necessarily required. Varying the DCR of the LF inductor also can be beneficial.

  15. #30
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    Without going off the tech deep end here regards Damping factor

    Most large solid state amps are class A/B and the power supplies are as rule unregulated, usually with bridge rectifier and then filtered with a capacitor ~~large electrolytic.

    Depending on the design, some have a stiff supply with a large transformer and large filter caps, this leads to low ERS and low supply impedance. The power supply behaves more as a pure current/voltage source.

    This and a high current output stage with numerous parrellelled transisters and negative feedback leads to a high damping and clamping effect.

    However, not all amps are created equal, hence the tonal difference.

    My view is that the speaker, particularly if bass reflex, should operate as a system that takes into account the X resistance of the amp, cables and DCR of the crossover. Speaker designers therefore take a punt on what they think is the "norm" for the amps output impediance/dcr of the cables etc.

    The effect of series DCR is particularly noticable at the FB of the box and is integral to the box design along with box damping.

    The classic example is the 4345, the tuning while empirically based considers the DCR of the woofer choke, about 0.50 ohms according the Greg Timbers and was fine tuned after extensive listening tests!!

    The thing is some of you are referring to a damping factors of 1000, that is 0.008 ohms, so how can the speaker sound right with 0.50 ohms? A lower dcr choke doesn't work thats why I asked G T.

    The reason is the total Q of the system QTS, which includes the driver mechanical (Qm), the electrical (Qes) and the compliance of the driver form a complex relationship with the box alignment parameters called Alpha and H to arrive at the box Volume (including the effects of filling) and port tuning.

    Yes, it is a complex tricky business, but thats where the black art and romance begins.

    Ian
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    Last edited by Ian Mackenzie; 08-25-2003 at 06:32 AM.

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