View Full Version : Interview with Quad's Peter Walker in 1978
I came across this courtesy of the Yahoo Quad group and thought I'd share the link with you all -
http://reocities.com/ResearchTriangle/Lab/6722/pwint1.txt
Some great home truths in there and possibly a bit of contention as well - the legendary Quad II's were designed and built without being listened to, except for nasty noises in extremis... Can't say I totally agree with it all, but this man was one of the legends, who knew his stuff, and who appeared to have a good and gracious sense of humour. I wish I'd met him, but never got the chance as a proposed factory visit to Quad co-incided with my leaving KJ and moving to the Linn/Naim/Rega dark side in the home counties - dealer visits for grunts like me were then restricted to Glasgow, Salisbury and the very occasional trip to the Southend area :lolsign:
StanleyB
16-09-2011, 08:03
the legendary Quad II's were designed and built without being listened to, except for nasty noises in extremis...
Weird, but I use a similar principle in many cases. The reason for that is because familiarity with a musical piece can cause the brains to 'make up' the difference in any perceived missing detail. So it helps to concentrate on what is present but shouldn't be there.
Some great home truths in there and possibly a bit of contention as well - the legendary Quad II's were designed and built without being listened to...
No doubt that Peter Walker knew his stuff as an audio designer, and is to be respected, but the above statement is quite incredible and shows the fallibility, and indeed futile arrogance, of extremist objectivist thinking, in that what measures well will automatically sound superb. Bollocks!! :doh:
Well at least I now know why stock Quad IIs, to my ears, sound so 'pipe & slippers' and musically as flat as a witch's tit... I sometimes wonder if, for these people, 'adequate' is considered enough, and striving for true excellence is almost treated with contempt? :rolleyes:
Yes, the best kit usually also always measures well (because it conforms to relevant electrical parameters), but what measures well doesn't always sound best (good, perhaps, but not necessarily best), and that's because the most talented audio designers realise that listening (and final voicing by ear), when designing equipment, is every bit as important as measuring - indeed more so!
Hey, at least Peter Walker was honest. If only others were the same. I wonder how much extensive listening to equipment is carried out at similarly objectivist-led companies, such as AVI and Cambridge Audio, or like Quad IIs, is simply churned out with zero subjective assessment as being 'adequate for purpose'? ;)
I don't do 'adequate'.
Marco.
Looks like this one might lead balloon on us:lolsign:
Let’s face it; it wasn’t going to be a big hit on a subjectivist forum was it? :eyebrows:
It’s a bit like saying “same class amplifiers having high input impedance, low output impedance, flat frequency response, low distortion, and low noise floor sound exactly the same when operated at matched levels and not driven to clipping.” Well, I mean you’re just not going to make friends here with that sort of talk. :lol:
What was interesting in the article was a brief insight into the real world economics of producing audio components for a market. I don’t think there was/is anything unusual in Quads approach to audio component design.
Looks like this one might lead balloon on us:lolsign:
Let’s face it; it wasn’t going to be a big hit on a subjectivist forum was it? :eyebrows:
Ok I'll bite :)
Quad did listen to their amplifiers because the designers and many of the Quad staff used them at home in their systems. Many of our cherished recordings spanning perhaps three or more decades were mastered in studios using Quad amplifiers, not to mention many broadcasters. But its true that the II just like the 303 and 405 were never assessed during the design stage using music.
They'll have been assessed using various noise and test tones because Quad held the view that an amplifier has only one primary function, that of ensuring that what appears at the output matches that on the input in all but magnitude at audible frequencies.
That task can be performed just as well with tones as with music because the amplifier simply responds to changes in voltage and current. It cannot tell what is passing through it, music or otherwise.
Liking what comes out of the amplifier is another matter. If the amplifier is technically faithful to the input and you don't like the result, then you don't like the music as recorded or replayed by your source!
If you prefer the music through a different amplifier, that amplifier is altering the signal in some way. I would say that unlike some 'objectivists' I'm all for a bit of manipulation of the signal if it gives a more enjoyable experience. Prefer to do it using EQ though.
Well hopefully I've reflated the balloon if nothing else :)
Rob
I think Rob & John are quite correct here and if you add damping factor to the equation, then I currently believe that much of what we hear from different amps can be almost neatly sewn up. Makes a wonderful case for active operation, where the losses in a passive crossover can be bypassed and the amp can drive the speaker coils directly (I don't hold with the view that active crossovers are as bad, because properly designed ones seem pretty transparent to me...
I think Quads approach did go against them in the mid 70's, because although many of the traditional speakers out there had benign loads, there was a new breed coming along that threw established thinking out of the window, had loads that could be quite cruel with all manner of phase and impedance shifts and this meant that a whole new kind of battleship amp was needed to be able to drive them. This culminated in the Apogee ribbon 1 Ohm type loading and giant Krell and Levinson style amps to drive them. A poor old under-cased Quad 405 would have melted under such stress (and many 405's all but did this if rock was played through them at high levels for any length of time..)
Having said that, the Quad 606 was and remains a real goodie, having a naturally musical and sweet tone once warmed up thoroughly - I mean no harshness or "forcing" of the musical signal (and even better with the later descendants I think), almost doubling the power into 4 Ohms and is a doddle to service and update if you wish. Still quite cheap too. You see, I reckon that if many of the pr@t amps had been assessed the way that old Radfords and Quads were, the added harshness in the designs would have been ironed out before being released to market - IMO.....
Lol - I'll get to this later! ;)
Marco.
Hi Rob,
Ok I'll bite :)
Lol – I’m glad that you have for a change! Don’t be scared to upset the 'resident faithful'. We like lively debates here on AoS! ;)
Quad did listen to their amplifiers because the designers and many of the Quad staff used them at home in their systems.
I’m sure that they did, but it doesn’t mean that such listening influenced the design process, which is what was of concern to me.
Many of our cherished recordings spanning perhaps three or more decades were mastered in studios using Quad amplifiers, not to mention many broadcasters. But its true that the II just like the 303 and 405 were never assessed during the design stage using music.
I suspect that any mastering would’ve been done using the solid-state Quad studio or broadcast amps of the day, and not Quad IIs. Heaven forbid, for the sake of accuracy, if it was the latter!
I have no beef with the 303 or 405, as they are different designs.
However, as far as I’m concerned, you cannot build a 'musically accurate' amplifier (i.e. that whose sound is genuinely musically convincing, since the end goal, after all, is to reproduce realistic and believable sounding instruments and voices, through a hi-fi system, by faithfully replicating, as closely as possible, the musical nuances of the source audio signal), without LISTENING to equipment as well as measuring it, during the design process.
It’s an amplifier’s ability to accurately reproduce those all-important nuances and subtleties, and not simply gloss over them, which to our ears, makes it musically convincing, and separates it from one which is merely accurate, up to a point, at reproducing the source music signal. Quite simply, our ears will readily detect the absence of those nuances, which test apparatus will likely have missed (as I do not believe that we can currently measure ALL that we can genuinely hear in audio), and thus will cause us to feel that the reproduced sound isn't 'real'.
In my view, relevant measurements aside, and taken as a given, only when equipment is then judiciously voiced by ear, by someone who genuinely understands music, and all its inherent complexities, does one faithfully capture those all-important musical nuances (depending on how good the ears are of the designer in question), which I have referred to above, quite simply because the technical limitations of our test equipment results in us currently being unable to measure all that needs measuring with music signals, in order to ascertain, with the sound of equipment, what is actually real (or rather as close to real as possible) and what is merely a competent copy of the source music signal.
As an aside, and I’m sorry to say it, but it pains me to read some of the absolutist stuff that Serge Auckland writes on pfm on this subject. He’s a nice enough chap, undoubtedly, but severely deluded if he genuinely believes that any audio equipment is *genuinely* sonically transparent. If only it were! Incidentally, Serge is most welcome to join and defend his views; in fact I would invite him to do precisely that, as it would no doubt make for an interesting debate, albeit it would most likely end in us agreeing to disagree.
I believe that there is no such thing as (genuinely) sonically transparent audio equipment. In my view, ALL audio equipment imparts its own sonic signature, subtly or otherwise on proceedings, by the very nature of the signal having to pass though a multitude of electronic components, wire and/or PCBs, all of which to some degree affect its integrity, and thus colours the music reproduced by the equipment in question, although none of this is likely to show up on our current test equipment. To be blunt, you’re in cloud cuckoo-land if you think that your favourite amp (or whatever) is sonically transparent...
I mean, let's get real, how can both Quad IIs and, say, the Quad 303 be considered as sonically 'transparent' or 'accurate' when they both sound different?? Yet both were presumably designed by Peter Walker to be "technically faithful to the input", such was his mantra, (and I could cite many examples of the same with equipment from other manufacturers). What's going on there, then? :scratch:
The answer, of course, is that neither amp qualifies as being genuinely transparent, as every amplifier made to date on this planet, valve or transistor, imparts its own sonic signature on reproduced music, in varying degrees of subtlety. Therefore, when assembling our hi-fi systems, all we can ultimately do is choose our preferred form of coloration, whether it be valve or transistor-derived, and enjoy our music through it on that basis. Genuine transparency in audio equipment is but a pipe dream!
They'll have been assessed using various noise and test tones because Quad held the view that an amplifier has only one primary function, that of ensuring that what appears at the output matches that on the input in all but magnitude at audible frequencies.
That task can be performed just as well with tones as with music because the amplifier simply responds to changes in voltage and current. It cannot tell what is passing through it, music or otherwise.
But a music signal is a very different thing from a noise or test tone signal.
Just because an amplifier ensures that what appears at the output matches that on the input in all but magnitude at audible frequencies, doesn’t automatically mean that it will succeed at accurately reproducing the source music signal.
The goal with music reproduction via audio equipment, after all, is to accurately reproduce MUSIC (not noise or test tones), which is probably why Quad IIs fundamentally fail at the former, and what happens when you don’t actually listen to the equipment you build! :doh:
Liking what comes out of the amplifier is another matter. If the amplifier is technically faithful to the input and you don't like the result, then you don't like the music as recorded or replayed by your source!
The problem is that "technically faithful to the input" can, in reality, mean a very different thing to being (genuinely) faithful to the source music signal.....
If you prefer the music through a different amplifier, that amplifier is altering the signal in some way. I would say that unlike some 'objectivists' I'm all for a bit of manipulation of the signal if it gives a more enjoyable experience.
The way I do it is embrace the fact that no piece of audio equipment or system can ever be truly 100% musically transparent or accurate, and simply choose components and build a system, which to my ears, best replicates the sound of real instruments and voices, based on my (extensive) experience of listening to them live. Therefore, from my listening experience to date, I intrinsically *know* how things should sound - and I'm far from alone in being able to do this.
Live, un-amplified, music is the benchmark I use to test my system against, and so I need no 'measurement apparatus', other than my brain and the God-given organs attached to the sides of my head (known as ears) in order to assess whether, on that basis, my system sounds musically convincing.
Well hopefully I've reflated the balloon if nothing else...
Well, if you’ve re-inflated it, I’ve probably just gone and burst it!! :lol:
Over to you now, mate.... ;)
Marco.
Actually Marco, my samples of II's and 303 actually sound pretty darned similar - into the BC2's anyway. I stick with the Quads downstairs because of the lovely warm glow from the KT66's, the warm glow from the 303 power light isn't quite the same somehow.... :ner:
Mind you, I'm seeing and hearing the old bridged D-60's in a whole new light nowadays with my sooper-dooper new mega-foo interconnects :D
Lol - fair enough, Dave. Any 303s and Quad IIs I've heard sound markedly different, in the way you'd expect valve and SS gear to do. For starters, 303s, to my ears, don't sound quite as flat and lifeless, or indeed, 'pipe & slippers'! ;)
Are those Mark Grant "mega-foo" interconnects? :eyebrows:
Marco.
Reid Malenfant
03-10-2011, 20:39
Dave, you may note that there is a capacitor on the output of the 303 & in all honesty it really isn't very large in the capacitance stakes ;) Ok, so the 303 may well have a bit more "damping factor" or should we call this output impedance as it varies over frequency, but in all honesty both amps lack a great deal of control that others take for granted ;)
What is that cap 2,000uf? In order to be more out of the picture it should have been 50,000uf as the bass response rolls off below 40Hz even with an 8 ohm load :rolleyes: Might be ok with a sealed box with say a 50Hz resonance but show it a reflex with a tuning frequency lower than 40Hz & you might as well be a hippo wallowing :eyebrows:
Dave, you may note that there is a capacitor on the output of the 303 & in all honesty it really isn't very large in the capacitance stakes ;) Ok, so the 303 may well have a bit more "damping factor" or should we call this output impedance as it varies over frequency, but in all honesty both amps lack a great deal of control that others take for granted ;)
Indeed! And especially in the case of the Quad IIs, no way are they "technically faithful to the input", as if that's how music is supposed to sound, I'm Angelina Jolie in a pink tutu!! :lol:
Marco.
From what i understand the engineers do listening tests but they are listening to their own tastes in music which is why some componenets are known for being good with certain music and not others.
Indeed, Colin. Of those who actually listen to the equipment they build, it will be voiced using the designer's taste in music as the benchmark, hence indeed why some kit excels more with one genre of music than others.
I prefer equipment though which has been designed and voiced to excel with all types of music - and it can be done! :cool:
Marco.
Some further thoughts on this, Dave:
Actually Marco, *my* Quad 303 and *my* II's actually sound pretty darned similar - into the BC2's anyway.
Yes, but haven't your Quad IIs been modified by Glenn Croft? I'm sure that I've seen you mention that they're been "Crofted". And if so, that's likely why they sound punchier, and somewhat 'livelier', and more akin to the sonic presentation of the 303.
Have you ever actually compared stock Quad IIs to the 303? :)
If you have, and you actually think that they sound "pretty darned similar", then our respective experiences are rather different!
Marco.
I'll get to it later :)
:popcorn: :popcorn: :popcorn:
Marco.
The problem for me is, all the other Quad II's in stock form I've heard have been with the truly atrocious 22 preamp, which in standard form smothered fine details with a huge thick blanket - unbelievable! At least "my" II's have a chance to breathe..
Now, and I hope Mark Grant will read this (and I know Alex and Dave W will back me up here on this), my "problems" with my HD1500 cables (neutrik pro phono to 1/4" jack, so can't be easily reversed) were to do with a certain perceived "stridency" in the sound. I think I can say now that it's NOT this cable, but an additive factor of the heavy-duty CD to preamp interconnect which still had a slight possible "enhancement" of upper-range details, coupled with a preamp that doesn't sound in the least bit "warm and valvey," despite the wonderful atmosphere it brings to suitably recorded music, a pair of lean and possibly "snappy" amps (damping factor of at least 400 even in bridged mode...) and the BC2's, which are crisper in balance than either the BC1's as I remember them, or Alex's rather lovely SP1's for that matter.
The first thing I did was to resurrect the supplied Micro-Seiki interconnect, re-fitting their phono's at the amp end. This gently toned things from CD down a touch. The second thing I've done is to make up some fresh cables with the Van Damme mic cable Dave gave me tp go between pre and power amps. The gauge of the conductors looks similar to the Pro-patch which works so well as a tonearm to amp interconnect, but the outer jacket is a double-thickness flexible "stuff" which makes it look a bit posher yet keeps it flexible.
The end result of the above is that the sound retains the atmosphere with the D-60's/Croft combination, yet is just a touch more "civilised" than with the MG cables. Had I Alex's SP1's (Anthony, I haven't forgotten :)), the MG cable would be fine, as Alex's samples were at our last get-together, but for the more wayward BC2's ;), I'm delighted with what I have at present - Siouxsie's recordings haven't sounded as good since I heard them on my mates old bolt-up Naim and 'Brik active system..
Mark, wasn't the 303 designed to sonically mimic the II's in many ways? I believe the output caps were the largest they could get back then (any bigger would have been too large and probably too expensive then as well. Mine have Rifa caps as replacements, but I think the values are pretty stock from memory. Since they're now screw-connecting, they'll be easy to replace with summat bigger in value one day..
http://i132.photobucket.com/albums/q8/DSJR_photos/DSCF1448a.jpg
Hi Rob,
Lol – I’m glad that you have for a change! Don’t be scared to upset the 'resident faithful'. We like lively debates here on AoS! ;)
I’m sure that they did, but it doesn’t mean that such listening influenced the design process, which is what was of concern to me.
I suspect that any mastering would’ve been done using the solid-state Quad studio or broadcast amps of the day, and not Quad IIs. Heaven forbid, for the sake of accuracy, if it was the latter!
I have no beef with the 303 or 405, as they are different designs.
However, as far as I’m concerned, you cannot build a 'musically accurate' amplifier (i.e. that whose sound is genuinely musically convincing, since the end goal, after all, is to reproduce realistic and believable sounding instruments and voices, through a hi-fi system, by faithfully replicating, as closely as possible, the musical nuances of the source audio signal), without LISTENING to equipment as well as measuring it, during the design process.
It’s an amplifier’s ability to accurately reproduce those all-important nuances and subtleties, and not simply gloss over them, which to our ears, makes it musically convincing, and separates it from one which is merely accurate, up to a point, at reproducing the source music signal. Quite simply, our ears will readily detect the absence of those nuances, which test apparatus will likely have missed (as I do not believe that we can currently measure ALL that we can genuinely hear in audio), and thus will cause us to feel that the reproduced sound isn't 'real'.
In my view, relevant measurements aside, and taken as a given, only when equipment is then judiciously voiced by ear, by someone who genuinely understands music, and all its inherent complexities, does one faithfully capture those all-important musical nuances (depending on how good the ears are of the designer in question), which I have referred to above, quite simply because the technical limitations of our test equipment results in us currently being unable to measure all that needs measuring with music signals, in order to ascertain, with the sound of equipment, what is actually real (or rather as close to real as possible) and what is merely a competent copy of the source music signal.
As an aside, and I’m sorry to say it, but it pains me to read some of the absolutist stuff that Serge Auckland writes on pfm on this subject. He’s a nice enough chap, undoubtedly, but severely deluded if he genuinely believes that any audio equipment is *genuinely* sonically transparent. If only it were! Incidentally, Serge is most welcome to join and defend his views; in fact I would invite him to do precisely that, as it would no doubt make for an interesting debate, albeit it would most likely end in us agreeing to disagree.
I believe that there is no such thing as (genuinely) sonically transparent audio equipment. In my view, ALL audio equipment imparts its own sonic signature, subtly or otherwise on proceedings, by the very nature of the signal having to pass though a multitude of electronic components, wire and/or PCBs, all of which to some degree affect its integrity, and thus colours the music reproduced by the equipment in question, although none of this is likely to show up on our current test equipment. To be blunt, you’re in cloud cuckoo-land if you think that your favourite amp (or whatever) is sonically transparent...
I mean, let's get real, how can both Quad IIs and, say, the Quad 303 be considered as sonically 'transparent' or 'accurate' when they both sound different?? Yet both were presumably designed by Peter Walker to be "technically faithful to the input", such was his mantra, (and I could cite many examples of the same with equipment from other manufacturers). What's going on there, then? :scratch:
The answer, of course, is that neither amp qualifies as being genuinely transparent, as every amplifier made to date on this planet, valve or transistor, imparts its own sonic signature on reproduced music, in varying degrees of subtlety. Therefore, when assembling our hi-fi systems, all we can ultimately do is choose our preferred form of coloration, whether it be valve or transistor-derived, and enjoy our music through it on that basis. Genuine transparency in audio equipment is but a pipe dream!
But a music signal is a very different thing from a noise or test tone signal.
Just because an amplifier ensures that what appears at the output matches that on the input in all but magnitude at audible frequencies, doesn’t automatically mean that it will succeed at accurately reproducing the source music signal.
The goal with music reproduction via audio equipment, after all, is to accurately reproduce MUSIC (not noise or test tones), which is probably why Quad IIs fundamentally fail at the former, and what happens when you don’t actually listen to the equipment you build! :doh:
The problem is that "technically faithful to the input" can, in reality, mean a very different thing to being (genuinely) faithful to the source music signal.....
The way I do it is embrace the fact that no piece of audio equipment or system can ever be truly 100% musically transparent or accurate, and simply choose components and build a system, which to my ears, best replicates the sound of real instruments and voices, based on my (extensive) experience of listening to them live. Therefore, from my listening experience to date, I intrinsically *know* how things should sound - and I'm far from alone in being able to do this.
Live, un-amplified, music is the benchmark I use to test my system against, and so I need no 'measurement apparatus', other than my brain and the God-given organs attached to the sides of my head (known as ears) in order to assess whether, on that basis, my system sounds musically convincing.
Well, if you’ve re-inflated it, I’ve probably just gone and burst it!! :lol:
Over to you now, mate.... ;)
Marco.
Lots to tackle there but many of the arguments overlap so I'll bullet point my response:
- Quad II sounding the same as a Quad 303 (or 405 or any other)
We cannot really look at amplifier sound and performance without considering the load conditions. Poor old Peter Walker was often misquoted and never actually said that all amplifiers sound the same. He actually claimed that all 'competent' amplifiers would sound the same where proper consideration had been afforded to the interface at each end.
What does that mean?
Well, the Quad II is a 1950s amplifier and was manufactured into the 1960s.
Like many valve amplifiers of the day (and a number today) it had relatively high output impedance and low power - some 15 watts on a good day if you were lucky.
Output impedance directly impacts the frequency response of the loudspeaker system where that system does not have a perfectly flat impedance characteristic. Very few loudspeaker systems do - planar systems being probably the only real example. In all other cases, a high amplifier output impedance will distort the power transfer characteristics and alter the system frequency response. It is one of the primary reasons why valve amplifiers sound different to solid state and it is very obvious with measurement.
The biggest change occurs where the impedance is at its most reactive - typically around the loudspeaker system bass resonance (and port area) and also around the crossover point(s). In these areas, the response is altered and often by several dB. The overall effect is to pull the frequency response into resembling the impedance plot as output impedance increases.
So what's that got to do with a Quad II sounding like a 405?
Everything - because the Quad II was designed to drive 1950s and 1960s loudspeakers which were typically of higher overall impedance than those in later decades, and generally less reactive. High overall impedance minimises the effect of high output impedance. So, for example, a Quad II will sound very like a 405 or 303 into original 16 Ohm LS3/5a, but quite different into a modern 4-6 Ohm design.
The plot below shows the result of experiments we made on a Tannoy LGM by driving from a low output impedance typical of SS and then from a 5 Ohm impedance. Note how the response and therefore the sound changes:
http://img.photobucket.com/albums/v637/zippy670/0R.jpg
http://img.photobucket.com/albums/v637/zippy670/5R.jpg
What you can see are deviations in excess of 6dB in the bass and 2-3 dB higher up the range. On a 16 Ohm loudspeaker system with a less reactive impedance characteristic these figures would reduce markedly, as would the sonic differences.
- Music is complex while test tones are simple and don't truly test the amplifier.
The amplifier simply responds to changes in voltage and current. Music signals can be defined by changes in voltage and current. A music signal is no more difficult to reproduce than a handful of test tones.
Humans perceive music as complex because we separate the individual strands both audibly and visually if we look at the waveforms, but the amplifier doesn't - it has no power of perception and only sees voltage and current.
On a slightly different point, asking an amplifier to reproduce 20khz at full output is a pretty tough test, and tougher than most music signals since you are asking the amplifier to swing fully and rapidly to doth DC rails. Might look simple and easy to humans but that's tough for many amplifiers.
Returning to Quad, they made the null test a feature of their testing and would invite competitors to the factory and ask them to submit their amplifiers to this test. Quad were able to demonstrate that you could null the amplifier output by injecting a portion back into the input in anti-phase. Now, if the amplifier were materially changing the signal passing through it in any way, it wouldn't null. But it did, indicating that signal complexity wasn't causing any difficulty over and above the lab test signals.
- The general objective v subjective debate and 'what we like'.
Objectivists tend to be labelled as white lab coat wearing boffins who use test instruments to asses equipment and want everything to have a flat response and no distortion. I am certainly not among that group, nor would I ever insist that someone must use a particular bit of kit because it measures well. For me this confuses two very distinct issues.
For me, to objectively assess two amplifiers is to compare them under blind conditions in order to discover, in as unbiased way as possible, any differences that might exist. Having done so and having found a real difference, having a preference is fine and will always remain subjective!
If an amplifier doesn't have a flat response and it has some slightly odd distortion on the signal, that's also fine if the listener accepts these things for what they are and enjoys the result. For me the whole objective thing is about discovering and explaining why things happen in a rational way. What I or anyone else might like is a different matter.
Anyway I've rambled long enough tonight but I hope that was useful.
Rob.
Reid Malenfant
05-10-2011, 16:24
Mark, wasn't the 303 designed to sonically mimic the II's in many ways? I believe the output caps were the largest they could get back then (any bigger would have been too large and probably too expensive then as well. Mine have Rifa caps as replacements, but I think the values are pretty stock from memory. Since they're now screw-connecting, they'll be easy to replace with summat bigger in value one day..
http://i132.photobucket.com/albums/q8/DSJR_photos/DSCF1448a.jpg
I have no idea Dave in all honesty :scratch: One thing that may lend some kind of credence to that is a certain quote:- "the closest approach to the original sound"... Effectively they were if you like attepmting to get them to sound the same or to add the least distortion :)
I think Robs post above is a rather good one indeed & he is quite correct. A good many speakers were full range drivers & 15/16 ohms DC resistance.
You are quite right about the caps as i mentioned on a thread with some Croft equipment pics only yesterday. Technology moves on & big value capacitors are much smaller in overall volume than they used to be back in the day! ;)
nice post rob, and i quite undestand where you are coming from
- Music is complex while test tones are simple and don't truly test the amplifier.
The amplifier simply responds to changes in voltage and current. Music signals can be defined by changes in voltage and current. A music signal is no more difficult to reproduce than a handful of test tones.
Humans perceive music as complex because we separate the individual strands both audibly and visually if we look at the waveforms, but the amplifier doesn't - it has no power of perception and only sees voltage and current.
On a slightly different point, asking an amplifier to reproduce 20khz at full output is a pretty tough test, and tougher than most music signals since you are asking the amplifier to swing fully and rapidly to doth DC rails. Might look simple and easy to humans but that's tough for many amplifiers.
Returning to Quad, they made the null test a feature of their testing and would invite competitors to the factory and ask them to submit their amplifiers to this test. Quad were able to demonstrate that you could null the amplifier output by injecting a portion back into the input in anti-phase. Now, if the amplifier were materially changing the signal passing through it in any way, it wouldn't null. But it did, indicating that signal complexity wasn't causing any difficulty over and above the lab test signals.
Its funny how my experence differs. in my opinion both these amplifiers dont so much change the signal as filter it, detail, air and realisim is removed that i know is in the signal source, much less so with the quad 11 amps(without their pre) in my experence ( i've owned /used both)
i quite take your point about impedance matching, but it can't be the whole story...
steve
I think you'll find it was the preamps which could take the most away.. the 33 in stock form could sound tight-as*ed and with a carrot up its backside. Suitably updated, and I don't mean with hundreds of pounds worth of Net-Audio replacement boards either, the sound ebbs and flows with the dynamics in the signal, the bass breathes now, which it didn't before and, even if it's not the last work in preamp-sonics, it's a darned sight better than in standard form IMO - mines a very late one by the way. The later preamps from the 44 onwards can be spruced up as well, showing how good the power amps could actually be.
The only Quad power amp I can't get on with, and that's because I don't listen exclusively to string quartets, is the 306, which to me sounds limp-wristed on anything with any percussion in it. The 405 in mk2 version is like a "grown-up" 303 to me and can be taken further these days and the 606 remains a secret bargain still, which can drive 4 Ohm loads without difficulty. The later 606 onwards had some little tweaks too IIRC, which again can be retro-fitted I understand.
Just my thoughts, obviously...
Reid Malenfant
05-10-2011, 20:54
The 405 in mk2 version is like a "grown-up" 303 to me and can be taken further these days and the 606 remains a secret bargain still, which can drive 4 Ohm loads without difficulty. The later 606 onwards had some little tweaks too IIRC, which again can be retro-fitted I understand.
Just my thoughts, obviously...
I have a pair of modified MK1s (by me :eyebrows:) which are more than capable of over 200W RMS both channels driven with music (4ohms). They'll keep cool enough to on music signals, just don't ask them to do a continuous output as they'll get a tad warm.
The output transistors have been replaced with higher gain 200W TO3 versions that were not available back in the day & obviously the poxy current limiting has been altered to...
As long as you know what you are doing, or someone who does then they can all be brought up to a much better specification :)
nice post rob, and i quite undestand where you are coming from
Its funny how my experence differs. in my opinion both these amplifiers dont so much change the signal as filter it, detail, air and realisim is removed that i know is in the signal source, much less so with the quad 11 amps(without their pre) in my experence ( i've owned /used both)
i quite take your point about impedance matching, but it can't be the whole story...
steve
Hi Steve,
The Quad II will have a different response to a SS amp in the loudspeaker crossover region which is where the impedance is usually quite reactive.
That's usually slap bang in the area that influences the perception of detail, presence and air to some degree. You could however replicate this on a SS amp with EQ.....
Impedance matching is certainly only one part of the puzzle but an important one that is often ignored. Distortion is the other culprit, not just the headline THD figure but the distortion spectrum beneath. How much IMD, do even or odd order harmonics dominate, how far do they extend etc.
The answer of course is to get very low THD so that you don't then need to worry about what sits beneath that headline figure. Distortion is only an issue if present in quantities that are audible. So going from say 0.005% to 0.0005% isn't going to be audible no matter what the content. Going from say 0.1% to 1% might well be audible if the latter contains lots of IMD, but it might not if it contains mainly 2nd harmonic distortion.
As long as you know what you are doing, or someone who does then they can all be brought up to a much better specification :)
I agree Mark, they are all products of their time and I'm sure that if PJW was still around and making amplifiers he'd do things differently. He was always happy to adapt and use new components and methods though always maintained that most of these advances simply made the products more reliable, smaller and more energy efficient, plus offering more power. He never claimed any sonic gains for successive products and would never attempt to convince an existing Quad owner to 'upgrade' if he felt there was no sonic benefit.
Sorry, I'm a bit of a Quad collector :)
The kit and all of the papers and related writings over the years.
If anyone enjoyed the Walker interview they might find this interview by his engineering assistant Mike Albinson interesting:
http://www.quadesl.org/Album/InterviewsReviews/MikeAlbinson/mikealbinson.html
Scary looking bloke :eek:
Rob
Reid Malenfant
05-10-2011, 21:05
Going from say 0.1% to 1% might well be audible if the latter contains lots of IMD, but it might not if it contains mainly 2nd harmonic distortion.
Ah yes, even harmonics sound musical, odd harmonics are not welcome here :eyebrows:
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