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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 20th Jun 2021, 1:18 pm   #21
merlinmaxwell
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Default Re: Listening for Quad amplifier differences

Quote:
I listen to the music.
Indeed, Flanders and Swan summed it up "We don't listen to music much, it's the Hi Fidelity" A song of reproduction https://www.youtube.com/watch?v=7fJmmDkvQyc Mum and Dad went to the show just after being married, I came along a bit later, truly a song of reproduction.

I will only accept observations as to amplifier differences when a proper, statistically valid test (i.e. double blind) has been done as opposed to someone changing amplifiers and knowing, up front, which one is being used. OT for this tread, the same goes for cables/interconnects.
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Old 20th Jun 2021, 1:40 pm   #22
Jez1234
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Default Re: Listening for Quad amplifier differences

I note with amusement that I spend half my time berating and arguing with those who think cables and fuses etc sound differently (they don't!) on audiophool sites and then find that on this site people think all amplifiers sound the same (they don't!).

I'll bow out from this thread as my participation would surmount to increasingly vitriolic disagreement with those who think all amps sound the same.
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Old 20th Jun 2021, 2:00 pm   #23
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Default Re: Listening for Quad amplifier differences

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with those who think all amps sound the same
That has never been said, just the Quad series here. Please stay on board, we may learn something.

(only slightly OT) One of the best things I did at school was CSE statistics, taught me a lot about perception. We had to define an experiment, mine was walk up to someone and say "guess a minute from now" and start a stopwatch. The result was a double humped curve, about 50/50 at 27 and 58 seconds, when asked, group 27 just guessed, group 58 used their pulse. If just asking a question can change the pulse by a few percent what use non blind studies?
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Old 20th Jun 2021, 2:14 pm   #24
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Default Re: Listening for Quad amplifier differences

I would like to know if the people back in the day were

A) Deaf
B) Deluded
C) Corrupt
D) Mislead
E) Mis-reported
F) Exploited
G) Combinations of the above

.... or

H) Honest


Noise exposure at home wouldn't have been as bad as today, so as long as someone didn't work with noisy machiney, their hearing was probably good if not better than today's average.

Stupid? I think not. People then didn't have modern technologies or disposable income but they were just as smart. Maybe more so, on average. It was fun, while working on the campus of a university, watching the odd moron terminally fixated on his cellphone falling into the loch.

I think Honesty was considered more important back in the day.

Perhaps the biggest advances in audio since the early 70s has been in the field of adjectives.

David
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Old 20th Jun 2021, 2:22 pm   #25
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Default Re: Listening for Quad amplifier differences

Oh, I don't think all amplifiers sound the same. Take careful note of the stated condition about being competently designed and about being operated within their specified capabilities.

One of the things learned in the seventies onwards is just how much headroom really is needed to avoid driving things into non-linearities. It's highly probable that an amplifier is going to get clipped, so it makes sense to design one to clip cleanly and to not have any lasting after-effects.

Certainly, I can throw things at a II, 303, or 405 which will allow them to be told apart by ear. But that would involve driving them outside their design limits.

There has been some actual progress made, and better amplifiers can be designed nowadays than could back then.

David
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Old 20th Jun 2021, 2:40 pm   #26
theoldtrout
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Default Re: Listening for Quad amplifier differences

I remember some wise words from Arthur Radford [I knew him well]: "All your distortion measuring sets, spectrum analysers and other measuring instruments don't tell the full story. The best instruments are those either side of your head". I wonder, reading a great deal about Peter Walker's design philosophy, if he placed too much emphasis on the what the lab instruments were telling him. All amplifiers do indeed sound different: The Quad II is OK, the 33/303 sounds very average as does the 34/405 - although the 405-2 is better. I've owned and serviced many of these amps but wouldn't have them in my system, although I do own a pair of Quad 989 electrostatics which do not get in the way of the music.
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Old 20th Jun 2021, 3:15 pm   #27
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Default Re: Listening for Quad amplifier differences

Quad 2 i liked very much a design classic
Quad 303 a great little amplifier if used within its power rating and a loudspeaker that does not dip below 8 ohms seems to be very smooth but has a bit of top cut
Quad 405 waited for it to be released with great anticipation but was very disappointed with its sound ( very transistor ) Known to be very poor with low impedance loads
I agree though about the cost of old vale stuff
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Old 20th Jun 2021, 4:51 pm   #28
Jez1234
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Default Re: Listening for Quad amplifier differences

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Originally Posted by merlinmaxwell View Post
Quote:
with those who think all amps sound the same
That has never been said, just the Quad series here. Please stay on board, we may learn something.

(only slightly OT) One of the best things I did at school was CSE statistics, taught me a lot about perception. We had to define an experiment, mine was walk up to someone and say "guess a minute from now" and start a stopwatch. The result was a double humped curve, about 50/50 at 27 and 58 seconds, when asked, group 27 just guessed, group 58 used their pulse. If just asking a question can change the pulse by a few percent what use non blind studies?
Moderation etc on this site is, ahem... rather more "conservative" than on sites I've been on for much longer and I fear that my taking an absolutist stance on something which several prominent posters and a moderator diametrically disagree with me on would not end well for me.

To try and wrap it up from my side of the argument then... I design and build hi fi gear professionally and make a living mainly from repairing and modifying amplifiers. I have designed and built literally hundreds of amplifiers over 40+ years and have heard profound differences between them. One of the worst sounding was a design of mine that measured so well it beat the THD analyser... I consider that neither I nor anyone else can offer any insight technically as to why this should be. It is, as our medical colleagues would cal it, idiopathic... for now anyway. One day we will understand dark matter... and maybe even why two amps with exemplary measured performance can differ subjectively such that the first sounds "open", "transparent", "effortless" and has a depth to the stereo image where you feel you could walk amongst the musicians... but the second equally well specified amp may sound "strained", "glassy" and with little stereo depth. Technical explanations for this have thus far eluded me as much as they have everyone else in the field!
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Old 20th Jun 2021, 6:37 pm   #29
Bufo Bill
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Default Re: Listening for Quad amplifier differences

Jez1234, you are allowed your own opinion here. Its when things get off topic, or into entrenched positions with no hope of compromise that threads get closed in my experience. You will not be banned for posting non political, non offensive opinions. Have a look at the forum rules again if you are unsure.
This is a great forum with few threads ever descending into personal "beefs" unlike most other forums of which I am a member. The moderators are key to this in my opinion.
Cheers from Bill.
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Old 20th Jun 2021, 6:38 pm   #30
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Default Re: Listening for Quad amplifier differences

This is a civilised forum. People are allowed to have different views on subjects and it would be awfully bad form to interfere with people's freedom to have their own opinion. We all should be able to differ without the world having to end. Wouldn't life be boring if everyone had the same beliefs and interests (just think of the queues!)

If we can disagree on things swap ideas and banter to and fro, then I see it as healthy.

A long time ago, people, companies etc thought the audio business was completely tied up by doing static distortion measurements and static frequency response measurements. People who trusted their ears said there was something else on the go and the issue of slew rate limiting, hang-up after clipping etc came to light.

This was a significant advance and came out of cooperation and respect. This must not be forgotten.

Just as before it, some 'measurists' were wrong in thinking they were measuring everything
after it, some subjectivists took the stance that the old measurements were off the ball, so therefore all measurements, current and future are wrong. One closed mind does not cancel a different closed mind.

The differences between the QuadII, 303 and 405 are interesting. They have a comfort zone and behave decently. BUT the comfort zones are different in extent and location. The Quad II has its liiitations, but it has a generous capability before you push it into issues.

The 303 has a smaller comfort zone and you do need to stay within it, or you will find limitations (slew rate and clipping sorts of things)

The 405 is weird. It relies on a class A amplifier to fill in the gaps left by an unbiased pair of power transistors. Yes, the maths of the bridge analysis is right, but there is a second analysis which is needed, of the effect of load impedance as well. You definitely can catch these amps out into awkward impedances.

But keep them in their happy regions and don't invoke any bad behaviour and they should be difficult to tell apart under non-demanding conditions. This is what I think Quad did in their comparisons and demos. I trust them to have been honest in reporting the outcomes, but they might have pre-cooked the books in choosing the conditions.

I don't have any Quad amplifiers. I've fixed quite a number of the various types.

QuadII is OK but under powered and overpriced for me to want my own.

303 ...is an early transistor design, dodging the germanium era of thermal instability, but before slew rate and clipping issues were addressed. It was a landmark in its day. Trouble is getting satisfactorily slow and stable power transistors. Again, not what I want, but for different reasons.


405...I'm uncomfortable about the overlap of the capabilities of the class A stage to fill-in properly if loads get awkward. I've had them on the bench and been able to catch them out.
Quad stuck with them, but there was no queue of firms wanting to licence the technique, nor did anything pop up when patents would have expired.

David
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Old 24th Jun 2021, 4:08 pm   #31
Jez1234
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Default Re: Listening for Quad amplifier differences

All 3 of the Quad designs are interesting in their own right but especially the II and the 405.

For me the 405, although in many ways a tour de force in audio lateral thinking, was reinventing the wheel... By the time it came out the issues with conventional power amps had pretty much been sorted.
For very best performance the bridge components need to be adjusted to each specific unit, hence moving the problem of setting bias in production to another area of the amp.. OK it's not quite as critical so I'll give Quad that one... just...

It also needs similar levels of loop gain for an arbitrary low level of THD as a conventional amp and this is the nail in the coffin lid for me. YMMV
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