Don't forget some decent speaker cable - opinions are divided on this
group but it does make a difference. Audio Innovations Silver Bi-wire at
£5/metre is good, or if you can run to it Chord Rumour 4 at £20/metre.
I've used both, had the AI stuff originally and upgraded to the Rumour 4
when I got the Arcam AVR250 amp.

--

Lots of snips.....

Remember when I bought my Quad ESL63s many moons ago, at the height of the
comics cable controversy.

Mr Walker gave his opinion: "The most important matter when considering
speaker cable is that they should be long enough to reach between the
amplifier and the speakers".

I'm not really a great fan of Quad products through bitter experience,
particularly of their legendary service department, but I do like some of
their definitions - a good amp being "straight wire plus gain".

Oh - and that bit about "all properly designed amplifiers when used within
their operating limits will sound the same" - er, why was the 405 power amp
replaced by the 405/2, with not much in common apart from the cabinet?

GMack

"Geoff Mackenzie" wrote in message
...


Don't forget some decent speaker cable - opinions are divided on this
group but it does make a difference. Audio Innovations Silver Bi-wire at
£5/metre is good, or if you can run to it Chord Rumour 4 at £20/metre.
I've used both, had the AI stuff originally and upgraded to the Rumour 4
when I got the Arcam AVR250 amp.

--

Lots of snips.....

Remember when I bought my Quad ESL63s many moons ago, at the height of the
comics cable controversy.

Mr Walker gave his opinion: "The most important matter when considering
speaker cable is that they should be long enough to reach between the
amplifier and the speakers".

I'm not really a great fan of Quad products through bitter experience,
particularly of their legendary service department, but I do like some of
their definitions - a good amp being "straight wire plus gain".

Oh - and that bit about "all properly designed amplifiers when used within
their operating limits will sound the same" - er, why was the 405 power
amp replaced by the 405/2, with not much in common apart from the cabinet?

GMack

The original 405 didn't provide enough current for anything other than
nominal 8 ohm loads. It struggled a bit even with 4 ohm loads. Given that
a nominal 4 ohm loudspeaker is allowed to go down to 3.2 ohms, and many go
below that, Quad felt they had to provide more current capability, hence the
405/2.

This is entirely consistent with "all properly designed amplifiers when used
within their operating limits will sound the same", the original 405's
operating limits were rather too limiting for real-world loudspeakers,
especially in Europe, which favoured 4 ohms much more than the UK did.

If you take a 405 or 405/2 and use them on, for example, 11-15 ohms LS3/5As,
I would very much doubt there could be any difference in sound, but with,
for example, Mission 770s, which were quite popular at the time, I would
expect the 405 to struggle, whilst the 405/2 would be OK. You may not have
been aware that QUAD published a modification to the 405 which turned it
into a 200w/4ohm mono amplifier by paralleling the two channels. I built a
few of these to use with Mission 770s and KEF 104/2s and they worked very
well.

S.

--
http://audiopages.googlepages.com

In article , Serge Auckland
wrote:


The original 405 didn't provide enough current for anything other than
nominal 8 ohm loads. It struggled a bit even with 4 ohm loads. Given
that a nominal 4 ohm loudspeaker is allowed to go down to 3.2 ohms, and
many go below that, Quad felt they had to provide more current
capability, hence the 405/2.

More to the point, the original IV limiting using on the 405 was
particularly severe for reactive loads - rather common for loudspeakers!

If you take a 405 or 405/2 and use them on, for example, 11-15 ohms
LS3/5As, I would very much doubt there could be any difference in
sound, but with, for example, Mission 770s, which were quite popular at
the time, I would expect the 405 to struggle, whilst the 405/2 would be
OK. You may not have been aware that QUAD published a modification to
the 405 which turned it into a 200w/4ohm mono amplifier by paralleling
the two channels. I built a few of these to use with Mission 770s and
KEF 104/2s and they worked very well.

Perhaps also worth recalling that around this time HFN organised a detailed
set of listening comparisons. The results of which showed that the
listeners couldn't tell one amp from another when all were used with the
same system gain and none were being taken outwith their limits. The amps
tested included the 405 IIRC.


Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Jim Lesurf" wrote in message
...
In article , Serge Auckland
wrote:


The original 405 didn't provide enough current for anything other than
nominal 8 ohm loads. It struggled a bit even with 4 ohm loads. Given
that a nominal 4 ohm loudspeaker is allowed to go down to 3.2 ohms, and
many go below that, Quad felt they had to provide more current
capability, hence the 405/2.

More to the point, the original IV limiting using on the 405 was
particularly severe for reactive loads - rather common for loudspeakers!

If you take a 405 or 405/2 and use them on, for example, 11-15 ohms
LS3/5As, I would very much doubt there could be any difference in
sound, but with, for example, Mission 770s, which were quite popular at
the time, I would expect the 405 to struggle, whilst the 405/2 would be
OK. You may not have been aware that QUAD published a modification to
the 405 which turned it into a 200w/4ohm mono amplifier by paralleling
the two channels. I built a few of these to use with Mission 770s and
KEF 104/2s and they worked very well.

Perhaps also worth recalling that around this time HFN organised a
detailed
set of listening comparisons. The results of which showed that the
listeners couldn't tell one amp from another when all were used with the
same system gain and none were being taken outwith their limits. The amps
tested included the 405 IIRC.

Yes, but the operative bit here is "none taken outside their limits". The
original 405 could be so taken fairly readily due to the limited current
capability, and, as you pointed out, the severe IV limiting on reactive
loads. I don't know which test you are referring to, so don't know what the
load was. I recall a similar test being done using Yamaha NS1000 monitors,
you may remember we corresponded about that one a year or two back.

S.


--
http://audiopages.googlepages.com

In article , Serge Auckland
wrote:

"Jim Lesurf" wrote in message
...


Perhaps also worth recalling that around this time HFN organised a
detailed set of listening comparisons. The results of which showed
that the listeners couldn't tell one amp from another when all were
used with the same system gain and none were being taken outwith their
limits. The amps tested included the 405 IIRC.

Yes, but the operative bit here is "none taken outside their limits".
The original 405 could be so taken fairly readily due to the limited
current capability, and, as you pointed out, the severe IV limiting on
reactive loads. I don't know which test you are referring to, so don't
know what the load was. I recall a similar test being done using Yamaha
NS1000 monitors, you may remember we corresponded about that one a year
or two back.

A number of similar tests were done during the late 1970s and early 1980s
with broadly similar conclusions. The one I had in mind was published in
the June 1978 issue of HFN. I've not had a chance to carefully re-read it
this morning, but from a quick scan, they used a Quad II, 303, and 405. On
page 75 the article says, "Yamaha NS 1000 loudspeakers were used (although
this would not have been Acoustical's preference)" They used a scope to
check there was no clipping or limiting that might show up.

Maybe some subjective reviewers came to fancy the NS1000 because it tended
to be what they'd call "revealing". i.e. causing current limiting in some
amplifiers so they could hear a difference when they wound the wick up.
:-) Afraid I've forgotten what we said previously about the NS1000, though.

The Nov 1978 issue re-visited this kind of test, and later comparisons were
expanded to use different amps and speakers. Martin Colloms also in the Nov
1978 issue produced some measured results showing the changes in frequency
response for some examples of amp-cable-speaker combinations due to cable
impedance interactions with source and load.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Jim Lesurf wrote:

More to the point, the original IV limiting using on the 405 was
particularly severe for reactive loads - rather common for loudspeakers!

I could write an article on the subject. I modified one (actually a family) of
my own designs to take account of complaints we had from owners specifically of
one single make/model of loudspeaker. EV SX500 btw.

When I heard it, I was convinced. There was a nasty rasp in the upperish
midrange. When I modelled it I was STUNNED that ANY loudspeaker manufactuere
let alone EV would let loose a speaker with such wild load phase angles.

Graham

In article , Eeyore
wrote:


Jim Lesurf wrote:

More to the point, the original IV limiting using on the 405 was
particularly severe for reactive loads - rather common for
loudspeakers!

I could write an article on the subject.

You mean something like the SCAMP (Society for Cruelty to AMPlifiers)
article in the Hi Fi News section of audiomisc.co.uk ? :-)


When I heard it, I was convinced. There was a nasty rasp in the upperish
midrange. When I modelled it I was STUNNED that ANY loudspeaker
manufactuere let alone EV would let loose a speaker with such wild load
phase angles.

Alas, SCAMP seems alive and well. :-)

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Jim Lesurf wrote:

Eeyore wrote:
Jim Lesurf wrote:

More to the point, the original IV limiting using on the 405 was
particularly severe for reactive loads - rather common for
loudspeakers!

I could write an article on the subject.

You mean something like the SCAMP (Society for Cruelty to AMPlifiers)
article in the Hi Fi News section of audiomisc.co.uk ? :-)

Very much so.

Graham

In article , Eeyore
wrote:


Jim Lesurf wrote:

Eeyore wrote:
Jim Lesurf wrote:

More to the point, the original IV limiting using on the 405 was
particularly severe for reactive loads - rather common for
loudspeakers!

I could write an article on the subject.

You mean something like the SCAMP (Society for Cruelty to AMPlifiers)
article in the Hi Fi News section of audiomisc.co.uk ? :-)

Very much so.

Keith Howard followed up 'SCAMP' with an article that established what the
worst choice of load phase angle would be for o/p device dissipation in
class A/AB operation. He tends to do the measurements for the HFN speaker
reviews. This was an issue we'd be discussing for a while.

Since then, he has tended to check each speaker to find at what frequency
it behaves 'worst' as a load, and then mention the results in the review.
This in terms of the resistive load that would place the same peak power
dissipation demands on the o/p devices. I don't think he always does this
as some speakers are 'gentle' loads, so their worst behaviour isn't a
concern. FWIW He also wrote about this for Stereophile IIRC.

Harder to assess the effect in secondary breakdown terms as that will vary
from design to design, so no single conclusion could be drawn about a given
speaker. Fortunately, the o/p devices these days should be less prone to
breakdown nowdays than back in ye days of yore...

It isn't a new problem. But speaker manufacturers simply tend to lob the
ball into the court of the amplifier designer and smile sweetly. I can't
complain too much as I've always favoured QUAD ESLs. :-)

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Jim Lesurf wrote:

More to the point, the original IV limiting using on the 405 was
particularly severe for reactive loads - rather common for loudspeakers!

That's a very interesting subject in its own right.

Back then, designers tended to be 'over-protective' of their output devices. No
doubt influenced by the fragility of early parts.

Things have moved on a bit. I tend no to look mainly at average dissipation as
opposed to instanteous V/I limiting now.

Can't say I've seen many failures.

Opps, giving my secrets away here.

Graham