Patrick Turner wrote:

IMHO, a well re-engineered Quad II will hold its own with a 300B amp.

Patrick Turner.

Not much of a challenge. A well-preserved or faithfully rebuilt Quad
II will hold its own with most modern amps.

But it is unfair to compare a beefy 18W PP NFB amp with an 8W SE ZNFB
amp. The proper comparison is with PP or SEPP 300B. But I take your
underlying point that more than half a century later it still takes an
exceptional amp to stand up to a Quad II.

I have and love Quad II, of course. I can remember when you could, and
I did, buy a really good pair of Quad II for 350 pounds sterling. With
the current prices for what appears to be scrap Quad II, the stakes
are getting a bit high. You can build a really fine PP amp with the
kind of money you need today to get good Quad II.

Andre Jute

On Wed, 08 Dec 2004 17:32:02 -0800, Andre Jute wrote:

snip

I have and love Quad II, of course. I can remember when you could, and I
did, buy a really good pair of Quad II for 350 pounds sterling. With the
current prices for what appears to be scrap Quad II, the stakes are
getting a bit high. You can build a really fine PP amp with the kind of
money you need today to get good Quad II.


It's not helped by Sowter discontinuing their Quad II clone OPT. There
used to be another company who also did very good clone OPTs but they
ceased trading in October this year. That leaves the sources for
replacement trannies just about bare I think. I don't think Quad can
supply them either now!

Perhaps Patrick may be interested? grin

--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info
Web: http://projectedsound.tk

"mick" wrote in message
news
On Wed, 08 Dec 2004 17:32:02 -0800, Andre Jute wrote:

snip

I have and love Quad II, of course. I can remember when you could, and I
did, buy a really good pair of Quad II for 350 pounds sterling. With the
current prices for what appears to be scrap Quad II, the stakes are
getting a bit high. You can build a really fine PP amp with the kind of
money you need today to get good Quad II.


It's not helped by Sowter discontinuing their Quad II clone OPT. There
used to be another company who also did very good clone OPTs but they
ceased trading in October this year. That leaves the sources for
replacement trannies just about bare I think. I don't think Quad can
supply them either now!

Perhaps Patrick may be interested? grin

--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info
Web: http://projectedsound.tk



I wonder why Sowter discontinued the Quad II clone OPT. It was
very good indeed., I would have thought there would have been
a demand. Maybe there was pressure from some quarter?

AFAIK, Woodside still produce a transformer. Take a look at
http://freespace.virgin.net/m.davis


Iain

Andre Jute wrote:

Patrick Turner wrote:

IMHO, a well re-engineered Quad II will hold its own with a 300B amp.

Patrick Turner.

Not much of a challenge. A well-preserved or faithfully rebuilt Quad
II will hold its own with most modern amps.

But it is unfair to compare a beefy 18W PP NFB amp with an 8W SE ZNFB
amp. The proper comparison is with PP or SEPP 300B.

True, but 8 watts is still able to get within 4 dB of the Quad II output
level.
So it depends on speakers and their sensitivity.

People bring me Quad II amps which they want to use with modern insensitive
speakers,
and they need a little tweaking to improve the class AB performance.

With a 16 ohm load, even on the 8 ohm tap, they ain't bad.
The preamp for them, the Quad 22, is not a wonderful item imho.
But with a better preamp, and a few mods, the Quad II will performs a bit
better.


But I take your
underlying point that more than half a century later it still takes an
exceptional amp to stand up to a Quad II.

I am not so sure. After comparing a triode PP Ab1 amp I made with 6CM5, and
using
"junkbox" OPTs, I found the 22 not quite as good, but then that was with my

6 ohms speakers, but heck, there wasn't a lot in it.

Here is again what I said in a recent post to pinky...

The simplest improvements to a Quad II a-

1, Fit individual RC bypassing to each output tube cathode
so bias current is 65 mA max or less for old tubes showing signs of wear,
ie, they won't balance in an existing amp.
2, At least have a GZ34 as the rectifier.
3, Remove the bulky low value boxed electros,
4, Install a CLC filter, 47uF, 2H, 100uF instead of the large cap for the
reduction of
hum appearing at the CT of the OPT.
5, Replace all the old Hunts caps, and carbon comp resistors with modern
caps
and metal films.
6, Make sure the tubes are in good operating order.
7, Set up the OPT settings for 8 ohms, and never use the 16 ohm setting,
8, Add stabilisation network to prevent oscilations into C loads with the 8
ohm setting,
9, Measure the thd and try swapping positions of the EF86,
and the KT66 to get the lowest thd at 3 watts into 8 ohms.
10, Fit an rca input socket so the Jones plug can be retired when using
more modern
preamps.
11, Fit IEC shielded input chassis plug for a standard IEC input lead.
12, Fit a mains switch to each 22 mono amp, to allow use with modern pres.

I did all this to a pair last July, and the owner was rapt.
He said the sound from his ESL57 was the best,
but also said that they still wouldn't push his ESL63 very well.

He also had ancient Quad mono preamps, both in very poor condition,
full of hums, noises, intermittencies, so I made a complete new stereo
preamp with the same chassis size as the 22,
since that seemed like less work and give a more convenient usage, and
perhaps better
sound; simple circuit, new Alps pots, NOS wafer source switch....

That lot was better than my 6CM5 junkbox special.

The Allen Wright school of thought would have us believe in
using a CCS between the OPT cathode winding CT, which makes the amp
incapable of class AB, and it can only give true balance differential
class A performance, and therefore good sound, but presumably with
sensitive speakers of highish Z, or at least
two 6 ohm speakers in series, so that whatever power is produced,
its only class A right up to clipping....


I have and love Quad II, of course. I can remember when you could, and
I did, buy a really good pair of Quad II for 350 pounds sterling. With
the current prices for what appears to be scrap Quad II, the stakes
are getting a bit high. You can build a really fine PP amp with the
kind of money you need today to get good Quad II.

I have another complete Quad II set just sent to me by a guy in Melbourne
with a long list of mods.......

There are thousands of these amps still out there, and they manage to
delight a lot of people.
Some who have gone modern to 303, or 405 amps have told me of their regret,

and I don't know if its just nostalgia at work.

I trioded a pair once using Sovtek KT88, and replaced the GZ34 with SS
diodes and capacitance,
and that gave a quite nice 20 watts of class AB1.
Still with the CFB windings; one cannot alter the transformers for single
primary winding use.

I realized I could have used the KT88 as the standard KT66 are used, ie,
with a fixed screen voltage,
but at a few watts I doubt there would be much change.
Maybe more po is available, even with the standard PS B+.

I get a few Leaks to rewire. I have a Point one to do now, rewind the power
tranny,
but this guy wants it kept as original as possible with regard to the
circuit,
just made safe with better connections.
He's only got the one.

Many Leaks were bought before stereo really caught on and became de-rigour
for the
younger set of 1960, who like today's kids have to have surround sound and
multi purpose disc players and wwwwiiiiidddeeee screen televisions, wheras
old
farts like me are quite OK with a decent stereo set, and I go out to watch
a movie,
TV died long ago.

Patrick Turner.







Andre Jute

mick wrote:

On Wed, 08 Dec 2004 17:32:02 -0800, Andre Jute wrote:

snip

I have and love Quad II, of course. I can remember when you could, and I
did, buy a really good pair of Quad II for 350 pounds sterling. With the
current prices for what appears to be scrap Quad II, the stakes are
getting a bit high. You can build a really fine PP amp with the kind of
money you need today to get good Quad II.


It's not helped by Sowter discontinuing their Quad II clone OPT. There
used to be another company who also did very good clone OPTs but they
ceased trading in October this year. That leaves the sources for
replacement trannies just about bare I think. I don't think Quad can
supply them either now!

Perhaps Patrick may be interested? grin

Not me.

I wind slightly different items to the Quad II.
Mine have thicker wire, which I can actually see while I wind on the turns...

It is amazing they do tend to last so long, and despite tubes saturating
and melting down without the owner noticing.

Its not a market I really want to crack, because of the percieved market value

of the OPT; I doubt ppl are willing to pay all that much.

I mainly only wind OPTs for the amps I build, or occasionally
if I have a total rebuild of an amp to do.
I made one exception this year where a guy wants a 20 kG OPT to suit a single
400 watt tube amp. Its just about done on my bench.
When you get above a certain VA, ready made audio transformers are thin on the
ground.
Most diyers here go to Hammond.

Maybe a chinese guy might wind up something......

Patrick Turner.





--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info
Web: http://projectedsound.tk

On Thu, 09 Dec 2004 13:48:20 +0200, Iain M Churches wrote:

snip

I wonder why Sowter discontinued the Quad II clone OPT. It was very good
indeed., I would have thought there would have been a demand. Maybe there
was pressure from some quarter?


Someone told me that they had stability problems with it - I don't know
for certain. It may have simply been costly to wind!

AFAIK, Woodside still produce a transformer. Take a look at
http://freespace.virgin.net/m.davis


Mike Davis is the one that went out of business in October... :-(

--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info
Web: http://projectedsound.tk