QUAD-II OPT core&winding details.

[Patrick Turner]

The page of Keith Snook has been recently mentioned here during
discussions about Quad-II amps.
http://www.keith-snook.info/QUAD-II-power-amp.html

I've emailed Keith about my concerns about the accuracy of the Quad-II
OPT schematic at the above page. He's agreed to look into what I have
explained in a long email to him which had an accompanying .gif file
giving what I think must be the correct schematic plus a revised
schematic showing what may be possible to include a wasteless
secondary winding configuration to suit 4 ohms. Such things are
inherently confusing.

I have a couple of spare Quad-II OPts and I will melt out the potting
mix, remove the OPT from the pot, and examine all and write up a
document so nobody will be confused in future.

Keith is mainly right in what he has shown in his nice photos except
that there are no exact core dimensions so its impossible to wind a
new OPT to best suit the existing pot size and to comply with the
interleaving pattern which Keith has so kindly mentioned at his
site.

I estimate the core may be similar to 28mm tongue wasteless E&I
pattern, but with slightly higher winding window size. I also estimate
the core stack is 28mm.

The OPTs I have wound to replace the orginal Quad OPTs have a 75mm
stack of 32mm tonge size. They will not be potted, but will have a
bell end and laid flat so one side of exposes windings project beneath
the chassis to allow connection to a board mounted over the top of the
windings. Tube rectifier and choke are deleted, 9 pin sockets and
octal sockets all have location revised, PT remains as is. They'll be
Quaner amps, with a high amount of class A from KT88/KT90/6550. .

The spare Quad-II OPTs I have will go into another amp I have which
has very inferior OPTs.

Patrick Turner.

[Patrick Turner]

Mr Keith revealed a little more information about the Quad-II OPT
design details, and he sent me a picture of the U&T laminations. I
have little reason to doubt that the OPT is as follows...

Core.
Overall plan dimensions of U and T type sections laid flat and
assembled together :-

64mm wide,x 90mm high.
Tongue T = 24mm
Window height H = 22mm,
Window length L = 42mm,
Stack S = 25mm.
Bobbin is that old 1950s brown board, 1.6mm thick.
Between cheeks distance = 36mm.

The cores are not wasteless pattern but were made taller with bigger
window to accomodate wind up and achieve a small footprint. Leak used
similar U&T laminations and Williamsons's original design had T = 32mm
but window was 75mm x 25mm, with 16mm around outside of window. There
may be some C-cores which have a similar ratio between window size and
Afe to some of those old patterns used in the 1950s.

After considering what Keith has said with greater depth there isn't
anything wrong with his analysis of what's inside Quad-II OPTs,
although anyone may be forgiven for becoming confused with the OPT
winding schematic. The Quad-II OPts are remarkably intricate designs
with 6 x S sections wound between 7 x primary sections so they do have
13 sections employing 26 layers of wire. Of course the winding losses
are quite high at 15% for 16 and 8 ohm strapping and there is not any
way I can see to make a better OPT which could fit into the same small
original volume because it is just too small.

Patrick Turner.





.. =II OPaOn Jun 14, 6:10*pm, Patrick Turner >
wrote:
> The page of Keith Snook has been recently mentioned here during
> discussions about Quad-II amps. http://www.keith-snook.info/QUAD-II-power-amp.html
>
> I've emailed Keith about my concerns about the accuracy of the Quad-II
> OPT schematic at the above page. He's agreed to look into what I have
> explained in a long email to him which had an accompanying .gif file
> giving what I think must be the correct schematic plus a revised
> schematic showing what may be possible to include a wasteless
> secondary winding configuration to suit 4 ohms. Such things are
> inherently confusing.
>
> I have a couple of spare Quad-II OPts and I will melt out the potting
> mix, remove the OPT from the pot, and examine all and write up a
> document so nobody will be confused in future.
>
> Keith is mainly right in what he has shown in his nice photos except
> that there are no exact core dimensions so its impossible to wind a
> new OPT to best suit the existing pot size and to comply with the
> interleaving pattern which Keith has so kindly mentioned at his
> site.
>
> I estimate the core may be similar to 28mm tongue wasteless E&I
> pattern, but with slightly higher winding window size. I also estimate
> the core stack is 28mm.
>
> The OPTs I have wound to replace the orginal Quad OPTs have a 75mm
> stack of 32mm tonge size. They will not be potted, but will have a
> bell end and laid flat so one side of exposes windings project beneath
> the chassis to allow connection to a board mounted over the top of the
> windings. Tube rectifier and choke are deleted, 9 pin sockets and
> octal sockets all have location revised, PT remains as is. They'll be
> Quaner amps, with a high amount of class A from KT88/KT90/6550. *.
>
> The spare Quad-II OPTs I have will go into another amp I have which
> has very inferior OPTs.
>
> Patrick Turner.