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John L Stewart John L Stewart is offline
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Smile Local Cathode FB, UL Tap at Ground Part 2

Here is a version posted by Yves Monmagnon & his collaberators Tomcik & Wiggins to RAT on Sep 1/ 2004.

Hey Patrick, it looks like Yves has you beat by a few years. Such is life.

Think of Darwin & Alfred Wallace on evolution. Few people remember Wallace. Or what about Edison & the Brit Swan & the incandescent light? Swan is now mostly forgotten except for their joint company Ediswan in the UK. And development of the first jet engine(s), independantly in the UK & Germany, only a few moths apart.

Cheers to all, John
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patrick-turner patrick-turner is offline
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Default Local Cathode FB, UL Tap at Ground Part 2

On 12 Nov, 10:16, John L Stewart
wrote:
Here is a version posted by Yves Monmagnon & his collaberators Tomcik &
Wiggins to RAT on Sep 1/ 2004.

Hey Patrick, it looks like Yves has you beat by a few years. Such is
life.

Think of Darwin & Alfred Wallace on evolution. Few people remember
Wallace. Or what about Edison & the Brit Swan & the incandescent light?
Swan is now mostly forgotten except for their joint company Ediswan in
the UK. And development of the first jet engine(s), independantly in the
UK & Germany, only a few moths apart.

Cheers to all, John


I am lucky to invent things a few moths apart from other dudes. One
mustn't let moths into one's mind lest the intellectual larvae eat
holes in one's thorts and you end up with many holes in ideas, and
empty sockets on amps you try to build, and not knowing why :-)

But yeah, Yves beat me alright. I wonder who beat him maybe 40 years
ago, but only to also be ignored by everyone, and forgotten so much
more quickly due to an absense of searchable Internet stuff?

But Yves is using a 6V6 only, and has an unbypassed screen, with its
Eg2 supplied through 15k and adjustable pot. That just doesn't look
right. If g2 is bypassed to cathode, circuit becomes pure beam tetrode
with CFB, and isn't too bad, except for tetrode spectra that still is
there, but merely reduced by the NFB. Better, IMHO, is to have a shunt
regged and fixed Eg2 at about 3/4 the anode B+. Then the supply R to
g2 don't load the anode circuit, and NFB is applied to g2 circuit
because the 6V6 works as 20% UL in terms of its open loop gain.
Trouble is that hardly any OPTs with a 20% UL tap are ever made. But
quite a few are supplied with 40% tap. To then avoid having huge grid
drive voltages = say 50% of the Vak, the load value is kept a bit on
the lowish side, so that PO is high for the equation PO = Va-k
squared / RLa. Say you have 2 x EL34. Loads are Typically 3k6 per
tube, so for 2 parallel tubes the RLa = 1k8, and for the 18 Watts
easily available you have Va-k = 180Vrms, so that 40% tap gives Vk-0V
= 72V, and Vg-0V = 90Vrmsd, not too hard to do with an 6EH7 with about
10mA and CCS in triode and with gain = 45, so Vin without NFB = 2Vrms.
Rout with 40% CFB is low enough to not use GNFB, but that's also easy
to do if needed if driver = EL84 and a secind paralleled 6CG7 input
tube is used with normal type GNFB, and only 9dB max NFB is needed to
make sensitivty about a volt.

I guess if I tried to get to the moon before 1969, the yanks wooda
spent yet more dough and beat me and the Ruskies!

Patrick Turner.

+-------------------------------------------------------------------+
|Filename: Yves Monmagnon SE 6V6 UL Tap to Ground Page 7W.jpg * * * |
|Download:http://www.audiobanter.com/attachment.php?attachmentid=314|
+-------------------------------------------------------------------+

--
John L Stewart


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John L Stewart John L Stewart is offline
Senior Member
 
Location: Toronto
Posts: 301
Smile

Quote:
Originally Posted by patrick-turner View Post
On 12 Nov, 10:16, John L Stewart
wrote:
Here is a version posted by Yves Monmagnon & his collaberators Tomcik &
Wiggins to RAT on Sep 1/ 2004.

Hey Patrick, it looks like Yves has you beat by a few years. Such is
life.

Think of Darwin & Alfred Wallace on evolution. Few people remember
Wallace. Or what about Edison & the Brit Swan & the incandescent light?
Swan is now mostly forgotten except for their joint company Ediswan in
the UK. And development of the first jet engine(s), independantly in the
UK & Germany, only a few moths apart.

Cheers to all, John


I am lucky to invent things a few moths apart from other dudes. One
mustn't let moths into one's mind lest the intellectual larvae eat
holes in one's thorts and you end up with many holes in ideas, and
empty sockets on amps you try to build, and not knowing why :-)

But yeah, Yves beat me alright. I wonder who beat him maybe 40 years
ago, but only to also be ignored by everyone, and forgotten so much
more quickly due to an absense of searchable Internet stuff?

But Yves is using a 6V6 only, and has an unbypassed screen, with its
Eg2 supplied through 15k and adjustable pot. That just doesn't look
right. If g2 is bypassed to cathode, circuit becomes pure beam tetrode
with CFB, and isn't too bad, except for tetrode spectra that still is
there, but merely reduced by the NFB. Better, IMHO, is to have a shunt
regged and fixed Eg2 at about 3/4 the anode B+. Then the supply R to
g2 don't load the anode circuit, and NFB is applied to g2 circuit
because the 6V6 works as 20% UL in terms of its open loop gain.
Trouble is that hardly any OPTs with a 20% UL tap are ever made. But
quite a few are supplied with 40% tap. To then avoid having huge grid
drive voltages = say 50% of the Vak, the load value is kept a bit on
the lowish side, so that PO is high for the equation PO = Va-k
squared / RLa. Say you have 2 x EL34. Loads are Typically 3k6 per
tube, so for 2 parallel tubes the RLa = 1k8, and for the 18 Watts
easily available you have Va-k = 180Vrms, so that 40% tap gives Vk-0V
= 72V, and Vg-0V = 90Vrmsd, not too hard to do with an 6EH7 with about
10mA and CCS in triode and with gain = 45, so Vin without NFB = 2Vrms.
Rout with 40% CFB is low enough to not use GNFB, but that's also easy
to do if needed if driver = EL84 and a secind paralleled 6CG7 input
tube is used with normal type GNFB, and only 9dB max NFB is needed to
make sensitivty about a volt.

I guess if I tried to get to the moon before 1969, the yanks wooda
spent yet more dough and beat me and the Ruskies!

Patrick Turner.

+-------------------------------------------------------------------+
|Filename: Yves Monmagnon SE 6V6 UL Tap to Ground Page 7W.jpg * * * |
|Download:http://www.audiobanter.com/attachment.php?attachmentid=314|
+-------------------------------------------------------------------+

--
John L Stewart
It seems Yves was a busy guy back there 8 years ago. Here is another of his thoughts. The 4CX250 needs forced air cooling so having the plate at ground would help.

But lots of other problems!

Cheers, John
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patrick-turner patrick-turner is offline
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Posts: 119
Default Local Cathode FB, UL Tap at Ground Part 2

On 14 Nov, 01:24, John L Stewart
wrote:
patrick-turner;963845 Wrote:





On 12 Nov, 10:16, John L Stewart
wrote:-
Here is a version posted by Yves Monmagnon & his collaberators Tomcik

&
Wiggins to RAT on Sep 1/ 2004.


Hey Patrick, it looks like Yves has you beat by a few years. Such is
life.


Think of Darwin & Alfred Wallace on evolution. Few people remember
Wallace. Or what about Edison & the Brit Swan & the incandescent

light?
Swan is now mostly forgotten except for their joint company Ediswan

in
the UK. And development of the first jet engine(s), independantly in

the
UK & Germany, only a few moths apart.


Cheers to all, John-


I am lucky to invent things a few moths apart from other dudes. One
mustn't let moths into one's mind lest the intellectual larvae eat
holes in one's thorts and you end up with many holes in ideas, and
empty sockets on amps you try to build, and not knowing why :-)


But yeah, Yves beat me alright. I wonder who beat him maybe 40 years
ago, but only to also be ignored by everyone, and forgotten so much
more quickly due to an absense of searchable Internet stuff?


But Yves is using a 6V6 only, and has an unbypassed screen, with its
Eg2 supplied through 15k and adjustable pot. That just doesn't look
right. If g2 is bypassed to cathode, circuit becomes pure beam tetrode
with CFB, and isn't too bad, except for tetrode spectra that still is
there, but merely reduced by the NFB. Better, IMHO, is to have a shunt
regged and fixed Eg2 at about 3/4 the anode B+. Then the supply R to
g2 don't load the anode circuit, and NFB is applied to g2 circuit
because the 6V6 works as 20% UL in terms of its open loop gain.
Trouble is that hardly any OPTs with a 20% UL tap are ever made. But
quite a few are supplied with 40% tap. To then avoid having huge grid
drive voltages = say 50% of the Vak, the load value is kept a bit on
the lowish side, so that PO is high for the equation PO = Va-k
squared / RLa. Say you have 2 x EL34. Loads are Typically 3k6 per
tube, so for 2 parallel tubes the RLa = 1k8, and for the 18 Watts
easily available you have Va-k = 180Vrms, so that 40% tap gives Vk-0V
= 72V, and Vg-0V = 90Vrmsd, not too hard to do with an 6EH7 with about
10mA and CCS in triode and with gain = 45, so Vin without NFB = 2Vrms.
Rout with 40% CFB is low enough to not use GNFB, but that's also easy
to do if needed if driver = EL84 and a secind paralleled 6CG7 input
tube is used with normal type GNFB, and only 9dB max NFB is needed to
make sensitivty about a volt.


I guess if I tried to get to the moon before 1969, the yanks wooda
spent yet more dough and beat me and the Ruskies!


Patrick Turner.
-
+-------------------------------------------------------------------+
|Filename: Yves Monmagnon SE 6V6 UL Tap to Ground Page 7W.jpg * * * |
|Download:http://www.audiobanter.com/attachment.php?attachmentid=314|
+-------------------------------------------------------------------+


--
John L Stewart-


It seems Yves was a busy guy back there 8 years ago. Here is another of
his thoughts. The 4CX250 needs forced air cooling so having the plate at
ground would help.

But lots of other problems!

Cheers, John

+-------------------------------------------------------------------+
|Filename: Yves Monmagnon PP 4CX250 Plates at Ground Page 7W.jpg * *|
|Download:http://www.audiobanter.com/attachment.php?attachmentid=315|
+-------------------------------------------------------------------+

--
John L Stewart- Hide quoted text -

- Show quoted text -


Upside down tubes look queer, and one might almost think the PNP tube
had been invented, which would be so handy to have, considering all
known tubes are npn types :-)

The 4CX250 data is a bit thin on ground, but appears to have Pda
rating of 250W, so I guess 300W from a pair is OK. But its always
possible to have tubes such as 6L6GC or a KT120 etc "upside down" and
have anode and OPT primary at 0V, and have the whole cathode and its
cathode bias R&C and grid at at -400Vdc. The drive to grid is then via
IST like Yves has in his schema. Triode operation means the screen is
also taken to 0V. So the cathode os where Va appears relative to 0V.
Filamants must also float at cathode Vdc bias of say -400V. So one
still ends up with up to 800pkV during normal use between pins 3 and
2, so 807 are probably most suitable. I see no problem having a
floating HT winding and B+ supply, and I have no problem with
Circlotron topology, especially with OTL designs where two equal
amplitude phases are used to drive OP devices, and easily produced by
an LTP. Having a B+ supply between an anode and an earthy OPT seems a
natural way to go to avoid having say 1,000Vdc across insulation of
OPT. In my 55 Watt class SE845 amps I ended ed up using split supply
rails, +600V and -600V which seemed a fairly good way to do it at the
time.

As I think about it now, for SET etc, having a floating B+ between
earthy primary and anode with +ve anode allws for possibility of
having the secondary in series with anode winding to convert the
isolationg tranny into an autotranny, and thus slightly changing the
turn ratio to a larger one giving higher anode loads ohms with the
same Sec load. The 100mAdc flow through sec windings of perhaps Rw =
0.24ohms gives 0.024Vdc at Vo, which would worry some because they
don't like any DC in speakers, but 0.024Vdc across 8 ohm voice coil
hardly does anything.
But the grounded SE OPT with UP primary tap begs for someone to ground
the tap, and have say 40% of Va-k at cathode and thus have CFB. But
adding sec in series with primary is then impossible lest you have 2
speaker OP terminals each with high Vac-0V signal which is dangerous.

Auto transformers are usually wound with one long winding with taps
out for smaller than the voltage input across all the winding. If one
applies this idea for an OPT where a typical TR is say 25:1, ie, 5k0:8
ZR, then one may think its OK to just use 1/25 of the primary turns to
power an 8 ohm speaker. But it ain't.
Even though auto tranny is said to be more efficient, the current in
shared winding is speaker output current - un-shared primary input
current, and where such a big difference between Ia and Iout exists,
you still have high current in the shared winding. And the HF coupling
is also very poor, despite the direct series connection between the
the P and S windings.

However, auto trannies are very useful and sensible for where step
down is no more than say 4:1, giving say 64r : 4r, which means using a
quad of 6C33C in circlotron makes an awesome amp because each tube
effectivle is loaded by 256 ohms in class A, an ideal load, and one
that does not cause smoke when OTL is attempted.

Now, the very curly question I have to ask is how does one design the
auto tranny to give best low leakage inductance and lowest winding
resistance losses?

One mat cite McIntosh and others who have done it, and the guy at
www.zeroimepedance.com and he uses a toroid, and what appears to be a
few windings all the same and with taps all paralleled and wound on
top of each other. But where is the design theory. Its different to
what one would use for an E&I. I don't want to know about other
products I could buy, but about how to design for myself. I've got
along that path for isolation trannies, but not for auto trannies.
Looking in Google, I didn't find much except I did notice stuff about
apps in large 3 phase PTs. Nothing about how to make a decent audio
auto tranny OPT.
autot high powrba byhow other L nd ds

Like some things, one has to just wind and measure, and maybe use of
bifilar is required. But the 'zero impedance' load matchig trannys are
supplied to audiophules to make their 4 ohm speakers look like 16 ohms
or 32 ohms to an amplifier, so Pda is much reduced and tube in OTL
don't smoke, THD is lowered while DF is raised, and the Phules end up
realising OPTs ain't so bad after all.

I tested a zeroimpedance tranny, and found bandwidth was from about
3Hz up to 1MHz, quite excellent, and surprising considering how rough
and untidy the turns look on the toroid.

But most toroidal OPTs wih normal isolation windings for say 5k0:8
have hopelessly high shunt C between pri and sec, often 20 times what
a 1/2 decent normal E&I tranny has, and seems its because they just
don't understand the need to use thicker insulation between windings
with high Pd changes between them. They must use Chinese Fools who
only work up to 60Hz, and who hate the price of insulation, and the
time to takes to put it in proper. Of couse nobody uses woven
insulation on toroids to allow varnish to soak right in easily. But
varnish increase effective thickness of insulation to increase the
dielectric constant so thus increasing effective C. AAAAHHHH, who said
working with stuff above 5kHz was to be easy?

But I am digressing of course.....

But I'd like to add another page to my website on auto trannies. They
are not bad things for circlotron designs using mosfets with the same
NPN structure so that PP class A then becomes quite awesomely linear.
Taps on auto tranny and each side of CT at 0V give zero Vdc at V0, and
one should be able to have a good range of load matches without high
winding losses or HF loss.

Patrick Turner.

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