[Ian Bell[_2_]]

I have found lots of stuff about the mu follower on the web, including a
claim it was invented in the 50s, but nowhere can I found out who
invented it and what for?

Any pointers?

Cheers

Ian

[Don Pearce[_3_]]

On Mon, 31 Aug 2009 10:58:42 +0100, Ian Bell
wrote:

I have found lots of stuff about the mu follower on the web, including a
claim it was invented in the 50s, but nowhere can I found out who
invented it and what for?

Any pointers?

Cheers

Ian

If it is any good, the chances are about 95% that it was one of
Blumlein's.

I suppose you might use it if you were desperate for all the gain you
could find, but would you really want to use a circuit whose operating
parameters were defined solely by the mu of the valve you happened to
have in it - parameters which would change radically as the stage
heated up, and even more so as the valve aged?

Personally I'd prefer one whose operation was defined by the passive
components, which are not subject to such whims, and which would allow
me to plug in whatever valve I had to hand without degradation.

Only asking...

d

[Ian Bell[_2_]]

Don Pearce wrote:
On Mon, 31 Aug 2009 10:58:42 +0100, Ian Bell
wrote:

I have found lots of stuff about the mu follower on the web, including a
claim it was invented in the 50s, but nowhere can I found out who
invented it and what for?

Any pointers?

Cheers

Ian

If it is any good, the chances are about 95% that it was one of
Blumlein's.


I wondered that but wasn't he killed during WWII so that would make it
hard for him to submit a patent in the 1950s - OK the man was a genius
but there are limits ;-)

I have found the original White Follower patent which was filed in 1943
and interestingly does not cite any other patents. Do you know if the
White pre or post dates the mu follower?


I suppose you might use it if you were desperate for all the gain you
could find, but would you really want to use a circuit whose operating
parameters were defined solely by the mu of the valve you happened to
have in it - parameters which would change radically as the stage
heated up, and even more so as the valve aged?

Personally I'd prefer one whose operation was defined by the passive
components, which are not subject to such whims, and which would allow
me to plug in whatever valve I had to hand without degradation.

Only asking...


You must have been away for a while then.

Cheers

Ian
d

[John Byrns]

In article 4a9bb748.2354972796@localhost, (Don Pearce)
wrote:

On Mon, 31 Aug 2009 10:58:42 +0100, Ian Bell
wrote:

I have found lots of stuff about the mu follower on the web, including a
claim it was invented in the 50s, but nowhere can I found out who
invented it and what for?

Any pointers?

If it is any good, the chances are about 95% that it was one of
Blumlein's.

I suppose you might use it if you were desperate for all the gain you
could find, but would you really want to use a circuit whose operating
parameters were defined solely by the mu of the valve you happened to
have in it - parameters which would change radically as the stage
heated up, and even more so as the valve aged?

Personally I'd prefer one whose operation was defined by the passive
components, which are not subject to such whims, and which would allow
me to plug in whatever valve I had to hand without degradation.

I thought the mu of a valve was relatively stable, unlike gm or ra which
tend to vary with age and etc?

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/

[Ian Bell[_2_]]

John Byrns wrote:
In article 4a9bb748.2354972796@localhost, (Don Pearce)
wrote:

On Mon, 31 Aug 2009 10:58:42 +0100, Ian Bell
wrote:

I have found lots of stuff about the mu follower on the web, including a
claim it was invented in the 50s, but nowhere can I found out who
invented it and what for?

Any pointers?
If it is any good, the chances are about 95% that it was one of
Blumlein's.

I suppose you might use it if you were desperate for all the gain you
could find, but would you really want to use a circuit whose operating
parameters were defined solely by the mu of the valve you happened to
have in it - parameters which would change radically as the stage
heated up, and even more so as the valve aged?

Personally I'd prefer one whose operation was defined by the passive
components, which are not subject to such whims, and which would allow
me to plug in whatever valve I had to hand without degradation.

I thought the mu of a valve was relatively stable, unlike gm or ra which
tend to vary with age and etc?



It is, and it varies little with current which in a mu follower is held
nearly constant anyway.

Cheers

Ian

[Andre Jute[_2_]]

On Aug 31, 10:58*am, Ian Bell wrote:
I have found lots of stuff about the mu follower on the web, including a
claim it was invented in the 50s, but nowhere can I found out who
invented it and what for?

Any pointers?

Cheers

Ian

Alan Kimmel, who brought mu-modes back to prominence with his mu-
stage, described in an article in Glass Audio about fifteen years ago,
merely said "they're not new".

The test of whether any mu-mode circuits were in use before the 1950s
is whether they appear in the MIT Radiation Laboratory Series, Volume
18, Vacuum Tube Amplifiers, which lists all useful circuits, including
the one that that escaped Langford-Smith et cie in the RDH, the SRPP
bootstrap. Paging through Chapter 11, which contains inter alia the
various two-tube constant current devices,I don't see any circuit with
the build-outs of a mu-follower.

This question of who "invented" the mu-follower was discussed on RAT
c1996-8, and before that, more authoritatively, on the Joe-Net
(official name "Sound-list"). I've forgotten the names mentioned now
but seem to remember that the origin was Japanese. The Joenet archives
were kept on the Harvard server the last time I looked, in case you
want to go searching.

Andre Jute
Visit Jute on Amps at
http://www.audio-talk.co.uk/fiultra/
"wonderfully well written and reasoned information for the tube audio
constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site containing vital gems of
wisdom"
Stuart Perry Hi-Fi News & Record Review

[Ian Bell[_2_]]

Andre Jute wrote:
On Aug 31, 10:58 am, Ian Bell wrote:
I have found lots of stuff about the mu follower on the web, including a
claim it was invented in the 50s, but nowhere can I found out who
invented it and what for?

Any pointers?

Cheers

Ian

Alan Kimmel, who brought mu-modes back to prominence with his mu-
stage, described in an article in Glass Audio about fifteen years ago,
merely said "they're not new".

The test of whether any mu-mode circuits were in use before the 1950s
is whether they appear in the MIT Radiation Laboratory Series, Volume
18, Vacuum Tube Amplifiers, which lists all useful circuits, including
the one that that escaped Langford-Smith et cie in the RDH, the SRPP
bootstrap. Paging through Chapter 11, which contains inter alia the
various two-tube constant current devices,I don't see any circuit with
the build-outs of a mu-follower.

This question of who "invented" the mu-follower was discussed on RAT
c1996-8, and before that, more authoritatively, on the Joe-Net
(official name "Sound-list"). I've forgotten the names mentioned now
but seem to remember that the origin was Japanese. The Joenet archives
were kept on the Harvard server the last time I looked, in case you
want to go searching.

Andre Jute
Visit Jute on Amps at
http://www.audio-talk.co.uk/fiultra/
"wonderfully well written and reasoned information for the tube audio
constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site containing vital gems of
wisdom"
Stuart Perry Hi-Fi News & Record Review


Thanks Andre, very usefull - time to put on my Holmes hat.

Cheers

Ian

[Ian Thompson-Bell[_4_]]

Andre Jute wrote:
On Aug 31, 10:58 am, Ian Bell wrote:
I have found lots of stuff about the mu follower on the web, including a
claim it was invented in the 50s, but nowhere can I found out who
invented it and what for?

Any pointers?

Cheers

Ian

Alan Kimmel, who brought mu-modes back to prominence with his mu-
stage, described in an article in Glass Audio about fifteen years ago,
merely said "they're not new".


Do you actually have a copy of this article? It seems to be no longer
available from AudioXpress.


The test of whether any mu-mode circuits were in use before the 1950s
is whether they appear in the MIT Radiation Laboratory Series, Volume
18, Vacuum Tube Amplifiers, which lists all useful circuits, including
the one that that escaped Langford-Smith et cie in the RDH, the SRPP
bootstrap. Paging through Chapter 11, which contains inter alia the
various two-tube constant current devices,I don't see any circuit with
the build-outs of a mu-follower.


The nearest I have come to it is in a US patent (2,659,775) from 1949
which describes a transformer-less output stage where the phase inverter
tube resembles the connection from the bottom tube anode to the top tube
grid via a capacitor in a mu-follower.

Does the MIT book include the White follower which was patented in 1943?

This question of who "invented" the mu-follower was discussed on RAT
c1996-8, and before that, more authoritatively, on the Joe-Net
(official name "Sound-list"). I've forgotten the names mentioned now
but seem to remember that the origin was Japanese. The Joenet archives
were kept on the Harvard server the last time I looked, in case you
want to go searching.


I'll check those out.

Cheers

Ian
Andre Jute
Visit Jute on Amps at
http://www.audio-talk.co.uk/fiultra/
"wonderfully well written and reasoned information for the tube audio
constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site containing vital gems of
wisdom"
Stuart Perry Hi-Fi News & Record Review

[Andre Jute[_2_]]

On Sep 1, 1:07*pm, Ian Thompson-Bell wrote:
Andre Jute wrote:
On Aug 31, 10:58 am, Ian Bell wrote:
I have found lots of stuff about the mu follower on the web, including a
claim it was invented in the 50s, but nowhere can I found out who
invented it and what for?

Any pointers?

Cheers

Ian

Alan Kimmel, who brought mu-modes back to prominence with his mu-
stage, described in an article in Glass Audio about fifteen years ago,
merely said "they're not new".

Do you actually have a copy of this article? *It seems to be no longer
available from AudioXpress.

I have a copy, sure, but not posted on my netsite because it is
copyright material. However, it is widely available, for instance at:
http://www7.taosnet.com/f10/mustage.html

The test of whether any mu-mode circuits were in use before the 1950s
is whether they appear in the MIT Radiation Laboratory Series, Volume
18, Vacuum Tube Amplifiers, which lists all useful circuits, including
the one that that escaped Langford-Smith et cie in the RDH, the SRPP
bootstrap. Paging through Chapter 11, which contains inter alia the
various two-tube constant current devices,I don't see any circuit with
the build-outs of a mu-follower.

The nearest I have come to it is in a US patent (2,659,775) from 1949
which describes a transformer-less output stage where the phase inverter
tube resembles the connection from the bottom tube anode to the top tube
grid via a capacitor in a mu-follower.

Does the MIT book include the White follower which was patented in 1943?

If I recollect correctly, yes. There's a problem with the MIT series,
in that these books weren't written by or for audiophiles, but under
pressure of war work to make electronics useful. These scientists
didn't name circuits as we would, and didn't care a damn about
patents. For instance, the SRPP is named only as a "two-tube series
arrangement". In consequence, unless you already know on which page to
find a circuit, as I do with the circuits that interest me (which
don't include the White -- a lot of fuss for very little result),
you're in for a lot of paging around. On the other hand, once you have
found the circuit you want, this book tells you far, far more about
the underlying mathematics than the RDH. For instance, it gives
formulae for adjusting SRPP circuits for lowest impedance or maximum
gain. I used this book as my starting point for my famous article on
building SRPP out of different kinds of tubes top and bottom.

Talking of starting points and the same thing having many names, when
investigating mu followers, you should also read an article (or pair
of articles) about boot strap circuits that appeared in, I think,
Wireless World; this is a near-complete history and the source of most
of the other historical references you'll find; among other things, it
names names, including the inventor of the mu follower. It was
referenced to RAT about a dozen years ago by someone who had "griffin"
in his e-mail address. I seem to remember John Byrns discussing the
articles, so perhaps he has a copy or can give you a closer reference
than I can manage from memory.

Andre Jute
Visit Jute on Amps at
http://www.audio-talk.co.uk/fiultra/
"wonderfully well written and reasoned information for the tube audio
constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site containing vital gems of
wisdom"
Stuart Perry Hi-Fi News & Record Review

[Ian Bell[_2_]]

Andre Jute wrote:
On Sep 1, 1:07 pm, Ian Thompson-Bell wrote:
Andre Jute wrote:
On Aug 31, 10:58 am, Ian Bell wrote:
I have found lots of stuff about the mu follower on the web, including a
claim it was invented in the 50s, but nowhere can I found out who
invented it and what for?
Any pointers?
Cheers
Ian
Alan Kimmel, who brought mu-modes back to prominence with his mu-
stage, described in an article in Glass Audio about fifteen years ago,
merely said "they're not new".
Do you actually have a copy of this article? It seems to be no longer
available from AudioXpress.

I have a copy, sure, but not posted on my netsite because it is
copyright material. However, it is widely available, for instance at:
http://www7.taosnet.com/f10/mustage.html


Yes, I have seen that. I did not realise that was the actual article -
for some reason I thought is was a separate document.

The test of whether any mu-mode circuits were in use before the 1950s
is whether they appear in the MIT Radiation Laboratory Series, Volume
18, Vacuum Tube Amplifiers, which lists all useful circuits, including
the one that that escaped Langford-Smith et cie in the RDH, the SRPP
bootstrap. Paging through Chapter 11, which contains inter alia the
various two-tube constant current devices,I don't see any circuit with
the build-outs of a mu-follower.
The nearest I have come to it is in a US patent (2,659,775) from 1949
which describes a transformer-less output stage where the phase inverter
tube resembles the connection from the bottom tube anode to the top tube
grid via a capacitor in a mu-follower.

Does the MIT book include the White follower which was patented in 1943?

If I recollect correctly, yes. There's a problem with the MIT series,
in that these books weren't written by or for audiophiles, but under
pressure of war work to make electronics useful. These scientists
didn't name circuits as we would, and didn't care a damn about
patents. For instance, the SRPP is named only as a "two-tube series
arrangement". In consequence, unless you already know on which page to
find a circuit, as I do with the circuits that interest me (which
don't include the White -- a lot of fuss for very little result),
you're in for a lot of paging around. On the other hand, once you have
found the circuit you want, this book tells you far, far more about
the underlying mathematics than the RDH. For instance, it gives
formulae for adjusting SRPP circuits for lowest impedance or maximum
gain. I used this book as my starting point for my famous article on
building SRPP out of different kinds of tubes top and bottom.


I managed to find Vol 18 on the internet in pdf format. Seems the whole
series is basically to do with radar but of course a lot of it is
generally applicable. I saw the SRPP in there but not the White.

Talking of starting points and the same thing having many names, when
investigating mu followers, you should also read an article (or pair
of articles) about boot strap circuits that appeared in, I think,
Wireless World; this is a near-complete history and the source of most
of the other historical references you'll find;

Yes I remember Wireless World very well from my teens in the 60s. Too
expensive for my pocket money then so I had Practical, Wireless instead,
but I shared a Wireless World with a neighbour.

As you say, a good source for things historical.


among other things, it
names names, including the inventor of the mu follower. It was
referenced to RAT about a dozen years ago by someone who had "griffin"
in his e-mail address. I seem to remember John Byrns discussing the
articles, so perhaps he has a copy or can give you a closer reference
than I can manage from memory.

Andre Jute
Visit Jute on Amps at
http://www.audio-talk.co.uk/fiultra/
"wonderfully well written and reasoned information for the tube audio
constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site containing vital gems of
wisdom"
Stuart Perry Hi-Fi News & Record Review