Re: First Mu Follower

Andre Jute wrote:
On Sep 1, 1:07 pm, Ian Thompson-Bell <ruffreco...@xxxxxxxxx> wrote:
Andre Jute wrote:
On Aug 31, 10:58 am, Ian Bell <ruffreco...@xxxxxxxxx> 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/
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