Mullard Circuits for Audio Amplifiers

by **Hugh Robjohns** » Wed Dec 19, 2018 1:26 pm

I was rummaging around the dusty corners of the Interweb the other day and came across a fairly decent scan of Mullard's audio circuits cook-book on the Sowter Transformers website.

http://www.sowter.co.uk/pdf/Mullard-Cir ... ifiers.pdf

Most valve audio equipment seems to be based on Mullard's designs, and the descriptions in here of how the circuits work is quite good. Thought some might find it an interesting and useful resource.

H

by **Folderol** » Wed Dec 19, 2018 2:55 pm

That's a great find. Mullard did an enormous amount of highly detailed research in those days, and were remarkably free with the information - OK, it sold valves, but still...
:clap:

by **MarkOne** » Wed Dec 19, 2018 3:51 pm

Excellent stuff!

Component manufacturers often used to provide application guides as companions to their product catalogues (perhaps they still do, I'm long out of that now)

I remember when I was actually a hands on engineer, whiling away time in our division's technical library collecting circuit ideas from Analogue Devices, Harris, TI, etc.

I was once talking to an ex-SSL design engineer and he admitted to me that they basically did the same thing - Take the component manufacturer reference designs and then build them really, really well

by **ef37a** » Wed Dec 19, 2018 4:02 pm

Grrr! Adobe reader won't open it, says it could be a damaged file?

Dave.

by **Kwackman** » Wed Dec 19, 2018 4:06 pm

ef37a wrote:Grrr! Adobe reader won't open it, says it could be a damaged file?

Dave.

Opens here ok, using Preview on a mac which won't open damaged files.
It's quite a large file- 53MB, maybe you tried to open it before it had finished downloading?

by **ef37a** » Wed Dec 19, 2018 4:22 pm

Kwackman wrote:
ef37a wrote:Grrr! Adobe reader won't open it, says it could be a damaged file?

Dave.

Opens here ok, using Preview on a mac which won't open damaged files.
It's quite a large file- 53MB, maybe you tried to open it before it had finished downloading?

Yes, that was it. I installed another .pdf reader and it worked then Adobe worked as well.
Grr again! Firefox, unlike IE, does not show the download in progress just BOOM! File on screen so you have no idea of the processing.

Anyway, had that book forever, as an impecunious apprentice I could not afford the transformers (valves and other bits no sweat) . Did build a 5-10 of sorts with a "lesser" rad spad OP traff.

There is another Mullard book about transistor designs, like to find that again.

Dave.

by **Wonks** » Wed Dec 19, 2018 4:25 pm

And works OK on my WIN10 PC.

by **Folderol** » Wed Dec 19, 2018 4:29 pm

For the sake of completeness, it displays fine on qpdfview under devuan Linux :wave:

It also brings back fond memories

by **wireman** » Wed Dec 19, 2018 5:54 pm

Circuit diagrams....

This reminded me of when I was at school and I purchased an ITT Radio, it came with a circuit diagram, not something you would get nowadays. I think I still have it somewhere, DIN output socket was a bit annoying.

by **Folderol** » Wed Dec 19, 2018 8:32 pm

ef37a wrote:There is another Mullard book about transistor designs, like to find that again.

Dave.

I'd love to see a copy of that!

Fun facts:
Who knew that the early European transistor type IDs followed the established valve format?

OC45 for example. The 'C' stands for triode, and the 'O' indicates a cold cathode :bouncy:

This has contiued a fair way into modern devices. The main change was the first letter where 'A' stands for a germanium devices, and 'B' for silicon.

So AD149 is a germanium power device and BA127 is a silicon diode (rectifier actually).

by **Sam Spoons** » Wed Dec 19, 2018 8:53 pm

Here you go http://www.introni.it/pdf/Mullard%20-%20Reference%20Manual%20of%20Transistor%20Circuits%201960.pdf

by **Hugh Robjohns** » Wed Dec 19, 2018 9:08 pm

Brilliant -- good find!

by **James Perrett** » Wed Dec 19, 2018 10:04 pm

I didn't have the Mullard books but a few of their circuits found their way into the old Henry's Radio catalogues which inspired me to build my first tape playback preamp.

by **Folderol** » Wed Dec 19, 2018 10:58 pm

Well that was a blast from the past :bouncy:

Great find thanks.

by **Wonks** » Wed Dec 19, 2018 11:06 pm

After all this nostalgia, I expect to see some lovely DIY gramophones produced during the Christmas break.

by **Sam Spoons** » Wed Dec 19, 2018 11:59 pm

At my age, nostalgia (or even, possibly, neuralgia) would involve a wind up gramophone. And, yes, I did have one as a child.....

by **Folderol** » Thu Dec 20, 2018 1:32 am

Sam Spoons wrote:At my age, nostalgia (or even, possibly, neuralgia) would involve a wind up gramophone. And, yes, I did have one as a child.....

So did I

by **mac.churchmouse** » Thu Dec 20, 2018 5:02 am

Sam Spoons wrote:At my age, nostalgia (or even, possibly, neuralgia) would involve a wind up gramophone. And, yes, I did have one as a child.....

+1
First record - played till totally worn out on a suitcase His Masters Voice gramophone given me by my parents - Eileen Joyce playing Debussy's Golliwogs Cakewalk. Then I started to collect those gold label opera singer 78s; Caruso, Gigli, Galli-curci, et al.
And I can still hear them in my minds ear 60 plus years later :-)

by **blinddrew** » Thu Dec 20, 2018 11:21 am

My first record player:

by **James Perrett** » Thu Dec 20, 2018 3:24 pm

Sam Spoons wrote:At my age, nostalgia (or even, possibly, neuralgia) would involve a wind up gramophone. And, yes, I did have one as a child.....

I still have the family gramophone here. It is a large floorstanding model with space for storing records on one side. When I was growing up in the 60's and 70's it served as a TV stand but it now just lives in a corner and just occasionally wound up to show how things used to be done.

SOUND ON SOUND

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Mullard Circuits for Audio Amplifiers