DIY tube mixer project from 1964

Courtesy of Mr. Burnley, here are scans of a tube mixer project from Practical Stereophony by H. Burrell Hadden, published by Iliffe in 1964

I've taken Mark's dual-page scans (six in all), converted them to 4-color GIFs to reduce the file size, and put them together in a 726kB ZIP file.

If this looks familiar, it's because some much poorer and incomplete scans have been up elsewhere on the web for a while. But at last, here's the whole thing in legible form.

> Mark's.. scans.., converted them to 4-color GIFs.., ...in a 726kB ZIP file.

My eyes begged for one of those 4 colors to be "white". Black is nice too. Pagination is convenient.

"Domestic Recording" stereo-mixer article in 900K PDF format.

Thanks, Mark. Thanks, Dave.

In this months PW - Practical Wireless Magazine (UK - get it from WH Smiths) I read about a couple of books written by Fred Judd about Mixer design (written by his widow - some intersting claims in there)
There is also an article on 30 years of the IC Audio Amplifier as well
Next month a series of articles for newbies on techie stuff is being written as well - this months taster is do with Oscilloscope for beginners

Very cool, PRR. Thanks.

I have Mark's orginal JPEGs if anyone wants to try the same with higher-quality original source material. I'd do it myself, but it's a crazy day here at work.

Ohh!!! Where can I get that article on oscilliscopes for beginners? Is it online anywhere? I just bought my first oscope, and would love a nice basic intro.

Try "oscilloscope" when you Google. You'll get more hits :wink:

Tektronix, the king of scopes, offers this primer:

1.5Meg PDF

I second tubejay's request.

Thanks,
Chris

[quote author="tubejay"]Ohh!!! Where can I get that article on oscilliscopes for beginners? Is it online anywhere? I just bought my first oscope, and would love a nice basic intro.[/quote]
Not on line but it is here...
http://www.pwpublishing.ltd.uk/

I got my first oscilloscope the other day as well.. and bought this £4 Babani book to try and understand it...
http://www.peats.ie/cgi-bin/shop/db.cgi?view=1&id=4556&type=6&path=19x4127x4128

[quote author="NewYorkDave"]Try "oscilloscope" when you Google. You'll get more hits :wink:

Tektronix, the king of scopes, offers this primer:

1.5Meg PDF[/quote]

I have, and that's the problem, there's just too much junk out there, and not much that seemed layed out well. I went through a bunch of pages about a month ago, and didn't see anything that was basic enough, and well done. At least that was my opinion. Plus so much of it was unrelated to how I would be using a scope.

Honestly, the way I first learned how to use a scope was I hooked it up to a signal source and monkeyed with the controls until I got a picture. Then as time went on, I learned the finer points of its operation both through reading and simply by doing.

I haven't looked at the schematics yet, but would you consider this a passive or active mixer?

Active.

very interesting design.

He says it's fader design is not quite as good as constant impedence
faders, but would we easily hear a difference?

Would it be practical to expand this to have another 6 mono channels.

very interesting design.

He says it's fader design is not quite as good as constant impedence
faders, but would we easily hear a difference?

Would it be practical to expand this to have another 6 mono channels?

>> I haven't looked at the schematics yet, but would you consider this a passive or active mixer?

> Active.

Almost Passive.

Yeah, it has the 1.5Meg feedback resistor. But if you work out the loaded loop gain, there aint a lot of feedback happening, and you would not know the difference if it were pure passive.

Is there more to the article? It mentions Plates 8.2 to 8.4, which I don't see. The value of the stereo channel fader is not given. A complete hook-up (not the block diagram) would be handy.

Also: the sum-difference mixing is novel. Is there a previous chapter to explain this to people who never worked this way?

I think the number on the bottom of page "116" should be 470KΩ not 470Ω.

> try the same with higher-quality original source material.

I don't see anything very wrong, even working from the 4-shade scans. It is a lot clearer than a FAX, better than some older Xeroxes. Text and drawings are perfectly readable.

> it's a crazy day here at work.

I have a madwoman trying to push a demo CD through ASAP, and a bunch of pit-bull musicians in her way, and nobody has the money. So even if I had more "us stuff" material to compile, I might not get to it this week.

...

I dunno, PRR. The loaded OLG of the summing stage is about 50 (34dB). Four sources are being summed with a gain of 3 (9.5dB), so that's a CLG of 12 (21.5dB) and thus 12.5dB of feedback. I grant ya, that's not enough to force the grid to be a true virtual earth summing node, but it's not quite passive mixing either. How 'bout we call it "passactive?" :wink:

No biggie, just wondering which section of the META to stick it in...

This isn't in any way to denigrate what's already been presented - I had forgotten about this book, of which I have a copy. The background to H. Burrell Hadden was that he joined the BBC in 1946, moved through the technical ranks and eventually became an instructor in 1959. He was closely involved with most of the BBC's original stereo experiments.

[quote author="PRR"]
Is there more to the article? It mentions Plates 8.2 to 8.4, which I don't see. The value of the stereo channel fader is not given. A complete hook-up (not the block diagram) would be handy.

Also: the sum-difference mixing is novel. Is there a previous chapter to explain this to people who never worked this way? [/quote]
No, there isn't any more to the article. The plates that relate to this are from 8.1 to 8.6, and unfortunately there isn't a complete hookup - what is given is, to say the least, rather incomplete. As far as the sum and difference system is concerned, there is a little more information, but it consists of no more than a description of the classic Blumlein MS recording technique, really. The purpose as far as this mixer is concerned is to provide width controls on the stereo channels. There is a stack of information about this available online, one way or another.

I think the number on the bottom of page "116" should be 470KΩ not 470Ω.

Click to expand...

I think that it should be too - and I have amended my version of the pdf accordingly. This isn't the smallest pdf in the world (7+ MB), but it does contain the plates, and the scans, whilst not absolutely perfect, are of a higher resolution. I don't want to leave it where it is for too long, but if anybody fancies transferring it to the archive, that's absolutely fine by me.

The pdf is presently here.

Wow... we go from one incomplete/illegible version to no fewer than three good-looking versions available online. Good work!

The scans Mark sent me were actually of a very high quality, but I'm afraid some quality was lost when I downconverted them to make the file size palatable. But now we have options for all connection speeds. This place is great. :green: