Simple valve oscillator for a valve organ?

[em536716]

For my dissertation, I’ve decided I want to attempt to build an organ using valve oscillators.

Is there any simple oscillator circuits out there which can achieve a full frequency octave or 2?

[M0FYA Andy]

I recall that there were various articles on building organs in magazines such as Practical Wireless 'back in the day', it might be worth doing a trawl through them online.

Andy

[GMB]

Do you mean a fixed frequency oscillator as was usually done for polyphonic organs, or a single oscillator that is tuned by the keyboard (like the Clavioline)?

[Ed_Dinning]

Hi Ed, a few booklets were available on the subject from Foulsham-Sams
Also The electronic musical instrument manual Douglas 1949
Frequency divider organs Douglas 1963
Electronic musical instruments Lewer from Electronic engineering

I think Douglas wrote for Radio constructor; most of the journals had the odd article in them about musical instruments, World radio history site is you friend here, if you have the time

The ones mentioned above outline a variety of techniques for note generation in both simple and complex manners, as well as details of the filters used to give the various "voices"

At grammar school in the 60's the electronics club started building one for the school, but it was still unfinished when I left from upper 6th

Ed

[em536716]

Originally Posted by GMB

Do you mean a fixed frequency oscillator as was usually done for polyphonic organs, or a single oscillator that is tuned by the keyboard (like the Clavioline)?

As I want mine to be polyphonic, each note would need to have its own oscillator and a set frequency. I could do a monophonic type with just one oscillator but it seems a waste to have 2 octaves and not able to play anything

[em536716]

Originally Posted by M0FYA Andy

I recall that there were various articles on building organs in magazines such as Practical Wireless 'back in the day', it might be worth doing a trawl through them online.

Andy

I’ll have to do some research! Thanks

[em536716]

Originally Posted by Ed_Dinning

Hi Ed, a few booklets were available on the subject from Foulsham-Sams
Also The electronic musical instrument manual Douglas 1949
Frequency divider organs Douglas 1963
Electronic musical instruments Lewer from Electronic engineering

I think Douglas wrote for Radio constructor; most of the journals had the odd article in them about musical instruments, World radio history site is you friend here, if you have the time

The ones mentioned above outline a variety of techniques for note generation in both simple and complex manners, as well as details of the filters used to give the various "voices"

At grammar school in the 60's the electronics club started building one for the school, but it was still unfinished when I left from upper 6th

Ed

That’s some brill info Ed. Did they ever get it finish or was it scrapped?

My idea is to just have some very basic oscillators forming 2 octaves worth of notes. Do you know if these booklets are available online?

Thanks

[Robert Gribnau]

Looks a bit like repeating this thread: https://www.vintage-radio.net/forum/...d.php?t=174169

[See_Mos]

I worked on one from the early sixties. It was polyphonic. Each note and half note had its own inductor tuned oscillator and each oscillator drove 5 dividers, one for each octave.

It drifted like crazy and had to be retuned very often

[Radio Wrangler]

Lucien Nunes has a commercially made one. You might like to do a search for his threads here on the forum. It's a monster and will give you an idea of what you're taking on. I think it uses the butler oscillator circuit. LC tuned circuit feeding the grid of a triode, with the cathode driving a tap on the inductor.

David

[GMB]

As I want mine to be polyphonic, each note would need to have its own oscillator and a set frequency. I could do a monophonic type with just one oscillator but it seems a waste to have 2 octaves and not able to play anything

OK, well its an awful lot of circuit. With valves you will also be needing a pretty big PSU. LC oscillators seem a popular solution, I presume because they can be made with low drift – but that's a load of big chokes to make too.

You might want to do the maths and calculate the cost before deciding to use ICs.

[Radio Wrangler]

For your dissertation?

What in? Presumably you have to be able to demonstrate some original research or original development. I've seen a number of cases where people chose their favourite hobbies for projects and theses/dissertations where they didn't get good grades because of lack of original work. Take care and have a chat with your course supervisor so you're clear on just what you need to achieve. A little steering in the beginning can have a big effect later.

David

[em536716]

It’s a bachelors degree in Music production, however the brief is pretty broad, which allows pretty much anything to be done as long as it releases to music, but main work which would need to be handed in now is mainly designs and plans.

[em536716]

Originally Posted by GMB

OK, well its an awful lot of circuit. With valves you will also be needing a pretty big PSU. LC oscillators seem a popular solution, I presume because they can be made with low drift – but that's a load of big chokes to make too.

You might want to do the maths and calculate the cost before deciding to use ICs.

I recently scrapped a portable ekco valve tv, which has quite a large mains tx.

I agree with you, a lot of circuit for not a lot of functionality. I’m trying to locate a practical tv mag guide on a simple design which I can develop from, any coils chokes needed, I’m sure I could ask Ed dinning or mike barker to make for me. It’s a bit of fun at the end of the day, I might even get it finished! Lol

[Radio Wrangler]

Originally Posted by em536716

It’s a bachelors degree in Music production, however the brief is pretty broad, which allows pretty much anything to be done as long as it releases to music, but main work which would need to be handed in now is mainly designs and plans.

Ah, you definitely should do a search for threads by Lucien on this forum. He rescues and archives large lumps of electronics like an entire major TV transmitter, but of interest to you is a church size electronic organ, all done with one valve oscillator per note.

https://www.vintage-radio.net/forum/...d.php?t=121108

The rack of oscillators is as overwhelming as the monolith in 2001


David

[FrankB]

I suspect you could copy the oscillator circuits from a commercially produced organ. Likely the patents have expired, but check first.

The ones I worked on (decades back) used 6SN7, 12AX, AU7, or 6CG7 dual triodes as the osc tube.

I rebuilt a Minchel Organ for my mother back in the late 70's. Basically the osc circuits were really simple. I don't have the service data anymore though.

[Bryan M]

There's a design in Practical Wireless October 1953, if that helps.

Bryan

[See_Mos]

Nice simple R-C oscillator does not need inductors. the parts list is in the February 1954 edition. Some values might be hard to find but could be made up of multiple values.

The articles are available free here

https://worldradiohistory.com/UK/Pra...PW-1954-02.pdf


As an aside, I really enjoy the 'On Your Wavelength' topics by Thermion, Some of the comments are as relevant today as they were back then.

[Hartley118]

A feature of a valve-based electronic organ is going to be some pretty wide temperature variations as it all warms up. So an outline study of the temperature stability of different oscillator circuits might make an appropriate chapter. It would be interesting to compare the figures with the typical temperature stability of a pipe organ.

Martin

[GMB]

I think you might get more fun from a monophonic synthesiser type of circuit. There is so much more scope for interesting sounds. Building something like a Moog using valves will be interesting!