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Old 26th Jan 2021, 10:10 am   #1
em536716
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Default Simple valve oscillator for a valve organ?

For my dissertation, Iíve 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?
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Old 26th Jan 2021, 11:51 am   #2
M0FYA Andy
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Default Re: Simple valve oscillator for a valve organ?

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.

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Old 26th Jan 2021, 12:56 pm   #3
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Default Re: Simple valve oscillator for a valve organ?

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)?
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Old 26th Jan 2021, 7:54 pm   #4
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Default Re: Simple valve oscillator for a valve organ?

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

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Old 27th Jan 2021, 4:30 am   #5
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Default Re: Simple valve oscillator for a valve organ?

Quote:
Originally Posted by GMB View Post
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
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Old 27th Jan 2021, 4:31 am   #6
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Default Re: Simple valve oscillator for a valve organ?

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Originally Posted by M0FYA Andy View Post
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

Iíll have to do some research! Thanks
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Old 27th Jan 2021, 4:33 am   #7
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Default Re: Simple valve oscillator for a valve organ?

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Originally Posted by Ed_Dinning View Post
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
Thatís 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
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Old 27th Jan 2021, 6:18 am   #8
Robert Gribnau
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Default Re: Simple valve oscillator for a valve organ?

Looks a bit like repeating this thread: https://www.vintage-radio.net/forum/...d.php?t=174169
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Old 27th Jan 2021, 10:27 am   #9
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Default Re: Simple valve oscillator for a valve organ?

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
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Old 27th Jan 2021, 11:15 am   #10
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Default Re: Simple valve oscillator for a valve organ?

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.

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Old 27th Jan 2021, 5:14 pm   #11
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Default Re: Simple valve oscillator for a valve organ?

Quote:
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 Ė 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.
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Old 27th Jan 2021, 5:26 pm   #12
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Default Re: Simple valve oscillator for a valve organ?

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
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Old 28th Jan 2021, 4:44 am   #13
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Default Re: Simple valve oscillator for a valve organ?

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.
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Last edited by Radio Wrangler; 28th Jan 2021 at 7:39 am. Reason: Post corrupted by my error. some text missing. David
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Old 28th Jan 2021, 4:48 am   #14
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Default Re: Simple valve oscillator for a valve organ?

Quote:
Originally Posted by GMB View Post
Quote:
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 Ė 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. Iím trying to locate a practical tv mag guide on a simple design which I can develop from, any coils chokes needed, Iím sure I could ask Ed dinning or mike barker to make for me. Itís a bit of fun at the end of the day, I might even get it finished! Lol
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Old 28th Jan 2021, 7:39 am   #15
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Default Re: Simple valve oscillator for a valve organ?

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Originally Posted by em536716 View Post
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


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Old 2nd Feb 2021, 12:18 am   #16
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Default Re: Simple valve oscillator for a valve organ?

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.
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Old 3rd Feb 2021, 10:13 am   #17
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Default Re: Simple valve oscillator for a valve organ?

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

Bryan
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Old 3rd Feb 2021, 2:40 pm   #18
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Default Re: Simple valve oscillator for a valve organ?

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.
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Old 3rd Feb 2021, 3:09 pm   #19
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Default Re: Simple valve oscillator for a valve organ?

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.

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Old 3rd Feb 2021, 5:17 pm   #20
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Default Re: Simple valve oscillator for a valve organ?

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!
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