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Old 1st Feb 2017, 12:39 pm   #1
EF80TVVALVE
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Default Building a Hammond Novachord

Hi all,

Alongside old radios and tellies and the like I have always had an interest in music and electronic music. One instrument that has always fascinated me is the Hammond Novachord, often referred to as the worlds first poly synth, I believe it was truly before its time and (due to the way in which music was created at the time) was never used to its full potential. Now the chances of getting my hands on one is very much impossible so I wondered what it would take to build one, maybe not quite full size or using more modern valves to keep it more compact than the original unit.

I would presume that the circuitry doesn't differ too much from Hammond organs produced at the time, the novachord sounds very much like an organ in a fair few of its settings so I would presume they were using valves available to them at the time. With modern circuitry it would be possible to reduce the size of many parts including the amplifier as I wouldn't want to make something as large as the original instrument.

Here is some information on the basics of the instrument here:
http://www.oldtech.com/synth/HammondNovaC1.html

I know there are a few valve organ and Hammond enthusiasts on the site who may be able to offer some advice on what it would take to build something like this. I'm looking at it as a long term project as it is going to take time to gather parts and make some plans, I will also need to study the circuitry of the Novachord and work out how it can be reduced in size although getting rid of the coke bottle valves would be a great start. I am still planning on keeping the controls the same along with the audio generated from the instrument but to fit it in a case around half the depth as the original would be better, maybe donating an Eavestaff Minipiano to the project may be a good idea as that would offer me a keyboard and some space once the mechanism is removed (with the option to add more for the circuits).

I thought I'd share the project I am planning here just in case anyone could offer some advice as this is completely new to me. I am hoping that my experience in repairing valve radios and televisions may help me some way but overall it will be a fairly big project, although one which I am more that willing to undertake.

Time to start the research!
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Old 1st Feb 2017, 1:04 pm   #2
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Default Re: Building a Hammond Novachord

Have you seen this thread?

I found it a most interesting read. Good luck trying to build one!!

Regards,
Lloyd.
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Old 1st Feb 2017, 1:16 pm   #3
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Default Re: Building a Hammond Novachord

Thanks for the link Lloyd, how nice it would be to find one! I wonder what the average price for an unrestored one is? Even if I'm buying from the US I've seen one advertised for $450 before although could you imagine the hassle of shipping! I have been interested in music for years, playing the piano most of my life and the novachord has been an interest of mine since the age of 9, it is an instrument that I have always wanted to own!

Regards
Bren
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Old 1st Feb 2017, 3:38 pm   #4
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Default Re: Building a Hammond Novachord

This is quite an exciting prospect! I hope it goes well.

Regards,
Paul
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Old 1st Feb 2017, 4:41 pm   #5
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Default Re: Building a Hammond Novachord

Hi Paul

Thanks for the well wishes, I hope it goes well too! I have contacted the owner of the Novachord in the link that Lloyd gave and will start going through some of the service info I have found. I am not too sure whether I will go for a full 72 key synth or maybe do three octaves that can be transposed through the 72 notes that the novachord had as music production has changed to the point that it could be used to record say three seperate tracks of music (for the bass mid and treble) that can be put together to make the desired music. I am hoping to use B9A valves to replace the large octals although will require some investigation, there are plenty of valves still available so we will see what I go for.

Cheers
Bren
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Old 7th Feb 2017, 2:52 pm   #6
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Default Re: Building a Hammond Novachord

Hi Everyone,

I have now had some circuit information sent to me. The Novachord basically works by something called a divide down circuit. I have attached a photo from the info of how this basically works. The Oscillator for note A is tuned for the top octave, this is then 'divided' by the frequency divider circuit. There are 5 divider valves per note, one for each octave; by halving the frequency at each divider the note produced is one octave lower than the input note (for example A6 divided once will be A5, divided again A4 etc). The outputting signals are then sent to the Control valve circuit, once a key is depressed the control valve will pass the signal through to the control box.

This is the method I will be using for the creation of my version. I am thinking of using B9A valves in place of the octals used in the original novachord as they will be easier to source and their smaller size will help to create a more compact design.

I do face one problem with this, from what I understand there is no component chart for the Novachord available to the public. I have been told that a version does exist from a chap who spent ages creating one but this I am told is something that is hard to get. I have asked for the contact details of the owner to see if I can get a copy as the project will be much more difficult with no idea of component values. I have been looking for alternative valve based divide down circuits but I can't seem to find any schematics available. This is the most important part of the circuit along with the control box circuit so it is essential that I have as much information as possible on them in order to build something that will work.

Cheers
Bren
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Old 7th Feb 2017, 3:53 pm   #7
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Default Re: Building a Hammond Novachord

Bren

Many of the simpler electronic organs generate each note of the top octave and divide these down in the way you describe. The Moog Polymoog also works in this way, but most polyphonic synths don't; they dynamically assign one of a limited number of voices to each key being played.

Have you considered the power supply requirements of building such a valve monster?
If you used, say an ECC82 for each top octave note then for each divider you would need 72 valves just to generate the tones for each note. These would require 6.3V at a total of 21.6 Amps for heater power and say 10mA anode current for each valve would require 0.72A total at 250 or 300V or so.
Such a power supply would be expensive, heavy, potentially hot and certainly dangerous.

John
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Old 7th Feb 2017, 5:26 pm   #8
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Default Re: Building a Hammond Novachord

Hi John,

Thanks for the help. I presumed this method was used with organs as I didn't think Hammond would have used this idea with the Novachord if they were not using it for their organs too. I do think that the schematics of the novachord will have very similar circuitry to Hammond organs produced at the time as to me it simply looks like an organ with extra circuitry for sound manipulation, probably why the novachord sounds so strongly like an organ in many of its settings.

The power supply is something I have thought about briefly and I made similar predictions to you regarding the power. This is primarily the reason of why I am thinking of incorporating a circuit in which I could lower the frequency of the top octave. This way I can use a smaller keyboard along with less valves and just tune it to the octaves that I want. This I believe is a much better approach in comparison to a full 72 note keyboard.

Cheers
Bren
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Old 7th Feb 2017, 5:39 pm   #9
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Default Re: Building a Hammond Novachord

There are lots of divider organs out there, and because they are large, they often go FOC. Some are even made by Hammond.

You're talking of a very large undertaking, a lot of valves and a lot of power... and a lot of money. Is there something special about the Hammond Novochord to reward the effort? and will that special something be there if you change the design or can't find the exact original design?

I don't want to sound negative, but I don't want you to suffer a bad disappointment if you go into it with too-great expectations.

David
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Old 7th Feb 2017, 6:13 pm   #10
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Default Re: Building a Hammond Novachord

Hi David,
My intentions originally were to build a valve synthesizer that uses divide down circuitry. I have been interested in building a synth for some time and once I came across the novachord I thought that this would be a good starting point as there seems to be a lack of information on valve divide down circuitry online.

Once I have an instrument made it will be being used for music production so I'm not too concerned about recreating the authentic sound of the novachord with all controls etc but to build something along similar circuitry to that of the novachord.

Considering what has been discussed I am thinking of going along the lines of making one with three octaves, tunable across the 88 notes of a keyboard as most modern syths are. In this way I will be saving on buying all of those extra valves needed along with components and it will also be much quicker to build and much more transportable.

Regards
Bren
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Old 7th Feb 2017, 6:15 pm   #11
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Default Re: Building a Hammond Novachord

Quote:
Originally Posted by EF80TVVALVE View Post
I thought I'd share the project I am planning here just in case anyone could offer some advice as this is completely new to me. I am hoping that my experience in repairing valve radios and televisions may help me some way but overall it will be a fairly big project, although one which I am more that willing to undertake.
Time to start the research!
I have to agree with David in advising caution.

Dan, the person responsible for the rebuild in the original thread, is one of this country's most experienced restorers of vintage keyboards and audio electronics - and he also has a substantial background in the electronics industry. This was one of the most difficult and intensive jobs he has ever undertaken.

If you don't have that level of experience and expertise, you might be better off considering a simpler project, at least to start with.
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Old 8th Feb 2017, 10:21 am   #12
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Default Re: Building a Hammond Novachord

Adapting an existing Hammond might be the best way.
Looking objectively, it isn't TOO big a project...
...compared with a COLOSSUS, for example!
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Old 8th Feb 2017, 11:30 am   #13
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Smile Re: Building a Hammond Novachord

Hi,
As a spotty youth of around fourteen, I had a dream of building a valve driven organ after seeing one in our local Methodist chapel. My idea was to use an EF80 oscillator for each note with the heaters in series with a dropper. I knew nothing about octave dividers, tone generators nor where to get the many components. All I had was a box of valves and access to an old piano keyboard! Oh well ....
I was very interested in the recent thread on here about a Miller church organ which sported 163 valves, most of them ECC83s.

Cheers, Pete.
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Old 8th Feb 2017, 11:49 am   #14
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Default Re: Building a Hammond Novachord

The Novachord shares certain features with a conventional valve divider organ, but differs in the way tones are keyed and filtered. Most true organs with electronic generators use subtractive synthesis, where harmonic-rich tones are generated and applied to different filters for each stop. By contrast, those with electromechanical generators typically use additive synthesis, where a tone is formed by adding 'pseudo-harmonics' in the form of higher pitches from the even tempered scale. This is how the traditional Hammond organ, with its electromagnetic tonewheel generator, generates different timbres. Multiple pitches from the generator are selected by each key and mixed at the desired amplitudes using the drawbars. For those unfamiliar with Hammond internals, at this time Hammond did not make divider organs. The tonewheel generator, developed from synchronous clock motors geared together (Hammond started out making electric clocks,) was the heart of all their signature instruments such as the B3 and A100, so the Novachord was a complete departure. They did use dividers in their late solid-state models, which many do not consider to be 'true' Hammonds.

Valve divider organs are hard work, I have four of them and the two bigger ones are heavy beasts:
* Burge 1-manual practice instrument, 6 octave generators
* Wurlitzer 2-manual entertainment spinet, 5 octave generators using 12FQ8 divided-anode double-triode oscillators & dividers
* Miller Norwich 2-manual drawstop church organ, 2x 6 octave generators
* Burge 3-manual concert instrument, 8 octave generators
The filtering schemes vary but all are subtractive and all the generators are based on one triode per divider stage. The Wurlitzer manages with about 40 valves, the Norwich and 3m Burge have around 90. The 1m Burge was the subject of an unfinished restoration here: Investigation and initial repairs to Burge divider organ

Divider systems have strengths and weaknesses. One factor that was historically limiting, and which the Novachord overcame only at the expense of doubling the valve count, was the need for audio keying. Because the dividers must run continually, it is that audio that must be keyed not the generators themselves, so to achieve anything more than a sudden switch-on and off by the key contact a variable attenuator stage is required per note. That was one of the reasons Compton stuck to electrostatic generators - they had complete control of each tone's amplitude using a proportional DC keying voltage, which the Hammond tonewheel generator could not offer, hence envelope shaping was a breeze. Sonically, the main shortcoming of all divider organs, indeed any single-generator instrument, is locked-phase. Any letter-name of note you play has a fixed phase relationship to any other note of the same name anywhere in the compass and on any stop. This is a significant drawback, as in a pipe organ a doubled chord played on registration of 10 stops will give you 20 fractionally different frequencies, the beats between which are an essential part of the rich, full tone that a pipe organ can create. All sorts of gadgets were invented to modulate and disguise the thin, dull sound of a single set of generators - moving speakers, variable tapped delay lines, electromechanically modulated filters. The only way round this limitation using electronic generators was found in the very top organs, which had a separate oscillator per stop per note. The largest required a complete room for the generators - my 4-rank Miller merely needs a cabinet the size of a double wardrobe. This is the one Pete mentions, it's actually 193 valves and its story is here: Miller Classic IV

Returning to your project, I agree with the above posters that a replica / simulation of a Novachord using valves is a major undertaking. They were not cheap instruments nor will the replica be, and Hammond had the advantage of highly developed manufacturing resources. You cannot readily adapt any existing organ to be technically 'like' a Novachord, because of the unique keying system. You might take an existing valve divider instrument (not a Hammond) as a starting point, but that would be a shame because there are very few of them left, most having been raided for their valves and transformers and then scrapped. I would estimate that less than 1 in 5000 organs found for sale today is a valve divider model.

Finally, if you haven't read the 'Electronic Musical Instrument Manual' by Alan Douglas it's a good read. Content varies between editions, an earlier one might have more coverage of topics relevant to the Novachord. Have fun, keep us posted. If you want to play a working valve divider organ, drop me a line.

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Old 13th Feb 2017, 6:35 pm   #15
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Default Re: Building a Hammond Novachord

Hi Bren,
As luck would have it, I have a copy of the esteemed book mentioned by Lucien.
There is a part-circuit in my edition, so I've made the best copy I can, and it is below with a rather good photo of a Novachord.
Around 1960 the BBC Light Programme used one to play interval signals when there would have been a gap when one programme finished slightly earlier than planned. I believe the announcers referred to it amongst themselves as "Old Groaner". - Not very complementary!
As you can see, its a rather complex piece of kit.
Good luck with the project,anyway. Tony
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Old 14th Feb 2017, 11:08 am   #16
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Default Re: Building a Hammond Novachord

I've purchased the CD mentioned. It reveals a remarkable instrument indeed. The music featured appears to be written specifically with it in mind.
I'd like to hear some known music arranged for it.
I can understand the BBC comment. It does have a wide range of groaning.
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Old 14th Feb 2017, 12:13 pm   #17
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Quote:
Originally Posted by Brigham View Post
]I'd like to hear some known music arranged for it.
Several of Vera Lynn's early hits were first recorded along with a Novachord, for example this one..https://www.youtube.com/watch?v=OvgM_xcx2GI The accompanist (a Mr Young) seemed to lack creativity as regards arrangements and playing style. I have a couple of these on 78s somewhere....
Regards, tony

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Old 14th Feb 2017, 12:50 pm   #18
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Default Re: Building a Hammond Novachord

Not all valve organs were big. Although I never saw the actual original thing, just a few boards and other broken bits, I know that one model was actually so small as to be a portable suitcase sized thing.

It had the usual master oscillators, but where it saved on space was the way the dividers worked - they were done using neons. This meant that the whole tone generating board was really quite small. I didn't get a chance to see exactly how it must have worked, but I had the impression that it used neon oscillators synched to the master oscillators.

The biggest parts of it were the stabilised PSU and the amplifier.
I still have the PSU.
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Old 14th Feb 2017, 1:25 pm   #19
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Default Re: Building a Hammond Novachord

You may be thinking of the Philips Philicordia, there's a thread on the forum on these from a few years ago here

https://www.vintage-radio.net/forum/...ad.php?t=96590

John
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Old 14th Feb 2017, 3:28 pm   #20
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Default Re: Building a Hammond Novachord

No, it wasn't that.

It really was a suitcase. Part of the shell of it remained and it had quite rounded corners.
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