[sdiy] Hammond Aurora Keybeds

Sat May 17 01:10:58 CEST 2025

Brilliant. I'll give them a cleaning later on, but for now i have to design
the circuit. Definitely have to think about the scaling and the variety of
cv ranges that might be needed.

O to 5 , -5 to +5, 0 to 10 and -10 to + 10

Obviously analog mostly scaling but the dac output has to be scaled
according to how many octaves are needed. I have to think about this a bit
more.  If the synth can do 10 octaves but you only have 44 keys then you'll
need some code and an input control to shift the keys up and down in some
orderly way. I've never built this kind of thing.

Mike

On Fri, May 16, 2025 at 5:22 PM Mike Bryant <mbryant at futurehorizons.com>
wrote:

> Palladium would make a lot more sense than chrome (which doesn't conduct
> well).  It's not quite as resistant to oxidisation as gold but near enough
> and was much cheaper back then.
>
> But anyway just clean it carefully.
>
> ------------------------------
> *From:* Tom Wiltshire <tom at electricdruid.net>
> *Sent:* 16 May 2025 21:46
> *To:* drheqx <drheqx at gmail.com>; drheqx via Synth-diy <
> synth-diy at synth-diy.org>
> *Cc:* Mike Bryant <mbryant at futurehorizons.com>;
> rburnett at richieburnett.co.uk Burnett <rburnett at richieburnett.co.uk>
>
> *Subject:* Re: [sdiy] Hammond Aurora Keybeds
>
> Didn't Hammond use palladium not gold? So it doesn't look like much (sort
> of dull silver colour), but actually, it's the same clean metal surface in
> was in 1940 when they put it together.
>
> But yes, they still get crap on them, but generally cleaning with a a
> cotton bud and alcohol is enough. Certainly don't use anything abrasive -
> that'll scrape off the expensive palladium plating.
>
> On 16 May 2025, at 18:32, drheqx via Synth-diy <synth-diy at synth-diy.org>
> wrote:
>
> The key wires are flat and bend quite a bit. Look like chrome  plated
> actually but the wire buss is not gold plated for sure.
>
> I have to give them a good cleaning first and then I'll look at them with
> a magnifier to see what's really going on.
>
> On Fri, May 16, 2025 at 8:42 AM Mike Bryant <mbryant at futurehorizons.com>
> wrote:
>
> Are you sure they'll be oxidised ?  The ones I used back in 70s all had
> gold plated wires and busses so they couldn't oxidise.  MIght be a bit of
> crap on them but never anything worse.
>
> ------------------------------
> *From:* Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of drheqx
> via Synth-diy <synth-diy at synth-diy.org>
> *Sent:* 16 May 2025 13:07
> *To:* rburnett at richieburnett.co.uk <rburnett at richieburnett.co.uk>
> *Cc:* synth-diy mailing list <synth-diy at synth-diy.org>
> *Subject:* Re: [sdiy] Hammond Aurora Keybeds
>
> Yes sir, and they are. They're not the multi-bus wire type but they are
> direct metal strip on wire and they're going to be oxidized to a certain
> degree.
>
> On Fri, May 16, 2025 at 6:17 AM <rburnett at richieburnett.co.uk> wrote:
>
> You can also do whatever flavour of switch de-bouncing that you want in
> software, if the key contacts are a bit old and scratchy!
>
> -Richie,
>
>
>
> On 2025-05-16 03:54, Ben Bradley via Synth-diy wrote:
> > "Each key closes a switch to a common bus."
> >
> > There's a couple things you need to make a "true analog" mono
> > keyboard. First is a constant current source to drive the resistor
> > divider, so that when more than one key is pressed the voltage remains
> > that of the lowest or highest key (unless you WANT a weird off-pitch
> > note effect when pressing more than one key). The other is  a separate
> > switch at every key that closes AFTER the key that gives the pitch
> > voltage as the key goes down, so that the proper voltage is sampled
> > and kept when the key is released. This is also the gate/trigger
> > output. Presuming there are several common busses, you need to bend
> > the contacts on each key to make sure these close in proper sequence.
> >
> > I don't see a problem of being off-pitch with a resistive divider, as
> > 1 percent resistors are cheap thesedays, whereas 1970s keyboards may
> > have used 5, 10 or even 20 percent tolerance resistors.
> >
> > But still, I'd as soon make a digital circuit to scan/read all the
> > separate inputs, one for each key, scan it into a buffer with a
> > microcontroller and do the highest/lowest/latest keydown logic in
> > software and the usual DAC for control voltage output.
> >
> > On Wed, 14 May 2025 at 22:54, drheqx via Synth-diy
> > <synth-diy at synth-diy.org> wrote:
> >>
> >> Hi all,
> >>
> >> I have the keybeds and draw bars etc. from a Hammond Aurora organ.
> >>
> >> These are not matrix type keybeds. Each key closes a switch to a
> >> common bus.
> >>
> >> Is this a good time for me to consider doing a volt
> >> /octave keyboard controller?
> >>
> >> I definitely don't want to midify these. That would be a waste.   I
> >> was considering building a voice per key synth because i love these
> >> key beds and it would be so unique, but I'm short on time like so many
> >> of us.
> >>
> >> Anyone know of a good kit to make a 1v/ oct controller, maybe with
> >> some added features.
> >> ________________________________________________________
> >> This is the Synth-diy mailing list
> >> Submit email to: Synth-diy at synth-diy.org
> >> View archive at: https://synth-diy.org/pipermail/synth-diy/
> >> Check your settings at:
> >> https://synth-diy.org/mailman/listinfo/synth-diy
> >> Selling or trading? Use marketplace at synth-diy.org
> > ________________________________________________________
> > This is the Synth-diy mailing list
> > Submit email to: Synth-diy at synth-diy.org
> > View archive at: https://synth-diy.org/pipermail/synth-diy/
> > Check your settings at:
> > https://synth-diy.org/mailman/listinfo/synth-diy
> > Selling or trading? Use marketplace at synth-diy.org
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy at synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy at synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
>
>
> ------------------------------
> *From:* Tom Wiltshire <tom at electricdruid.net>
> *Sent:* 16 May 2025 21:46
> *To:* drheqx <drheqx at gmail.com>; drheqx via Synth-diy <
> synth-diy at synth-diy.org>
> *Cc:* Mike Bryant <mbryant at futurehorizons.com>;
> rburnett at richieburnett.co.uk Burnett <rburnett at richieburnett.co.uk>
>
> *Subject:* Re: [sdiy] Hammond Aurora Keybeds
>
> Didn't Hammond use palladium not gold? So it doesn't look like much (sort
> of dull silver colour), but actually, it's the same clean metal surface in
> was in 1940 when they put it together.
>
> But yes, they still get crap on them, but generally cleaning with a a
> cotton bud and alcohol is enough. Certainly don't use anything abrasive -
> that'll scrape off the expensive palladium plating.
>
> On 16 May 2025, at 18:32, drheqx via Synth-diy <synth-diy at synth-diy.org>
> wrote:
>
> The key wires are flat and bend quite a bit. Look like chrome  plated
> actually but the wire buss is not gold plated for sure.
>
> I have to give them a good cleaning first and then I'll look at them with
> a magnifier to see what's really going on.
>
> On Fri, May 16, 2025 at 8:42 AM Mike Bryant <mbryant at futurehorizons.com>
> wrote:
>
> Are you sure they'll be oxidised ?  The ones I used back in 70s all had
> gold plated wires and busses so they couldn't oxidise.  MIght be a bit of
> crap on them but never anything worse.
>
> ------------------------------
> *From:* Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of drheqx
> via Synth-diy <synth-diy at synth-diy.org>
> *Sent:* 16 May 2025 13:07
> *To:* rburnett at richieburnett.co.uk <rburnett at richieburnett.co.uk>
> *Cc:* synth-diy mailing list <synth-diy at synth-diy.org>
> *Subject:* Re: [sdiy] Hammond Aurora Keybeds
>
> Yes sir, and they are. They're not the multi-bus wire type but they are
> direct metal strip on wire and they're going to be oxidized to a certain
> degree.
>
> On Fri, May 16, 2025 at 6:17 AM <rburnett at richieburnett.co.uk> wrote:
>
> You can also do whatever flavour of switch de-bouncing that you want in
> software, if the key contacts are a bit old and scratchy!
>
> -Richie,
>
>
>
> On 2025-05-16 03:54, Ben Bradley via Synth-diy wrote:
> > "Each key closes a switch to a common bus."
> >
> > There's a couple things you need to make a "true analog" mono
> > keyboard. First is a constant current source to drive the resistor
> > divider, so that when more than one key is pressed the voltage remains
> > that of the lowest or highest key (unless you WANT a weird off-pitch
> > note effect when pressing more than one key). The other is  a separate
> > switch at every key that closes AFTER the key that gives the pitch
> > voltage as the key goes down, so that the proper voltage is sampled
> > and kept when the key is released. This is also the gate/trigger
> > output. Presuming there are several common busses, you need to bend
> > the contacts on each key to make sure these close in proper sequence.
> >
> > I don't see a problem of being off-pitch with a resistive divider, as
> > 1 percent resistors are cheap thesedays, whereas 1970s keyboards may
> > have used 5, 10 or even 20 percent tolerance resistors.
> >
> > But still, I'd as soon make a digital circuit to scan/read all the
> > separate inputs, one for each key, scan it into a buffer with a
> > microcontroller and do the highest/lowest/latest keydown logic in
> > software and the usual DAC for control voltage output.
> >
> > On Wed, 14 May 2025 at 22:54, drheqx via Synth-diy
> > <synth-diy at synth-diy.org> wrote:
> >>
> >> Hi all,
> >>
> >> I have the keybeds and draw bars etc. from a Hammond Aurora organ.
> >>
> >> These are not matrix type keybeds. Each key closes a switch to a
> >> common bus.
> >>
> >> Is this a good time for me to consider doing a volt
> >> /octave keyboard controller?
> >>
> >> I definitely don't want to midify these. That would be a waste.   I
> >> was considering building a voice per key synth because i love these
> >> key beds and it would be so unique, but I'm short on time like so many
> >> of us.
> >>
> >> Anyone know of a good kit to make a 1v/ oct controller, maybe with
> >> some added features.
> >> ________________________________________________________
> >> This is the Synth-diy mailing list
> >> Submit email to: Synth-diy at synth-diy.org
> >> View archive at: https://synth-diy.org/pipermail/synth-diy/
> >> Check your settings at:
> >> https://synth-diy.org/mailman/listinfo/synth-diy
> >> Selling or trading? Use marketplace at synth-diy.org
> > ________________________________________________________
> > This is the Synth-diy mailing list
> > Submit email to: Synth-diy at synth-diy.org
> > View archive at: https://synth-diy.org/pipermail/synth-diy/
> > Check your settings at:
> > https://synth-diy.org/mailman/listinfo/synth-diy
> > Selling or trading? Use marketplace at synth-diy.org
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy at synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy at synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
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> Selling or trading? Use marketplace at synth-diy.org
>
>
>
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