Analogue-sequencer

> My plan is to build a P3 in the same case as an Oakley 3031 and tbDAC to

> Problem number one is that the new 3031 has a wider board that won't fit
the
> walnut case, so I have to get another case, anyone knows a hammond
supplyer
> in the UK that holds a large selection of cases?

I'm not sure how you want to lay it out internally, but I quite like the
idea of building an angled desktop rack, and then fitting a rack mount P3 at
the bottom, with a couple of rack mount synths and drum modules above.
Sort of a proper hardware version of Reason.
This could be more flexible if you ever decide to upgrade or sell the
TB3031.

> The MIDI signal path would probably be: in > P3 > tbDAC > out. The new
> tbDAC should according to Tony have a quite fast midi thru respons. How is
> the P3 doing on this? Do you think the delay would be to long if
connecting
> a keyboard thru all the units?

The P3 soft thru is not as quick as a hardware thru, as it is merging the
incoming data with the data it generates itself, so it has to wait for a
complete message to arrive before it sends it on (i.e. 3 bytes)
In practice this means there will be a minimum 1ms delay between the first
byte of a message arriving at the input, and the first byte of this message
being send through the output. It'll take longer if another message is
already being sent by the P3's sequencer engine.
This latency is a feature of 'merged' midi itself rather than P3.
Unless you are heavily using controller data, or massive polyphony, it won't
be noticeable.

> Now a power problem. I found an AC transformer 12V 1A at home, this would
> probably be good to power the 3031. Could I use the same to also power the
> P3? 1A should be ok, and as I understand it the P3 could also be powered
by
> AC, but I am not very good at these things and would feel much more
> confident if I got some feed back from any of the more experinced builders
> on this list.

The P3 power input has a diode on it that will rectify AC, or block
reverse-polarity DC, so P3 can be used with either AC or DC supply.
The diode is followed by a smoothing capacitor and 5v regulator, which needs
an input of at least 8v in order to provide a smooth 5v supply to the board.
So your AC or DC input needs to be at least 8v too (in fact it can be
slightly less for AC, as the rectified peak voltage is always higher than
the specified RMS voltage, but lets not get confused).
Too high an input voltage will cause excessive dissipation in the regulator
heatsink, but 12v will be no problem at all.
P3 uses about 250mA, so a 12v input will cause the regulator to generate
less than 2 watts of heat.

Cheers,
Colin f



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> Now a power problem. I found an AC transformer 12V 1A at home, this
would probably be good to power the 3031. Could I use the same to also
power the P3?

No, you can't. If you have a single winding on the transformer, you can
connect this to the TB3031 or the P3. But you can't have both. The P3
will want one of the wires from the transformer to be ground, the TB3031
will want it floating. Connecting the two together compromises the
TB3031.

However, if your transformer has true double secondaries [0-12, 0-12]
you can use one winding for each unit. Ground the TB3031 to the P3's
ground and all will be well.

If you have a split secondary, or centre tapped winding [ie. 12-0-12],
you could wire the TB3031 as shown in the User Guide for a split
secondary, and wire the P3 between one of the windings and the 0 volt
tap.

But a 12V winding will produce in excess of 18V... Colin's P3 will be
disipating quite a lot of heat, around 5W!!

I would use separate transformers for each. A small transformer is only
a a few quid.

Official safety disclaimer: Any wiring of mains powered components must
be done so at your own risk. Mains voltages can and do endanger life. I
am not responsible for your actions and or consequences arising from
this e-mail's contents. I recommend that you buy two wallwarts.

Regards,

Tony Allgood                         www.oakleysound.co.uk

Oakley Modular Synthesisers      Penrith, Cumbria, England

Tony,

> I would use separate transformers for each. A small transformer is only
> a a few quid.

just playing devils advocate, why not Use a switch mode :-)

Paul (hiding)

> why not Use a switch mode :-)

Why use a switch mode?

Honestly, even two 250mA transformers are going to be:

Cheaper
Quieter
Less dangerous (exposed high voltage)
Smaller

At higher currents these points don't hold, but for both the TB and P3;
a linear is a simpler option.

Tony




 

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