How many oscillators from the Oakley buss

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Dr Gris
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How many oscillators from the Oakley buss

Post by Dr Gris » Wed Nov 22, 2017 7:14 pm

I guess the title says it all..
I have three oscillators atm, but I'm thinking of adding more.


Also, is the pitch out jack from the midiDAC a separate buffered cv from the buss?

Cheers
//Magnus

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Synthbuilder
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Post by Synthbuilder » Thu Nov 23, 2017 4:44 am

The limit is set by whatever is driving the bus. Which if you are using the midiDAC is the KeyCV (Pitch) output. There is only one buffered output on the midiDAC which is shared with the Bus and the Pitch socket.

I've never ever tested the maximum load for the midiDAC's KeyCV output. But it's going to take quite a few VCOs to load it up sufficiently enough to notice a pitch drop. I don't think you'd have any problem with ten VCOs which is a 10K load, ie. 1mA at 10V output.

Tony

Dr Gris
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Post by Dr Gris » Thu Nov 23, 2017 12:31 pm

Great!!
Thanks for your reply.

Best
//M

Schlumpfhut
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Post by Schlumpfhut » Thu Nov 23, 2017 1:55 pm

Correct me if i'm wrong - to me it apperas that the Oakley Bus is acting as a kind of passive multiple. So if one gets into the unlikely situation of emcoutering a pitch drop would it be possible to design some buffred multiple or even use existing circuitry to compensate?

Thx very much in advance

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Synthbuilder
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Post by Synthbuilder » Thu Nov 23, 2017 4:14 pm

Schlumpfhut wrote:Correct me if i'm wrong - to me it apperas that the Oakley Bus is acting as a kind of passive multiple.
It is indeed a passive multiple but it is expected to be driven from a low impedance buffered source. The midiDAC's KeyCV output is such an output. This means that any loading affects caused by adding VCOs should be small enough not to be noticeable.

Generally, when any output is likely to be used to process KeyCV I tend use line driver circuits rather than circuits that have the usual 1K output impedance. So as well as the midiDAC, the VRG, which may be used for pitch glide, and the Fourmix and Multimix, which could be used to control VCO pitch, have line drivers.

Tony

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Post by Dr Gris » Tue Dec 12, 2017 3:19 pm

Instead of starting a new thread...I have the same question regarding the gate bus.

Best
//M

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Synthbuilder
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Post by Synthbuilder » Wed Dec 13, 2017 3:52 am

Dr Gris wrote:I have the same question regarding the gate bus.
This one is a little harder to answer as the output resistance of the gate output of the midiDAC is around 11K pull up and 1K pull down. If you are using my envelope modules and with a +5V gate you can probably run up to six ADSRs or VRGs without problem. Other makes of envelope modules will behave differently.

You could certainly try it and see what happens. Either way, it's not going to harm the midiDAC. If it doesn't trigger the envelopes reliably then you should use a buffer, like one channel of the Multimix, to create a low impedance driver for the gate.

Tony

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Post by Dr Gris » Fri May 04, 2018 10:44 am

I can happily report that my midiDAC is driving 6 VCO's, 4 ADSR/VCA's and 1 VRG without problem with the bus.
I'm also sending pitch from the panel socket to a mult that goes to various 1V/oct on filters (only one filter/patch for now)

Very handy to have this normaling that I can override anytime :tu:

//Magnus

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