VMB Virtual Cables: cross connect or not?

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AB2EZ
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Location: Princeton, NJ

VMB Virtual Cables: cross connect or not?

Postby AB2EZ » Sun Apr 29, 2018 4:09 pm

Scott
et al.

When I use the VMB virtual cables for VAC1, I have used them as recommended by Scott:

E.g. VAC1 output from transceiver => VMB virtual channel input. VMB virtual channel => B2 (aux virtual channel output) . WSJT input => Aux VMB virtual channel output

But, everything seems to work fine if (alternatively) I use the virtual cables on a straight through basis

E.g. VAC1 output from transceiver => VMB virtual channel input. VMB virtual channel => B1 (virtual channel output) . WSJT input => VMB virtual channel output

Is there really an advantage of using the cross connected arrangement over the straight through arrangement?

Stu
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w-u-2-o
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Re: VMB Virtual Cables: cross connect or not?

Postby w-u-2-o » Mon Apr 30, 2018 1:19 pm

Stu,

There are two advantages. One, it is not bizarre ;) Two, you can use ASIO.

In terms of being "bizarre", any audio engineer would look at you in a very funny way if you hooked it up that way. That's not to say it won't work, because it does, and it will, even on a regular analog mixing board, it's just simply not done that way. Traditionally each "instrument" (in this case PowerSDR and WSJT-X) is always assigned a separate channel and the audio routed between them as required. This provides a measure of both isolation and flexibility.

Don't forget that to get the transmit audio moving you have to do the same arrangement on another channel, e.g. if you have RX out --> B1 --> WSJT-X In, then you are also going to need WSJT-X Out --> B2 --> TX In.

However, I suspect it can get even more bizarre than this. Because of the virtual nature of the connections, you might actually be able to assign simultaneously as follows, although I have never tried it because my audio engineering background would not normally have me think this way:

RX out --> B1 --> WSJT-X In
WSJT-X Out --> B1 --> TX In.

This might work because of the half duplex nature of the setup.

On the other hand, if you are using ASIO for low latency between PowerSDR and VMB then you will be stuck doing it the traditional audio engineering way, as the ASIO driver will not allow you to split or double up on device assignments.

73,

Scott
AB2EZ
Posts: 94
Joined: Sun Apr 09, 2017 2:29 pm
Location: Princeton, NJ

Re: VMB Virtual Cables: cross connect or not?

Postby AB2EZ » Mon Apr 30, 2018 3:37 pm

Scott

Could it be that the block diagram of VMB is not what you are assuming it to be?

I.e. Could it be that each of the two virtual inputs of VMB is the input end of a 1-way (unidirectional) virtual cable... with the other end terminating on an associated digital cross-connect (but not directly connected to any of the VMB digital outputs). If you select B1, then that virtual input (1-way digital stream) is connected (via the cross connect) to the virtual channel digital output port. If you select B2, then that virtual input (1-way digital stream) is connected to the auxiliary virtual channel digital output port. If you select some combination of A1, A2, A3, B1, and B2... then that virtual input (1-way digital stream) is connected (via the digital cross connect) to the selected digital output ports.
Inside of the VMB application, this process does not (in and of itself) produce feedback if you direct either virtual channel input to the same virtual channel output. Naturally, if you are using the VMB virtual channel to connect the VAC1 receiver output to the WSJT input, then you must use the auxiliary virtual channel to connect WSJT output the VAC1 transmit input. In that case you would not direct the virtual channel to output B2, because doing so would connect the WSJT output to the WSJT input... which could produce crosstalk from output to input inside the WSJT application.

Stu
Last edited by AB2EZ on Mon Apr 30, 2018 4:04 pm, edited 2 times in total.
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w-u-2-o
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Re: VMB Virtual Cables: cross connect or not?

Postby w-u-2-o » Mon Apr 30, 2018 4:03 pm

AB2EZ wrote:Scott

Could it be that the block diagram of VMB is not what you are assuming it to be?
No, I'm pretty sure about it, no assumptions required, Vincent wrote a pretty good manual ;)

https://www.vb-audio.com/Voicemeeter/VoicemeeterBanana_UserManual.pdf

It's a straight shot virtual mixer with a number of interesting busing options.

The one important way it differs from a "real" hardware mixer is that every input and every output is capable of connecting to more than one "device" at the same time.

73!

Scott

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