Yorkville VGM14 - Manuel (Page 7)

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A slight modification to a balanced patch cable will help achieve noise cancellation
when connecting the VGM14 to an unbalanced unit. Simply modify one end of a bal-
anced patch cord and de-solder the wire from the ring tab, then resolder the wire to the
shield tab making sure that it does not touch anything else. Now re-assemble the plug
and mark it with some tape for future reference. This will be the end that you plug into
the unbalanced music source (this will also work with an RCA connector).
For best performance when connecting turntables, a phono RIAA pre-amplifier must
be used to connect to the VGM14 inputs.
Connecting signals to both types of inputs on any one channel (Mic and Line In) is
NOT recommended. To do so may change the gain of the input circuit.
3. Insert Jacks
These are 1/4-inch Tip-Ring-Sleeve (TRS) connectors, combining send and return func-
tions for patching outboard signal processing directly into a channel. A suitable patch
cable for this function (e.g. Yorkville model PC-6iSPH) would consist of a single TRS (ste-
reo) 1/4-inch plug and two lengths of shielded cable with a common ground branching to
two regular (mono) 1/4-inch plugs. The TRS wiring is tip/send, ring/return and sleeve/
ground. Since the PC-6iSPH comes with the leads marked Tip and Ring, connect the Tip
plug to the input of the signal processor (EQ, compressor, echo, etc.); connect the Ring
plug to the processor’s output. The TRS plug would go into the Insert jack.
The send function is post-Gain and post-HPF (high-pass-filter). Alternately, the Insert
jack may be used to send an audio signal from that channel to a powered monitor (some
people want to hear only themselves). Simply use an unbalanced shielded patch cable –
in this one case, a balanced cable will not work. Be sure to insert the plug only to the
first “click” when using the Insert as a channel send, otherwise the signal is interrupted
and the channel will not work. If this happens, you have inserted the plug too far. Simply
pull the plug out gently to the first stop.
4. Gain Control
The VGM14 features active channel input circuitry with exceptionally high audio headroom.
The Gain control adjusts the input gain level to match it with the input audio signal level.
There are two gradation circles on the gain controls, the outer one (-24 dB to +60 dB) is
the gain for the Mic Input, the inner one (-36 dB to +45 dB) is for the Line input. This con-
trol has a wide range of 84 dB and is very useful to the user when setting the gain.
Here is a quick way to ensure that the Gain is adjusted correctly for the highest head-
room and lowest noise during a sound check. First turn the Channel Fader to the infin-
ity symbol. With a music source playing into the mixer’s channel, turn the Gain control
clockwise until the Set Level LED begins to flash. Having the Set Level LED flashing
shows you that you have the optimum gain setting for the music level on that channel
input. Having the Set Level LED remain on continuously indicates that you should turn
down the Gain control until the Set Level LED is flashing. Having the Set Level LED
remain on continuously indicates that the input audio compressor is active. Now turn
up the Channel Fader to the desired audio level for the overall music mix. How to use
the input audio compressor is explained below.
The VGM14’s Clip LED will turn on at 3 dB below the onset of actual clipping. It’s okay to
have this LED flash occasionally during music peaks. You’ll find that this, or any audio sys-
tem, performs with less distortion (and less noise) when the gain controls are set properly.
Input Wiring tips:
1. For all input connectivity use shielded wire only. Cables with a foil shield or a high-
density braid are best.
2. When changing input connections, turn down the level controls on the mixer to
eliminate pops and thumps out of the loudspeakers.
3. Keep input connection cables as short as possible to minimize noise and hum.