3.2 Rear Panel Jacks
3.2.1 Loops, Sends, Returns
The Loop System consists of “Send1”, and the switch able/programmable “Send2”.
“Return A” with parallel or serial option and “Return B” ( VH4S only)
The individual channel volume controls determine the signal strength at the send jacks.
The range is - ... to +10dB. The output impedance is 4.7 kΩ. If you want to use the loops,
then connect the “Send” to the input of the Effects unit. Be sure and adjust the input
level of the effects unit to the amplifiers level. Most effects units have a led bar or other
level control devices. The Output of the effects unit must be connected to one of the two
return jacks, parallel or serial. If you use the parallel return, then the signal can be mixed
to the original signal via the front panel mounted “Mix” control.
3.2.2 Send 2 Functions
Send 2 has an edge over send 1: it is switch able and midi programmable. This is
especially handy if you are using a multi effects unit in this loop, but don’t want it in the
signal path all the time, but only when you are using it’s effects. You can activate or de-
activate this loop by pushing the red ”Send2” button on the front of the amp, or by
assigning it a midi command. More on midi programming later in this program.
3.2.3 The Returns: Parallel or Serial?
Which is better for you? Read on.
There are 2 ways to handle effects signals. If you use the serial return, then the signal
path of your VH4 is interrupted, the signal is sent to the processor, gets more or less
processed, then sent back to the serial return into the power amp. Digital effects units
often digitize this signal, then process it, then convert it back to analog, then send it to
the amp. This is called ADA conversion. It is necessary for digital effects units to do this
to your guitar signal, so that it becomes a digital code which the processor can read and
understand. Your tubes, however, need a old fashioned analog signal, so the processor
needs to convert the signal back to analog before it goes back to the amp. Generally,
even in highest quality effects processors, this causes a change in the original signal,
typically a loss of tonality and warmth, also noticeable as a “harder” sound. When you use
the serial loop for an effects unit like this, then your signal will have been ADA converted
at least once. Tone junkies and vintage freaks alike will more than likely have hives
developing by now. But - as always, there is a better way. Use the Parallel loop and the
mix control in the front determines how much effect signal is being added to the original
signal, which now still flows through the amplifier. There is always an analog connection
between the send and return jacks; a parallel loop!
Important: You must set the mix control on the effects unit to 100% wet when using the
parallel loop. Otherwise there will be nasty phasing problems resulting in unsatisfactory
tone. The signal portion that is unaffected by the mix control in the effects unit would
reach the amplifier at a different time due to the cabling, and cause phasing cancellations.
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