User manual

3.2 Rear Panel Connections
3.2.1 Send/Return Loop
The System consists of 3 separate Loops. It allows creation of effects path in either serial,
parallel, or switched configurations. The individual channel volume controls determine the
signal strength at the send jacks. The range is - ... to +10dB. The output impedance is 4.7
kOhm. 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 led bar or other level control devices. The Output of the effects unit
must be connected to one of the return jacks, parallel, switched, or serial. If you use the
parallel return, then the signal can be mixed to the original signal via the rear panel
mounted “Volume” control.
3.2.2 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 Herbert 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 an 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. Using the Parallel loop
and the mix (labeled “Volume”) control on the back 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.