Overview; Preamplifier; Insert Point - Joemeek TwinQ User Manual

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Overview

The Joemeek twinQ is like having two channels of a professional recording
studio in one box. It takes microphones or instruments, amplifies them,
compresses and equalizes them ready to be recorded. Simple to use yet
extremely powerful, the twinQ will bring out the best in any microphone or
instrument and give the gloss of a professional studio production to all your
performances. As well as recording it will also be found useful for live work.
Think of the twinQ as four separate items of equipment:
• The Preamplifier
• The Joemeek Optical Compressor
• The Meequalizer
• The Fader

Preamplifier

This is the all-important front end to the twinQ. Its job is to accept any
type of microphone, instrument or other source of audio signal, and make
it loud enough. Microphones often need rather a lot of amplification, while
guitars, keyboards and CD players need less. Mics need to be connected
to low impedance inputs, while instruments prefer high impedance inputs.
To ensure correct impedance matching, the inputs are split into an XLR
connector for Mics, and 1/4" jack "Line" and "INSTRument" connectors for
everything else. A switch on the front panel decides which input connector is
active, the XLR or the 1/4" jacks. The LED next to the switch lights to show
that the Line inputs (jacks) are selected. In other words:
Switch out (LED off) = "Mic"
Switch in (LED on) = "Line" or "Instr"
The main control, labelled "Input Gain", covers a range of amplification
from 10dB to 60dB. In many other preamps the action of the Gain control
is rather uneven, with the 40dB to 60dB range being crammed into the last
1/6th of a turn. All Joemeek preamps use a specially designed control that
ensures smooth operation over the whole range of rotation. The (0) symbol
next to the 25dB mark, means unity gain, or 0dB, for a signal in the Line
input. Hence for Line inputs the range of gain adjustment either side of this
mark, is +35dB, -15dB.
The PEAK LED lights 6dB below clipping, so occasional brief flashes are
OK but if it's on all the time you need to back the Input Gain off!
HPF means "high-pass filter". Mainly for use with microphones, this helps
remove stage rumble, handling noise and "pops". The LED lights when active.
TECHNICAL STUFF
Very low noise - does it matter? Yes and no, it all depends what you are
doing - what really matters is "signal-to-noise ratio". All electronics produce
a certain amount of background noise - it's in the nature of things. Providing
there is only a relatively small amount of noise, the signal will cover it up, or
"mask" it. So providing the signal is much bigger than the noise, you won't
be aware of the noise. In other words the "signal-to-noise ratio" needs to be
a big number, ideally such as 80dB or 90dB.
So how do you achieve that in practice? The trick is to keep the microphone
as close to the sound source as possible without overloading it, so as to get
as much signal out of it as possible. Then you set the Gain control to give
only as much gain as is needed to get a decent level into the recorder.
Of course when there is no signal going on, you may hear the background
noise of the electronics. In that case, given the amount of gain in a typical
studio monitoring system, this noise "floor" should ideally be in the region of
7 -80dBu or lower, in order for it not to be noticed.
Both Mic and Line inputs are electronically balanced. Note: although the
Line input is not normally used for microphones, it can also be suitable
for some high output unbalanced microphones, such as battery
powered Electret types.
The Mic input (XLR) is balanced and wired as follows:
Pin 2: + (hot)
Pin 3: - (cold)
Pin 1: ground
The Line input (jack) is balanced and wired as follows:
Tip: + (hot)
Ring: - (cold)
Sleeve: ground
The front panel Instrument input (jack) is balanced and wired as follows:
Tip: + (hot)
Sleeve: ground (NB: use a mono jack plug).
Note that if something is plugged into the Instrument input, anything
plugged into the rear panel Line input will be cut off.
PHANTOM POWER
Most high-quality studio mics are "Phantom powered", which is to
say they have electronics inside them, which get their power from the
preamp. Most mics require a supply of 48 Volts, so Phantom Power is
often labelled "48V". The "48V" switch turns this power on or off and
a red LED lights when active. When switching the Phantom Power
on, quite a loud thump may be produced, so it is a good idea to turn
down the Output Gain (or to momentarily select the Line input), when
pressing the switch. When using dynamic or ribbon mics, do not turn
Phantom Power on. It probably won't do any harm but it certainly won't
do any good, so leave it off! Consult the microphone handbook if you
are unsure what kind of mic you have.
The twinQ microphone preamplifier uses state-of-the-art electronics and
has an equivalent input noise of around -128dBu (with 150ohm input
load). Despite all the hyperbolae and obfuscation, the theoretical best
possible performance for silicon-based electronics is about -132dBu.
So the preamplifier design used in the twinQ and all other NextGen
Joemeek products approaches this limit. To improve significantly on this
would require highly specialised electronics and probably a vat of liquid
Nitrogen to cool it!
The maximum gain available from the preamp is 60dB, in which case
the noise floor will be -68dBu. This is actually quite noisy - if you record
that noise onto a digital recorder and play it back you can definitely
hear it. In practice of course, you do not record and play back "silence"
and the rest of the mix will probably be more than 70dB louder than
this noise and will mask it completely. Even so it is generally a good
idea not to use gains greater than 40dB or 50dB and indeed, it should
rarely be necessary to do so.

Insert Point

This is simply an unbalanced "Send and Return" jack on the rear panel.
It allows you to patch any other pieces of equipment into the signal
path, such as an effects processor or noise gate. To use it you will need
a "Y" lead wired as follows:
Tip: send
Ring: return
Sleeve: ground
When no jack is inserted, the socket is internally linked, or "normalled",
so that the signal flows uninterrupted. Note that the Insert Point is after
the Preamp but before the Compressor and EQ.