In the previous part 1 section we learned how to make the main DJ mixer circuit stage, in this section we will investigate the other associated main stages of the mixer design.
How it Works
Very little can probably be said about
how exactly the LM382 operates since many of the circuitry is comprised inside the IC. The majority of the frequency determining elements are
on the chip just the capacitors tend to be attached outside the body.
The LM382 has got the handy feature of obstructing ripple on the supply
path around 10 dB. Hence significantly lowering the high quality
dependence on the power supply.
output through each preamplifier could be applied into this headphone amplifier circuit. To
be able to cue signals prior to mixing them into the output it is
strongly recommended that if headsets are used, include a 100 ohm
1 watt resistor which may be installed in series with the output.
is primarily to safeguard your ears and decrease the power dissipation
of the LM 380 or else a little heatsink could be needed. The volume
control could be attached to the trunk of the mixer since it is not
necessarily tweaked frequently.
The VU meter circuit utilized in the mixer board is quite fundamental, yet well suited for several similar audio level indicator purposes, distortion presented into the output
signal can be as much as 2% THD, therefore we highly recommend the VU board.
Possibly you may leave out RV4 and D1 from the mixer board and hook up point X to
the input of the VU panel. Calibration set up is performed through the
preset on the VU board, give a signal input via the mixer until
eventually the output is merely distorting the amplifier, and fine-tune
the preset to signify +3VU.
the boards using the overlay sketches, to save your time we have placed
all the PCB layouts collectively, here.
The picture exhibits the general
layout we made use of, however this is universally adaptable, ours had been
constructed into a wooden box along with metal front side and bottom
nevertheless a metallic container could be a lot more ideal within an
electrically raucous atmosphere.
Inter-board cable connections could be
figured out from the specific circuits and overlays.
contacts needs to be as small as you possibly can and retained far from
the mains wiring. We actually relocated the power button directly to the
backside of the panel to minimize hum pickup and grounded to the metal
box, having an light weight aluminum shield round the mains transformer
to guarantee minimal hum pickup) If this is carried out unscreened cable
connection may be used without issues.
How it Works
VU circuit comes with an input impedance approximately 1M and
consequently will never load the mixer output by virtually any visible
The IC features a gain of 43dB, the signal can now be ampliﬁed through Ql to attain sufficient level and push the VU meter needle.
With no signal circumstances the voltage in the penetration of D1, D2
drops to 0V due to R8. Each time a negative proceeding signal shows up
at collector of Q1, C3 tends to discharge within the negative peaks.
Difference between negative and positive highs is shifted via D2 to C4
and therefore is indicated on the VU meter reading.