aion Lab L5, Руководство пользователя

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L5 PREAMP DRIVE CHANNEL 3
USAGE
The L5 Preamp Drive Channel has the following controls:
• Volume controls the amount of gain in the first stage, before the EQ and drive section.
• Bright (toggle switch) adds a treble-bleed capacitor to the volume control, which keeps it from
getting dull at lower volumes.
•
Treble
and
Bass
form a standard 2-band Baxandall control. Each band is flat at the 12:00 position,
and can either cut (CCW) or boost (CW).
• Frequency selects the frequency that will be boosted or cut by the Mid control for the semi-
parametric midrange.
• Master sets the output volume after the drive section of the preamp.
• Comp Level sets the threshold of the compressor at the end of the circuit.
•
Comp On/Off
(toggle) disengages the compressor.
CIRCUIT DESIGN NOTES
Power supply design
Like most solid-state preamplifiers of the era, the L5 operated on a b/-15V supply. This voltage
can’t be supplied by an external adapter, and the current draw of the circuit is too high to use a charge
pump.
When developing the original Lab Series L5 Preamp , we adapted a supply scheme from Alesis rack units
in the early 1990s that involved a 9VAC adapter and an AC voltage tripler. This was then rectified to
b/-19V DC and regulated down to 15V on each rail.
This solution used cheap and readily-available parts, and it has worked very well for several years since
the L5 Preamp was first developed. But the power adapter requirement has always been the major flaw.
A 9VAC adapter will destroy most other pedals if it’s plugged in, and if you own one, there’s an infinitely
higher chance that it’ll be mistaken for a 9VDC adapter and plugged into the wrong pedal at some point.
Because of this, when developing the IVP Preamp project in 2021, we set out to find a reliable way to
/-15V from a standard DC adapter. Fortunately, there are a few more options available today
than there were in 2015 when the L5 Preamp was originally developed, and a high-quality DC-DC
converter module will give us exactly what we need. They’re not cheap (USD$9-15 each), but once you
account for the fact that you no longer need a specialized power adapter, the total cost is about the
same. We have begun using these DC converters in all of our preamp projects going forward, including
this new variant of the L5 that started it all.
See the build notes on page 8 for more information on the specific DC-DC converters that are
recommended for use in this project.