aion Lab Series Manual - Page 13
Browse online or download pdf Manual for Amplifier aion Lab Series. aion Lab Series 20 pages.
Also for aion Lab Series: Manual (15 pages), Manual (20 pages)
BUILD NOTES, CONT.
Channel 1 midrange and volume potentiometer values
The Lab Series amplifier used 2.5kA potentiometers for both Midrange and Volume of channel 1. This
is a non-standard value today and not available from any standard parts suppliers. Tayda Electronics
carries 2kA, which is certainly close enough and will work fine in this circuit. But in the new version of
the L5, we included parallel and tapering resistors on the PCB so standard pot values could be used.
For the midrange pot, we recommend using 5kA, with a 5k1 resistor in parallel (R7). Since it's wired as a
variable resistor, this drops the resistance value to 2.5k and only steepens the curve slightly.
The volume pot is wired as a true potentiometer with all three terminals used, so it's a little more
complicated. For this, it's recommended to use a 10kB pot with a 2k7 resistor (R11) between pins 2 and
3 and a 1k resistor (R12) between pins 1 and 2. This will give a good approximation of a 2.5k pot, and the
resulting taper will be very close to logarithmic.
LM13700 vs. CA3080
Our original L5 Preamp project used CA3080s as in the original amp. These have been discontinued for
a long time, and while they have been reissued and are not terribly hard to find, they are expensive.
The LM13700 is essentially a dual version of the CA3080/CA3094 and is still readily available. Since the
L5 circuit uses two CA3080s, it seemed like a good opportunity to replace them with a single LM13700.
The only change that this required was to add a second 100k resistor (R77) to cut the compressor LED's
voltage in half, since the LM13700's I
pin sits at twice the voltage of the CA3080's pin. This extra
ABC
resistor prevents the LED from staying on all the time, which was the only side-effect of substituting the
LM13700 in place of the CA3080.
Bypass PCB component orientation
Due to the height of the DC converter and electrolytic capacitors, the components on the switching PCB
are mounted on the bottom, the same side as the footswitch. This is in contrast with most other Aion FX
projects where the switch is mounted on the bottom of the switching sub-board and the components
face up. Components are always mounted to the side with the silkscreen footprint.
L5 PREAMP
13