Heavenly Red v1.0
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8
Biasing
Biasing this effect is very difficult. Start by setting the following switches:
•
9V
•
Boost Off
•
Red Channel
•
Plexi Off
•
Structure Off
•
Buffer Off
•
Pre-EQ to taste
Set the pots as follows:
•
Max Gain
•
Volume 90%
•
Presence 90%
•
Bass, Middle, Treble 50%
With a digital multimeter measure the Voltage at the drain of
Q4
. Turn
VR4
so it is at ½ of the input
voltage from your wall wart. Usually that is about 4,5V. Now do the same with
Q3
and
VR3
,
Q2
and
VR2
,
Q1
and
VR1
. Now you have your effect set to a good starting point from which you can
experiment with alternate settings. This is best done by ear.
Take your time and hear what the effect is of turning the different BIAS pots (
VR1-VR4
) on the sound.
Now turn on the Structure and see if it still sounds ok. If not, adjust the settings. Turn the structure
off and boost on and check it again. Adjust if necessary. Finally turn both boost and structure on.
Chances are it will squeal like a pig. This is not specific to this build and you can try to find a better
setting by turning the bias pots and keep wiring as short and/or shielded as possible.
Squealing
First of all, the effect will surely start squealing like a pig at max gain, max volume, structure and
boost on. If you can build/have a small audioprobe, check the drain on Q4. That is the spot where the
squeal will originate from.
To tame the beast, first try to lower the volume to 75%. Unity should be around 50% so you do not
need to worry it will not reach unity. Secondly you can lower the presence a bit. If it still is not in a
workable range for you, there is an extra capacitor added to the board
C23
. Experiment with values
between 10n and 47n. However, higher values will come at the cost of loss in gain.
Also always double check your soldering, especially with ground pads. Keep wires as short as
possible.
Lastly you can try to rebias the transistors to stop squealing. As said before take your time to find out
what works and what not. Changing one thing may also have an effect on other settings, especially
when it comes to biasing!
Содержание Heavenly Red
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