Quad 606 MK I and II DIY upgrade illustrated guidelines version 1.41
These are the illustrated step-by-step guidelines for upgrading your Quad 606
MK I or 606 MK II with the Dada Electronics upgrade-kit. This kit can also be
used for the 707and 909, the 707 and 909 is basically a 606 MKII with the
extra Quad Bus input circuit. The 606 MKI has a square casing; the 606 MKII
has beveled edges like the 707 and 909.
This kit is based on the highly successful one we developed for the 306 range
of amplifiers.
We will replace all electrolytic capacitors on the amplifier modules, input
connectors, some resistors and capacitors in the input- and feedback circuit
like Quad did in the 909. Low quality capacitors are replaced by Silvered-mica
capacitors. All the cabling will be replaced by Hi Q cabling in the original
colors.
We will also adapt the input-sensitivity (as an option) by increasing the local
feedback in the input-circuit. This further increases the signal-to-noise ratio
and makes the amplifier better adapted to modern sources.
We strongly advise to replace the power supply capacitors, but these are
depending on the type of 606.
Replacing the output transistors and drivers is an extra option; it will increase
the output peak current at difficult loads.
In some 606 amplifiers there is a mechanical hum. This is generated by the
transformer. Although Quad tried to solve this with a special suspension kit,
there is only one solution, replacing the transformer with a toroidal, like Quad
did in the 606 MKII, 707 and 909. We can do this kind of work, but only in one
of our shops.
