Oakley OMS-820 - Manual (Page 10)

Components
For general information regarding where to get parts and suggested part numbers please see
our useful Parts Guide at the project webpage or http://www.oakleysound.com/parts.pdf.
Some special considerations for this project
The BC550 and BC560 devices are discrete low noise transistors. The former is NPN, while
the latter is PNP. You can replace the NPN with BC549, and the PNP with BC559. Quite
often you see an A, B or C suffix used, eg. BC550C. This letter depicts the gain or grade of
the transistor (actually hfe of the device). The OMS-820 is designed to work with any grade
device although I have used BC550C and BC560C throughout in my prototype.
The board mounted pots are Spectrol 248 or BI TT conductive plastic types and are held onto
the board with specially made Oakley pot brackets. Three pot brackets and an extra set of nuts
are required and these are provided with the ‘pot bracket kit’. You could use any pot type you
want, but not all pots have the same pin spacing. Not a problem, of course, if you are not
fitting them to the board.
All the electrolytic capacitors should be radially mounted. The working voltage (WV) of the
capacitor is not critical, but chose one that will fit on the board. I would use 25V for the 22uF
and 63V for the 2u2 capacitors.
The pitch spacing of the polyester capacitors is 5mm (0.2”). These types come in little plastic
boxes with legs that stick out of the bottom. Try to get ones with operating voltages of 50V,
63V or 100V. They may be called polyester film or metallised polyester capacitors.
L1 and L2 are leaded ferrite beads. These are little axial components that look like little
blackened resistors. They simply consist of a single piece of wire going through the middle of
a ferrite cylinder. They are available from most of the mail order suppliers. Find them in the
EMC or Inductor section of the catalogues.
All ICs are dual in line (DIL or DIP) packages. These are generally, but not always, suffixed
with a CP or a CN in their part numbers. For example; TL072CP. Do not use SMD, SM or
surface mount packages.
U4 is a 4001 device, and is part of the classic 4000 series of CMOS logic. Many companies
make this device and as such the device ends up having all sorts of names. eg. CD4001,
MC14001, 4001BE. All types should work but try to avoid the 4001UBE, this is an older
device and is very prone to static damage. Either way a good quality IC socket is
recommended for this chip. You’ll need a 14-pin type.
The LEDs are standard 5mm round types. You can chose either flat topped or domed top. Flat
tops tend to look better, although the viewing angle is not normally as good. The LED
labelled OUT is a bicolour LED. I like red/green ones the best, although other colours are
available. Try to get the three single colour LEDs from the same range of LEDs, that is, the
same manufacturer and type. You can choose from different colours in the same range. The
three single colour LEDs are driven from the same current source, and by choosing the from
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