Oakley 3U User Manual - page 7
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 op amps are any high quality dual audio op-amp. The design has been tested with
OP275G, JRC4558, TL072 and OPA2134A. All parts work very well, but there are slight
audible differences in the part selected for U1. I will ask the builder to experiment here, but I
did like the results when using the OP275G in both U1 and U2. Use a socket for U1 and you
can swap chip types with ease.
The diodes are just ordinary 1N4148 silicon diodes. However, there is some scope in playing
around with the diode types in positions D1 and D2, and positions D3 and 4. Indeed, some
useful results can be obtained in using germanium diodes, like the OA91 or 1N34A, in
positions D1 and D3. This makes for asymmetrical distortion but I have not found the results
to be especially different in synthesiser use. You could also use two diodes in series for one
of the places, eg. D1 could be replaced by one 1N4148 and a 1N34A in series.
U3 and U4 are three terminal regulators. They are listed as 100mA devices and are +5V and
-5V respectively. They are very common devices – but be careful you don't get the surface
mount versions. You need the plastic TO-92 ones and not the SOP-8 package.
You will also need a PC mount horizontal double pole double throw switch. These are
sometimes called DPDT or 2PCO (two pole changeover). This type of switch has two sets of
contacts inside, each one has a wiper that can move between two other contacts. These sorts
of switches have six solder tags. Watch out for sizes, there are many different types of toggle
switches. The ones I recommend are Multicomp's part 1MD1T2B4M6RE which is available
from Farnell as part number 947-3270. Alternatively, Rapid sell a plastic bezelled one that
will fit, their part number: 75-0020.
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