Focusrite 315 Mod
Focusrite 315 mod variation 1
In this closeup, single opamp input stage has replaced stock three opamp input stage. Single opamp employed is OPA-627, chosen for excellent balanced input specs (common mode rejection, etc). The opamp output stage (not showing) is also replaced with OPA-627, chosen for excellent output drive capability. An old transformer from an API console is added to balance the output (there are several good choices for output transformer available on the market today).
Two relay boards are stacked to add the functions of:
- Hard relay bypass. Tied to the original bypass circuitry, true full bypass is accomplished, whereas in the stock unit input and output amps are still engaged during bypass. As one would expect from hard relay bypass, signal still passes through the 315 when power is off.
- Transformer bypass. On the front panel, the fine gain pot is changed to a pot+push/pull switch. By means of the switch the transformer can be bypassed. With this mod a transformer of warm coloration can be chosen as needed. Circuit values are carefully chosen so there is no gain change when switching transformer in and out.
Focusrite 315 mod variation 2
In this closeup, single opamp input stage has replaced stock three opamp input stage. Single opamp employed is OPA-627, chosen for excellent balanced input specs (common mode rejection, etc). This version of the 315 came stock with a toroidal output transformer, and the opamp output plus booster transistor stage is left intact. An old transformer from an API console is added to balance the output and provide warmth (there are several good choices for output transformer available on the market today).
One relay board adds the functions of:
- Hard relay bypass. Tied to the original bypass circuitry, true full bypass is accomplished, whereas in the stock unit input and output amps are still engaged during bypass. As one would expect from hard relay bypass, signal still passes through the 315 when power is off.
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