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07-18-2022, 02:54 PM
Hi Jim
MICRO already has bags of gain available - probably too much for most players - and it is very important to use the control on your guitar called 'Volume' - hehe. Most guys leave it at '10' but here is a situation where using it is important.
The input stage has a small gain of about 3, which itself may be too high already for some guitar pickups like those on a Les Paul. This is why the notes mention changing R17 from 10k to 3k3. The Edge control can boost the gain of the stage to quite high levels, either broadband or just for treble depending on the value used for C8.
The J201 has a transconductance of one-third what the 2N5485 has, so i would expect the J201 to have lower maximum gain but there may be little difference in the MICRO application.
You can reduce the maximum gain of the PA by slashing either trace going to the Blast control and jumpering the break with a resistor. Blast plus the added resistor work against R44 (10k) to set the gain as A=1+(R44/Rnew). For example, if the new R=1k, then maximum gain is reduced to 1+(10k/1k)=11, which is quite a drop from >300. But try it first and hear the sounds possible.
MICRO has a pretty compact layout, so be careful soldering to avoid solder bridges.
Have fun
MICRO already has bags of gain available - probably too much for most players - and it is very important to use the control on your guitar called 'Volume' - hehe. Most guys leave it at '10' but here is a situation where using it is important.
The input stage has a small gain of about 3, which itself may be too high already for some guitar pickups like those on a Les Paul. This is why the notes mention changing R17 from 10k to 3k3. The Edge control can boost the gain of the stage to quite high levels, either broadband or just for treble depending on the value used for C8.
The J201 has a transconductance of one-third what the 2N5485 has, so i would expect the J201 to have lower maximum gain but there may be little difference in the MICRO application.
You can reduce the maximum gain of the PA by slashing either trace going to the Blast control and jumpering the break with a resistor. Blast plus the added resistor work against R44 (10k) to set the gain as A=1+(R44/Rnew). For example, if the new R=1k, then maximum gain is reduced to 1+(10k/1k)=11, which is quite a drop from >300. But try it first and hear the sounds possible.
MICRO has a pretty compact layout, so be careful soldering to avoid solder bridges.
Have fun
