jonnyxjuturna wrote:On a similar note I currently have two 1megs in series to get that 2 meg resistance. But I could substitute in a 2.4meg in that spot
Most people only have 2M2, and would stick that in: It's only 10% higher, some resistors are up to 5% higher with tolerance, another 10% is unlikely to make that much difference.
jonnyxjuturna wrote:I am using a bs170 as previously suggested in this thread for my transistor
BS170 is a mosfet, but the original circuit uses a BJT - a bipolar junction transistor. Any medium gain npn BJT (e.g. 2N5088/9, MPSA18, 2N3904, BC547/8/9, 2N4401, BC108/9 etc...) will probably sound similar
to the original.
The mosfet on the other hand might
work, but it's not guaranteed. Mosfets usually have similar value resistors from drain (collector) to +9v as they have from source (emitter) to ground, and they usually have a half supply bias voltage applied to the gate (base): Have a look at the AMZ mosfet booster, zvex super hard-on, or catalinbread chili picoso to see an equivalent single stage booster using a BS170. I'd imagine a mosfet in this circuit would sound different to the original EM drive, and I would try any BJT first.
The key point here is that the design is pretty simplistic: Grounded emitter amplifiers are running at full tilt, and are not that stable, different transistors with different characteristics will behave quite differently e.g. resulting in splatty fuzz if you're unlucky. A "better" design (e.g. with an emitter resistor, and some base biasing - look at the EHX LPB-1) would be less reliant on the *right* transistor to get a good sound, but you may well be lucky and get a nice sound you like with what you've got.