Personally, I dont think the turbo mod is necessary. The effect of it isn't all that different from just engaging the single frequency SC high pass on most program material, but if you want it, and still use the SC switch as is, here is how to do it! 1. Build the stock unit first - and get it working! Sometimes, beginners will take on too many things, which will create too many variables, which ends up causing problems, that lead them to giving up. Success is guaranteed by taking everything one step at a time, and it also makes remote assistance easier, so... Get the stock unit working first! 2. Get a turbo board from expat audio
https://expataudio.myshopify.com/products/gssl-turbo-pcb 3. Do the shopping If you built the GssL from the kit, this will be a good exercise, since you already know the components involved. You may make an error, so you have to do a second order, but mistakes are a part of learning, and the value of learning how to do this stuff is much greater than just another compressor in the rack. Resistors - you will want to make sure they are through hole. 1/4 Watt will do for this board, but more is fine - be aware, that they start getting bigger at 1 Watt! Capacitor - The brown discs are fine for ceramic, and for the electrolytic cap, the voltage rating isn't all that critical here, since its in the signal path. You can use a 25V for the 22uF, or you can use a higher voltage rating (voltage rating indicates how much it will take) Note that they get bigger and more expensive, so dont just grab one rated for 400V . IC - A search for the TL074 will result in a lot of hits in the search engine of most shops. If it's got TL074 in the name, its a TL074, makers and noise specs will vary - you can go for one that says "low noise" or "audio", and make sure to get a through hole, not an SMD part (SMD = surface mount) (and add a 100nF wima cap to the list,youll need it for the SC filter) 4. Populate the board
One small change, since were implementing the SC switch already in the unit - lift the positive terminal on the 22uF cap, and add a wire to it, and add a wire to the pad it was going to.
4. Hook up the switch
Then, use the unused side of the DPDT switch to add another cap going to the wires you just prepared. This is tapping into the same spot in the paralleled circuit, and you are just doing the same thing with another side of switching.
5. Follow the installation from Expat
http://expataudio.com/diy/Turbo/TurboInstallationManual.pdf
Done...