****PLEASE NOTE**** Like many other designers, I am always striving for improvements. When I designed this amp, the pre-amp section was intended to have an immense amount of gain. This was done mainly with guitarists in mind:- for that “front-end overdriven sound”. However this may not be everybody’s requirements so........... if you find you have too much gain there are a couple of modifications you can do.
(1). Change both the anode (plate) resistors of the first ECC83 from 330k and 220k respectively to 100k (each). Also change the two cathode resistors from 1k8 to 1k5. And/or, you can do both of these changes to bring the gain right down)……..
(2). Simply change the ECC83 for an ECC82, I have done this on some of my amps when necessary and this does the job perfectly, without any change of quality within the tone circuit itself!