To all the owners of a transistor amplifier V3.0 from http://www.high-amp.de out there in the world. Here is a support how to update your amplifier to the version 4.0 that will be coming out soon. The items below are refered to the following schematic:
http://high-amp.de/html/transistor_v3_schematics.html
- replace the four resistors R07x and R08x with 51K/1W resistors to increase the current in the second stage to 4mA
- replace the two resistors R11x with 200 ohm resistors to increase the current in the last stage to 15mA
- replace the resistors R56, R57 by a constant voltage source as shown below (one per chanel)
- If you are using the 2SC5466 in the last stage replace it by the 2SC5353 (Q06x).
The 2SC5466 can not handle 15mA because of the nonlinear hfe-curve above 10mA (bad performance especially in high frequencies, missing resolution).
What do you have to expect from the update?
You will improve your amplifier significant to a very fine resolution over the complete frequency range with very deep and structured basses and an excellent reproduction of high frequencies. I would warmly recommend to you to perform this update. You won't regret.