2007-05-28 Working on Zen 9
I am working on Pass's Zen 9.
My plan is to simplify the circuit by lowering the output power, and using high performance heatsink, from Pentium4.
VCC is reduced to 20V with extra idle current (2.5A), without active load. Output capacitor is one of the most expensive and critical device. By using BTL circuit, I am planning not to use output capacitor.
I will report the process and the result asap.
2007-05-13 more on Kaneda #168
I will write about more details on opamp based on Kaneda’s #168 preamp, and its modification.
The original amplifier consists of discrete OPAmp (described later), -20dB attenuator (2 registers) at input, and feedback circuit (50KR volume (A-curve) plus 1KR). The output impedance of the OPAmp is very high (current output) and the voltage gain of the OPAmp is proportional to its load, where the load is 50KR Volume plus 1KR), which determines gain and NFB of the circuit. If its output load (i.e. input impedance of the power amplifier) is large enough, both OPAmp’s gain as well as closed circuit gain are proportional to the volume, thus its NFB rate is independent from the volume position.
The OPAmp part consist of 4 J-FET, 3 BJT, 1 Zener, 10 Register, 1 pot, 1 capacitor powered by +/- 26V power supply.
First stage is N-Ch J-FET (2 of 2SK246) differential circuit with 2mA ccs (2SC1775A, 2reg, 1 HZ6C2) at its common source. 200R Offset control pot is inserted into the common source, and 1K8R are connected to each of source and +VCC.
2nd stage is P-CH J-FET (2 of 2SJ103) differential circuit. Unlike its first stage, 2nd stage uses one register 3K6R in place of ccs.
3rd stage is SEPP of 2 BJTs (2 of 2SC959). Upper BJT’s emitter is connected to the output through 47R register, collector is connected to +VCC. Its base is connected to one drain of 2nd stage P-Ch FET, and one end of 1K6R, while the other end of this register is connected to the output. Lower BJT has same circuit, except that collector is connected to the output, emitter through 47R and base through 1K6R are connected to –VEE. 2nd stage output currents drive 1K6R of upper and lower side of SEPP. Thus both the output stage operates as collector follower. The idle current of the output stage is about 7mA. There is a phase correction R+C connected between drains of the first stage (i.e. gates of 2nd stage.)
Dr. Kaneda describes every detail of the amplifier, all parts from transistors, capacitors, registers, and all other parts, as well as register and capacitor orientation, wiring of specific universal PCB uses hand-wounded 7 strings of cable elements out of specific cable. Every one of wiring cable orientation is off course specified, so that his reader can exactly copy his original amplifier. It is, however, impractical to acquire all the parts, almost all subscribers have to arrange anyway.
Despite the difficulty to completely copy the original, various amplifiers inspired by his design are so popular in Japan, by the contributions of many DIY experts including Konton, Jinson, Zuka, Ks, prost, and number of people who subscribed Jinson's “Mini-Amp” PCB.
It is obviously true that Dr. Kaneda's circuit design itself is so superior in the sound quality even after various modifications.
I would appreciate you try to understand their web pages by youreslf, some of them retired working on DIY, some others communicate mostly in Japanese, and almost all of their webs are available only in Japanese.
I would translate and post in this page, provided that the original writer wants to do so.
There are several uniqueness in Dr. Kaneda's and other experts designs.