I have bought that receiver now (177€ new), and even out of the box, the sound is quite good. It seems to be the only receiver below €1000 on the market that uses discrete extended beta transistors. Everybody else I have looked at (Sony, Marantz, Denon, Yamaha) use Darlingtons of questionable beta linearity.
The input stages of the Onkyo power stages are not well-balanced (about 8% imbalance I seem to recall). Changing a resistor or adding a current mirror and changing the comp cap will make them into very decent power amplifiers.
The other thing I am suspicious about is the R2S15211 IC that seems to do all analog switching and volume control. This monster thing is controlled by only a data and a clock line if am reading the schematic correctly. So if the protocol was known, I could program a PIC to snoop the commands and implement a decent routing and volume control with relays and a PGA chip.
Michael, the service info you uploaded is schematics only. Do you know if the full manual contains more info about the control of this chip? I would buy the full manual if it did.
Thanks
Eric
The input stages of the Onkyo power stages are not well-balanced (about 8% imbalance I seem to recall). Changing a resistor or adding a current mirror and changing the comp cap will make them into very decent power amplifiers.
The other thing I am suspicious about is the R2S15211 IC that seems to do all analog switching and volume control. This monster thing is controlled by only a data and a clock line if am reading the schematic correctly. So if the protocol was known, I could program a PIC to snoop the commands and implement a decent routing and volume control with relays and a PGA chip.
Michael, the service info you uploaded is schematics only. Do you know if the full manual contains more info about the control of this chip? I would buy the full manual if it did.
Thanks
Eric
You are right, this could be a Renesas part. Unfortunately, that partcular part number is not listed. Comparable parts have a typical (!) distortion (not distortion + noise) of 0.005% at 0,3V RMS output at 1k with 10 k load, worst case is stated as 0.05%. Typical and worst at 2 V RMS output are 0.03 and 0.1%.
Unless they are being very conservative, this chip might well be the weakest link in this AV receiver.
All similar parts (6 or 8 channel volume control + input selector) had a three wire interface with clock, data and latch. There were a few I2C devices but those were only stereo.
Unless they are being very conservative, this chip might well be the weakest link in this AV receiver.
All similar parts (6 or 8 channel volume control + input selector) had a three wire interface with clock, data and latch. There were a few I2C devices but those were only stereo.
Actually, I have found R2S15902 which does have a two wire interface. It uses 24 bit control words, and a latch of the previous 24 bits is generated if data is high at the falling edge of clock.
I should be able to verify if my part uses the same protocol. If so, it should be possible to figure out the relevant codes.
I should be able to verify if my part uses the same protocol. If so, it should be possible to figure out the relevant codes.
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