adding pre-outs to an inexpensive HT receiver.

[Nigel Goodwin]

Originally posted by brianuk
Hi Nigel,

Are you saying that that is four of the 6 analogues at line level before the Power amps?

No, that's TWO of them, each output chip has two feeds, out of phase with each other, as they are bridged amplifiers. There are six amplifier chips in total, one for each speaker.

Im a bit of numpty see

If it is then how on earth did you get this information ?!

From the service manual!.

[montreal]

Is this receiver a 6.1 type?


Have you located where the source of the sub-woofer output is?

In Canada we have a Sony receiver called the STRDG500S which is 6.1 at 100 watts per channel and sells for the equivalent of 240 euros.

It looks like my best bet so far against the Creative DDTS-100.

[Nigel Goodwin]

Originally posted by montreal
Is this receiver a 6.1 type?

No, a 5.1 type.

Have you located where the source of the sub-woofer output is?

Like all the other channels, it's directly out of an 80 pin SM chip (there are two of them) to the output IC.

In Canada we have a Sony receiver called the STRDG500S which is 6.1 at 100 watts per channel and sells for the equivalent of 240 euros.

Interestingly enough, it's only rated at 100W in the USA and Canada?, elsewhere it's rated at 85W. BTW, the manual is dated Feb 2006.

[montreal]

Originally posted by Nigel Goodwin


No, a 5.1 type.



Like all the other channels, it's directly out of an 80 pin SM chip (there are two of them) to the output IC.



Interestingly enough, it's only rated at 100W in the USA and Canada?, elsewhere it's rated at 85W. BTW, the manual is dated Feb 2006.

I realize now that yours is designed to connect to a non-powered subwoofer.

I don't think the 6.1 Canadian model is exactly like your 5.1 model. The box is much larger here. I suspect they use the same power amp chips.

It looks like your power supply is single pole and the use of the bridging is to double the output voltage at the speakers.

On the schematic, the voltage on the chips for the outputs (pins 2 and 17) seems to be at 13,6 volts. That may be a DC bias or the AC rms signal strength when fully driven.

If its a DC bias (typical of unipolar power supplies), do they get rid of this bias voltage with large de-coupling capacitors or do they present the same live 13,6 volts simultaneously on both the plus and minus terminals of each speaker output using a shielded plastic plug? If so, it would be dangerous to let either speaker wire contact ground.

[brianuk]

I dont suppose I could be cheeky and ask for a copy of that manual or just a couple of scans

I want to

[Nigel Goodwin]

Originally posted by brianuk
I dont suppose I could be cheeky and ask for a copy of that manual or just a couple of scans

It comes as a PDF as part of Sony Assist, but the PDF's are password protected - with the password hidden inside Assist somewhere (so I don't know what it is).

[Nigel Goodwin]

Originally posted by montreal

It looks like your power supply is single pole and the use of the bridging is to double the output voltage at the speakers.

Yes, that's correct - it's common on many small Sony HT units.

On the schematic, the voltage on the chips for the outputs (pins 2 and 17) seems to be at 13,6 volts. That may be a DC bias or the AC rms signal strength when fully driven.

DC, as expected from a bridged amp with a single supply.

If its a DC bias (typical of unipolar power supplies), do they get rid of this bias voltage with large de-coupling capacitors or do they present the same live 13,6 volts simultaneously on both the plus and minus terminals of each speaker output using a shielded plastic plug? If so, it would be dangerous to let either speaker wire contact ground.

They use a stupid two pin plastic plug, that you can't buy anywhere - and buying replacement speaker leads is INCREDIBLY expensive! (about £120 for a set of leads last time I checked!).

Yes, it is 'dangerous' if you short the plugs to chassis, but generally the amp just shuts down in protection mode.

[montreal]

Originally posted by Nigel Goodwin
DC, as expected from a bridged amp with a single supply.

Nigel,

So your power amp is actually a bridge formed by 2 amps driven with inputs that are 180 degrees out of phase to achieve the voltage doubling.

I imagine for this reciever to work correctly, all analog (stereo) inputs must be converted to the digital domain so that the sound processor can apply all the bass management features and surround sound emulation for stereo inputs.

Each analog input might have its own A/D converter followed by a digital switch or there may be an analog switch following all the analog inputs followed by a single A/D converter. In any case, I imagine the sound processor deals with only one source at a time and knows exactly what to do with it.

The net result is that the sound processor must have exactly 6 digital outputs which must each be converted back to analog and then split in two paths so that one path can be inverted to feed the pair of power amps in bridge formation.

How easy is it for you to identify the outputs of the 6 D/A converters? Are they CXD9674 or CXD9675? If so, there are 2 pins per output channel in these D/A converters - one non inverting the other inverting.

[Nigel Goodwin]

Originally posted by montreal

How easy is it for you to identify the outputs of the 6 D/A converters? Are they CXD9674 or CXD9675? If so, there are 2 pins per output channel in these D/A converters - one non inverting the other inverting.

As I mentioned previously, all six channels (actually 12 outputs) come directly from two 80 pin SM chips - I presume all the processing and conversion is done in those?. I wouldn't expect the numbers of them to be at all useful, I presume they are custom chips?.

EDIT: I've just been and checked the manual, there are actually THREE 80 pin chips, feeding two output chips each. They are labelled 'Stream Processor' and are CXD9634Q's.

[montreal]

Originally posted by Nigel Goodwin



EDIT: I've just been and checked the manual, there are actually THREE 80 pin chips, feeding two output chips each. They are labelled 'Stream Processor' and are CXD9634Q's.

Nigel,

So you have 3 CXD9634Q chips labled Stream Processors where each drives 2 CXD9646Z dual power amplifier chips with 33 ohm resistors in series in each path which connects a Stream Processor chip output to a power amp chip input.

If so, I would assume that each 9634 is for 2 of the 6 audio channels and each 9634 contains at least 2 D/A converters to create the 2 analog channels plus 2 extra inverters to provide an out of phase signal for each bridged pair of power amps.

Any chance of you posting an attachment that shows one of the three 9634 processor chips?


Thanks