davidsrsb said:
Well, at least they split the 5V line in +5VA and +5VB, it's better then nothing...
But that's why we replace the 4,7R resistors by low-ohmic inductors, and replace the 47n ceramics by a large el-cap + 100n.
The best thing is to get rid of anything in series with the supply-line of course, and use a regulator for every pin. This is not as hard as it seems, because you can just leave a series resistor in there, and put a shunt regulator behind it. But then again, unless you want to use TL431's, you would still need a PCB with parts to build a good shunt...
Ray.
Tomorrow I am moving the two audiocom super regs (+/- 12V) from the usual place (Q801/Q802) and placing them right next to the op amps where the feed resistors go.
I will post pics tomorrow after fitment.
I wont bother replacing Q801/Q802 as they only power HDAM , muting and op amps because the HDAM and muting is removed.
I will post pics tomorrow after fitment.
I wont bother replacing Q801/Q802 as they only power HDAM , muting and op amps because the HDAM and muting is removed.
rowemeister said:Tomorrow I am moving the two audiocom super regs (+/- 12V) from the usual place (Q801/Q802) and placing them right next to the op amps where the feed resistors go.
I will post pics tomorrow after fitment.
I wont bother replacing Q801/Q802 as they only power HDAM , muting and op amps because the HDAM and muting is removed.
Are you going to jumper Q801/802 and use the PCB traces for raw supply?
Ray.
6h5c said:
Hi rowemeister!
Some mod eh? I think you will like the OPA627 + OPA132 even better. Make sure you put the 627 after the DAC and 132 in the filter.
What Guido means is that the regs are o.k. obviously, but the noise is not coming from them, it's coming out of the DAC!
Take a look at the datasheet. The SM5872 has separate +5V lines for the digital part (pins 15 & 16), the analog part (pins 17, 19, 21, 22, 24, 26) and the clock part (pins 2 & 27). Since the supply lines of the DAC are not separated completely now, some (digital...) noise will be coupled to other (analog...) stages. If you tie the clock part to the supply of your external clock and the digital part to the +5V you use for the decoder, you can fit a third (clean) +5V for the analog part. Have I 'translated' this correctly Guido?
The key is to separate these lines. You can do that by looking at the board layout.
The clock part is just two internal gates that used to form the oscillator, but they still carry the 16,9MHz. It's easy: it is already separated, it get's +5V through RD01. You should tie it to the external clock supply to keep all the noise in one place.
The digital AND the analog part get +5V through U164. Then through RD04 to the digital part, and U200 to the analog part. If you take these two out, you have separated these parts too
Ray.
I did not try or measure much, just did what i thought was right.
Since the clock is generated by the dac i assume that the output stages are latched with that and not with the incoming i2s signals (i need to read the datasheet to verify
)So jitter on incoming i2s (from decoder) I ASSUME is not that important. Feeding the clock circuit in the dac with a clean powersupply should be to minimize jitter on the latching.
So i used the same 5V for clock and dac clock circuits (there is a limit to the regs i was willing to use, only 8 left... :->. This should minimize jitter. Then i used a second reg for the analog supply to minimize noise going into the dac's analog outputs.
I left the digital powersupply of the dac and the decoder and the rest of the stuff (controllers etc) to the players +5. Just 'upgraded' the filter components as usuall.
took out the hdam too recently. really worth it!
Hi Guido,
Well, I didn't measure it either... Just followed my own common sense.
I use exactly the same configuration, starting from the same viewpoints.
Seems to work fine and with some regulators to spare
I looked into the DAC datasheet, it's input data is latched: "isolating them from jitter or skew on the input circuit clocks"
Ray.
Well, I didn't measure it either...
Just followed my own common sense.I use exactly the same configuration, starting from the same viewpoints.
Seems to work fine and with some regulators to spare
I looked into the DAC datasheet, it's input data is latched: "isolating them from jitter or skew on the input circuit clocks"
Ray.
Now then....
I am so happy
I have revised my reg pcb quite heavily and now run seperate regs for Digital , Analogue , Clock and DAC clock voltage rail.
Also I have fitted two Audiocom regs next to the op amps.
And soldered my chips to the browndog pcb's with silver loaded solder.
First of all I listened to it with just the regs sorted and OPA2134. There was a better clarity, not a lot but enough to notice, it just seemed more open, more air etc
Then I fitted the Browndog OPA627 , OPA132 pcb to one channel and tested against each other using the balance.
Whhoooo
I had independant listeners doing a blind test and everyone said how much clearer and better the right hand channel sounded. And it was much better, no top end nasties compared to the left channel, a much tighter bass and the clarity wow!
So incase you have not guessed the right channel is the OPA627/OPA132 combo.
cheers 6h5c for the advice on the combo and cheers to simon who kept telling me the OPA627 was better
So here are a few pics.
I am so happy
I have revised my reg pcb quite heavily and now run seperate regs for Digital , Analogue , Clock and DAC clock voltage rail.
Also I have fitted two Audiocom regs next to the op amps.
And soldered my chips to the browndog pcb's with silver loaded solder.
First of all I listened to it with just the regs sorted and OPA2134. There was a better clarity, not a lot but enough to notice, it just seemed more open, more air etc
Then I fitted the Browndog OPA627 , OPA132 pcb to one channel and tested against each other using the balance.
Whhoooo
I had independant listeners doing a blind test and everyone said how much clearer and better the right hand channel sounded. And it was much better, no top end nasties compared to the left channel, a much tighter bass and the clarity wow!
So incase you have not guessed the right channel is the OPA627/OPA132 combo.
cheers 6h5c for the advice on the combo and cheers to simon who kept telling me the OPA627 was better
So here are a few pics.
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An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
