Marantz CD63 & CD67 mods list - Page 19 - diyAudio
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Old 11th January 2006, 09:08 PM   #181
guido is offline guido  Netherlands
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Quote:
Originally posted by rowemeister
Here are some pics from my mod.

The reg pcb houses two circuits

1) 5V rail with 5V Audiocom Invisus with coils and 3 Blackgate 16V 100uF caps powering the DAC and Decoder

2) 12V rail with 12V superreg with coils and 2 Blackgate FK 16V 100uF caps powering Audiocom superclock II.

Both circuits are fed +20V from HexFED diodes.
I guess the decoder and the digital powersupply pen of the dac are still polluting the analog and clock powersupply of the dac? I would have done that differently (i actually did )
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Old 11th January 2006, 10:33 PM   #182
SimontY is offline SimontY  United Kingdom
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mmm, hdam bypass, sounds so good. There's my evening gone, rediscovering anything I put on! Constantly blown away by the detail, clarity, precision and dynamics (something I didn't expect!), particularly in the bass! Listening to some old REM it often reminded me of what electric bass sounds like live on a powerful PA system. I've heard many noises and bits of distortion and hiss I'm sure I haven't ever heard before.
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Old 11th January 2006, 10:45 PM   #183
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Quote:
Originally posted by SimontY
mmm, hdam bypass, sounds so good.
Now you understand the power of the marketing.
This Hdam are publicized by Marantz and the "guru" Ken Ishiwata , as the 8 World Wonder...
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Old 11th January 2006, 10:51 PM   #184
SimontY is offline SimontY  United Kingdom
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Quote:
Originally posted by Tube_Dude


Now you understand the power of the marketing.
This Hdam are publicized by Marantz and the "guru" Ken Ishiwata , as the 8 World Wonder...
Yeh, it's ridiculous really! That it can sound so much better when you disable the circuit, that's *supposed* to set it apart, is just madness!

Or maybe we've all done other mods at the same time and are hearing cumulative benefits.
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Old 12th January 2006, 08:04 AM   #185
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Guido said:
Quote:
I guess the decoder and the digital powersupply pen of the dac are still polluting the analog and clock powersupply of the dac? I would have done that differently (i actually did )
I have actually designed the regs pcb so that I can later fit a TX if need be.

The regs used should be nearly zero noise (according to Audiocom).

I have 5 super low noise regulator pcbs fitted to this cdp and surley the noise on any line will now be minimal!
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Old 12th January 2006, 09:08 AM   #186
6h5c is offline 6h5c  Netherlands
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Quote:
Originally posted by guido


I guess the decoder and the digital powersupply pen of the dac are still polluting the analog and clock powersupply of the dac?

Quote:
Originally posted by rowemeister

I have actually designed the regs pcb so that I can later fit a TX if need be.

The regs used should be nearly zero noise (according to Audiocom).

I have 5 super low noise regulator pcbs fitted to this cdp and surley the noise on any line will now be minimal!
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.
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File Type: jpg sm5872_block.jpg (42.7 KB, 1620 views)
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Old 12th January 2006, 09:48 AM   #187
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Ok I under stand all that.

I can sort this out

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Old 12th January 2006, 10:13 AM   #188
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Now then.. with out the service manual infront of me, are the decoders 2 5V inputs the same or is one analogue and one digital?
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Old 12th January 2006, 10:39 AM   #189
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Got manual and I see it has analogue and digital supplies.
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Old 12th January 2006, 10:42 AM   #190
6h5c is offline 6h5c  Netherlands
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Quote:
Originally posted by rowemeister
Now then.. with out the service manual infront of me, are the decoders 2 5V inputs the same or is one analogue and one digital?
Greetings fellow tweaker!

Well, I guess for the decoder you can say the same as for the DAC. The SAA7345 has three different 5V connections actually. One for the analog front-end, where the analog HF signal enters the chip, and two for digital internal logic and I/O buffers. All this wisdom came out of the datasheet of course.

I already experimented a bit with this, and placed an RC filter (1mH + 220u low-ESR) in each powerline, but the chip didn't seem to like it. I think it has to do with internal reference voltages or something like that. The chip doesn't like too high impedances between the different power lines. There's a note also about this in the datasheet.

In the CD67 (which uses a similar SAA7372) they separated the 5V lines a bit by using two RC feeds for the analog and digital part and by inserting ferrite inductors in the digital lines.

Ray.
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