PCM56 build- design ideas - diyAudio
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Old 29th June 2012, 01:55 PM   #1
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Default PCM56 build- design ideas

After hearing fellow DIYers in this forum ranting about PCM56 (especially Bernhard), I decided to give it a try. I'm convinced that the channel switching using 74HCU04 is more than adequate, anything more that that requires a jig to hold my head in the chair.
SPDIF processing is done using twistedpearaudio's WM8805 kit, which basically takes care of jitter issues (to my standards). Looking at datasheet, the PCM56 has relatively poor power supply rejection so independant regulators at every input is a MUST. Since 8 regulators are required for for stereo, my laziness calls for the 7xx5 series.
Output current is converted using 240R resistor, and amplified with OPA627 (with RFI well taken care).


The midrange, trebles details is absolutely stunning. Can say something like TDA1541 after the DEM reclocking & stuffs..
Running without the MSB trim, it does the Sheffield disc track 40 quite well, something that even WM8740 and PCM1798 struggles with.

BUT... Would like to gather opinion from the brave souls who has tried this DAC (esp Bernhard):
Bass seems missing. Or is it that the neutrality of the DAC makes it seems missing?
Im using +/-5v. Any improvements going for higher supply voltage?
Is opamp IV a better match to this chip? Or any output stage that compliments well?

Cheers,
Colin
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Old 29th June 2012, 02:12 PM   #2
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Old 27th July 2012, 09:50 AM   #3
erin is offline erin  Australia
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I only have experience with pcm58, it also seems a little bass light. I wonder if this is a characteristic of BB dac chips of this era?
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Old 28th July 2012, 04:43 AM   #4
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If you found the PCM58 bass-light, you have not implemented it well enough. It's one of the most punchy of the BB ladder dacs, IMO.
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Old 28th July 2012, 08:03 AM   #5
erin is offline erin  Australia
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Got a link to a good implimentation?
Any tips or tricks you care to share?

Its only the really low bass I have an issue with. PCM58 is one of my favourite DAC chips and I would like to make it sound better.
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Old 28th July 2012, 06:09 PM   #6
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Always been fond of the PCM58, myself, though the PCM1702 is my current favorite. Much, much larger than standard lytics on all the supply pins, plus films, and simple, no-feedback output stage w/passive i/v is how I like it best.
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Old 29th July 2012, 09:31 PM   #7
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Quote:
Originally Posted by skyraider View Post
After hearing fellow DIYers in this forum ranting about PCM56 (especially Bernhard), I decided to give it a try. I'm convinced that the channel switching using 74HCU04 is more than adequate, anything more that that requires a jig to hold my head in the chair.
SPDIF processing is done using twistedpearaudio's WM8805 kit, which basically takes care of jitter issues (to my standards). Looking at datasheet, the PCM56 has relatively poor power supply rejection so independant regulators at every input is a MUST. Since 8 regulators are required for for stereo, my laziness calls for the 7xx5 series.
Output current is converted using 240R resistor, and amplified with OPA627 (with RFI well taken care).


The midrange, trebles details is absolutely stunning. Can say something like TDA1541 after the DEM reclocking & stuffs..
Running without the MSB trim, it does the Sheffield disc track 40 quite well, something that even WM8740 and PCM1798 struggles with.

BUT... Would like to gather opinion from the brave souls who has tried this DAC (esp Bernhard):
Bass seems missing. Or is it that the neutrality of the DAC makes it seems missing?
Im using +/-5v. Any improvements going for higher supply voltage?
Is opamp IV a better match to this chip? Or any output stage that compliments well?

Cheers,
Colin
You could say bye bye to the opamp and use 1k for I/V instead.
I have never had the impression of missing bass.
With a scope or true rms multimeter and a test CD you could check frequency response.
Also for nonos I suggest filtering.
cs8416 + pcm56p
This can not be used with other than 200 ohms Ri/v.
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Old 16th August 2012, 05:28 AM   #8
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Been tweaking with the chip for some time now, logically speaking the bass cannot go missing. Its possible that the bass is just clean.... super duper clinically surgically clean... Takes some time to get used to.

Bernhard, I went through the passive IV but the limitation is that the DAC has to drive something down the chain.. It is too much to ask for the DAC to drive passive EQ into signal cable into a preamp volume pot... I prefer to mount a beefy driver right in my source to drive a passive preamp.

Current implementation is using OPA861 current buffer-> passive IV-> OPA627 buffer. Imaging and tone neutrality is excellent. This is truly an under-rated DAC chip.
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Old 16th August 2012, 05:31 AM   #9
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Quote:
Originally Posted by erin View Post
Got a link to a good implimentation?
Any tips or tricks you care to share?

Its only the really low bass I have an issue with. PCM58 is one of my favourite DAC chips and I would like to make it sound better.
Hi Erin,

I think the bass is there but just too clean... refer to my previous post, I might replace the OPA627 buffer with Jfet discrete buffer. This might introduce some 2nd harmonics back into the music..
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Old 16th August 2012, 06:07 AM   #10
erin is offline erin  Australia
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I totally agree that it is super clean. But..... my TDA1541 goes deeper and sounds better to my ears. But they are different PCB's etc. totally different boards and output stage. Its not a fair comparison. I will work on my PCM58 DAC when I get some time. I know it has a lot of potential. I think the output stage on mine is letting it down.
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