I have a Sony X7ESD CDP which uses a pair of Burr Brown PCM58 DACs and has the facility to adjust the DAC for maximum linearity by means of tweaking four small trimmer potentiometers.
The method is to play a CD with a recorded 0dB 1KHz sine wave and observe/measure the distortion of the analogue output. You then adjust the MSB for minimum distortion before moving onto the next less significant bit and so on.
I'm trying to find out what equipment I need to be able to do this adjustment and I understand that I need a spectrum analyser of some sort. A 'proper' benchtop spectrum analyser is a very expensive bit of equipment but I have seen small USB devices for under £100 which may be enough for my purposes.
Something like this one:
http://www.velleman.co.uk/contents/en-uk/p972_Velleman_PCSU01_Mini_PC_USB_Oscilloscope.html
I don't suppose it helps but I already have an Tektronix analogue oscilloscope.
Any advice will be much appreciated.
The method is to play a CD with a recorded 0dB 1KHz sine wave and observe/measure the distortion of the analogue output. You then adjust the MSB for minimum distortion before moving onto the next less significant bit and so on.
I'm trying to find out what equipment I need to be able to do this adjustment and I understand that I need a spectrum analyser of some sort. A 'proper' benchtop spectrum analyser is a very expensive bit of equipment but I have seen small USB devices for under £100 which may be enough for my purposes.
Something like this one:
http://www.velleman.co.uk/contents/en-uk/p972_Velleman_PCSU01_Mini_PC_USB_Oscilloscope.html
I don't suppose it helps but I already have an Tektronix analogue oscilloscope.
Any advice will be much appreciated.
Hello Mike, you can use a sound card and an FFT analyzer on a PC. There are some free FFT software around, almost any could do.
As lcsaszar has mentioned, all you need is a sound card and software. An oscilloscope is not required.
Sound cards such as the Behringer UCA202 or the more expensive Focusrite Scarlett 2i2 have been used by diyers in conjunction with software such as Arta or RMAA to do FFT spectrum analysis to measure distortion. A low level sine wave, usually 1kHz at -60dB, (not full strength 0dB) is used.
If your cd player has the trimmers already installed, perhaps it was already trimmed at the factory for lowest distortion?
Sound cards such as the Behringer UCA202 or the more expensive Focusrite Scarlett 2i2 have been used by diyers in conjunction with software such as Arta or RMAA to do FFT spectrum analysis to measure distortion. A low level sine wave, usually 1kHz at -60dB, (not full strength 0dB) is used.
If your cd player has the trimmers already installed, perhaps it was already trimmed at the factory for lowest distortion?
Thank you both for your replies, very helpful and much appreciate!
The player already has the trimmers installed but it is 30 years old now so I thought readjustment might be necessary by now.
I too think that 1kHz at -60dB should be correct (that's what other people have used from what I've read) but the Sony service manual for this player clearly states 1kHz at 0dB.
Do you happen to have a link to somewhere I can download a -60dB 1kHz sinewave file?
The player already has the trimmers installed but it is 30 years old now so I thought readjustment might be necessary by now.
I too think that 1kHz at -60dB should be correct (that's what other people have used from what I've read) but the Sony service manual for this player clearly states 1kHz at 0dB.
Do you happen to have a link to somewhere I can download a -60dB 1kHz sinewave file?
Room EQ Wizard (REW) program, which also does spectrum analysis, has a generator that can generate -60dB sine waves that can be saved.
This website can also generate sine waves at -60dB:
Custom Sine Tones | Audio Test File Generator
I have a diy AD1865 dac that I MSB trimmed and it made a big difference in sound. So it is worth the effort to check.
This website can also generate sine waves at -60dB:
Custom Sine Tones | Audio Test File Generator
I have a diy AD1865 dac that I MSB trimmed and it made a big difference in sound. So it is worth the effort to check.
Thanks folks, I've just purchased a Focusrite Scarlet 2i2 audio interface and I've downloaded Arta software.
I'll let you know how I get on with it all.
I'll let you know how I get on with it all.
Another old thread…
But, in another thread (link below) I was wondering if anyone knew of a converter using all four trim pots per chip. It seems Sony did! Was this an ES only thing, and perhaps the difference between that, and their standard components? (I know they did many other upgrades as well)
Can you (or did you) verify the circuit used? I’m reasonably certain it is a resistor from the chip pin to the trim pot to ground. But wanted to be sure.
And we’re you able to trim it up better in your case, and if so, was it an audible difference?
Burr Brown PCM58P Upgrade?
But, in another thread (link below) I was wondering if anyone knew of a converter using all four trim pots per chip. It seems Sony did! Was this an ES only thing, and perhaps the difference between that, and their standard components? (I know they did many other upgrades as well)
Can you (or did you) verify the circuit used? I’m reasonably certain it is a resistor from the chip pin to the trim pot to ground. But wanted to be sure.
And we’re you able to trim it up better in your case, and if so, was it an audible difference?
Burr Brown PCM58P Upgrade?
Hi Jim,
The Sony CDP-557ESD uses the 2x PCM64 and has four trimmers per DAC chip. The Sony CDP-X7ESD has the same but with 2x PCM58.
On Sony players you only seem to get the adjustment facility on the very top end models. Even nice models such as the CDP-338ESD do not have the adjustment facility.
I've found the way that works best for me is to play a -90dB 1KHz test tone from a CDR. I then use a set of headphones to adjust the trimmers for lowest noise (strictly in the sequence dictated in the service manual).
I've found it can make quite a significant improvement.
The Sony CDP-557ESD uses the 2x PCM64 and has four trimmers per DAC chip. The Sony CDP-X7ESD has the same but with 2x PCM58.
On Sony players you only seem to get the adjustment facility on the very top end models. Even nice models such as the CDP-338ESD do not have the adjustment facility.
I've found the way that works best for me is to play a -90dB 1KHz test tone from a CDR. I then use a set of headphones to adjust the trimmers for lowest noise (strictly in the sequence dictated in the service manual).
I've found it can make quite a significant improvement.
I figured it would be an improvement, or the facility wouldn’t be there.
I don’t think I could do the adjustments “ by ear” but very good to hear that I’m on the right track with the idea.
I don’t think I could do the adjustments “ by ear” but very good to hear that I’m on the right track with the idea.
Hi Jim,
I think you've got the wrong impression about doing this adjustment 'by ear'. You aren't listening to music and trying to discern a tiny difference in SQ. What you'll hear is a tone which will reduce in volume as you get towards the optimum adjustment and then the tone will change slightly and increase in volume as you go past the optimum point. It's very very obvious and not at all tricky. Try it.
I do it with a -90dB 1KHz tone and a cheapo set of earbuds.
I think you've got the wrong impression about doing this adjustment 'by ear'. You aren't listening to music and trying to discern a tiny difference in SQ. What you'll hear is a tone which will reduce in volume as you get towards the optimum adjustment and then the tone will change slightly and increase in volume as you go past the optimum point. It's very very obvious and not at all tricky. Try it.
I do it with a -90dB 1KHz tone and a cheapo set of earbuds.
That is encouraging.
Right now, I'm trying to work out a daughter board so I can access and trim all four bits.
The original board is such crap, I'm hoping some sort of piggy-back thing can be used under the chip to access the additional pins. I have no idea however, and may be hacking into the board...
Right now, I'm trying to work out a daughter board so I can access and trim all four bits.
The original board is such crap, I'm hoping some sort of piggy-back thing can be used under the chip to access the additional pins. I have no idea however, and may be hacking into the board...
Another method, but it needs some instrumentation:
DAC linearity test CD
Here are the tracks:
DAC linearity test CD
DAC linearity test CD
DAC linearity test CD
Here are the tracks:
DAC linearity test CD
DAC linearity test CD
Thank you for those files!
I have downloaded the .ZIP files and will see about burning a CD shortly. If I didn't bring them all home...
I have a scope here at work as well. It might even work!
Regarding the output signal amplification- do you think it's at all wise to use the analogue output for the scope input, or should I be pulling something right off the chip?
I don't normally do anything like this, so I need some hand-holding...
I have downloaded the .ZIP files and will see about burning a CD shortly. If I didn't bring them all home...
I have a scope here at work as well. It might even work!
Regarding the output signal amplification- do you think it's at all wise to use the analogue output for the scope input, or should I be pulling something right off the chip?
I don't normally do anything like this, so I need some hand-holding...
The analog voltage between two digital steps is so small that you need some amplification before the scope input. It is -96dB referred to full scale. Even then the waveform on the screen will be rather noisy.
I don’t think there is a better drop-in chip. I think this is the last of the mono chips; after this they are all stereo.
PCM63, PCM1702 and PCM1704 all came after the PCM58 and all of them are mono. Still, PCM58 is available and cheap, which makes it attractive.
That’s certainly interesting. Are they pin-for-pin drop in replacements? They would still need the first bit re-adjusted for each chip so it doesn’t eliminate that adjustment but it sounds interesting.