Is it possible to replace a WM8740 by the new WM8742 in a 740C Cambridge Audio CD player? WM8742 is 16-32bits 192khz and the wm8740 is 16-24 192khz capable.
I've been looking at the data sheets. I think (but not positive) that it depends on if the the DAC is being controlled by software or hardware. Doesn't look like it.
For instance in hardware control mode, pins 27 and 26 tells the 8740 what sample rate the audio data is in, whereas pin 27 tells the 8742 what format (PCM or DSD) the audio data is in.
Moreover there are even bigger differences in software control mode.
For instance in hardware control mode, pins 27 and 26 tells the 8740 what sample rate the audio data is in, whereas pin 27 tells the 8742 what format (PCM or DSD) the audio data is in.
Moreover there are even bigger differences in software control mode.
Hmmm... makes me wonder what Wolfson mean when they claim it is pin-compatible with the WM8740 and WM8741?
Wolfson Microelectronics plc: WM8742
May wish to read this:
Rega Apollo DAC change to WM8742 - pink fish media
And follow the link to the Wolfson presentation.
Rega Apollo DAC change to WM8742 - pink fish media
And follow the link to the Wolfson presentation.
They should be able to tell you. The Wolfson presentation held the quote that the WM8742 was "totally pin compatible with the WM8741". I infer that to mean backwards compatible.
I don't see anything in the datasheets to suggest there is no compatibility dropiing in the WM742, you just will *NOT likely* get DSD operation from it because you probably don't have a DSD clock in the player.
Let us know what Wolfson and in particular Cambridge Audio say, as I think what benefit (if any) you get is based more on how Cambridge Audio have engineered the player.
Cambridge audio answer to replacing WM8740 by Wm8742 on 740C CD Player :
" The 740C is designed and made with the WM8740. Our products are not user serviceable, and are not designed to be modified. It is not possible to simply replace a DAC with a newer one, as they will have different circuitry and components and may not be compatible. "
" The 740C is designed and made with the WM8740. Our products are not user serviceable, and are not designed to be modified. It is not possible to simply replace a DAC with a newer one, as they will have different circuitry and components and may not be compatible. "
That sounds like a stock "don't mess with our player" remark. The last part "may not be compatible" means they won't tell you if it is or isn't!! I thought Cambridge Audio were better than that as they seem to have helped people modify the 640P phono stage on another forum.
Wolfson answer :
Unfortunately, there are differences between the functionality of the WM8740 and the WM8742 and there are not completely pin compatible. Also, we do not have information relating to how Cambridge Audio are using the WM8740 within the CD player. Therefore we cannot be recommended replacing the WM8740 with the WM8742.
Unfortunately, there are differences between the functionality of the WM8740 and the WM8742 and there are not completely pin compatible. Also, we do not have information relating to how Cambridge Audio are using the WM8740 within the CD player. Therefore we cannot be recommended replacing the WM8740 with the WM8742.
Hmmm.... I find it hard for them to say they are "not completely pin-compatible" when they use the words "totally pin-compatible" in that presentation of theirs. Also the guy of at PFM managed to change his WM8740 to the WM8741 with just a slight power supply adjustment. I would have thought this was a better option for you anyway as you wouldn't gain anything from the WM8742 and the Cambridge is using Anagram Tech's filtering technology as far as I know, so you have no need of on-chip digital filtering.
It looked to me that pin 27 in hardware mode is held low to signify PCM data, and it detects clock frequency in software mode and automatically switches to bitsream if it 'sees' a DSD frequency clock. Other than that, I didn't see any difference between the WM8742 and WM8741 - and we already know the WM8741 can go in to the Cambridge Audio 640C Mk2.
Perhaps FatMarley at PFM has some info you do not and has had better help from Wolfson - sometimes it depends who answers the support call. It may be worth going on to PFM and sending him a PM about it.
it also depends if they are doing software or hardware control of the 8740. IIRC, the registers arent't same between 8741 and 8742 ...
I contacted Profusion PLC in the UK - an authorised reseller of Wolfson chips and asked about software compatibility.
We know the Pink Fish Media forum guy 'FatMarley' replaced his WM8740 chips in his Cambridge Audio 640C and this only required changing power supply regulation a little.
With regards to software control mode differences, a Profusion PLC respindent to their enquiry service said "Software would be compatible between WM8741 and WM8742, but not with the WM8740."
Given the WM8741 was put in the 640C without issue, it may go in the 740C, but then again, we don't know exactly what is different.
If the chips are run in hardware control mode, then a straight swap should be possible, although you will not gain any DSD functionality by doing so. In fact, I would wonder why use the WM8742 at all...use the WM8741 as it performs better.
The real question is about software mode. It depends how critical this player is... if it was mine and I had a separate player or DAC, I would take the chance and carefully replace the two DAC chips and then run through all PCM sampling rates the unit was designed to support to see if it still functioned correctly. If it didn't, I would drop in the WM8740's again. The problem is the tricky soldering may require you to have some new WM8740 on hand. However, this is what I personally would do and not a recommendation.
We know the Pink Fish Media forum guy 'FatMarley' replaced his WM8740 chips in his Cambridge Audio 640C and this only required changing power supply regulation a little.
With regards to software control mode differences, a Profusion PLC respindent to their enquiry service said "Software would be compatible between WM8741 and WM8742, but not with the WM8740."
Given the WM8741 was put in the 640C without issue, it may go in the 740C, but then again, we don't know exactly what is different.
If the chips are run in hardware control mode, then a straight swap should be possible, although you will not gain any DSD functionality by doing so. In fact, I would wonder why use the WM8742 at all...use the WM8741 as it performs better.
The real question is about software mode. It depends how critical this player is... if it was mine and I had a separate player or DAC, I would take the chance and carefully replace the two DAC chips and then run through all PCM sampling rates the unit was designed to support to see if it still functioned correctly. If it didn't, I would drop in the WM8740's again. The problem is the tricky soldering may require you to have some new WM8740 on hand. However, this is what I personally would do and not a recommendation.
Hi:
I mention I am a Wm8740~WM8742 diy D/A fans.
My D/A structure is H/W setup CS8416 and WM8741 working and no DSD function.
So Not support DSD (WM8741,wm8742 only)play and let PC feed SPDIF signal to D/A and play music.
I am diy WM8740 D/A first then direct change into WM8741 (just IC to IC) and circuit change nothing..
Btw WM8741 have beter codec IP design than WM8740.
WM8740 Low-freq. responce got a little humming and rough(my wife tell me her feeling ).
Wife tell me just check michael jackson's ...bit it check woofer sound.......ooxx your... so I got change because this D/A is working in my wife coffee shop.
Maybe That's reason why Linn streamin choice WM8741 already.
WM8741 have better sound filed of the deep carved.
There are also have WM8742 on market too. still pin to pin and IC to IC.
For your reference WM8741 > WM8742 > WM8740 ........(base sound color.. because codec IP is different my personal opinion).
ASter
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