Hi Chris,
Not a hijack. Perfectly on topic as far as I can see.
The current requirements are pretty modest although I haven't measured them myself. Most of the power is probably consumed by the irritating blue LEDs on each rail. I will remove them next time I've got it apart to save my retinas.
I used a couple of little toroids from Rapid electronics. Part no. 88-2502 (9+9v 15va) for the 5v supplies and 88-2506 (15+15v 15va) for the +/- 12v supplies.
You can connect these directly to the terminals on the board.
Kevin
Not a hijack. Perfectly on topic as far as I can see.
The current requirements are pretty modest although I haven't measured them myself. Most of the power is probably consumed by the irritating blue LEDs on each rail. I will remove them next time I've got it apart to save my retinas.
I used a couple of little toroids from Rapid electronics. Part no. 88-2502 (9+9v 15va) for the 5v supplies and 88-2506 (15+15v 15va) for the +/- 12v supplies.
You can connect these directly to the terminals on the board.
Kevin
Have a schematic of a similar DAC I got a few months ago on eBay.
It may not be exactly the same as the model you guys recently purchased, but is does use the CS4397/8416 chips and 2 opamps.
Would be interested in any successful mods you come up with on bypassing the second opamp and coupling caps.
PM me with your email if any of you want a PDF of the schematic.
I can't post is as the file is too large.
Cheers.
It may not be exactly the same as the model you guys recently purchased, but is does use the CS4397/8416 chips and 2 opamps.
Would be interested in any successful mods you come up with on bypassing the second opamp and coupling caps.
PM me with your email if any of you want a PDF of the schematic.
I can't post is as the file is too large.
Cheers.
Just been looking at page 11 of the Cirrus datasheet - interesting that they appear to suggest using the NE5532 op-amp too, and in their top of the line DAC... I think I'll pop my 5532s in again and have another listen, though it sounds so good with the LM4562s I'm probably wasting my time.
Would it be worth while to replace the PSU diodes, and if so what would be an 'ideal' replacement?
- J
P.s. I too have the datasheet, but wasn't sure about the legalities of posting it here as its for a current product?
Would it be worth while to replace the PSU diodes, and if so what would be an 'ideal' replacement?
- J
P.s. I too have the datasheet, but wasn't sure about the legalities of posting it here as its for a current product?
I have just found This rather useful application note (referred to by the CS4398 eval board application note) which details the design of low pass filters with differential input.
The filter stage posted on lampizator.eu didn't look right to me and has just occurred to me that the reason there is a DC offset at the output of the first Op-Amp stage after removal of the coupling capacitors is that the value of R14 is incorrect. To achieve common mode rejection down to DC it needs to be the same value as R8 (36K). The 14.7K resistor is then no longer required.
Looking at the application note they have made input impedance of the filter stage much lower (close to the 1K minimum AC load resistance specified for the CS4398) so maybe there is a noise advantage to be gained by recalculating all the component values around the filter stage accordingly. It would probably also depend on the final choice of Op Amp, its' bias current and output drive characteristics, of course.
Kevin
The filter stage posted on lampizator.eu didn't look right to me and has just occurred to me that the reason there is a DC offset at the output of the first Op-Amp stage after removal of the coupling capacitors is that the value of R14 is incorrect. To achieve common mode rejection down to DC it needs to be the same value as R8 (36K). The 14.7K resistor is then no longer required.
Looking at the application note they have made input impedance of the filter stage much lower (close to the 1K minimum AC load resistance specified for the CS4398) so maybe there is a noise advantage to be gained by recalculating all the component values around the filter stage accordingly. It would probably also depend on the final choice of Op Amp, its' bias current and output drive characteristics, of course.
Kevin
Yep. (You'd also need to change R14's counterpart in the other channel, of course). You would also lose the output muting, unless you left the relay contacts in the output path. I would leave a low value resistor in series with each output in case you get stability issues or the output is accidentally shorted.
The fact that the eval board uses a 5532 may or may not be significant. It could have been done to show the quality achieveable with very low cost output parts. I note they use LTC1128s in the balanced output stage. I can't believe it would sound worse with a LM4562.
Kevin
Thanks for that Kevin - I think I'll try this route then.
Is output muting really necessary? I have been using an Audiosector/Peter Daniel NOS DAC for some time and that doesn't use one, and - to date - no problems yet using a PC as a source, or a CD player. Unless the TDA1543 has muting built into it of course?
Is output muting really necessary? I have been using an Audiosector/Peter Daniel NOS DAC for some time and that doesn't use one, and - to date - no problems yet using a PC as a source, or a CD player. Unless the TDA1543 has muting built into it of course?
OK, so for those wishing to implement the 'Op-Amp' mod - using an LM4562, these are the steps involved (please jump in anyone if there's any obvious mistakes!) :
1) Remove both NE5532s. Insert one (only) LM4562 in the first op-amp socket - the one nearest the center of the board.
2) Remove the following 4 capacitors: L+ / L- / R+ / R-. Replace with wire links.
3) Replace R14, and R17 (both 22k) with 36k.
4) Run a wire directly from the output pins (1 and 7) of the LM4562s to the phono sockets (via the output rely if you prefer this added safety measure).
- John
1) Remove both NE5532s. Insert one (only) LM4562 in the first op-amp socket - the one nearest the center of the board.
2) Remove the following 4 capacitors: L+ / L- / R+ / R-. Replace with wire links.
3) Replace R14, and R17 (both 22k) with 36k.
4) Run a wire directly from the output pins (1 and 7) of the LM4562s to the phono sockets (via the output rely if you prefer this added safety measure).
- John
These DACs don't do any HDCD decoding themselves. They will accept data with up to 24 bits resolution but it would require the player or an external decoder to decode the 16 bit output of the HDCD and generate the extra bits. That's as far as I understand it anyway. I don't know a great deal about HDCD, to be honest.
Kevin
Kevin
johnm,
Opamps; LM4562 sound much better than the NE5532's; faster with more top end.
You should give the OPA2107's a try. IMO, not as digital sounding as the LM4562's, kinda of tube like qualities; but this is subjective, so please don't bash me on this...
Just got some LME49860's which I plan to break in on my small DAC project board and compare to the OPS2107's.
Cheers
Opamps; LM4562 sound much better than the NE5532's; faster with more top end.
You should give the OPA2107's a try. IMO, not as digital sounding as the LM4562's, kinda of tube like qualities; but this is subjective, so please don't bash me on this...
Just got some LME49860's which I plan to break in on my small DAC project board and compare to the OPS2107's.
Cheers
I'm looking at one of these boards as well. I was planning on removing the caps and tapping the signal at that point. I'm looking at building a small "daughter board" with all the analog side components. I'm looking at using a INA134 as a balanced to unbalanced converter followed by a LM4562 used as a lowpass sallen-key filter. Does anyone see any problems with this arrangement? Is there going to be a DC offset to worry about, and if so, how much?
gabrielbecheanu said:
You won't be able to compare using that DAC, unless you will compare the analog output from your player.
The digital output will not output the 20bit PCM when you play HDCD CD's (that's the equivalent resolution of an HDCD disc). My DVD player has an option to send out PCM (16bit) or bitstream HDCD to be decoded by the receiver.
PS: As software player, any new Windows Media Player can decode HDCD if you have a 24 bit soundcard (MS owns the HDCD from 2002).
Couldn't resist the urge to have a play tonight:
Step 3 was not required on my board. The 36K resistors have been replaced with 22k so the imbalance that was causing the DC offset is gone.
There is another set of caps between the output of the first op-amp and the input to the second, which is configured as a non-inverting amplifier with a little gain (very little) then there are some more caps down by the phono sockets!
I will draw the circuit in all its' glory when I get a chance but the second Op Amp stage is not worth bothering with, as suspected. You can tap the output from the cap position between the two stages (already a 1k resistor in series with the output here) and bypass all those caps and the mute relay.
Haven't listened to it on anything but my less then great setup in the workshop but it works, minus 8 electrolytic caps from the signal path. There are a few clicks and bangs thanks to removal of the mute circuit. It seems sometimes the DAC ends up outputting a nonzero level when you pause a track, for example, and there's a click when you restart. There's some odd noise on the output if you remove the digital input too, so maybe some kind of mute circuit is a good idea.
Still, looks promising so far.
To Fenris: What you propose sounds like it would work fine. I'm not sure how much you'd gain over the existing first OpAmp stage which doesn't seem too bad as a combined filter and balanced to unbalanced conversion. Only one way to find out. I doubt you'll see any DC offset worth worrying about. After removing the 4 caps on the DAC outputs I saw perhaps a couple of mV of DC on the output of the first stage.
Kevin
Step 3 was not required on my board. The 36K resistors have been replaced with 22k so the imbalance that was causing the DC offset is gone.
There is another set of caps between the output of the first op-amp and the input to the second, which is configured as a non-inverting amplifier with a little gain (very little) then there are some more caps down by the phono sockets!
I will draw the circuit in all its' glory when I get a chance but the second Op Amp stage is not worth bothering with, as suspected. You can tap the output from the cap position between the two stages (already a 1k resistor in series with the output here) and bypass all those caps and the mute relay.
Haven't listened to it on anything but my less then great setup in the workshop but it works, minus 8 electrolytic caps from the signal path. There are a few clicks and bangs thanks to removal of the mute circuit. It seems sometimes the DAC ends up outputting a nonzero level when you pause a track, for example, and there's a click when you restart. There's some odd noise on the output if you remove the digital input too, so maybe some kind of mute circuit is a good idea.
Still, looks promising so far.
To Fenris: What you propose sounds like it would work fine. I'm not sure how much you'd gain over the existing first OpAmp stage which doesn't seem too bad as a combined filter and balanced to unbalanced conversion. Only one way to find out. I doubt you'll see any DC offset worth worrying about. After removing the 4 caps on the DAC outputs I saw perhaps a couple of mV of DC on the output of the first stage.
Kevin