My pcm2704 + AD1955 DAC has three OP275s at the output, and as I am planning some upgrades to it, I wonder which ICs to try on the sockets.
OPA627 are my first choice and already ordered them from eBay. Let's hope they are not fakes.
Another option would be the LM4562. Same thing with the seller. As I can not buy from Mouser or Digikey, eBay has to be my source. Any serious reliable vendor there?
What other alternatives to try for the ICs?
OPA627 are my first choice and already ordered them from eBay. Let's hope they are not fakes.
Another option would be the LM4562. Same thing with the seller. As I can not buy from Mouser or Digikey, eBay has to be my source. Any serious reliable vendor there?
What other alternatives to try for the ICs?
What needs to be improved, or what are you looking for? Anything you aren't happy with the actual configuration?
The sound is not as involving as I know it can be.
Particularly now that I am playing higher resolution files, straight from my computer by network.
Particularly now that I am playing higher resolution files, straight from my computer by network.
I have had great luck with eBay opa627s, just have to go to the better vendors.
They really need a quality film cap across the power pins also, .01 - .1 uf.
They really need a quality film cap across the power pins also, .01 - .1 uf.
Before rolling opamps, spend some time optimizing the power supply cleanliness. All opamps benefit from this.
Then swap out your OP275s next to the AD1955 with LM6172s and replace the feedback capacitors with 4.7pF.
Then swap out your OP275s next to the AD1955 with LM6172s and replace the feedback capacitors with 4.7pF.
Try Farnell element14 UK - Electronic Components Distributor
Or RS Components | Electronic and Electrical Components
They both ship worldwide.
Hi,
the OPA275 is not the best OPAmp in any way, but replacing it with another OPAmp doesn´t improve matters much imho.
A simple discrete I/V converter plus decent Buffers sound much better to my ears.
jauu
Calvin
the OPA275 is not the best OPAmp in any way, but replacing it with another OPAmp doesn´t improve matters much imho.
A simple discrete I/V converter plus decent Buffers sound much better to my ears.
jauu
Calvin
NO!!
Unless you patd some serious $$$ (>$20 EACH), those OPA627s are almost GUARANTEED to be fakes!!
Fortunately I have some 627s that I got as samples directly from BB a long time ago, when manufacturers still supplied samples for free.
Pity at the time I asked for several more 637s, instead of 627s, and the 37s need a minimum gain of 5, which is not the case on this output.
As this DAC has an unbalancing trio, there is no gain.
I am not sure about the LM6172, which I would love to use too, and I also have a few. The 6172, and other similar National video buffers, seemed to do marvels on Philips DACs. But I don't remember what you had to add if you used them so as not to oscillate. I did try them on a Sony CD player I modified, and the sound was marvelous.
Pity at the time I asked for several more 637s, instead of 627s, and the 37s need a minimum gain of 5, which is not the case on this output.
As this DAC has an unbalancing trio, there is no gain.
I am not sure about the LM6172, which I would love to use too, and I also have a few. The 6172, and other similar National video buffers, seemed to do marvels on Philips DACs. But I don't remember what you had to add if you used them so as not to oscillate. I did try them on a Sony CD player I modified, and the sound was marvelous.
Believe it or not, different economies have varying scales of value, so the US dollar value isn't always the first indicator of a legitimate component.
There is a simple ohms test that can be performed on the opa627, can search for that.
For the price I had paid, it didn't seem worth trying too many other sand-based op amps.
All my stuff has burson discretes now, and I will try the eBay discrete op amps next if/when I need any that is.
There is a simple ohms test that can be performed on the opa627, can search for that.
For the price I had paid, it didn't seem worth trying too many other sand-based op amps.
All my stuff has burson discretes now, and I will try the eBay discrete op amps next if/when I need any that is.
For the supplies, I should trying properly arranged 317/337 first. And then Jung regulators.
About the LM6172, which capacitor you suggest to replace? C40-41 and C42-C43 for 4.7pF? Isn't that a bit too different?
Which discrete opamp?
Sorry, which test is that to test if 627 is fake or not?
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I see no schematic here so I'm at a loss to know what the relevant caps are called on your board.
The ones you need to change for best performance with the LM6172 (I have done this mod myself on an AD1955 DAC) are the ones between pins 1,2 and between 7,6 of the IC.
Changing the caps doesn't change the frequency response, just improves the perceived depth. Slower opamps need bigger caps as their slew rate is a limitation, the LM6172 barely has a slew rate limitation.
What happens if I leave those caps values? BW will shrink and the chip will sound bad?
I would like to try them on another DAC I'm using now.
I would like to try them on another DAC I'm using now.
Calvin,
thank you for reply
would you please give us an example of simple discrete I/V and buffer
Even more if you consider the DAC output is differential, so we would need a differential discrete buffer, which is tricky if you do not have 0.1% parts.
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