Hello,
I want to add a buffer to my passive preamp, so that it can drive almost any power amp. I have found a design that uses the OPA627 on this page , and would like to build it. For the power supply, I came up with the attached design. Because I've never build a preamp PSU before, any comments are welcome.
I haven't figured out the values for the resistors yet. The 4u7 caps are tantalum (I have a bunch of those). Also, I would probably add one last small elcap and some small MKT's near the opamp. All diodes are 1N4001s.
I want to add a buffer to my passive preamp, so that it can drive almost any power amp. I have found a design that uses the OPA627 on this page , and would like to build it. For the power supply, I came up with the attached design. Because I've never build a preamp PSU before, any comments are welcome.
I haven't figured out the values for the resistors yet. The 4u7 caps are tantalum (I have a bunch of those). Also, I would probably add one last small elcap and some small MKT's near the opamp. All diodes are 1N4001s.
Attachments
Hello starbase218,
Check this article. It contains PSU schematic: http://www.stereophile.com/solidpreamps/54/index1.html
Another one:
http://headwize.com/projects/showfile.php?file=pawliw1_prj.htm
Similar idea like yours. You can tune those PSUs to your need.
Check this article. It contains PSU schematic: http://www.stereophile.com/solidpreamps/54/index1.html
Another one:
http://headwize.com/projects/showfile.php?file=pawliw1_prj.htm
Similar idea like yours. You can tune those PSUs to your need.
The second article mentions that all the PSU electronics are for one channel only. For stereo, everything after the transformer is doubled. Isn't this overkill?
The reason I'm asking is that I would like to build the entire PSU in one enclosure, and the source select/volume/buffer electronics in another, so that both channels would be fed off the same PSU.
The reason I'm asking is that I would like to build the entire PSU in one enclosure, and the source select/volume/buffer electronics in another, so that both channels would be fed off the same PSU.
You might want to read this if you're going to use lm317 : http://www.acoustica.org.uk/t/3pin_reg_notes1.html
Thanks for the link. I've updated the design to incorporate some of the changes. I think it's starting to look a bit like Rod's project 5B 🙂.
I've also come across some topics mentioning opinions on the OPA627 and other opamps, and their specific "sound". What I liked about the passive preamp was that it didn't have a sound of its own, and I would very much like to preserve as much of that quality as possible, while going active. But I am a bit unsure which opamp to use. Some described the OPA627 as sounding "dark".
I've also come across some topics mentioning opinions on the OPA627 and other opamps, and their specific "sound". What I liked about the passive preamp was that it didn't have a sound of its own, and I would very much like to preserve as much of that quality as possible, while going active. But I am a bit unsure which opamp to use. Some described the OPA627 as sounding "dark".
Attachments
Hi,
opamps tend to perform better with very low noise power supplies.
This is particularly valid for pre-amps which have to work with low level signals.
You could look at discrete Vregs for the 627. Maybe even a CCS with shunt regulator. GK is running a thread on this now.
opamps tend to perform better with very low noise power supplies.
This is particularly valid for pre-amps which have to work with low level signals.
You could look at discrete Vregs for the 627. Maybe even a CCS with shunt regulator. GK is running a thread on this now.
AndrewT said:
Ok, but how much is "enough"? Aren't regulators like LM317s widely used in preamps, even more expensive ones? Btw, who is GK? 🙂
Regarding opamps, I have read good things about the OPA2134. It's also less expensive than the OPA627, so I think I'm ging with OPA2134.
Hi,
http://www.diyaudio.com/forums/showthread.php?postid=1359176#post1359176
It was buried in power supplies, sorry for misinformation.
http://www.diyaudio.com/forums/showthread.php?postid=1359176#post1359176
It was buried in power supplies, sorry for misinformation.
The 317/337 pairs should be just fine. These regulators are underestimated, especially when the adjust pin is bypassed with an appropriate capacitor.
Personally, I think it's only worth going for a very low noise supply (the Jung regulator and such) when you are dealing with very small signals, eg the output of a DAC, or a phono preamp.
Personally, I think it's only worth going for a very low noise supply (the Jung regulator and such) when you are dealing with very small signals, eg the output of a DAC, or a phono preamp.
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