BoyElroy
500+ Head-Fier
- Joined
- Apr 10, 2002
- Posts
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Alright, I may be totally out of my mind, but I came across something recently that I wanted to run by my esteemed fellow DIY'ers.
I rebuilt my Gilmore PSU and tried many different approaches to taming the heat/oscillation issue with the opa548. While adding a non-inductive 10 ohm resistor in series with the output caps works, I felt that when used in the psu of my Gilmore preamp (driving my Apogee stage speakers) it veiled the sound a bit and smeared a lot of detail.
The Tweak:
As a workaround, I removed the 10 ohm resistors and placed a single .120 uf poly cap between the -V in (pin #2) and ground. I did this only for the negative leg.
The result:
The bass was tighter and seemed to go lower. The highs were especially affected, resulting in a noticeably more transparent and clearer soundstage. In general, it sounded as if a layer of muddiness had been removed.
All the heat issues disappeared as well. The opa548's and 317/337's cooled down and things got back to normal. I'm using 5 uF poly caps before the opa548's and 1 uF Hovland Musicaps as my output caps.
Question:
By coupling the -Vin pin of the opa548 (negative leg only) with ground, would anyone know how this affects the current output? When using smaller caps (.01 uf caps from Radio Shack), the oscillation actually manifests itself as an audible high-pitched whine. Larger caps (.5 uf to 1 uf) , don't really stabilize the oscillation it seems as the negative leg opa548 overheats.
So, the .1 to .120 uf caps seem to do the trick, resulting in much better sound. I'm not sure, though, whether what I'm hearing has any grounding in measured performance or whether I'm seeing and hearing Pixies, as it were.
Thanks all!
I rebuilt my Gilmore PSU and tried many different approaches to taming the heat/oscillation issue with the opa548. While adding a non-inductive 10 ohm resistor in series with the output caps works, I felt that when used in the psu of my Gilmore preamp (driving my Apogee stage speakers) it veiled the sound a bit and smeared a lot of detail.
The Tweak:
As a workaround, I removed the 10 ohm resistors and placed a single .120 uf poly cap between the -V in (pin #2) and ground. I did this only for the negative leg.
The result:
The bass was tighter and seemed to go lower. The highs were especially affected, resulting in a noticeably more transparent and clearer soundstage. In general, it sounded as if a layer of muddiness had been removed.
All the heat issues disappeared as well. The opa548's and 317/337's cooled down and things got back to normal. I'm using 5 uF poly caps before the opa548's and 1 uF Hovland Musicaps as my output caps.
Question:
By coupling the -Vin pin of the opa548 (negative leg only) with ground, would anyone know how this affects the current output? When using smaller caps (.01 uf caps from Radio Shack), the oscillation actually manifests itself as an audible high-pitched whine. Larger caps (.5 uf to 1 uf) , don't really stabilize the oscillation it seems as the negative leg opa548 overheats.
So, the .1 to .120 uf caps seem to do the trick, resulting in much better sound. I'm not sure, though, whether what I'm hearing has any grounding in measured performance or whether I'm seeing and hearing Pixies, as it were.
Thanks all!