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In Reply to: RE: Parts Changes to Improve Imaging? posted by atkinsonrr on April 16, 2018 at 13:04:21
The feedback loop C and R quality can have a significant influence
Follow Ups:
Thanks, fmak. I have a Caddock "white flag" TF series on hand. I was planning to put it in the feedback resistor position in the power amp. Do you think that will be a good choice? And was planning on using a Silmic II for the cap there.
You have to try combinations and listen. What is the value of the feedback cap? Electrolytics are not best if the value is smallish.
Hi fmak.
Yep you're absolutely correct. I hadn't even checked the value at the feedback cap yet. Turns out its only 100pF. It's listed in the parts list as only "100pF 50V SMD 0805". From searching around it seems likely its a ceramic cap.
I'm a bit torn as to whether to try replacing the caps. I've been done in before by messing with SMDs, but I do have a few 100pF (through-hole) mica caps on hand. So am tempted to try to get a couple of well-matched micas soldered onto the SMD pads to see if an improvement can be had. Would it be accurate to say that most feel mica's sound significantly better than ceramics?
Will for sure try the big Caddock resistors. When I replaced the stock input resistors in my preamp with the same TF series Caddocks, the signal appeared noticeably cleaner. So am encouraged they will prove beneficial in the feedback loop, as well.
SMD soldering - try lowering the soldering iron temperature a bit, put a bit of solder on the tip, then the tip to the SMD connection.
Thanks Fred-- Will give that a try once I decide if and what to upgrade those feedback caps to.
You can use a small polypropylene or one of the high end (Japanese) silver micas. Removing the smd cap is no problem.
You can also try one of the higher cost NPO ceramics.
Bet they'll sound great.
"The needs of the many outweigh the needs of the few or the one"
Vulcan Proverb
Already have! I ordered after you and I talked about the 1830's and I have 50 of em (in .01uf/63V) sitting right here.
Just a reminder that Brick says that the voltage can start out much higher than the 42v you are measuring. One way or another I'd like to hear your comparison. The kp-1830 does come in higher voltages that 63v as I think I mentioned. T456
"The needs of the many outweigh the needs of the few or the one"
Vulcan Proverb
Instead of putting the original film caps back in at the output of the DAC, I made a mega cap of three Vitamin Q's, one K75 and one K40Y to get equivalent uF.
The Russian K40Y PIO cap was the cap that seemed to give me the change in soundstage initially. I can report that the soundstage is back. So I am confident that it's this particular cap in this particular position that is doing the soundstage magic. Not sure I will be able to try the KP1830s in this position due to voltage, and I am too happy with the sound to mess with it!
The K75 is another Russian cap. It is polypropyline in oil. Some have reported it imparts a very full colorful midrange. One poster said it's "like biting into a fresh peach". And the midrange is now, for want of a better word, luscious. I would say overall sound quality is now best to date. I think this combo of caps is a keeper for the DAC output.
Also yesterday I removed the .01uF Vishay 1837 MKT caps I had bypassing the Mudorf Supreme and Clarity film caps in tweeter and midrange crossovers and replaced with .01uF Cornell-Dubilier 940C. Will be letting the crossovers settle in, but I think this did result in increased clarity with more "air". Not as smooth as the 1837s though, and the 940Cs could prove to be too much of a good thing. Will see how they sound in a couple days....
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