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A while ago I asked about the benefits of bypassing power supply electrolytics with film caps in a power amp. Well, I did it (Solen MKPs at about 5-10% of the values of the electrolytic caps--that's about the most I had room for) and indeed found it very effective at improving the sound quality.
Now I am wondering how beneficial this would be in my preamp. It is a Wright Sound WPL11, phono plus a very simple linestage, CRCRC PS in a separate chassis with umbilical. There is a reasonable amount of space for bypass caps in the PS, but not enough to completely replace the existing 'lytics.
I am wondering if the potential benefit is as great as in a power amp, or a lot less. I also wonder if it is worth looking in the signal chassis to see if there is a B+ decoupling filter between the stages, to add a Fastcap there too. I do not plan to do anything to the coupling and RIAA caps.
Follow Ups:
Hi JJ, I also have replaced the power supply electrolytics in several of my preamp rebuilds with film caps with excellent results. I used Solens 25uf to 30ufx400vdc which is more that adequate for any mini tube and most octal preamp tubes. The price of the Solens is almost competive with electrolytics but the performance is many times better. If you can find a way to use film caps in the power supply you will not be disappointed. good luck dak.
Hi Dak,
I measured the voltage at the main filter caps in this preamp power supply, and it is about 430VDC so the 400V Solens probably wouldn't be good to use. There are 630V Solens but I need three 22 µF caps and they wouldn't quite fit in the available space. I may be able to fit 3 x 18 µF 630V or a combination of smaller sizes in parallel pairs e.g. 6 x 10 µF. Any suggestions on the best way to go, assuming I still want to totally replace the electrolytics?
Thanks,
JJ
IF you have room topside, the mundorf tube cap is a good choice, but is more expensive. But, if the voltage is right at 400 vdc, it may be ok to use the 400 volt Solen. Film caps do not fail catastrophically like electrolytics since they are "self healing". Or, you can use the origingal electrolytic as the primary filter cap then run the B+ thru a dropping resistor or thru a filter reactor would be even better then to your film cap B+ supply. I did that with an Audio Electronic Supply AE-1 preamp and the results were outstanding. In that preamp there are 4 6sn7 tubes, and i used 4 Solen 400v 27uf caps, one per tube for the B+ supply. If you use a dropping resistor make sure its a non inductive type like Kiwame or carbon composition. My 6sn7 preamp was on the shelf for years as my 6dj8 type preamps were all more revealing. Then i did the power supply changes and upgraded the caps and resistors in the 6sn7 preamp and now it is the best sounding preamp in my lineup. good luck, Dak
When you bypass electrolytics with 10% of the value,its very beneficial because the film caps are ultra low esr and they are probably doing 90% of the filtering and energy delivery at most levels.The time the electrolytics may kick in is at high transient demands.
In a preamp however,I would use film caps everywhere I could in place of electrolytics as opposed to just bypassing them.I am running six 35uf@500v cde film caps in my mac c20 preamp and the sound purification and character is one of the purest I have ever heard.You can still use electrolytics like on the DC filaments but I would disconnect the high voltage electrolytics in the preamp because you don't need tons uf when you use film caps in a preamp being there is not the current demand in a preamp like there is in an amp.You can bypass electrolytics but I think its foolish because the film caps are so much better and if you need tons of storage,just use the film caps with electrolytics.
Diversity of opinions on any one technical subject,almost always causes confusion for the listener.
Edits: 04/19/11 04/20/11
are very space efficient caps, perfect for power supply use. I like the sound quality. Doesn't have the metalized Solen thinness or edge, faster than the typical HID/motor run cap.
As for power amps, depends where you're using them in the power supply. Input stages, yes, screen supplies, yes. SE output stage, yes. Push-pull output stages or phase inverters, doesn't seem to have much effect. As always YMMV
Stuart
WHOA! Don't touch that!
Stuart
The mundorfs are great.I put a couple of the flat packs in my Eico hf81.The solens need lots of break in time and they get better but,I notice the can solens are a much better cap and it may be because of the winding technique.
Diversity of opinions on any one technical subject,almost always causes confusion for the listener.
Mike,
You bring up a good point. Sadly, the manufacturer, in this case, Solen, gets a reputation based on the popular product. Solen has the line of cheap metalized caps that lots of us have used. Never mind that they are very cheap and that's why we bought them, the bottom line is that all Solen caps are unfairly tainted by this bias.
VH Audio comes at it from the other end of the spectrum. Their TFTF caps are some of the finest made, so all VH caps, deserving or not, benefit from this reputation.
The big picture then, is that if you start out making cheap stuff, it's much more difficult to earn the trust and respect of a client looking for a better product. He's likely to look elsewhere. OTOH, if you start out making the best, even your lesser products have a very good chance at acceptance in the marketplace.
I must confess guilt here. When looking for a good cap, I'm inclined to look away from Solen. I bought some Russian caps based on the K40Y9 reputation. What a mistake that was. I did find that the Wima FKP (film and foil) caps are much better than their most popular MKP metalized caps, but sadly are not made in large sizes that I could find.
Have you tried the big Obbligatos?
Stuart
WHOA! Don't touch that!
Stuart
I like the obligatos.. You didn't like the k40s? My gawd thats the most popular cap on the forum and when used in the mix can produce fantastic results.Of course,there are a couple k40 values I don't like such as the .15 and the .022@1kv..The rest I have had great luck with..Solens I never use in the audio path unless its the white film and foil ones.I use a lot of sonic caps and some soniccap plats because they sound like a paper in oil with a twist of teflon. I really like vit Qs but I only use them in amps.
Diversity of opinions on any one technical subject,almost always causes confusion for the listener.
Mike, I gotta luv ya, but wouldn't it be more fair to say that KY40s are the most popular cap at your house?
Lew
Just a technicality but I really do believe its the most single used cap on the forum amongst vintage equipment upgrades and even Diyers..The price performance of those caps is incredible. I just don't think many DIyers cotton to paying 30 to 60 dollars plus,for a jensen or V cap when you have a cheap alternative.I don't use them exclusively but I use them whenever it makes a nice difference.
Diversity of opinions on any one technical subject,almost always causes confusion for the listener.
I've had several failures of Jensens and so would not use one if you gave it to me. I am shy of all oil caps based on that experience and the similar experience with the very expensive VTV silver/oil caps, which are fortunately no longer available. In one amplifier, 3 out of 4 failed and leaked goo all over nearby components. Yet I am willing to give KY40s a try, maybe.
My favorite oil caps are the vit Q,pyramids,and Astrons.Even the pyramids all perform well,even the 20% ones.
Diversity of opinions on any one technical subject,almost always causes confusion for the listener.
in 630V?
I wouldn't mind trying some out in a power amp, coupling to output grids.
Stuart
WHOA! Don't touch that!
Hi Stuart,
No luck... K40Y-9 .68s are only available up to 400 V; and 1.0 uf were only made to 200 V.
..
WHOA! Don't touch that!
I DO like the K40Y9s. BUT at first I bought some other caps, forget the numbers, but they are PIO and green, maybe K72? Those are still in a box after trying those out.
My point was just because the K40Y9s are great (and I use them in RIAA networks) doesn't mean that other Russkie caps are also great.
I also agree about the Sonicaps. Use them (Gen I) in my Tympani crossovers. Replaced Auricaps. Not a lot of difference. Also used a pair of Platinums in a phono stage. Pretty good. One step down from TFTF. A tad bright.
Stuart
WHOA! Don't touch that!
Gotcha
I didn't like the green ones either but,the larger green ones were ok in some numbers.They had a ton of ruskie greens and as you say some made me sick. Wheezer and I hated the k75s as couplers.The k42s are metallized paper in oil but the k75s are teflon or film,I can't remember which.
Diversity of opinions on any one technical subject,almost always causes confusion for the listener.
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