Replacing Caps in Amps

Discussion in 'DIY' started by JoshMorr, Feb 1, 2016.

  1. JoshMorr

    JoshMorr Friend

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    I know that replacing input and output capacitors in older stereo amps with better quality audio caps is a fairly common practice, but has anyone here done it to their headphone amps? It certainly voids the warranty - but so do most of the headphone mods. Lots of people "roll" caps in their DIY Cracks, wondering if anyone has tried this on a current production amplifier.

    I was thinking if there is a simple solid amp out there that with a few tweaks (better power supply, upgraded caps, etc) sees a significant improvement and outperforms its value proposition with some minor mods. Something along the lines of a O2, magni, or something unknown from ebay. Looking for a decent design where the manufacturer cheaped out on parts to get the bottom line down. It would be fun to make a $100 amp sound like a $500 one, or a something along those lines.

    Currently researching, but recommendations would be helpful.
     
  2. dBel84

    dBel84 Friend

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    I would be weary of most if not all solid state design with caps directly in the signal input or output. Tube amps generally do use a capacitor in the output and hybrids use a coupling cap for many of the designs. I don't know if it made any particular difference - I convinced myself that it did of course but I switched out the not unreasonable clarity cap on my Liquid Glass for a paper in oil AmpOhm version with the same capacitance and suitable voltage.

    There is a lot said about capacitor quality in general

    http://www.humblehomemadehifi.com/Cap.html

    my 2c - if a simple capacitor change elevates the said amp from mediocre to OMG fantastic, there needs to be more psychoacoustic analysis.

    this is very different when taking a decade old amplifier and changing all its power caps ( average continuous use life expectancy is about 8 years - loads of white papers on this ) , you can literally revive the old codgety beast into a delicate petal. as an example - I saw a cyrus II power amp sell for $125 on Agon several weeks ago - this has a formidable headphone output which directly couples to the circuitry , I suspect even without any power cap tinkering this amp would sound better than most $500 amps.

    ..dB
     
  3. Mr.Sneis

    Mr.Sneis Friend

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    This is something that I've been much more interested in lately; boutique caps are now very expensive AND harder to get in small quantity so a simple tweak can not only void your warranty but is also very costly.

    I'm trying my hand at a few small projects for now but TBH I know I am in way over my head; hopefully I can learn something though.

    In the limited experience I do have, it seems to me that old gear with old caps it is usually overblown how many people point blame at old electrolytics. I don't think I have yet spotted a truly blown cap yet.
     
  4. dBel84

    dBel84 Friend

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    It's generally not the clearly blown old caps that are the problem. It is the insiduous failure from leaky caps that are no longer functioning as designed - more relevant for power rail caps . I will try and dig out some of the old trusty references.
    . .dB
     
  5. zerodeefex

    zerodeefex SBAF's Imelda Marcos

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    Rumor has it that dB has the world's best transDAC as well.
     
  6. dBel84

    dBel84 Friend

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    I will have to send it over for you all to give it a listen , i think this has more to do with the upgraded voltage regulators as well as a heavy hand at low esr and supression caps.
     
  7. Mr.Sneis

    Mr.Sneis Friend

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    Bringing this one back up. I don't have extensive experience like some of the other guys, but I've been recently learning a little bit about general preferences wrt cap choices especially when burning through the Mouser site for hours on end.

    Interested to know if there is a rough rule of thumb for caps and/or ranking for stuff that is still obtainable in 2016, something like:

    Power Supply: Panasonic FM or FC, Nichicon PW or HW
    Signal Path: Elna Silmic II, Nichicon KZ/KW/FG, OR Film caps if possible

    There's so much choice and all over the board in terms of pricing, it's too bad Blackgates and Elna Cerafines are NLA.

    I found an interesting 2007 post b/w Tom and Doug where they are gently butting heads! http://www.head-fi.org/t/259735/panasonic-or-nichicon
     
  8. Mikoss

    Mikoss Friend

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    I like Panny FM's and Silmic II's myself, but I think they are fairly cheap caps in the grand scheme of things. There are a couple sites where people have gone to the painstaking task of cap rolling... Giving a fair amount of subjective opinion on lots of different exotic caps.

    I also found a video where a musician picked up a bunch of different caps for tone control on his guitar and recorded each. (I like the sound of the vintage Sprague Orange Drops myself).

    I also heard mban's Bottlehead Mainline with some Mundorfs and the tone was very organic sounding.

    I believe cap rolling to be worse than tube rolling, but I also believe that a well designed circuit could probably benefit from some synergy among its components.

    Here are some links... (Sorry if they're mobile, I'm on my phone)

    http://tech.juaneda.com/en/articles/electrolyticcapacitors.html

    http://www.humblehomemadehifi.com/Cap.html



     
  9. fastfwd

    fastfwd Friend

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    So my power amp sounds fine, even with around 125K hours on the tubes. But I got a good deal on a pair of holy-grail Telefunken 6922s, and Upscale Audio was selling the right 6CA4s at the same time, so I opened up the amp to fix it even though it wasn't broken.

    Which I'm glad I did, because it turns out that it IS broken:

    [​IMG]

    Wouldn't normally be a big deal, but COVID-19 has closed my office and deprived me of my electronics lab access. Which means I need to buy not only replacement caps, but also a solder station, solder, solder wick, flux, flux remover, helping hands, dikes, and a mat. Sigh.

    Anyway, as long as I'm going to all that trouble, I guess I'll replace all eight power-supply caps. Any reason not to use Nichicon LKS series at around $10 each?
     
    Last edited: Aug 14, 2020
  10. batriq

    batriq Probably has made you smarter

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    They look good.. wish they were rated 105 degrees. When I looked into something similar earlier I got the LGW, but the values you're looking for are hard to find (I looked at a few datasheets, only the LKS seems to have 12000@63V)
     
  11. Azimuth

    Azimuth FKA rtaylor76, Friend

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    Can I ask another question about caps if you don't mind?

    I am the proud owner of this Theta DS Pro Basic II and looking at the board it has a crap ton of tantalum capacitors on the board. Now it is from 1991 and eventually the power caps are going to need replacing on the power supply, I just wonder on these tantalum's.

    What I wonder is a) should I worry about replacing them to keep this thing working (basically will they fail), and also b) would any MKP caps or others might be an upgrade? Tantalum was much cheaper than MKP caps back in the 90's, but now the price is much lower. I guess I kind of worry about the delicate unobtanium parts inside, especially the sensitive Motorola DSP chip.

    So what is the consensus on replacing older tantalum caps?
     
  12. monacelli

    monacelli Friend

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    The little mustard yellow tantalum caps? I wouldn't touch them. They don't use a liquid electrolyte, so they don't tend to dry out and require replacement like aluminum electrolytic caps. They're generally just used for local decoupling anyway, keeping noise off of the DC rails immediately next to the Vcc pin of an IC. So my opinion would be to consider replacing aluminum electrolytic caps if your gear is beyond ~25 years old, but to leave the tantalums alone. There are so-called wet tantalum capacitors, but I haven't seen them commonly used in audio gear. Here is a link with some more info about tantalum caps on DigiKey's website:

    https://www.digikey.com/eewiki/display/Motley/Tantalum+Capacitors
     
  13. Azimuth

    Azimuth FKA rtaylor76, Friend

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    Fair enough. But that article makes me even more weary:

    Did they just say firecrackers? I just hope these are more of the mil-spec/fail-safe kind.
     
  14. fastfwd

    fastfwd Friend

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    Thanks. Yeah, not a lot of choices with those specs. Not from real companies, at least, and I didn't want artisanal fairy-dust capacitors for this application.

    Anyway, the job is done. Old caps and tubes are out, new caps and tubes are in. I discovered that one of the old 125,000-hour tubes had started to develop a slight hiss, so maybe it was finally getting close to the end of its life.

    [​IMG]

    It's late, so all I know so far is that the amp can play quietly without starting a fire. Tomorrow I'll find out how it actually sounds.
     
    Last edited: Aug 20, 2020

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