Solid-State Power Amp Adventures

Discussion in 'Power Amps' started by Marvey, Jan 24, 2017.

  1. uncola

    uncola Friend

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    Philharmonic audio new philharmonitors.. only 85db but supposed to be an easy 8ohms nominal
     
  2. MrTeaRex

    MrTeaRex His head's not fat, he's my brother!

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  3. uncola

    uncola Friend

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    Ps audio is a great company with amazing customer service.. haven't heard the s300 tho
     
  4. uncola

    uncola Friend

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    The Vidar is about to come out, don't you want to see how that is? Or you need class d for its power/low heat?
     
  5. mrflibble

    mrflibble Almost "Made"

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    Nord Acoustics have recently released budget versions of their Hypex nCore amps: NORD ONE MP NC122, NC252, NC502, power outputs are 125W, 250W, and 500W into 4 ohms, respectively. The basic models cost £699, £749, and £849, respectively. For an extra £50 you can have the special edition case which looks really nice.

    Unfortunately, the prices exclude VAT in the EU but there is £100 off the 252 model at the moment, with this voucher code: 100NC252MP .
     
  6. PTS

    PTS Friend

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    In your experience, how long can the caps stay good in a SS amp? I have a re-badged Odyssey Stratos that's around 17 years old and even though the caps inside look perfectly fine, I do worry I'll eventually get some audible degradation. Is it unheard of for caps to stay good for 20... 30... years?

    I'm close to buying a modern Odyssey amp, just so I don't have to worry about it aging, plus Klaus has apparently designed sonic improvements in that time.
     
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  7. Armaegis

    Armaegis Friend

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    The lifespan of caps varies widely on the individual cap and temperature. It's not unheard of for caps to last 30 years, but in general I'd say 20 is roughly when you should consider recapping, and shorter if the amp runs really hot and you leave it on all the time. If in doubt, you can just email Klaus and ask him what he thinks, since it's his design after all.
     
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  8. dBel84

    dBel84 Friend

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    "Three things matter to the lifespan of electrolytic capacitors: ripple current, time, and temperature.

    The ripple current is the big one - if an amplifier runs heavily into Class A and near-maximum power dissipation all the time, this means maximum internal heating in the reservoir caps (thanks to ripple^2*esr) and so the shortest life. But for light loads like preamps and cd players where ripple currents are small, c.1-200mA roughly, this is not usually a guiding issue, because light currents do not drive up the caps internal temperature wildly.

    You'll typically find many new electrolytic caps are rated for 2,000 hours at 85 degrees Celsius or thereabouts. You can often find 105degC rated versions, too, and it is worth choosing these if they will fit.

    Electrolytic capacitor life basically follows the Arrhenius equation, where a change of 10degC roughly doubles or halves the rate of reaction. So while a 2-or-3000hr rating is usual for capacitors at full rated temp (to the point where ESR doubles from 'new' value), the reality is rather better at lower (internal) temperatures. Suppose your cap runs at about 35degC inside a well-ventilated case, or a lightly loaded piece of equipment (preamp/cd player):

    Based on a rated life of 2000hrs at 85deg C that suggests a useful life around (2^[85-35/10])*2000hrs at 35degC = 2^5*2000 = 7.2yrs."

    This being said , I have tube gear from the 50's that still "work" in stock form - still, they could do with a little loving. The flip to this is that manufacturers like NAIM recommended a full cap reservice every 7 years.

    If you do not plan on keeping the gear, I would just keep using it till you replace it, recapping the big power electrolytic will give it another lease on life. I recapped my 20 year old Linn power amp for this exaKt reason.

    ..dB
     
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  9. uncola

    uncola Friend

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    Klaus is an advocate of regular cap replacement.. I think he said once 12 years is long enough to hear improvement after replacing.. but he also recommends leaving amps on 24 7
    I definitely recommend Odyssey amps.. 20 year warranty and one free warranty transfer so you know Klaus is confident in his build quality and reliability
     
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  10. Priidik

    Priidik Friend

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    There are also some advances in cap manufacturing. The present ones are slightly better, than those produced 30y ago.
    Probably last longer too. This needs to be considered in context of same manufacturer and same type of caps.
     
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  11. PTS

    PTS Friend

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    Thanks for the tips all. Was also thinking about trying the new Schiit Vidar, I wonder how it would stack up against an Odyssey amp?
     
  12. uncola

    uncola Friend

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    here are some internal pics of my odyssey kismet mono amp in the smaller khartago chassis..
    http://imgur.com/a/3WtpB
     
  13. Hrodulf

    Hrodulf MOT: Sonarworks

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    I don't want to go all Stax Mafia on it, but soldering could've been better. Also some of the layout choices are dubious. Nothing critically wrong, but still...
     
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  14. Priidik

    Priidik Friend

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    Grandpapas of amp design would cringe at the use of fuses in output.
    I suppose this with crowbar is rather fool proof. I bet rolling fuses there net some actual differences in sound, hehe.
     
  15. PTS

    PTS Friend

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    Nice pics, uncola. Are you using the Kismet (in Khartago case) monos as part of your main system? If so, what did it dethrone to get there? I'm always curious to see how Klaus' amps stack up against the competition.
     
  16. uncola

    uncola Friend

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    they dethroned my chinese goldmund mimesis clone speaker amp and my emerald physics ep100.2 amp but the kismet monos took up so much shelf space in my small bedroom setup I eventually replaced them with cherryamp inline maraschinos which are so tiny I can hide them behind my monitor.. also they generate no heat which is a big bonus this summer in hawaii(I have no air con). The inline maraschinos are close enough to the kismets that I don't mind the slight downgrade. I kept the kismets for when I eventually set up a 2 channel system in the living room in the future
     
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  17. Priidik

    Priidik Friend

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    Hey, so I would need some amp advice.
    I will be building 12''-6''-1'' three ways, 8 ohm nominal, roughly 90dB/2.83V/m sensitivity speakers soon.
    I'm quite sure I will be powering MT side of my future speaker with JL Hood kind of amp.
    The bass side is now difficult for me to decide. I think 12'' 91dB/2.83V/m unit in vented cab need something a bit more than the puny JL Hood (not so much raw power, but it won't have good grip on the drivers).
    Crossed at 200 Hz, most likely LR2. This should give me some choices, as f-d up treble or 'edge'.. whatever is not an issue here.
    • I liked what Ncore made to bass (super quick, almost off limits dr, but dry and lacking in tonal shading), so one option would be to get these and build big ass linear psu for each. Buck for real engineering sweat and minerals is low though. And no, Ucd Hypex doesn't cut it, so I won't even consider eBay class-D.
    • Diy a high power, dc coupled class-A and turn off household heating, hehe (output resistance is still not very low)
    • Get Vidar instead (slightly afraid that Ncores or better mosfet amps will outperform it for bass)
    • Diy over the top mosfet out class AB (been readin' some Cordell latelly)
    I have spare resources to tackle only one from the list. Thoughts?
     
  18. uncola

    uncola Friend

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    You already know you like Nc400 sound so I'd say go with that, and tune it even further with your power supply :)
    the hypex switching mode power supplies are supposed to be good though..
     
    Last edited: Aug 15, 2017
  19. JeffYoung

    JeffYoung Almost "Made"

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    Hi Priidik,

    Have you considered any of the Firstwatt designs for the MT?

    And when you say Ucd Hypex doesn't cut it, do you mean for bass, or do you mean full range? My PSA subwoofers are ICE powered, which I would guess are in the same class as the Ucd, and they sound terrific. I do cross-over even lower, though (~ 60 Hz) since it's a sub.

    If it were me, though, I'd want to get some return out of not living in one of the warmer parts of the world. I'd go DIY high-power class-A. ;)

    Cheers,
    Jeff.
     
    Last edited: Aug 15, 2017
  20. Priidik

    Priidik Friend

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    Only strong point in favor of these vs the others is that I have tried them, doesn't make them better than others or even automatically suitable. @Serious had counter points in using very different amps for bi-amping. Perhaps the quick and clinical nature of Ncore won't go well with with the nature of class-A.

    Perhaps another wave of diy itch will be something Firstwatt, as of now I have shitloads on my plate to finish up.
    I tried UcD next to Ncore. There is no comparison, the UcD sounded veiled and subdued, even in bass. Perhaps up to 60 Hz it won't matter too much.
    Climate here is rather appropriate for Class-A, not too dissimilar to Ireland. Golf stream dictates us the same shitty weather.
     
    Last edited: Aug 15, 2017
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