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A single bypass cap? OK! Great! But bypassing the bypassed caps? Pretty bad idea when it involved something like that in the picture.The unit in the picture was sold as Non functional Parts unit on ebay a few days ago.
And you have guessed it what went wrong with it!
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.Thou shall not stand where I type for I carry a bottle of Certified Audiophile Air and a Pure Silver Whip.
Edits: 07/19/16Follow Ups:
Unexperienced people should not put "anything anywhere".
I sent mine down to John Hillig to have him install the "Ultimate Upgrade" package, and got it back less than a month ago.
The upgrade package cost $599 plus return shipping, and involved replacement of most components. The upgraded SP-2 sounds great - I seriously doubt that I could have bought another preamp that gave me anything remotely close to that kind of performance for that outlay. If someone could pick up the butchered one for peanuts and send it to John, it might be a chance to get a damn nice preamp for comparatively low money, although I'd talk to him first to make sure it isn't a minefield...
Take the power supply.If you are already using a film cap,why would anyone bypass it thinking you will lower ESR or ESL? You won't.It's already ultra low by nature of film caps..Even ESL of capacitors by nature,are only a few hundred pico henries so their rising effect on impedance, only emerges when system frequencies exceed 100 MHz.In RF circuits that would make sense.If you bypass a lytic with a film cap that is 10% or more of the value of the lytic,that will be effective because much of the energy delivery duties at static levels will be handled by the film cap as well as storage duties..It will dip into the lytic under higher dynamic conditions.Using a .1uf to a .22uf will do little to nothing IMHO.I guess some think that tiny value film caps can lower ESL to the point where higher freq riding on the rail can't get filtered out.That may be somewhat true,but I have never witnessed it with measurement.
Now,in the case of the photo where the caps in question are used for signal,the same principles apply as far as bypassing in this case.Bypassing with that many caps does nothing but cause phase shift issues. Some companies bypass with a single small value film cap across a larger film cap.This is why you might see a 4uf bypassed with a .47uf..Remember the 10% rule I like to use even applies to film caps in this case.Typically,I don't bypass film caps in the power supply but here in the case of signal caps,it might make more sense to some people. They think that larger value caps don't pass higher frequencies as well so they bypass it to reinsert the higher frequencies.It may or may not be a tad faster,depending on design parameters.Now,have you ever wondered why they use such a large cap in the preamp output stage of tube preamps compared to years ago? It's to be able to drive a lower impedance. A lot of people that buy tube preamps,will be using them with solid state amps which are a much lower impedance than a tube amp.Many will also be driving subwoofer amps from the preamp along with their tube amp.If you are just going to drive a tube amp and nothing else,you don't need a 3uf to 4uf cap in the output of the preamp to drive a 250k to 500k load.I have people take out the large caps and put in a .47uf and they hear all the same bass as before, only with much more clarity on mids and highs.Try it sometime.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 07/19/16 07/19/16
Nicely put, Michael. I would just add that the need to "reinsert" the highs by bypassing a large coupling cap with a smaller one isn't something I've ever been able to measure. In fact, while some DIYers do this "just in case," I take the opposite approach. I refuse to do it for fear of introducing some form of sonic smearing of the signal. That's something we can't measure, and I'd rather be safe than sorry. :)
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Buy Chinese. Bury freedom.
I refuse to do it for fear of introducing some form of sonic smearing of the signal. That's something we can't measure, and I'd rather be safe than sorry. :)
That's always been my fear but I know there are way's to do it but you would have to do it with equal value caps of the same brand,value,and type.
It is very hard to measure specs under dynamic conditions because the amp or preamp is constantly changing in the sweep pattern..A good spectrum analyzer can do some of it, but interpreting what it is telling us beyond the fundamentals can be challenging..Bottom line,don't bypass signal caps.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
yes bypassing caps sound wrong for me
i tried it many times and always go back to a single quality cap
some people like it and enjoy it but its not my sound
Sometimes it can be beneficial, but from experience it can do more harm than good. It has to be done carefully. You can't just throw blindly a cap into another. Careful listening is needed.
Personally I prefer installing a lonely good capacitor instead of making a "garland"
Bypassing means creating a new resonant circuit.
l'Audiophile (1980-1985, french hifi/diy magazine) did measurements about this bypasing but even the old HP and Tektronik manuals warned for this. Nóthing new her.
Mikey,You can not select bypass cap values and types with electronic measurement devices.
Its done 100% BY EAR !!! Its subjective, requires listening, and good aural discrimination.
With great love,
Jeff Medwin
Edits: 07/20/16
I would hate to guess if some exotic driver circuit or cascaded voltage amp designed from a spice program got the feedback loop correct. Yes,we can hear peaks,dips,imbalances,and even phase shift some of the time.I have never had a spice figure perfect parameters as far as feedback goes.I have always had to tweak with test gear.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 07/31/16
!
The Mind has No Firewall~ U.S. Army War College.
What's with the 8ga speaker wire from the IEC connector to the PC board two inches in length? I estimate that preamp pulls less than 200ma at 120v. That hacked in 8ga wire is doing absolutely nothing over the OEM 22ga.
Furthermore is that speaker wire approved for line voltage? I'll bet not!
This is an excellent example of hacking an otherwise good product. I am certain, even without listening, these mods compromised the OEM performance.
nada aqui
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Buy Chinese. Bury freedom.
I wonder if the cap the space is marked for was a circuit change at the factory and no longer used, or removed by the bozo that added the rest of the caps. Can't quite make it out in the photo, but looks like a resistor in its place?
Though I would use a much larger resistor than that.
The picture is baffling ...
Did anyone notice, that's an awful lot of Black Gate N caps $$$$
Maybe he was possibly trying to make a larger value Super-E config using multiple smaller values.
But is that even possible to achieve?
I built an amp for a guy and he brought it back at one point. He'd bypassed the PSU caps with all kinds of stuff. The dangerous thing was that since he didn't understand the schematic he just used boutique caps that were well reviewed. A few were marked 150v when the HT was over 300v. Lucky they didn't blow up.
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