[terry parr]

however, after reading an article over on head-fi, the op of a thread on different caps that he's tried on different amps is making me investigate the possibility of replacing the caps in my CARVER CM-1090 to Mundorf "silver-in-oil" caps in order to warm-up the sound of this integrated.

i have just recently become the proud owner of a pair of Magnepan MMG loudspeakers.  the only two amps i've tried with these speakers are the CARVER, and an older JVC RX-317. 

and believe it or not, the JVC actually sounds better with these speakers.  (fuller, more fleshed-out bass response and an overall more "smoother" sound as you go up through the mids to the highs). 

the CARVER just seems a bit more "peaky" up top and doesn't reproduce the lows as well as the JVC does through these speakers. 


anyone here that can add to my knowledge, (based on your direct experience) as far as comparing the before-and-after differences in sound signature when replacing caps?  and what other related components that i'd need to replace if i were to do this?

OR, anything else that i could try to warm up the sound of this amp?  if not the caps, then what? 

obviously, my knowledge in this area is next to nothing.  i would just appreciate some guidance from some of you who have "hands-on" experience when dealing with replacing parts in an older integrated in order to modify the sound signature.   

[paul79]

Topology of the piece rules the day vs the choice of coupling caps. You could color the sound some with caps, but I don't believe you will ever get what you want from it with coupling caps alone.

It is also possible that the old electrolytic capacitors need replacing. This will likely give the best results with what you have.

Best advise is to restore the amp, simply replace the amp with something more to your liking, or find a warm sounding source to play through it.

[avahifi]

To answer your question, a coupling capacitor is normally used in an electronic circuit to block DC from one part of the circuit to another while passing the necessary AC signal component.

Depending upon the impedances of the circuits involved, the coupling capacitor may need to be a large value (10 microfarads or larger).  Large value capacitors in general are large physically too and may not fit in the available space on a circuit board.  Electrolytic capacitors are the most space efficient capacitors packing ten times or more the capacitance of a film capacitor in the same space so are often required.  However electrolytic capacitors have, in general, poorer ultra high frequency response characteristics.

Thus often a smaller value "bypass capacitor" is used in parallel with the large value coupling capacitor to provide better theoretical high frequency performance. The idea being that the high value capacitor handles most of the audio range and above, while the small high frequency capacitor picks up the very high frequency range where the large capacitor might give up.

Note however that most of the "bad press" regarding the use of electrolytic capacitors alone in the signal path comes from a lack of understanding that normal electrolytic capacitors are polarized.  They only work properly if the positive side of the electrolytic always sees a positive signal.  It the electrolytic sees a reversed signal (positive side sees a negative voltage or vice versa) then the electrolytic capacitor breaks down and best case distorts, or worse case fails completely and often explodes!

Unfortunately in the past bad engineering put polarized electrolytic capacitors in the signal part in locations where the negative swing of the audio signal caused the the capacitor to distort (original Dynaco PAT-5 preamplifier for example).  A fix for that of course is to make sure the capacitor is used in an application where the positive side is always seeing a nominal level of positive DC (biased on properly).  Then the AC component of the signal always goes from more positive to less positive, but always positive.  Then the electrolytic never breaks down and distorts.

Another little understood characteristic of capacitors is a specification called dissipation factor.  This is the tendency of the capacitor to hold a charge even after it has been completely discharged.  This would be a bad thing if the capacitor was used in a circuit where it was completely turned off (except at initial power up or power down).  However if an electroltyic capacitor is properly used in a circuit where it is always biased on in normal operation, then the capacitor is not changing state at all and the dissipation factor issue does not exist.

Thus proper use of electrolytic capacitors is just fine.  However at Audio by Van Alstine, to remove any doubts, we do use premium polypropylene capacitors as much as possible in the signal path and do install bypass capacitors wherever they have a chance of being beneficial.

Note that "Farad" is a strange standard name for the unit of capacitance.  Named for Michael Faraday of course, a pioneer in basic electronics.  However one way to make a 1 Farad capacitor is to cover a football field with a sheet of aluminum foil, then lay a sheet of plastic film on that sheet of foil, and then lay another sheet of aluminum foil on the film, and then roll the whole thing carefully up.  It is a very large capacitor indeed! Of course using modern methods very low voltage rating one farad or more capacitors are available in rational sizes.

One other observation is that almost all "ears only" evaluation of capacitors is done without any standard ABX testing.  This allows anticipation bias to rear its ugly head time after time. Because ears only capacitor evaluation is almost always done without use of the basic tool, the capacitor meter, sonic differences are also often misinterpreted.  The problem is that the value of a capacitor IS NOT THE VALUE PRINTED ON IT.  It is the value it actually is.  A 10& tolerence 10 microfarad capacitor can be anythiing between 9 microfarad and 11 microfarad and meet specifications.   Actually a 10% tolerance capacitor is almost guaranteed to be at least 5% off in value because all the tight spec capacitors have been culled out by the manufacturer and sold at higher prices for the tighter specification.   Anyway, if you replace a 9 microfarad capacitor with an 11 microfarad capacitor in you pride and joy audio component  then you just changed the value by 20% and likely changed the circuit performance.  Can you hear this? Sure, but it was not because you changed to a wonderful sounding capacitor, you change the circuit operation.  Testing without measurements is like a car magazine running competitive tire tests without using a pressure gauge and wheel balanced.  Enough said.

Finally even after going to the expense of redesigning our circuit boards to "upgrade" all our signal path capacitors to polypropylene types, direct ABX testing of identical units with the original mylar film capacitors against those with polypropylene capacitors yielded no audible differences at all.  Darn!

Finally to resolve the issue once and for all, our new Vision Adjustable phono circuits use no capacitors at all in the signal path.  This makes all the capacitor tests in the world redundant in this case.

Regards,

Frank Van Alstine

[HsvHeelFan]

Background info on Frank's excellent information:

Let's start with Capacitance:

http://en.wikipedia.org/wiki/Capacitance

and once that is understood,  a look at Capacitor's:

http://en.wikipedia.org/wiki/Capacitor


HsvHeelFan

[Vulcan00]

Thank You very interesting,

Finally even after going to the expense of redesigning our circuit boards to "upgrade" all our signal path capacitors to polypropylene types, direct ABX testing of identical units with the original Mylar film capacitors against those with polypropylene capacitors yielded no audible differences at all.  Darn!


Regards,

Frank Van Alstine

You found no difference in sound between Mylar and polypropylene capacitors. Polypropylene cap. have a better rating of Dielectric Absorption (DA) than Mylar which is better than regular electrolytic cap. but Teflon cap. have a significant better DA rating than Poly cap.

I am interested if you have ever evaluated Teflon capacitors?

[Davey]

I think the OP is probably referring to a "shunt" configuration when referencing "bypass."  This is one of those definitions that has been skewed greatly in meaning by the audiophile industry......and is not literally correct. 

Just FYI, the more correct, and original, definition of "bypass" is a capacitor used to bypass a resistor in an amplifier circuit to increase AC gain but not alter DC biasing.  Examples would be seen in televisions, Ham radio gear, old audio amplifiers, etc, where a capacitor would be placed in "bypass" around the cathode biasing resistor in a vacuum tube stage.  There some other examples in solid-state circuits as well.

Cheers,

Dave.

[avahifi]

Since as I pointed out above, dissipation factor is irrelevant when the part is correctly used in the circuit, and since Teflon capacitors are not available in all the capacitance, voltage rating, and physical sizes we need, there is no real point delving further into this.

Frank

[Folsom]

Coupling Capacitor: Couple, it's to apply one thing to another. In the case of the signal path (Single/Balanced in) you are coupling the AC signal from source/volume to the amplifier. But as Frank said, it's to block DC; it's not necessary to get AC into an amplifier, wire alone does that fine. The sonic signature of the capacitor will be added every time it's in a path. These vary greatly even though if you measure them on a machine they appear about the same as far as one can tell, most of the time. The size of them is in relation to the impedance (opposition to flow of electricity in the form of music in this case) of the amplifier. The higher the impedance of the amplifier, the smaller of a signal coupling capacitor/s can be used! You can calculate the "corner frequency" to know what you need. This is useful if you want to mod your current equipment but want to know how small you can go say with Mundorf capacitors; because the .01uf is going to be a HELL OF A LOT CHEAPER than the 10uf. A simplified way to do it, 50/input impedance (Kohm) = uf 

ex. 50/25k = 2uf, 50/60k = .8uf (1uf would be suitable since you can't buy .8uf)

Bypass Capacitor: These get used in a lot of places. They're typically very small which means the corner frequency is really high, like maybe even in the radio frequency ranges like 200khz-mhz! They are actually coupling capacitors meant to get a desired frequency range from one spot to another, "bypassing" the device that isn't allowing the frequency or they're creating a second path to end up with a better end product from the combination of both. In the case of using one in a speaker crossover or the signal path, they're typically small enough to couple just high frequencies. The biggest reason isn't because the other capacitor can't do high frequencies, it's that for say $10-20 a piece you can get the quality of a damn good capacitor at the frequencies a tweeter plays in, while not having to buy a $200-500 capacitor that has that same quality for the entire frequency range. You'd be better off with the overall better capacitor that costs 10x as much or more. However for cost concerns this means a lot, since the end product will double the price of the capacitor used. Also you'll notice the better quality in capacitor in the higher frequencies more than at the lower so it's money well spent conservatively. ($200 capacitor in bulk price, two per channel, $400, with markup is like $800 , and with some manufactures that do retail it's going to be more! or a $10 capacitor, 2x $20, $40-60 difference in price by the time it gets to you)

 

[Folsom]

I think the OP is probably referring to a "shunt" configuration when referencing "bypass."  This is one of those definitions that has been skewed greatly in meaning by the audiophile industry......and is not literally correct. 

Just FYI, the more correct, and original, definition of "bypass" is a capacitor used to bypass a resistor in an amplifier circuit to increase AC gain but not alter DC biasing.  Examples would be seen in televisions, Ham radio gear, old audio amplifiers, etc, where a capacitor would be placed in "bypass" around the cathode biasing resistor in a vacuum tube stage.  There some other examples in solid-state circuits as well.

Cheers,

Dave.

Except that shunt implies a direction of current change. The current doesn't change in the configuration of a signal bypass capacitor, as the end product is identical. I wouldn't call it a shunt unless it was an RIAA network or something else...

Your original example does change the amount of current from one place to another, as you said to increase/maintain gain.

[Folsom]

BTW!

If you want to improve the sound you're better off with PFC/conditioning of the power. At almost any cheapness of gear better power will make it easy on the ears.

[terry parr]

i was skeptical when i was reading the article over on head-fi concerning this.  but, at the same time i wanted to keep an open mind. i was still hoping that maybe i could get some of the results that the writer of the above mentioned post said that he was getting.

but, this gets complicated.  maybe he was able to hear the differences as he was describing them according to the different amps that he was using.  i'll be using different amps that were designed and made differently than the ones he used in reporting these different results.   ("different topologies" as paul79 says).  true.
 
in my limited knowledge of the engineering behind this, i was thinking certain types of caps could easily be "slotted-in" from one amp to another.  well, after this thread i know now that it's not that simple.  different amps have their circuit boards built differently, and certain different caps may not fit on the board in the amp where i want to make a change.

and, after reading what frank van alstine and paul79 wrote, maybe replacing the electrolytics with new ones of the same type will make the most sense (especially in an amp this old).  unless, as mentioned earlier by paul, i have a complete restore done.  and i don't think i'm doing that.

some of the changes that i was thinking about making to this amp probably arn't even possible.   

so, it's pretty much a matter of:  "it is what it is", as far as the sound characteristics of this (or any other amp) goes.

based on what i now know, i'll see, after talking with my repair tech about what's possible. and it won't be what i thought it could be.  but now i know. 


i appreciate everyones' knowledgeable replies.


thanks, guys.             

 

[Folsom]

Wrong.

You're not constrained to the footprint of the board. If you can find the capacitors, you can replace them.

Lets say the input cap is 5mm diameter, electrolytic crap, and you want a mundorf that's like 2 inches diameter... You solder one end to the board, and the other to the input RCA jacks instead of going through the wires from the RCA jacks to the board, to the solder holes for the 5mm capacitor. Hell you can even have the leads of a capacitor go to the 5mm placements. The biggest trick is mounting the capacitors so they don't go flying all over.

Relax, it can be done pretty easily in most things.

[Davey]

Except that shunt implies a direction of current change. The current doesn't change in the configuration of a signal bypass capacitor, as the end product is identical. I wouldn't call it a shunt unless it was an RIAA network or something else...

Your original example does change the amount of current from one place to another, as you said to increase/maintain gain.

You must not be old enough to have repaired hundreds of televisions and amplifiers with "bypass" capacitors that failed. 
If you have access to some old electronics text books you'll find many chapters on "bypass" configurations just as I described.

Regardless, semantic explanations don't interest me.  In this particular case everybody is obviously talking about disparate valued capacitors wired in parallel (shunt) with each other to allow some sort of magical result.  I get that.

The historical circuit topology reference was just an FYI.  Sorry it distracted.

Cheers,

Dave.

[terry parr]

well dave, your post didn't "distract."  (slightly "veered", maybe).  i'm just kidding. all input has been welcomed.  it's been quite a lot to consider, and to be honest i haven't quite digested it all, yet.  the info you provided "added to", rather than "distracted from."  it'll give me another point to raise when i talk to the service tech tomorrow morning.

he's a local guy that i've never used before.  i just hope he has a feel for how a component can affect the overall sound in a music system,  and not only for just how different components and equipment pieces "measure."         

according to the last post by salis audio, i'm not necessarily restricted to the spacing on the circuit board afterall.  hmm.  (ding!)

i knew i was asking this question on the right board.  some of the info has been a bit confusing, especially when first reading it,  but after what i know now, and then after talking with the repair tech tomorrow, i should have a more fuller understanding of what's possible.


appreciate everybody's help.  i'll never understand half of what some of you guys know, but i did want to understand more as far as what's possible when it comes to some specific  changes that i'm thinking about making to this amp.   


     

[Davey]

"Bypass" and "shunt" are somewhat interchangeable and both can describe a variety of different uses.  It's semantics.

Unfortunately none of us can offer any solid advice regarding your original query since "warming up" the sound of something is a very subjective objective.  There isn't necessarily a specific capacitor parameter/type you could associate with this effect.

My suggestion to "warm up" your system would be to utilize a parametric equalizer to boost the midrange.    That's a quantifiable and tangible change to your system.

Dave.

[avahifi]

I am going to repeat myself because it appears that nobody is listening.

My observation is that almost all "ears only" evaluation of capacitors is done without any standard ABX testing.  This allows anticipation bias to rear its ugly head time after time. Because ears only capacitor evaluation is almost always done without use of the basic tool, the capacitor meter, sonic differences are also often misinterpreted.  The problem is that the value of a capacitor IS NOT THE VALUE PRINTED ON IT.  It is the value it actually is.  A 10& tolerance 10 microfarad capacitor can be anything between 9 microfarad and 11 microfarad and meet specifications.   Actually a 10% tolerance capacitor is almost guaranteed to be at least 5% off in value because all the tight spec capacitors have been culled out by the manufacturer and sold at higher prices for the tighter specification.   Anyway, if you replace a 9 microfarad capacitor with an 11 microfarad capacitor in you pride and joy audio component  then you just changed the value by 20% and likely changed the circuit performance.  Can you hear this? Sure, but it was not because you changed to a wonderful sounding capacitor, you change the circuit operation. Testing without measurements is like a car magazine running competitive tire tests without using a pressure gauge and wheel balancer.

Any comments on these observations other then oh no no no?

Frank Van Alstine

[werd]

I like you Frank. Aside from the power cable differences. Having said that if I ever bought an amp from you I would get you to hardwire the power cable.

[avahifi]

We can evaluate power cords with our ABX box too.  Simply provide everything in the test system with known real good sounding power cords, use two identical preamps and power amps, and provide one of each with our standard power cords.  See if anyone can hear the difference.  Wanna bet on the results?

I will need 5 real good sounding IEC power cords temporarily donated to make the test.  One each for the DAC and phono preamp sources, one each for the preamp and amp getting the best power cords, and one for the ABX box itself.  I can supply the two standard ones needed for the control preamp and amp.

Speakers in use normally here now, a set of Janszen zA2.1 electrostatics and a set of Philharmonic 3s.  My Salk HT3s are back to Jim for refinishing and sale towards a set of Exoticas.

Frank