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commsysman
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The critical contribution of coupling capacitors in amplifier sound

Over the years, with much experimenting and listening, I have found that a very major part of amplifier sound quality is directly due to the input coupling capacitors used. This is equally true for the output coupling capacitors of the preamp. Certainly the designer of the circuitry must do the job properly, but given that this is accomplished, and given that the amplifier has adequate power and power-supply stability to do the job at hand, the purity of the sound is very dependent on the coupling capacitors used.
I have upgraded the input capacitors over 20 years on my Audire Forte 200w amplifier from 1)Black gate electrolytics (original), to 2)MIT Multicaps, then 3)TRT Infinicaps, then most recently to 4)TRT Dynamicaps.
Each of these changes was an unmistakable sonic improvement, but the Dynamicaps are a true breakthrough in dynamics and incredibly pure sound; they were a major breakthrough, rather than just a noticeable upgrade.
I have also auditioned many other amplifiers I could afford (under $4000) in my home over the years and found them disappointing (after they received great reviews in Stereophile or other magazines), and not equal in sound quality to my Audire; so I still have it.
So-why do you NEVER see the type of coupling caps employed ever given the most cursory mention in magazine reviews of amplifiers or preamplifiers?? In my opinion, many things that are FAR less significant are brought out in detail in reviews, so why no mention of this critical subject?

To give this some perspective, from 1993 to 2005 I used an Audio Research LS2-B preamplifier in my system. It came from the factory with MIT Multicaps in the output stage. In early 2005 I purchased an LS-16 Mark II, which was a huge improvement for my system over the LS2-B. I noticed that it had the TRT Infinicaps in it but, but of a physical type different from Infinicaps I had seen before (white body with Green epoxy ends, as opposed to the silver body on the ones in my amplifier since 1999). Perhaps that was the last phase of product evolution before they changed the name to Dynamicaps; perhaps the difference there is minimal? That is an open question...does anyone know about that?
But the point is, the LS-16 Mark II WAS a huge upgrade in dynamics, sonic purity, bass drum definition, clarity of massed voices and soloists...everything!
I decided to do an experiment with the LS2-B, which I still had; I upgraded its output caps from the MITs to the latest Dynamicaps. The improvement did not quite bring it up to the sonic levels of the LS-16, but I would say that 60-70% of the difference between the two preamps was instantly erased. It was a big deal, indeed. Now it did cost over $150 for the capacitors, which for a product designer is a lot of bucks to put into a product, but man what a difference!!
I am glad I have the LS-16, because it is quite amazing, but had I known about the improvement the Dynamicaps would make in the LS2-B...I would certainly have upgraded it years ago (They came out in 2003). And $150 for the parts is sure a lot less than $4000 for the new preamp!!

Well, anyway, I think audio enthusiasts(and especially audio reviewers) need to consider this subject to a greater degree than currently seems to be the case for most people.

Floyd Martin

Jeff Wong
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Re: The critical contribution of coupling capacitors in amplifie

Hi Floyd - I agree that critical parts changes can make a world of difference in the sound of a component. I think the issue is that the more expensive the part, the bigger the mark up in retail price. Adding $150.00 caps to a component at the manufacturing level would likely tack on another $1000.00 (or more) to the retail price. I would think because the manufacturer would have a much bigger outlay of money up front just to make the things, they'd want to cut down on the time to recoup the costs by jacking up the price. Think about CD players that use crappy 59 cent NE5532 opamps or TL072 devices. A $3.60 Burr Brown 2132 would make a huge improvement in the sound (I know, I've done it in many machines), but, it's 6x the cost up front! Multiply that by the hundreds or thousands of units being made and the expense is prohibitive. It's easy for us to tweak because our outlay is for 1 or 2 sets of parts. A manufacturer won't want to lay out all that extra money up front, and they wouldn't be able to build at the planned price point.

JoeE SP9
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Re: The critical contribution of coupling capacitors in amplifie

You might also want to try replacing some critical resistors with Vishays. I have modified my Hafler and Adcom amps following an article from The Audio Amatuer published years ago. It was titled POOGE, progressive optimization of generic amplifiers. Replacing all the capacitors and resistors with higher quality parts is the key to better sounding electronics. I also replaced the input and output connectors the rectifier diodes and the transformers with toroidals. A used $250 Adcom with $250 of high quality parts can be illuminating. The difference is amazing!

Jan Vigne
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Re: The critical contribution of coupling capacitors in amplifie

"So-why do you NEVER see the type of coupling caps employed ever given the most cursory mention in magazine reviews of amplifiers or preamplifiers?? In my opinion, many things that are FAR less significant are brought out in detail in reviews, so why no mention of this critical subject?"

"Well, anyway, I think audio enthusiasts(and especially audio reviewers) need to consider this subject to a greater degree than currently seems to be the case for most people."

Sir, your query is at once both pertinent and surreal. Audiophile Nervosous is a strange and complicated beast that must be taken at face value and cannot be lumped into one statistical and equitable group. As you state, the value of coupling cap brands is in your "opinion" of great importance. Suggesting that any one piece or a certain brand of component or a single component within a system has an overriding, superior effect, either positive or negative, to the sound quality of the system is a sure way to create civil strife and disharmony among the many competing sects which make up this conglomerate labeled "audiophile". Ask yourself and five audiophile friends which is the most important component in a system and stand back for the disagreements.

Those of us who get our hands inside of a component from time to time wouldn't dispute your basic assumption that a few revisions to the cost-is-an-object equipment most of us own will result in performance gains. Most especially as a component gets a few grey whiskers. It would be difficult, however, to agree on which caps, resistors and so forth offered the best sound quality just as it is impossible to get audiophiles to agree on anything else brand specific. The general information provided in most reviews give a brief description of "audiophile grade" components and that is probably about as good as it will get or should be.

Many would-be audiophiles can be frightened away if they feel they have to worry about specific brands of components under the hood. I think Stereophile does a decent job appealing to both the seasoned veteran and the new up and coming, next generation of listeners/buyers. Suggesting that Component "A" sounds better than Component "B" merely due to the inclusion of certain brands of caps and so forth is likely to be a bit too much information. We went through a period where the emphasis on what connectors, internal cabling, pots and so forth influenced buying decisions. I, for one, am not interested in returning to those days of one-ups-manship merely because your cap is black and mine is red. How much of a component's sound do we attribute to a paper in oil cap vs. a polypropylene device? There's a discernable difference between the two as a group but how do we get a gaggle of audiophiles to agree which they prefer? We can't even agree on which rubber puck to place under our pre amps. Or whether to use spikes under our speakers.

Despite the emphasis many reviews place on proper power supply design, board layout and construction, transformer design and so forth, in twenty five years of selling high end audio, I have yet to find a client who asked me to remove the top cover of an pre or power amplifier, CD player or even tuner to view for themself the apparent quality of the product. At times I wish they had since what was inside was what they were paying for and showing them my goods vs. the competition's would have made my point more effectively than even playing music could. However, the general public doesn't know an electrolytic capacitor when it stares them squarely in the face. They cannot read a schematic nor point to a DAC chip. So what are we to do? How much education does the client require when the final sound is what counts and there are many ways to design and build a quality component?

I would hate to get into the various tube factions' type of disputes over which single component creates the "sound" of an amplifier. Winged "C" over NOS or the other way around. Triode or pentode operation? It gets rather tiresome after a short while. What?! Your amplifier has 6dB of negative feedback? You poor sot, you! Tsk, tsk.

At this point I would say let the internals be a matter of interest only to those who really care. If the client needs to know the amplifier has a certain cap or output device brand, they will ask. Otherwise let's not inject another level of mysticism and joo-joo into the buying, and listening, process. If you are handy with a soldering iron you can make the adjustments yourself after the warranty has expired.

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