Audio Research Reference 5SE modifications/bypassing output caps

I do take exception to Atmasphere's comments about using a bypass cap across power supply filter caps.  My experience with bypass caps in a PS is exactly the same as with coupling caps.  I can always hear the effect of the bypass cap and it causes a loss of coherency and usually an artificial brightness and thinning of the midbass.  In my opinion it is always the better course to use a single very high quality cap rather than a combination of caps.

I'm not going to take issue with this- with most power supplies for single-ended circuits this is probably true. I do most of my work with fully differential circuits and often with high capacitance values in our power amplifiers- in the latter case its often helpful to bypass the electrolytic right at its terminals to reduce ripple current problems, which prolongs the life of the part. In our MP-1 which has a five foot umbilical connection, we have found it helpful to bypass the power supply connections inside the preamp, which helps reduce noise.

It is logical that using even a high quality cap of a different type to bypass a large coupling cap could produce timing differences as well as other effects due to differing dielectrics.  In the past I have replaced ARC mylar and polypropylene coupling caps with larger polystyrene caps which I also would bypass with smaller polystyrene caps of the same manufacture.  This did improve the sound of both amps and preamps. As I do not have access to smaller value caps of the same type and manufacture as the larger coupling caps in the ARC Ref 5 SE I shall not bypass them.  Thanks for all the comments. 

I agree with Atmasphere that bypassing a coupling cap results in smearing and a generally incoherent sound.  This is especially true when the coupling cap is a high quality cap like a V-Cap CuTF (my favorite).  And this is also true even when the manufacturer used bypass caps in the original design.  For example, for a long time ARC used a cocktail consisting of a large value film cap (either a Rel-Cap or MIT) bypassed with one or even two .01uf InfiniCaps.  You would think an established company like ARC would know what they were doing but not in this case.  For each of my ARC preamps, I was able to improve the sound quality by removing the bypass cap and letting the base cap (especially the 5uf MIT base caps) do all the work.  The InfiniCaps always added an unnatural sheen and spotlighting of the treble along with making the midbass too thin and anemic.  With today's better film caps like the copper V-Caps this would be even more true.

I do take exception to Atmasphere's comments about using a bypass cap across power supply filter caps.  My experience with bypass caps in a PS is exactly the same as with coupling caps.  I can always hear the effect of the bypass cap and it causes a loss of coherency and usually an artificial brightness and thinning of the midbass.  In my opinion it is always the better course to use a single very high quality cap rather than a combination of caps.

Bypassing power supply caps is a good thing. Bypassing audio coupling caps results in smearing- the more resolution you have- the more you can hear it. The caps have different ESRs, different dielectric coefficients; its easy to see why this is so.

So the thing to do is simply use one cap and give it your best shot.

Well, there’s "need" and there’s desire.

I don’t know of ANY audio film caps that need to be bypassed at all.

Anything you do from this point is really "desire" to change things. There is no absolute, objective best we can point to. If you like the sound of say a Clarity with a splash of Mundorf, then that’s what you like.

I personally don't like the Mundorf house sound (speaking only of the caps) at all, so you won't catch me attempting a mix. That doesn't mean you could not though.

Best,

E

Thanks to all for your comments.  I agree that only larger coupling caps may benefit from a bypass cap and that some of the newer caps are designed to minimize the need for bypass caps. As I stated, I do not know whether the large output coupling caps in the Ref 5 SE are designed to obviate the need for smaller bypass caps.  I do know that ARC as a matter of general practice  will not usually endorse modifications to their gear.  I started this thread in hopes that someone has experience with bypassing the output coupling caps on the Ref 5 SE and could comment on their value.  I suspect that if I want to find out if bypass caps on these output caps benefits the sound of the Ref 5 SE, then I shall need to do the experiment.

@monoogan Reminds me, a lot of the latest generation caps like Mundorf Supreme use exotic windings to achieve much of the benefit of bypassing.

That's why they are so physically large for the uF.

I meant to say "output caps are kind of unique..."

I know the older Ref and LS preamps that used the WonderCaps had multiple value bypass caps stacked on the output coupling cap.

My guess is that they judged whatever they are using now wouldn't benefit from it.

I find bypass caps work better (if at all) only with larger caps (>= 5uF).

That's a rough guideline. Bypass caps are kind of unique in that you can increase the total cap value all you want to without affecting the "response" very much, and indeed, in some preamps with smaller bypass caps (2-4uF) adding significant capacitance may indeed be a good thing.

I do worry sometimes if there is a difference, whether it is an important one or not, or a good one or not. Too many audiophiles get seduced by "different."

So I have not bypassed those in particular, but I have bypassed other 10uF caps with a "budget" copper film cap to good effect. Why don't you try them? I use the Audyn TruCopper 0.1uF caps. If they do nothing for you, then I suggest no other cap will either.

Best,

E