2. amps-preamps
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Preamp Caps?Auricap,Mundorf, Hovland, jensen,solen

Hello,
I have a preamp with only 2 Signal caps directly in front of two tubes shot right out to the amps, extreme simplicity and excellent sound. This is the first preamp that came stock with Auricap's I have owned or heard, most in the past have always had Multicaps, Kimber caps in my previous pre's. I can say I think the Auricaps are quite a bit better but not that expensive or the end all-be all that I understand. Now I have had some crossovers and a Preamp with Solen fastcaps in it, and they are the best in Bass I have heard out of all of them, not that it makes them superior just an observation. I have also purchased Jensens oil and put them in Tube equipment in the past, not bad but did not blow my doors off.. And Finally Hovlands, not my Cup if you know what I mean, I found them the most expensive and the least impressive, could be the mix of component used in, but whatever too dry for me. Mundorf is a little newer on the scene to me and I thought the Hovlands were pretty obscene in cost, however these are the new Cost and hype leaders from what I can tell today. I am considering trying the Mundorf Silver in oil supreme caps at no small cost to see if they are gonna create more magic than the Auricaps. . What is the character of this cap? I want very 3d and open yet still have some intimate warmth and very powerful bass. Is this a cap worth venturing over all the other explanations I left here? Needs a liquid sound, and get that fairly deep bass solen seems to be capable of for only a couple dollars a cap, cause I do not want to soften the already slightly soft Tube bass. Thanks to all that know about this tweaking and expereance with these caps . . Again its only 2 Caps, very easy to install so its hard to keep my hands off, but do not want to go backwards or waste the cause if its not gonna be very significant in this specific application, Anybody know of any good tube equipment or preamps using these mundorf super caps? By the way my tubes are Mullards NOS. Preamp manufacture would seem to be irrelevant here and yes I am pretty dang happy with the sound for the money already, but there is always more right 
undertow
tom_munro
162 posts
 
The original caps in my UV were a paralleled pair of 1uf Russian PIOs and 1.5uf Auricaps for a total of 2.5uf per channel. What you are describing with your 4uf OIMP and .1 TFTF is similar to my experience with the 3.3uf OIMP. I tried a .01, .1, and .22 TFTF bypass with the 3.3uf OIMP, and although the .22 worked best, there was still a discernable cutoff point where I could hear the softer OIMP take over. And, yes the 3.3uf was a little to heavy handed in the bass, so that's why I gave the 2.7uf a try. The bass is more proportional, and overall the 2.7uf OIMP is quicker and more transparent. These qualities allow the TFTF to blend in better. Having tried both the .01 and .1 TFTFs, the .22 TFTF is not as tilted up on top, and has more body in the upper registers. The input impedance of my last two amps is 100k ohms, so the smaller value caps work fine. The deHavilland UV is a tube preamp.
reb1208
518 posts
 
I would like to comment that the above posters are going about selecting capacitors the "right" way. That is, to experiment with your specific piece of equipment and letting your own ears be the judge. There is no right or wrong in capacitor selection, it is a sonic recipe. Often a combination of two different caps.
sherod
1,690 posts
 
Thank you Tom, for your detailed reply. I have tube monoblock amps that also have an input impedance of 100K ohms. As I understand the formula for determining the preamp output cap value, the lower the cap value, the lower the bass -3db roll-off point, correct? Also, Tom, when you put in the OIMP 2.7 uf caps, did you put them in alone and break them in before you put on the Teflon bypass caps or did you put everything in together and go through the long break-in period?
sherod
1,690 posts
 
Well, here's my situation. I recently replaced two 4.0uf Hovland Musicaps for equal value V-Cap OIMP(oil impregnated) caps in the output of my preamp. After about 400 hours of break-in( ample time, I would imagine) I determined that the OIMP V-caps were superior in most respects, particularly in allowing more information through, especially in the highs. However, in my extended listening sessions, I've found that the OIMP has a slight sonic signature of a little extra warmth, fullness and perhaps a roundness or softness, if you will. This signature is easy to live with because it is euphonic and actually adds a texture or coloration that enhances rather that detracts from the listening experience. However, being the anal perfectionist that I am and wanting a purer and more neutral characteristic of tones and timbres, I decided to bypass the OIMP with a smaller( .1uf) V-cap teflon. After going through the unbearable time of break-in for the Teflons( I'm currently approaching 400 hours) I have concluded that although the teflon bypass caps do indeed take some of the over-warmthness away and nicely extend both frequency extremes, the overall sound has a shelved-effect. It's difficult to explain this phenomena, but it's like a tilting up of the frequency where all the frequencies seem a little thinner and elevated. This isn't a too bright sound, just an over-elevation of tonal balance. I'm now frustrated because I thought that maybe I had hit the ultimate synergy with the V-Cap combo. I haven't given up just yet, though. I'm thinking that maybe, the .1uf Teflon value might be either too large or too small. I'm not sure because this cap evaluation is relatively new to me. So maybe other members might be able to make some suggestions. My tube monoblock amps have an input impedance of 100K ohms and the preamp has roughly 600 ohms output.
jeffreybehr's avatar
jeffreybehr
805 posts
 
Sherod: "As I understand the formula for determining the preamp output cap value, the lower the cap value, the lower the bass -3db roll-off point..." No, Sherod, that's backwards. The formula for determining the -3dB ("filter") point of a hi-pass cap is F = 159155/RC where F = frequency in Hertz, R = resistance in Ohms, and C = capacitance in microFarads. Since the F is in the denominator of the fraction, a larger C causes F to decrease. So higher-value cap = lower filter point.
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