Output Capacitor Upgrading Questions

[Paul Joppa]

This question made me think, and I came to an interesting conclusion.

Technically, it is preferable to connect the outer foil to the lowest impedance point, usually the output of the previous item. That would be the 6080 cathode in the case of Crack.This allows any capacitively coupled noise (usually hum) to drain to ground most easily.

But Crack is an OTL, with an output impedance that is about the same as the headphones - in the range of 100-150 ohms. So again, at least technically and in theory, it won't make any significant difference - the impedance is quite low in either direction, and you don't know which is higher anyhow, unless you plan to use only one headphone and that headphone is either unusually high impedance or unusually low impedance.

 

[langendorf]

This question made me think, and I came to an interesting conclusion.

Technically, it is preferable to connect the outer foil to the lowest impedance point, usually the output of the previous item. That would be the 6080 cathode in the case of Crack.This allows any capacitively coupled noise (usually hum) to drain to ground most easily.

But Crack is an OTL, with an output impedance that is about the same as the headphones - in the range of 100-150 ohms. So again, at least technically and in theory, it won't make any significant difference - the impedance is quite low in either direction, and you don't know which is higher anyhow, unless you plan to use only one headphone and that headphone is either unusually high impedance or unusually low impedance.

Thanks for the reply. I just wasnt shure. But is there not a whay to mesure the lowest impedance?

 

[Paul Joppa]

Sorry, guess I wasn't clear. Here's another shot:

The Crack output impedance, as I said, is 100-150 ohms. Headphones are rated for impedance, usually, between 30 and 600 ohms. If you are using 500 ohm headphones, then they are higher than 100-150 ohms and the outer foil should go to the amp side. If you have 30 ohms phones, then it would go to the headphone side. If the phones are 120 ohms, it shouldn't make any difference. In practice, I doubt it would make a noticeable difference no matter what phones you have, since all these impedance are quite low relative to the reactance of capacitive coupling between the cap and anything else in the circuit.

Of course, lots of unexpected things turn out to be audible. There is only one way to tell, and that's to try it yourself. Because of the DC voltage being blocked by the capacitor, it would be wise to give the cap a hundred hours or so of music after reversing it, to see if there is a break-in effect which needs to be reversed along with the capacitor.

 

[[email protected]]

If I remember, the longer leads on the Solens are attached to the outer foil.  You can email them to verify.  Naturally, I forgot to mark my caps before I snipped mine to the desired length.  My amp is absolutely dead quiet so I'm not going to make a point to change anything.  However mine is wired, it is sounding just fine.

 

[Paul Joppa]

Oh yeah - forgot to mention - you can always wrap the cap in copper tape and ground it, thus shielding the outer foil so the whole thing is irrelevant.  :^)  Like the Gordian Knot, sometimes brute force works best.

 

[Laudanum]

If I remember, the longer leads on the Solens are attached to the outer foil.  You can email them to verify.  Naturally, I forgot to mark my caps before I snipped mine to the desired length.  My amp is absolutely dead quiet so I'm not going to make a point to change anything.  However mine is wired, it is sounding just fine.

I wasnt concerned about it at all so just got the Mundorfs I used where I wanted them and installed them.  EXCEPT, I intended to orient the second one the other way around so atleast in and out was on the same sides for both caps.  I forgot.  I chalk it up to just another of many "duh" moments for me  
So anyway, assuming that the Mundorfs are consistently labeled, one of them is connected outer foil to input and the other, outer foil to output.  I realized it right after I soldered them in and strapped them down.  Oh well.  Maybe one day I'll flip one of them around.  It's not like I can hear one channel is audibly noiser than the other so it hasnt been a priority. 

 

[Noskipallwd]

I used a pair of Hovland musicaps in a build recently, and like the Auricaps the manufacturer gives instructions on orientation of the caps. Not much explanation of the consequences of not following the instructions.

Cheers,
Shawn

 

[Grainger49]

Oh yeah - forgot to mention - you can always wrap the cap in copper tape and ground it, thus shielding the outer foil so the whole thing is irrelevant.  :^)  Like the Gordian Knot, sometimes brute force works best.

I just might try grounding the outer shell of a KK Teflon.  They all come with a metal shell.  I will try to solder very quickly.

I used a pair of Hovland musicaps in a build recently, and like the Auricaps the manufacturer gives instructions on orientation of the caps. Not much explanation of the consequences of not following the instructions.

Cheers,
Shawn

Shawn,

Good point!  That is so often not stated.  The caps are not polarized so they won't blow up if put in "backward."  The result is it might pick up noise or hum without the "proper" orientation.

 

[HF9]

Good point!  That is so often not stated.  The caps are not polarized so they won't blow up if put in "backward."  The result is it might pick up noise or hum without the "proper" orientation.

Right, the caps will sometimes mark off inner-foil and outer-foil sides. When the outer foil lead is connected to the point of lowest impedance, it can potentially make the sound ever-so-slightly cleaner and more detailed. Read here for more details: http://www.laventure.net/tourist/caps.htm

 

[Grainger49]

I doubt with the ringing in my ears I would hear it.  Then again I am very sensitive to proper absolute phase.  I guess I will give it a read.

Thanks for the link.

 

[matthewmckay]

A little heads up about the Bypassing...

I had zero luck trying to bypass the electrolytic coupling caps in the crack.  The least detrimental sounding that I tried was with .01uf Audiocap thetas, but I am certain the amp sounds better without them.  All of the different caps I tried, (burned in using Grainger's method for about 5 days), seemed to add some zingy, etching crap in the higher frequencies. 

I did however, have very good luck using one of the same thetas to bypass the last electrolytic in the power supply.  There is a noticeable reduction is my noise-floor with this cap in place, and since it's addition, I no longer have any desire to replace the electrolytic coupling caps with larger film ones.

I also tried a 2.2uf, 1.0uf, and .1uf Solen (individually) in the same location and found these caps to be detrimental to the sound... in ways that are hard to describe.  I found the music less involving with any of the solens in this position, and after 15-20min of listening, would have to turn the music off because it was giving me a headache.  There is a very strong difference between the solen and the thetas in this position.

Encouraged by the success in the crack, I decided to try all of these variants in the seduction power supply as well... with very similar results.  The solens sounded much worse in place than without, and the .01uf audiocap thetas made a noticeable improvement.  I have had several friends over to confirm these observations with the seduction, and it was a unanimous vote of improvement when I had the theta bypassing the final cap in the power supply.  (several A or B sessions on a selection of tracks, not indicating what I was doing when connecting or disconnecting the alligator clip)

My thoughts now...

1) Solen caps are not suitable in these bypass applications ( I will probably avoid the brand in the future )

2) Bypassing the electrolytic coupling caps in the crack does not yield positive results.

3) .01uf Audiocap thetas made a noticeable improvement in my crack and seduction power supply (not so much in the coupling bypass)

I have already ordered more thetas for additional experimenting with the quickie.

 

[Raksasa]

I did however, have very good luck using one of the same thetas to bypass the last electrolytic in the power supply.

Hi Matthew,

What values did you use here ?

Is your Crack speedballed ?

Cheers,

John T.

 

[BNAL]

I have not had good results with Solen caps either. I did not try it in the Crack, but in other projects and never liked the results.  I have a 2.0uF Clarity bypassing the last electrolytic on the power supply and like the results. Currently I'm burning in 0.22uF Russian Teflon caps to bypass the electrolytic output caps. I hope that I get better results. I will make sure that I give them enough time to get good and burn in. I'm currently two weeks in and plan on giving them another week.

 

[matthewmckay]

.01uf /600v was the value for the thetas, I have the speedball installed, alps blue pot, and CMC swiss red copper RCAs, ... other than this and the bypass cap, the amp is stock.

here is a link.. they are $4.91

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=027-700

 

[earwaxxer]

A little heads up about the Bypassing...

I had zero luck trying to bypass the electrolytic coupling caps in the crack.  The least detrimental sounding that I tried was with .01uf Audiocap thetas, but I am certain the amp sounds better without them.  All of the different caps I tried, (burned in using Grainger's method for about 5 days), seemed to add some zingy, etching crap in the higher frequencies. 

I did however, have very good luck using one of the same thetas to bypass the last electrolytic in the power supply.  There is a noticeable reduction is my noise-floor with this cap in place, and since it's addition, I no longer have any desire to replace the electrolytic coupling caps with larger film ones.

I also tried a 2.2uf, 1.0uf, and .1uf Solen (individually) in the same location and found these caps to be detrimental to the sound... in ways that are hard to describe.  I found the music less involving with any of the solens in this position, and after 15-20min of listening, would have to turn the music off because it was giving me a headache.  There is a very strong difference between the solen and the thetas in this position.

Encouraged by the success in the crack, I decided to try all of these variants in the seduction power supply as well... with very similar results.  The solens sounded much worse in place than without, and the .01uf audiocap thetas made a noticeable improvement.  I have had several friends over to confirm these observations with the seduction, and it was a unanimous vote of improvement when I had the theta bypassing the final cap in the power supply.  (several A or B sessions on a selection of tracks, not indicating what I was doing when connecting or disconnecting the alligator clip)

My thoughts now...

1) Solen caps are not suitable in these bypass applications ( I will probably avoid the brand in the future )

2) Bypassing the electrolytic coupling caps in the crack does not yield positive results.

3) .01uf Audiocap thetas made a noticeable improvement in my crack and seduction power supply (not so much in the coupling bypass)

I have already ordered more thetas for additional experimenting with the quickie.

Interesting experience with bypassing.... From what I have read there have been more reports of negative effects from bypassing attempts than positive. I was very skeptical going into the whole concept.

I did have a very positive effect from bypassing my ampholms paper/oils with mundorf siliver/oils in my speaker crossover. I was surprised. I really didnt expect it to work. I just happened to have the mundorfs around and I thought I would give it a try. I was planning to use the mundorfs as a coupling cap but I didnt end up building that amp. Anyway - not sure how a pure mundorf silver/oil crossover would compare - cant affort it! Quite happy for now.

 

[Raksasa]

.01uf /600v was the value for the thetas, I have the speedball installed, alps blue pot, and CMC swiss red copper RCAs, ... other than this and the bypass cap, the amp is stock.

here is a link.. they are $4.91

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=027-700

Thanks Matthew. 

John

 

[Raksasa]

Hello again,

I just found some Mundorf Supreme silver/gold/oil 0.1 uf 2% 1200 vdc caps lying around.

No idea what I got them for. 

Probably for bypassing something in a valve amp.

Might try one bypassing final PS electro. Is this cap OK for this purpose in Crack ?

Can someone please confirm which is the FINAL PS cap - 1, 2 or 3 ? I didn't build my Crack, BH did.
I'm guessing 3.

Cheers,

John

 

[BNAL]

John,

It is number 1.

 

[Raksasa]

John,

It is number 1.

Shows how much I know.  

Thanks Brad  

 

[Noskipallwd]

A little more about bypassing... There are a few different opinions on the pros and cons of bypassing. If you go to the Audience (Auricap) site they state that one should never bypass output capacitors. Their reasoning is that this can cause smearing of the sound. When you bypass you are splitting your signal in two, (each channel), from what I understand differences in charge and discharge rate, however small, can cause an audible difference in the signal when recombined(smearing). There is also the possibility of parasitic capacitence, there are others here with much greater knowledge on these subjects than I, maybe they will chime in.

Cheers,
Shawn