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Dynaco / K40 PIO cap voltage effect on sound?

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Posted on March 15, 2017 at 16:34:57
Dingojazz
Audiophile

Posts: 865
Location: Sonoran Desert
Joined: January 3, 2005
With the option of adding .22 uf 1000v K40 PIOs to the VTA Dynaco Mk IIIs, (currently enjoying .22 uf 400v K40s as output coupling cap)wondering what might be the pros/cons of going to the 1000v cap? (I gather from the archives that they may be slower to break in.)

If it's one of those subjective, YMMV-type benefits, then ok, I'm willing to take the empirical route. That said, before I tear into the current set up, I'm curious what sonic benefits, if any others might have found to derive from simply switching to the larger units.

Thanks,

K.

 

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RE: Dynaco / K40 PIO cap voltage effect on sound?, posted on March 15, 2017 at 19:15:02
Tre'
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Posts: 12157
Location: So. Cal.
Joined: February 9, 2002
" (currently enjoying .22 uf 400v K40s at outputs)"

I'm curious what you mean by "at outputs"?

Can you be more specific as to where in the circuit you have these caps?

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Sure...that would be , posted on March 15, 2017 at 21:13:41
Dingojazz
Audiophile

Posts: 865
Location: Sonoran Desert
Joined: January 3, 2005
the main/output coupling caps..

Thanks,

K.

 

RE: Dynaco / K40 PIO cap voltage effect on sound?, posted on March 16, 2017 at 01:19:09
twystd
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Posts: 2572
Location: Austin,Texas
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My experience with caps is that often the higher voltage caps might sound better, however they seem to take longer to break in. This is of course very subjective, and is hard for even me to accept as fact, considering it is dependent on my somewhat questionable aural memory.

I do however have a possible hypothesis. I've seen evidence that the reason for some caps of the same value but different materials and construction sounding different, is because of the internal damping effect of the various dielectrics and construction, on the conducting foils. This internal damping could possibly vary the amount of movement between the foils in relation to each other, due to the varying electromotive forces put on them by the AC signal.

The different dielectrics, such as PIO, mica, and Teflon, and their varying ability to damp, could explain the difference we hear in tone. So maybe there is a case for higher voltage caps, and their necessarily thicker dielectrics.

My perceived break in time with the higher voltage caps could also be explained. It may take longer for the electromotive force and the ensuing vibration between the foils to physically settle in a thicker dielectric. Having said all that, go for it, see what you think. Just make sure you leave adequate break in time for the higher voltage cap, before making any judgments.

twystd

 

RE: Dynaco / K40 PIO cap voltage effect on sound?, posted on March 16, 2017 at 08:38:56
GeorgePope
Audiophile

Posts: 17
Location: Havant , UK
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For the same type of cap , same value but higher voltage , the dilectric is thicker . The size of the cap will increase as will the production cost . ESR will also increase

As for how a higher voltage caps sounds , that's up to the listener . I tend to use as small a cap as possible in terms of voltage rating as I tend to go for mylar/foil , paper/foil types which tend to be much larger than the typical modern metallised polypropylenes

George

 

RE: Sure...that would be , posted on March 16, 2017 at 11:56:47
Tre'
Industry Professional

Posts: 12157
Location: So. Cal.
Joined: February 9, 2002
I guess you mean the coupling caps from the driver stage to the grids of the output tubes.

Is 400 volts enough?

When you first turn it on, the full B+ will be applied to the caps until the tubes warm up and start drawing current.

I would use the 1000 volt caps just for that reason.


Tre'


Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: the main/output coupling caps..., posted on March 16, 2017 at 12:01:17
DAK
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December 0, 0000
Is somewhat a contradiction in terms.
The output capacitor usually refers to a capacitor in the output stage of a preamp before the signal goes to the output jack.
Tube Amplifiers would not have a capacitor output but a output transformer, unless it is a OTL amp.
A coupling capacitor joins different gain stages in the amp and blocks the DC component allowing the signal (AC) to the next stage.

 

According to, posted on March 16, 2017 at 12:37:35
Dingojazz
Audiophile

Posts: 865
Location: Sonoran Desert
Joined: January 3, 2005
the circuit designer/supplier, Roy Motram and Bob Latino of VTA, 400v is adequate to the purpose. But, as you point out, upping the rating would provide additional capacity/insurance.

Thanks,

K.

 

Yes,, posted on March 16, 2017 at 12:41:12
Dingojazz
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Posts: 865
Location: Sonoran Desert
Joined: January 3, 2005
As Tre clarifies below, these are the caps coupling the driver circuit to the power (output) tubes.

Thanks for further clarification,

K.

 

RE: Dynaco / K40 PIO cap voltage effect on sound?, posted on March 16, 2017 at 17:21:33
Michael Samra
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Contributor
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June 24, 2005
Like Twystd said,higher voltage caps typically do sound better.The K40Y caps are wonderful in the VTA circuit but you want to mix caps.I would go with 630V K40s because you will not fit the 1000v ones in there and the 630v ones sound as good as the 1000v ones in there and they fit..

"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

Thanks Mike, does that mean, posted on March 16, 2017 at 19:36:38
Dingojazz
Audiophile

Posts: 865
Location: Sonoran Desert
Joined: January 3, 2005
You suggest a film and foil or teflon cap for the C2 "driver" cap (.1 uf) position to go with the k 40s ?

K

 

I replaced the input caps...., posted on March 16, 2017 at 22:16:26
Cougar
Audiophile

Posts: 2425
Joined: June 25, 2001
With Jensen copper foil PIO caps and left the K40 's in the output coupling spot in my VTA-120 amp. Now after 100hours breaking it's starting to open up and sound really nice! Very musical with a sweet mid and very good bass. I don't know how long the K40's have to break-in to sound their best but can only imagine how how much better it will get with more hours of breaking in.

I'm very happy I made this purchase to build this kit.

 

RE: Thanks Mike, does that mean, posted on March 17, 2017 at 12:14:41
twystd
Audiophile

Posts: 2572
Location: Austin,Texas
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If you can fit them in try these.

twystd

 

RE: PIO voltage rating on VTA amp coupling caps, posted on March 17, 2017 at 15:32:54
Bob Latino
Manufacturer

Posts: 200
Location: New England
Joined: May 21, 2007
Those caps look at about +225 VDC on the inner lead and about -40 to -50 VDC on the outer lead (depending on the bias setting). This is a voltage swing of less than 300 volts. A 400 volt rated cap here is more than enough to do the job.

Bob

 

Thanks all, posted on March 19, 2017 at 19:04:57
Dingojazz
Audiophile

Posts: 865
Location: Sonoran Desert
Joined: January 3, 2005
for your input Mike, Bob et. al. for the helpful responses

K.

 

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