8uf vs 10 uf 450v in amp build?

[Oddvar]

Hi,  Will there be a significant difference between 8uf vs 10 uf 450v in amp build?  I have to 8uf's in my sparebox, but the layout states 10uf 450v?

[tubenit]

Having used both on V1 tubes, my experience is there is little to no difference in tone.

With respect, Tubenit

[pdf64]

For parts such as most ecaps, that have a wide ‘tolerance to nominal’ spec, 8=10.

[Oddvar]

Sounds reasonable, thanks.

[jjasilli]

Alternate view:  for the last filter cap some vintage amps, like the Bassman, used an 8uF cap.  Some people swear they can hear a difference with a 10uF cap & that 8 sounds better.  I'm one of these people     This does not apply to 8uF caps earlier in the chain.  But if a 10 was called for earlier in the chain, and all I had was an 8, I'd use it, at least in my own amp.

[st]

I believe you when you say you can hear the difference between 8uF and 10uF, even if I sure can't. But if you're that picky, you shouldn't even py attention at nominal values. As PDF noted earlier, old nominal 8uF caps were probably anywhere from 6 to 16uF, new!. Your average modern 10uF cap is very likely to be closer to your beloved 8uF. 

[jjasilli]

There are articles on this.  I repaired a Bassman that was blowing fuses - bad rectifiers.  So re-capped it, etc.  Newer Bassmans have  a 10uF, so I replaced it with the older 8uF stock value.  Didn't expect to hear a difference.  The owner & his friends could hear it too, and all were pleasantly surprised.


However, since more variables are involved -- all the caps & plate resistors were replaced -- I guess I can't be sure the 8 made the difference.

[kagliostro]

As told there are many variables


You can try modern not ecaps that nowaday are available also  with those values at affordable price and you can be sure there will be someone that can distinguish It by brand


Franco

[tubeswell]

No difference. In most amps, the filter caps work with resistance* to make R/C filters that shunt very low frequency to ground (so that the power supply rail remains 'tight' for the majority of the signal bandwidth seen by the gain stages).
The relationship between capacitance and resistance affecting frequency is defined by the equation f = 1/(2Pi.R.C), where f = frequency (in Hz), R = resistance (in Ohms), C = capacitance (in Farads) and 2Pi = 44/7. Remember that 1uF = 1-millionth of a Farad, so 8uF = 0.000008F
So if you start plugging tiny changes in C into this equation, you'll quickly see that the answer doesn't change much.
Say you have a 22k dropping resistor going to the 10uF: 1/[(44/7) x 22,000 x 0.00001] = 0.7Hz (everything down to 0.7Hz is shunted)
Now swap that 10uF for 8uF: 1/[(44/7) x 22,000 x 0.000008] = 0.9Hz (everything down to 0.9Hz is shunted)
My ears can't differentiate a 0.2Hz difference sonically.
Even if you have a 10k resistor with 10uF, the shunt frequency is 1.6Hz, and with 8uF, 2Hz.  (My ears can't differentiate a 0.4Hz difference either).

*Some amps have choke filters

[jjasilli]

Tubenit has a recent thread on whether different types of caps make a tonal difference. There are numerous articles and threads on this general topic throughout the internet.  Some people swear by stacking caps: placing an oil cap in parallel with a plastic cap for the full capacitance value.  People can have quite dogmatic opinions about these things one way or the other, often whether they have tried it or not.


Even so, without blind tests, it's still just your opinion.  The statement that an 8uf cap must sound the same as a 10uF cap is merely a hypothesis. Unless and until objectively proven, dogmatism is unjustified.   

[Oddvar]

It's going into the upper right corner, C38/37.

[jjasilli]

It's better to use a schematic.  Then use the component # to locate it on the layout diagram.

[tubeswell]

Those are the last pair of filter caps in a split rail in the supply chain. Each is dropped through a 15k resistor. The difference between a 10uF cap and an 8uF cap in that position is 0.3Hz. Which I highly doubt you will hear clean.

[tubeswell]

The statement that an 8uf cap must sound the same as a 10uF cap is merely a hypothesis. Unless and until objectively proven, dogmatism is unjustified.   

True. Math is pure dogma. Calculus is purely integral dogma. :-)

[jjasilli]

I don't doubt the math.  But math is also used to prove that SS amps sound great. 

[shooter]

But math is also used to prove that SS amps sound great. 

until they distort, but I was sleeping at that point in math class