[tranhieu]

After reading through the massive thread about diymod, I'm thinking about pulling the trigger in the near future but the questions of which cap to choose is still unsolved. My best choice now would be the Mcap Supreme 800vdc 6.8uF which runs about 25 pounds each. Though a friend told me to go with the Russian FT3. From the orgy cap thread I'm a bit sold but still since no one has mentioned about using them with diymod before I don't know if I can use them for a 5.5g diymod.
Also, what caps should I use as bypassing caps? and at which values?

 

[FallenAngel]

Well, FT3 go up to 0.47uF so unless you go with a 100K input amp or parallel a couple together, they're too small.  MCap 6.8uF on the other hand is much larger than necessary.

 

[tranhieu]

So if I want to use the FT3 I must use some resistors to adjust the input resistance?
I thought the higher the value the better due to the cutoff frequency?

 

[FallenAngel]

That's not exactly how an RC filter works.  You can parallel some FT3 together to get the value you want but that will get VERY big VERY quickly.
 
For recommended values, read http://www.ecp.cc/cap-notes.html

 

[tranhieu]

Thanks, that will take some time to read the whole thing
Also, what about bypassing caps? Do they really have any effect or the difference is not audible? I've only seen bypassing caps in some fullsized amps so I guess they might do the diymod good?

 

[FallenAngel]

It's a good read and highly recommended, but I quoted it for the cap size to input impedance values.
 
Bypass caps have quite an effect.  Personally, I wouldn't do much with bypass caps for simple coupling, just use the money you'd spend on a cap + bypass cap to get a nicer coupling cap.

 

[tranhieu]

er... what do you mean by simple coupling? I'm not very familiar with cap rolling

 

[FallenAngel]

I just wrote "simple coupling" as it's just a cap on the output of a dac.

 

[tranhieu]

ok~ so I measured the input and ground on my pot which reads around 45kohm, is that the resistance that I need to take as the reference for the caps?

 

[FallenAngel]

Yep, so aim for 1uF or more

 

[tranhieu]

Now that I've read that article and played around with the other threads, your words seem much clearer
But I still have one question: is there any golden rule for choosing which cap should go with which cap to make a coupling or it just comes down to preference in the end? like in my case, what are the other caps that can go with the FT3 to make a coupling?

 

[FallenAngel]

No golden rule, if you can afford good quality film caps (and they fit), you use them everywhere.
 
If you really don't care about size (those FT3s are really HUGE), put 2 in parallel for each channel and use those, it's not likely to get better than that.

 

[AudioCats]

if you have plenty of room, the FT is the way to go. Or 2.2uf Mundorf Silver-oil.

 

[tranhieu]

For the FT3 the highest value I can find here is 0.22uf so I guess it can only be used for coupling, not as bypassing caps? It's said that the bypassing cap can be of lower quality so which one should I go with here? The mundorf silver oil is quite expensive to be used for bypassing isnt it?

 

[FallenAngel]

You can get 0.47uF FT3s.
 
I think you have the bypass vs coupling cap idea backwards - small caps generally used for bypass and should be of higher quality than cap they bypass.
 
Both FT3 and Mundorf Silver/Oil are expensive.