F5 power amplifier

[ichiban]

No such thread found by search james and since we are discussing the F5 please go ahead and give your opinion on the different caps and there associated sound. here!

f5-listening-impressions-discussion

http://www.diyaudio.com/forums/pass-labs/155599-f5-listening-impressions-discussion.html

 

[jameshillj]

Thanks ichiban, that's the one - full of good info.

The capacitor thread is called "best electrolytic capacitors" and last post was may 20th and there was another one talking specifically about 10,000uF caps but can't find it myself, sorry - perhaps someone can assist?

 

[serious_lee]

How does this look for part placement?

I plan on mounting a third sink for a back plate, but you get the general idea. I was thinking the thick plate in the front would be a nice mount for the heavy toroid.

Thanks,
Everett

 

[AndrewT]

I wonder if the smoothing caps will run cooler if the PSU is turned upside down to place the caps in contact with the perforated bottom plate?

 

[serious_lee]

Are they really at risk for running that hot? I plan on using 50V caps in case that matters.

 

[labjr]

I wonder if the smoothing caps will run cooler if the PSU is turned upside down to place the caps in contact with the perforated bottom plate?

It would probably stop the heat from rising and make the caps run hotter.

 

[bear]

assuming that the top plate is not solid and there is a vent somewhere the convection upwards from the bottom though the holes will not be insignificant... I doubt that mounting the caps upside down would have any benefit compared to the work involved in doing it.

_-_-

 

[bobodioulasso]

My F5 caps are not heating.

 

[Renron]

If the caps are getting hot from passing energy, maybe the voltage rating is too small

Ron

 

[a.wayne]

I was talking about this one

Yeah, Bear, I'm a bit off topic about that - sorry.

In a similar way, jackies & umut, the thread of "the best 10,000uF capacitor ..." has good discussion of the properties of various caps - a whole lot of good info there, better than I can do.

OK, i see which thread !

Thanks ichiban, that's the one - full of good info.

The capacitor thread is called "best electrolytic capacitors" and last post was may 20th and there was another one talking specifically about 10,000uF caps but can't find it myself, sorry - perhaps someone can assist?

 

[a.wayne]

If the caps are getting hot from passing energy, maybe the voltage rating is too small

Ron

Seems reasonable to think this would be the culprit ....

 

[Blues]

With the correct cap voltage rating, ambient temp in unventilated box with hot heatsinks is our concern...

 

[bear]

do not build unventilated boxes.

???

 

[Blues]

Unless it looks like a PL Aleph...

 

[Nelson Pass]

The only disadvantage is that dust and cat hair accumulate
inside.

 

[a.wayne]

Unless it looks like a PL Aleph...

 

[bear]

The only disadvantage is that dust and cat hair accumulate
inside.

I'll take the dust over the heat... dust comes out with a vacuum & brush.

Cat hair? Well, that comes out too... Worst case I put the whole thing
into the tub hit it with cleaner and hose it off... once every 5-8 years if ur in a very very dusty dirty environment. I'm not. And I run electrostatic air cleaners as well...Ymmv.

if you want to get really into it, you could make a provision for a HEPA single layer material on the "intake" side (bottom) that would effectively screen out 99.9% of that stuff...

Heat and things like caps do not go together... imo.

_-_-bear

_-_-bear

 

[Neutrality]

In the F5 manual the power supply is shown with a 0.0033uF cap used for mains filtering.

Would it be ok to use a 0.22 uF X2 275VAC cap instead?

Does it matter much which size you use?

 

[Neutrality]

In the F5 manual the power supply is shown with a 0.0033uF cap used for mains filtering.

Would it be ok to use a 0.22 uF X2 275VAC cap instead?

Does it matter much which size you use?

Furthermore, I am most likely going to be using a 500-800VA transformer, with 230VAC primary/2 x 18VAC secondaries.

What size NTC is necessary? I am going to use the NTC in conjunction with a softstart circuit, where the NTC will act as the ballast resistor as well. The point is to make it more "safe" and fool proof. The relay would bypass the NTC putting alot less stress on it and in the event that the relay or circuit controlling the relay fails, the NTC will still be inline securing operation of the amplifier. With a fixed value ballast resistor, if the relay fails, the ballast resistor goes up in smoke, I want to avoid that situation.

Is one CL60 still enough or should I go for 2 x CL60 in series?

 

[Neutrality]

Hmm, thinking more about it, a CL60 has a max steady state current of 5 A, 800 VA transformer would draw min. 3 A, wouldnt it be better with a little more margin than that?