Output Coupling Capacitors

[Jim R.]

That has to be some sort of record!  Congrats.

-- Jim

[roger_s]

I like your idea.  I've been toying with various ideas for securing those caps to the top plate; the glue gun idea didn't last long.  Strictly based on that photo I've been toying with not using either of those two terminal strips and going point-to-point but using strips as supports for those caps makes for a pretty elegant solution.

You could hop on over to Radio Shack and buy an extra 5 lug terminal strip, then add it to the 2nd bolt on the 6080.  Then the big honkin caps can fit between those two strips, with the caps tied between the outside terminals on the two strips.  I would jumper from the cathode pins of the 6080 (3 and 6) to the outside terminals of your added T-strip, then the wiring for the headphone outputs can be retained.  

You will, undoubtedly, have to bend the leads of the caps around their bodies a bit to get them to fit, but it should work fine.  

Here are some rough dimensions if anyone's considering these caps:

Each lead is 2 3/8" long.  The body's 2 5/8" long and 1 3/4" tall.

[Grainger49]

Thanks, Paul.  I forgot to ask if there will be one or two of these PSU caps.  I'm assuming you're using dual supplies so as to balance the transformer secondaries on the PT-3, so I'm therefore assuming two big psu caps.

-- Jim

Jim, I looked at the picture of the Crack belly and there are 3 caps in the power supply.  One has to be for the heaters, the other two are for the high voltage. 

[Paul Birkeland]

The three caps are all power supply caps for the B+.  It took a CRCRC to really get the Crack nice and quiet.

On the layout, I would suggest sticking pretty close to what is there in stock form, as the upgrades that are coming down the pipeline will be somewhat harder to install without some terminals on the T-strips available.

[Paul Joppa]

The newest:

http://www.cde.com/catalogs/944U.pdf

The littlest one is 100uF and less than 2" tall. For about $300 you can replace the last PSU and the output caps. Plus the cost of a second chassis box to mount them...

Here's the big guys:

http://www.cde.com/catalogs/947C.pdf

CDE makes more kinds; these are just what's at Mouser.

[Jim R.]

Thanks, Grainger and PB.  I'm really looking forward to this kit.

-- Jim

[Jim R.]

Ok, I goofed big time when I asked:

Thanks, Paul.  I forgot to ask if there will be one or two of these PSU caps.  I'm
assuming you're using dual supplies so as to balance the transformer secondaries...

Afterreading this again I realized how stupid that was.  Of course you're not using dual supplies as there is only one output tube ;-)

Ok, putting on my dunce cap and going to sit in the corner for a while :-).

I got a 6080 the other day and just love the look of it as it resembles a giant 6sn7.  Just never saw a tube quite with a form-factor like this.  I was expecting a big ST type like the 6AS7s I had a while ago.

-- Jim

[Paul Joppa]

Dude, you were right the first time. The output tube is a dual power triode, and a dual-mono power supply would be perfectly reasonable. Just not at the $199 price point ...

[Jim R.]

Ok, that's true too :-).  Point taken.  Thanks for making me feel not quite as stupid :-)

-- Jim

[Dyna Saur]

From the Crack "belly Shot" the PSU looks to be C-R-C-R-C, amd AC filaments for the two valves.  I'll SWAG those WW power resistors are around 270 ohms @ 5W ?

Would bypassing the two  100 uF output caps with something like 2.2uF @ 250V film, or "Green Kommie Kaps" be a useful upgrade?

Looks like I got the next to the  next to last one of the first run!   yahoux!!!!

/ed B in NC

[Paul Birkeland]

You are spot on with all your conjectures. 

I would vote for removing the last Panasonic Electrolytic and substitute a 200uf @250v Solen in its place  

Bypassing should be fine, you will get diminishing returns adding bypasses before the last cap in the supply.

I am out of town and on a computer without modeling software, but I'd imagine substituting Triad C-7X chokes for the 270 ohm resistors will drastically reduce the required capacitor size for sufficiently low ripple.   Finding space for all that could be pretty rough...

[machinehead]

PB, which software do you use?

[Paul Birkeland]

I use good old PSUD-II.  You can simulate the stock power supply, jot down the ripple, then start messing around adding chokes and different caps to see if you can stay under the stock level. 

[machinehead]

I will probably get shot for asking this on this forum, but....

Is there a sonic advantage to using tubes for power supply regulation, or could
you more tightly control it with semiconductors, and just use the tubes for the signal path?

[Grainger49]

Bottlehead uses tubes for voltage regulation in the Foreplay III, Paramount and Eros.  So it is easy to say that they like it.  The regulator circuits use solid state devices and tubes.  So if PJ, Doc, and the rest thought that an all SS circuit was best they would design it that way.