Anyone notice how large the 500pF cap is in a Rocket?

[Mark]

https://tubeamparchive.com/viewtopic.ph ... t&start=30

I was building my board up and I find it hard to believe that cap is really a 500pF cap, it looks about the same size as a 1000pF to 3000pF silver mica cap. Notice it is roughly the same size as the 25uF bypass cap. The links goes to Rocket pictures.

https://tubeamparchive.com/viewtopic.php?t=18134

Also check out the Ingrid shots, the 500pF cap isn't all that big in this amp.

http://www.voxamps.com/downloads/circuits/acbass.jpg

The AC-30 bass amp used a 1000pF cap, I can't say I've heard one of these amps thought.

I'm not suggesting I've found something new or that those who previously supplied info weren't as forth coming as they should have been. It just seems a bit odd to me, I'd think cap would have to be in the order of 2200pF to make a significant difference tonally.

Any thoughts?

[Mark]

To clarify on this topic, I've had two people tell there are larger 500pF silver mica caps out there which resemble the one I've seen in Allyn's build.

Mind you, I am curious as what a larger cap would sound like?

I seem to remember Callaham's version of these amps used a larger cap in this position.

[Blackburn]

Hey Mark, I agree that the Rocket layout does show a rather large looking 500pf coupler. Not sure what to make of that, but is it documented what brand was used in the original? I like old stock Hershey bar (CDE) micas that I've pulled from things. Aerovox too. I've been using a new blue ceramic 470pf in mine for now. I might switch it out later for something else.

On another note, I was hoping you'd let me know where you sourced your red polypropylene caps. Are those by Panasonic?

David

[Mark]

Hi David, thanks for the reply, I got the caps from RJ, I assume they are Panasonics, but they are whatever he supplied. Shoot RJ and email.

[Jackie Treehorn]

The panasonic caps have an M in a box logo on them. M for Matsushita.

Actually, it looks like those are the polyester variety.

Nice board, Mark. Are you putting the orange drops in the tone stack?

[dave g]

No reason you can't use a larger cap. I prefer a .001 or .002uF there.

[Mark]

Thanks for the replies. I am going to use Mallory caps for the tone stack. I had a look at the specs for the Panasonic caps and they are metalized polyester. I can get them quite easily locally and I might as well put them in. I doubt there will be any difference in tone compared to the caps RJ supplied.

I have heard polystyrene caps make a difference but I'm sure there were other factors at play.

I experimented with caps with my Champ clone, I switched between 715's and other caps such as Jupiters and Sozos, there was no difference in tone at all. I even got several other people to listen and they agreed there was no difference in tone.

In the end I like look of the Jupiter red caps over the yellows and the Sozo blue caps. What made a difference was component values.

[Mark]

While I off topic I'm going to used Ted Weber pots with a 30% taper for the treble pot and the treble cut pot. I used them in a D'Lite to #0102 conversion and they worked a treat.

[martin manning]

Is the physical size difference in the 500pF just a 1kV vs. 500V rating?

[Reeltarded]

Of course not. That would make sense. Please don't ride the magic unicorn.

[Mark]

http://www.suntan.com.hk/Mica-Capacitors/

I thought this link is interesting as I always thought SM stood for silver mica, however it is a Suntan brand name.

http://www.simicelectronics.com/dipped_ ... citors.htm

Has some info on different case sizes such as DM10 and DM12. I think we might be looking at a DM15 or DM19 case. I can't the case effecting tone, not sure if vibration and durability enter into it.

Speaking of riding the magic Unicorn did you see this thread.

https://tubeamparchive.com/viewtopic.php?t=22071

All the magnets are full of vintage flux. They stopped making that a while ago.