Capacitor Orientation in an Express

[shaunf]

Hi All,

I'm going to be starting my first Express build and overall second amp build within the next week or so, and have been doing lots and lots of reading on this forum over the last few months in preparation.

I've read some posts regarding the importance of the correct orientation of capacitors, with reference to their outer foil.

I'm fairly new to electronics, but want to give it a go to detect the outer foils using that guitar cable tester.

Does anyone have a diagram that perhaps shows how to correctly orientate the capacitors in the amp once I have determined their outer foils?

Thanks in advance,
Shaun

[Colossal]

Here you go (see attached). The black bars shown on the caps represent the outer foil.

[toner]

Here you go (see attached). The black bars shown on the caps represent the outer foil.

or maybe skip that and buy caps that are all correctly marked... mallory orange drops are... sozo's are... sprague orange drops aren't if i remember correctly... or just build the amp and then you can mod it later with different caps to listen and learn. listen to the orientation thing, its subtle but there..

[shaunf]

Hi Colossal, Thanks very much for the document! Much appreciated!

Toner: I have a full parts kit on the way from RJ, and so the caps he supplies could very well be marked already, but the information suppled by Colossal will still be very valuable in terms of how to correctly orientate them on the board.

I should hopefully be able to collect my package from the post office within the next few days. Very excited to finally get going.

Thanks again for the help!
Shaun

[Colossal]

Hi Colossal, Thanks very much for the document! Much appreciated!

You're welcome, glad it will be of use. That drawing has been vetted by other members here as well.

Toner: I have a full parts kit on the way from RJ, and so the caps he supplies could very well be marked already, but the information suppled by Colossal will still be very valuable in terms of how to correctly orientate them on the board.

I should hopefully be able to collect my package from the post office within the next few days. Very excited to finally get going.

Thanks again for the help!
Shaun

Even though the real-deal Mallory PVC series polyester caps you are getting from RJ have the line on them, I am pretty sure I remember reading that it does NOT necessarily indicate the outer foil. I could be wrong, but I feel fairly confident that I read that. I would test them anyway; it's a good exercise and it will confirm whether or not the printed line is valid. Yes, the cap orientation can make a difference in the noise floor of an amp. Everything you can do to make those small, incremental improvements in your build will go towards getting a great sounding amp.

[shaunf]

Hi Colossal, Thanks very much for the document! Much appreciated!

You're welcome, glad it will be of use. That drawing has been vetted by other members here as well.

Toner: I have a full parts kit on the way from RJ, and so the caps he supplies could very well be marked already, but the information suppled by Colossal will still be very valuable in terms of how to correctly orientate them on the board.

I should hopefully be able to collect my package from the post office within the next few days. Very excited to finally get going.

Thanks again for the help!
Shaun

Even though the real-deal Mallory PVC series polyester caps you are getting from RJ have the line on them, I am pretty sure I remember reading that it does NOT necessarily indicate the outer foil. I could be wrong, but I feel fairly confident that I read that. I would test them anyway; it's a good exercise and it will confirm whether or not the printed line is valid. Yes, the cap orientation can make a difference in the noise floor of an amp. Everything you can do to make those small, incremental improvements in your build will go towards getting a great sounding amp.

Thanks for the advice. I'll definitely do the testing regardless of the markings.

Do you think guys here would be interested in following a build thread, or is this old news now?

[Colossal]

Do you think guys here would be interested in following a build thread, or is this old news now?

Build threads are always welcomed. Always good to share your experiences and if you have questions along the way, you will have many eyes on your build. This can be really helpful if you are unsure about any aspect.

The eye candy is always fun.

[Decko]

Hi All!

Had some discussion with Dave on the side about cap foil side placement.

I've seen some images where the foil side is exactly opposite as the PDF that was posted.

In fact, the later portion of my TW circuits have the foil side pointed the opposite direction. I just took it for granted that it was correct.

So to clear matters, could you clarify the following:

Does orientation of the signal and coupling caps matter?

If so what is the proper orientation? Martin?

Danny

[ampgeek]

The foil can be used to drain away extraneous AC to ground and keep it out of the direct signal path. The correct orientation is with the foil connected to the lowest impedance path to ground.

The correct orientation is fairly obvious in stage coupling caps. The lowest path is back through the power supply smoothing capacitor. The other end is *typically* the grid of the next stage which is a wire hanging in a vacuum (e.g., large impedance!).

It is not so obvious in the other areas (e.g., tone stacks, voltage dividers, etc..) and requires analysis.

So...yes...it does matter. But..I don't think you would know it in the absence of an extraneous AC signal large/close enough to induce the noise in the first place.

Cheers,
Dave O.

[Decko]

Hi Dave O,

Thanks for your input on this subject.

"extraneous AC signal injected into the signal path" - what type of noise would this induce at the speaker?

Thanks,
Danny

[ampgeek]

My pleasure Danny!

What you would hear at the speaker depends on the source and where it is leaking into the signal path.

A poor lead dress issue that leaks...say...120 Hz B+ into the post first stage coupling cap area would get amplified by all of the stages and be easily heard at the speaker.

The field from a flourescent over head light would show up as an obnoxious higher frequency buzz at the speaker.

My variable temp soldering station throws out a hell of a buzz through the ether. I either have to shut it off or cover up the amp in question in it's shielded chassis whenever I am doing tweaks on the bench.

Hope that helps!
Dave O.

[Paultergeist]

Here you go (see attached). The black bars shown on the caps represent the outer foil.

I just stumbled across this....this looks really helpful for the objective of orientating outer-foil capcitors for the least noise.

While I can probably extrapolate some insights from this layout, I am actually building a Rocket clone (the PDF image linked above was for an Express). Is there an equivalent image for a "Rocket" circuit floating around here? -- that would be super helpful!

Thanks for any assistance.

[10thTx]

In case someone doesn't know how to test for cap orientation. There is some useful information here:

http://www.el34world.com/Forum/index.php?topic=11427.0

With respect, 10thtx