Precision Electronic Pots

[hdahs]

Just wondering if anyone has used them, and thought that they were worth the extra dough. One of the perks of my day job is the ability to get parts at dealer pricing from CE Dist, etc.

Thanks

[syscokid]

Just wondering if anyone has used them, and thought that they were worth the extra dough....

I do, and I like them a lot. They work like a good pot should, and judging by specs and build quality, they should last to till the next round of dinosaurs come back. And most important: They look very cool...
However, if your heart is set on soldering to the back of these...that could be a dealbreaker!

......One of the perks of my day job is the ability to get parts at dealer pricing from CE Dist, etc.

Thanks

That would be a No-Brainer!

[hdahs]

My heart is not set one way or the other, but is there a reason you can't solder to the back of these?

[syscokid]

The housing is made of stainless steel.

[syscokid]

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[hdahs]

Thanks Greg. Did you find that relocating the ground buss, to be a hassle?

[syscokid]

Actually...It's a lot easier! Every pot does not have to be grounded to the buss wire. Only the Volume(s), Middle, and Presense Pot need to have the buss wire slipping thru the hole of the 3rd lug on these pots.

Here's an excellent drawing by SDM on alternate grounding using this method: http://home.comcast.net/~jbjdav26/2204/2203altgrnd.jpg" onclick="window.open(this.href);return false;
The only difference is he has grounded the Presense Pot at different location for the ultimate in hum/hiss control. You can still continue the buss wire from the Middle Pot to the Presense, to keep it simple. Or, try it both ways and listen if you can hear a difference between the two.

[avguy49]

Just to add my 0.02 to this post, it has been my experience that going to the effort to "star ground" an amp is well worth the effort. I have made this modification on many Marshalls and other types of amps with a HUGE reduction in the hum / noise floor. The link posted by syscokid is a good reference place to start, also you can search for "Star Grounding" here in the Metro forum to pick up on various threads about the deal. It does require a little effort and having your "thinking cap" on straight, but WELL worth the effort I assure you.

Good luck bro!,
Philly

[hdahs]

Thanks guys. If someone wouldn't mind, what exactly is defined as "star grounding"? I hear the term a lot, but am unsure of whether it means one central ground, several strategically placed grounding points, or something completely different. I know pedal builders who employ this as well.

Thanks!

[avguy49]

Here is a good link for an explanation of the technique: http://www.aikenamps.com/StarGround.html

~Philly

[syscokid]

Boy!..............Did you, open up a can of worms...

OK, I was just kidding...

novosibir posted this recently as I was trying to get more info on alternate grounding a couple of months ago. A few links to a lot of info:

By principle and theoretically joey is right - the best grounding scheme is:
- each stage does have its own filter cap
- all grounds of every stage are connected to their corresponding filter cap negative (sub star)
- all sub stars are routed together in the order, as the circuit is running (ground bus) - still isolated from the chassis (!)
- the ground bus is connected to the chassis at only one point

That's the way, how I'm doing the grounding in my own amps.

But in Marshalls, Fenders, aso. and in their derivates & clones not seldom are some (or more) designer bugs - and sometimes you may think, that the amp designers better should have been selling burgers at McD, instead of designing tube amps.

But anyway, there's a way, not to make all the efforts of a chassis free ground w/ a separate ground bus in a marshall-esqe amp, to get it (almost) dead quiet. The way is, to USE the chassis instead of a ground bus as a ground plane. The different 'sub ground spots' have to be well choosen and proven by empiric, what I've done and refined over years in a lot of different Marshall amps, which I've modded, upgraded or just serviced - and that's, what now is known as the "Larry's grounding scheme".

To get the idea, how my grounding scheme is done, first read some:

http://forum.metroamp.com/viewtopic.php ... 25&start=0" onclick="window.open(this.href);return false;

http://forum.metroamp.com/viewtopic.php ... 1&p=335678" onclick="window.open(this.href);return false;

http://forum.metroamp.com/viewtopic.php?f=15&t=27641" onclick="window.open(this.href);return false;

http://forum.metroamp.com/viewtopic.php?f=4&t=25351" onclick="window.open(this.href);return false;

And some additional hints:

NEVER use a PT bolt as a ground spot!
ALWAYS run the OT's secondary common to the speaker jack! Don't ground it anywhere to the chassis!
Run a regular (22 AWG) cable from the speaker jack's shield to the spot, where the PI is grounded.
Use lock washers between the ground lugs and the chassis, to enable good contact.

One of the designers bug mentioned beyond is the double filter in the 2204 for screens & PI w/ common ground.
Here I'd recommend to give this filter (one or both halfes - try it, what you like better!) to the screens and I'd mount an additional filter only for the PI, what then will be grounded to ground #3 of my grounding scheme.

Larry