Replacing JJ 50m+50m radial can with CE Manufacturing advice

[AardvarkBry]

I built a Trinity Trip Top a while back, and I was wondering if anyone thinks replacing the JJ 50m+50m 500v radial can with a CE Manufacturing can was a worthwhile investment? I replaced all the electrolytics with polypropylene, and I added a filter choke. If if will improve the performance of my amp, which CE would be a good replacement? Will the 40/40/40 525 work? The only other one I see that is remotely close are the 80/40/30/20 525. The 100/100 sounds too big of a jump.

 

[john12ax7]

F&T makes a 50/50 @ 500V. But how old is the amp? Electrolytics wear out over time and need to be replaced.  But if they are fairly new I wouldn't replace them just because.

 

[AardvarkBry]

It's a new amp. I just built it about 6 months ago. There was a noticeable difference when I replaced the other electrolytic caps with the polys. I wasn't sure if there would be as pronounced a difference with the radial can?

 

[buckethead]

If it is improvement "soundwise" that you're seeking, I wouldn't change that cap, it won't change how that amp sounds imho. Which other electrolytics did you replace? Cathode bypass caps?

 

[AardvarkBry]

All of them. The only electrolytic left, is the radial can. My end game is both sound, and quietness. I do a lot of recording with the amp. There is the slightest, barely perceptible 60hz hum, that has improved slightly, with every little adjustment I've made. On a gig, or performance, it's completely not noticeable, but in the studio, through a condenser, it's there, during the dead quiet parts.

 

[buckethead]

Ah ok wow. Why not replacing that can cap with two polypropylene caps then? Just to get everything up to the same standard -  and man, this amp will last forever. I myself wouldn't upgrade any of my amps to film caps in the psu, because of the "benefit-cost ratio" but seems like it works for you, so go for it.
Besides that, maybe you can narrow down where the hum comes from? I'd pull the preamp tubes one after another to hear where the hum happens and then go from there doing more specific changes to parts or layout to get rid of that annoying hum.

 

[AardvarkBry]

That's an interesting idea. I'd have to come up some sort of housing since they would be on the outside of the amp. I wonder if it would all fit under the tube cage? Those things are huge! I have tried just about everything trying to track down this little hum. I completely rebuilt the entire amp, twisting all the leads tighter, covered them with aluminum tape. I did buy NOS RCA tubes, and it's seems probably it's one of the tubes. Just bought a set of brand new matched tubes. Waiting on them to arrive, so I can swap them out and check.

 

[AardvarkBry]

That JJ can has a ground pin on it. If I were to connect two polys together, what would I send to ground, whatever I came up with to for housing?

 

[buckethead]

The first thing I would try is to remove the PI tube - if the hum is gone you can leave the pwr amp out of the equation, meaning the hum is happening in the preamp or PI. From there put the PI tube back in and remove the two preamp tubes - again no hum means clean PI+pwr amp section and so on. That would be my workaround in case no oscilloscope is available. But I guess you probably tried that already...

Oh yeah those film caps are huuuge. Some people put them in old electrolytics cans, also to replicate the looks, but those 47µ 600V+ caps are just brutal. Maybe it is possible to find the cause of the hum after all and save some cap-money

The ground pin on the JJ is just like twisting two leads of two seperate caps together

 

[AardvarkBry]

I have tried pulling tubes. The PI and preamp tubes didn't cause any change. When I pulled the power tubes, and just used the preamp out line, the hum went away. I had some old kt88s and swapped them out. It reduced the hum quite a bit, but didn't eliminate it. The kt88s were really old International Service Masters in an old mono block that has been used a ton, so I'm not so confident those tubes were great. Hopefully when I get these brand new matched power tubes, it will be gone, and I won't mess with the can cap.

 

[buckethead]

Aha interesting! I just went through the trinity layout, are the speaker jacks isolated from the chassis?

 

[AardvarkBry]

They are those metal 1/4" Switchcraft jacks. I don't remember, but they look there's just a metal washer screwed right onto the chassis. That's probably the issue right? They need those fiber washers don't they?

 

[Ricardus]

If it's new why are you replacing it?

I seriously doubt in a double blind test you would hear any differences.

 

[radardoug]

Ah the old double blonde test! Is it the same as the double brunette test? hehe!

 

[AardvarkBry]

Thank you for all of your help everyone. Hopefully, buckethead helped me track down the source of this insidious microscopic 60hz hum, and it'll all be a moot point. It seems the unanimous consensus is that changing the can cap won't have any noticeable effect on the sound of the amp. I will say, that since I have this tiny little hum, changing out the other psu electrolytic caps with poly ones had a fairly noticeable effect on hum reduction. Maybe without the hum, there would be no noticeable difference, who knows?

 

[john12ax7]

My initial impression was you were looking to replace one electrolytic with another.  Going to PP film will present a lower impedance in the power supply so could possibly help.  If it has a tube rectifier be sure to check it's current limits.

How are you running the tube heaters?  This is another way to mitigate him,  by balancing,  elevate the level,  or go DC. Some things to consider if the tube swap doesn't solve it.

 

[buckethead]

It was just an idea with the speaker output jacks, maybe you can optimise the gnd layout there and get rid of some hum, but besides that the gnd layout from trinity looks really good to me. Maybe lift the jacks from the chassis, let them float in the air and make a manual connection to the star ground for testing purposes. But it's a long shot...

In the trinity layout, the heaters are elevated to 50V balanced through a 200Ohm trimmer.

I attached the layout for reference

 

[Whoops]

I built a Trinity Trip Top a while back, and I was wondering if anyone thinks replacing the JJ 50m+50m 500v radial can with a CE Manufacturing can was a worthwhile investment?

No it's not a worthwhile investment the JJ is fine.

 

[dio.pm]

so whatever happened to this ? I am looking to get one of these myself, but it might be too much for a first amp build!

 

[AardvarkBry]

so whatever happened to this ? I am looking to get one of these myself, but it might be too much for a first amp build!

I love the amp! For live performances, it’s phenomenal. For recording, there’s a slight 60hz hum, not a huge deal. I suspect that is partly due to the power at my house is very dirty. It’s an old schoolhouse from 1902, in the middle of nowhere, in this little valley, with no reception, and ancient power lines, and some crazy McGuivered electrical work. I always have little mystery hums and buzzes in a lot of my recording gear. The Furman strip helps.

As far as the build, it was a lot of fun. It was a ton of work. It took me a couple of weeks of working several hours a day, to complete. It’s also a little intimidating, poking around with a multi meter, dealing with up to 500 volts. But everyone who’s ever heard it has been blown away by the way it sounds.