Thanks for the input Euro 21.
I went back and forth on the ground point for considerable time.
my first choice was a front to back 16 gauge ground bus , grounded to the chassis at the input tube socket.
Then I went to a star ground with a tag strip mounted longitudinally to the rectifier tube socket. Pretty close to the center of the chassis.
I was happy with this set up until…
…I became concerned about the rectifier 120 Hz noise getting into the ground and ended up in the back corner—routing everything away from the rectifier tube and HT wire to the choke.
Likely a needless worry… But I just didn’t know for sure. Brand new at this, and could not find anything definitive on the web.
Is routing a ground wire across the high tension wire off the rectifier tube a concern?
Went full on brute force and star grounded everything. Likely unnecessary, a complete pain in the *** and maybe a source of troubles. Not going to unwind it at this point. Hopefully is okay…
Next build will either be a ground bus or star with short wires and intermediate star grounds as you suggested.
Lessons learned.
Thanks again and keep the suggestions coming.
I went back and forth on the ground point for considerable time.
my first choice was a front to back 16 gauge ground bus , grounded to the chassis at the input tube socket.
Then I went to a star ground with a tag strip mounted longitudinally to the rectifier tube socket. Pretty close to the center of the chassis.
I was happy with this set up until…
…I became concerned about the rectifier 120 Hz noise getting into the ground and ended up in the back corner—routing everything away from the rectifier tube and HT wire to the choke.
Likely a needless worry… But I just didn’t know for sure. Brand new at this, and could not find anything definitive on the web.
Is routing a ground wire across the high tension wire off the rectifier tube a concern?
Went full on brute force and star grounded everything. Likely unnecessary, a complete pain in the *** and maybe a source of troubles. Not going to unwind it at this point. Hopefully is okay…
Next build will either be a ground bus or star with short wires and intermediate star grounds as you suggested.
Lessons learned.
Thanks again and keep the suggestions coming.
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Thank you for the kind words.
Fashioned the capacitor clamps out of stainless steel hose clamps 1 1/2” (plenty big) from amazon. Used a strip of paper wrapped around the capacitor as a template. Make first clamp and tweak it as round as possible by hand and test fit. Adjust template as needed. Best to leave 3+ mm gap to ensure proper tightening.
Caps are Titan HD (do NOT use the Titan Pro) 60uF and 25uF. 370VAC. (Word is they should tolerate somewhat higher DC voltage). Best quality I could find that would meet my size requirements. One and three-quarter inch diameter stated size(they actually measure larger and are not perfectly round).
My first choice was AmRad but they are only available in the 440 VAC and physically much too big for this project. ASC capacitors seem very popular and come highly recommended also, but I could not find any.
Caps were “brush finished” using scotch bright, ultrafine followed by Mirka Merlon microfine. Put a brushed finish on the clamps also, but did not use the microfine pad. The harder stainless steel does not need it.
Wrap them on the bench and spin them by the terminals. The key is straight line. No side to side motion whatsoever and very carefully unwrap. I first did the top by standing them on their head on top of the scuff pad and spinning them in the exact same spot.
The resulting finish is very easily scratched, and some gentle buffing after install is required. (Tape off anything you don’t want scratched on amp then wrap the caps with microfine pad and gently go back-and-forth like buffing a shoe).
produces a very nasty fine aluminum dust. Be sure to blow that off before polishing the amplifier.
The clamps are a real pain to install. Almost need a third hand. One to push the cap up from the bottom the other firmly seat the clamp and a third to tighten the screw. On your own, you can get pretty close and don’t tighten it all away slowly pushing it into place and then tightening as you go. I don’t suspect that this clamp would hold up to the rigors of commercial production or shipping—likely it would work its way loose.
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The most ridiculous point is the PT(0) -middle- and first capacitor negative point connection.
There is the rectification noise and first capacitor ripple noise the most disturbing thing. This connection be as short as possible.
From the first capacitor negative short wiring (another wire, than the former) required to the second capacitor negative.
The second capacitor negative pole is THE ground point, the ground bus joins here.
There is the rectification noise and first capacitor ripple noise the most disturbing thing. This connection be as short as possible.
From the first capacitor negative short wiring (another wire, than the former) required to the second capacitor negative.
The second capacitor negative pole is THE ground point, the ground bus joins here.
I’ve read in several other posts the 1st cap should “ground“ directly to the PT 0 and everything else to the star. No?
very frustrated with this grounding scheme. My first inclination was to go exactly as you said…center the star and include local grounding points. I made a last second decision to change without giving it enough thought and managed to make the simple complex.
Thanks again for your input.
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I suppose at this point, I will stay the course. Only two more wires to run. Hopefully no hum. But never again. Despite my complaints, I am still having fun!
Couldn’t quite follow your post euro 21 Likely due to my lack of reference and experience. Any elaboration or further suggestions are welcome.
Nonetheless, measured ripple at the speaker terminal 0.5mV. Seems reasonable for an AC heated triode.
A quote lifted from EML website: “Anything below 3 millivolt at 8 Ohms is a good achievement, and such an amplifier below 1 millivolt can be called a fine piece of work”
Nonetheless, measured ripple at the speaker terminal 0.5mV. Seems reasonable for an AC heated triode.
A quote lifted from EML website: “Anything below 3 millivolt at 8 Ohms is a good achievement, and such an amplifier below 1 millivolt can be called a fine piece of work”
Sounds stunning. Bests Elekit 8600 and 8900 for me. If you have read the entire thread, you know this was a warm-up. Learned a little and have some ideas for the driver circuit for my next 45 project based on member input. This one sounds great and, for my listening, bests anything I have. Based on advice here it could get even better…Anyone in Arizona wants to drop in for a listen drop me a line. For now time to enjoy the music. Thanks all!
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