The Amp Garage

martin manning wrote: ↑Thu Feb 01, 2018 12:19 pm See Blencowe’s Valve Wizard site: http://www.valvewizard.co.uk/Grounding.html

Seconded, his data is outstanding, and his books are great, not only does he point out that star grounding is very effective, but other types of very successful grounding schemes.

I greatly enjoyed his books.

~Phil

I agree on Merlin's grounding. I had to go back to his article several times(I'm a little slow) but once I got it, it made perfect sense! My interpretation is that it's all about controlling where currents travel and thinking about each node in the power supply as a separate power supply. Now I have to go back and rebuild my first builds!

Nothing to see too Trainwreck (move along) ... So suggest this thread be in "technical" section, and then made sticky.

Best .. Ian

Makes sense to me, done and done

~Phil

I have read multiple times on this forum and other forums that the preamp should be grounded at the input jack. Does that mean that the preamp ground is through the mechanical connection of the input jack? To make a good ground, you would have to tighten the jack pretty tight to get a good enough connection to the chassis. If you use a Plexi face plate, it seems like that might crack the faceplate. Also, the cliff jacks I have been using are isolated, so there would be no connection to the chassis if I use those jacks.

What I have been doing is to drill a hole for the preamp ground buss as close to the input jack as possible and then connect the ground of the input jack to that ground buss with 18 gauge solid copper wire.

Is this OK? I can't see any other way if the input jack is isolated. Any other suggestions?

Mike

In most cases the cliff jacks are insulated and they won't make a connection. Also the jacks themselves, even if they do, often wiggle loose over time, and build up corrosion that can make that ground weak at best if not have it removed totally. The best method is to create a drill hole with a solder tab type connection on the chassis right next to the input jacks as close as physically possible and make that the ground connection. the input jacks themselves can still be a 'redundant' ground at the same spot, but if they wiggle loose, it won't harm things, and having two grounds within less than an inch is pretty close to the same in my experience.

~Phil

mwelch55 wrote: ↑Tue Jul 17, 2018 5:53 pm I have read multiple times on this forum and other forums that the preamp should be grounded at the input jack.

I have posted about this previously. I am the outlier here. I never ground at the input jack, yet, I get good results. I was taught by someone (online) who I respected, to run a buss from the input to the PI, attaching ground wires clustered by gain stage. Then from the PI end, ground at a single chassis lug that also has the high potential grounds (power cathodes, PT CT, main filter, speaker, etc.) It works for me. I'm not looking for debate on it. It's a simple point, there is more than one way to get a good result. Please do what works for you.

Phil, have you built any high gain amps with this ground at the PT end?

While the PT ground works, the idea is that it lowers the noise floor at the input side of the chassis.

Are your amps noise free?

Phil_S wrote: ↑Mon Sep 19, 2022 8:56 pm

mwelch55 wrote: ↑Tue Jul 17, 2018 5:53 pm I have read multiple times on this forum and other forums that the preamp should be grounded at the input jack.

I have posted about this previously. I am the outlier here. I never ground at the input jack, yet, I get good results. I was taught by someone (online) who I respected, to run a buss from the input to the PI, attaching ground wires clustered by gain stage. Then from the PI end, ground at a single chassis lug that also has the high potential grounds (power cathodes, PT CT, main filter, speaker, etc.) It works for me. I'm not looking for debate on it. It's a simple point, there is more than one way to get a good result. Please do what works for you.

Phil S, That's the way I have done it too with excellent results, and an engineer I respect very much with 50+ years in the audio industry told me to do it that way too. I think there are likely many ways to get good results.

Greg

Hi all, FWIW I updated to fill in the missing diagrams (tried to link but for some reason that didn't work so had to upload them). Been meaning to do this--sorry it took so long! Hopefully the article makes more sense. Sadly Mr. Kimura passed away sometime last year from ALS (otherwise known as Motor Neuron disease or "Lou Gehrig's disease"(RIP). (Note that the original was altered since I did my translation so the final version on his site is a bit different from the one here.)

Thanks Dai.

Moderators, maybe this thread should be moved to the new FAQ area?

soundmasterg wrote: ↑Tue Jan 10, 2023 6:41 am

Phil_S wrote: ↑Mon Sep 19, 2022 8:56 pm

mwelch55 wrote: ↑Tue Jul 17, 2018 5:53 pm I have read multiple times on this forum and other forums that the preamp should be grounded at the input jack.

I have posted about this previously. I am the outlier here. I never ground at the input jack, yet, I get good results. I was taught by someone (online) who I respected, to run a buss from the input to the PI, attaching ground wires clustered by gain stage. Then from the PI end, ground at a single chassis lug that also has the high potential grounds (power cathodes, PT CT, main filter, speaker, etc.) It works for me. I'm not looking for debate on it. It's a simple point, there is more than one way to get a good result. Please do what works for you.

Phil S, That's the way I have done it too with excellent results, and an engineer I respect very much with 50+ years in the audio industry told me to do it that way too. I think there are likely many ways to get good results.

Greg

Just to note that from https://www.aikenamps.com/index.php/technical-q-a Aiken advises -

If you are using isolated input jacks, run a 0.01uF cap from the ground/sleeve connection directly to the chassis with as short a leads as possible.

Elsewhere he explains that he learnt this through bitter experience, in which a customer in an area with high EMI experienced problems that were solved by the cap.
The wire inductance between the input and the chassis screen is the cause.