Thoughts About Converting My Tweedy 5E3 to a Brownface 6G3?

Amp Mad Scientist said:
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You don’t want anything to go to the power supply ground , but the power supply, That is a safety ground.

Then a separate ground of only the heater center tap( green/yellow and the red/yellow) combined together with each only as their own separate ground at a different point away from the power ground.

Then a third separate ground that has the the cathode bias ground, reservoir filter cap grounds, and the ground to the 220K swamp resistors.

And finally another ground at the input jack for the rest of the pre amp grounds.

I know this sounds pushy, almost like a dick, but I recently had hum issues in two amps that was my own doing. Combining the center taps of the power transformer center and the filament ground to anything else is a bad,bad,bad idea. Separating those two grounds to a separate point of their own cures a sh*T load of hum
 
I'm definitely listening to all the advice regarding grounding the circuit. But in the last couple of years I have moved away from some of the multipoint grounding schemes and became interested in the 'grounding to a single point scheme' at the input jack or very close to it. The only exception being that the AC cable is grounded all by itself, and the OT is grounded with the speaker jacks where they are mounted to the rear of the chassis. I have not tried it yet, but I thought of isolating the OT and the speaker jacks from the chassis, and running a ground wire from the isolated speaker jacks to the buss bar that leads to the single point ground in the front of the circuit board. TTR member @ivan H , suggested this idea by having me look at what Mr Michael Mortimer of Modulus Amplification is doing with his products. Rob Robinette seems to be doing something very similar too. The only build that I have applied this technique is to my recent 5E3 build: Extremely quiet! Then again, following the multipoint "Larry grounding scheme" has worked very well too. Love the simplicity of the single point style...:

Modulus Tweed Deluxe Layout.PNG

T-Rex said:
Your rectifier looks off a bit. THe yellow wires go to pins 2 and 7 with the yellow going to the OT and B+ off of pin 8 too
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Yeah, my bad. I didn't notice those wires shifted off their proper locations when I was moving the other end of the 5v heater wires while using the layout software.


T-Rex said:
The green /yellow ground in the drawing needs removed from the positive end of the cathode bias, that's a direct short to ground. The positive end of the cathode bias is tied together bypass cap positive/ resistor and they go to pin 8 as shown in your drawing.
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That's another trick I learned from Rob Robinette: Elevate 6.3v Heater Center Tap
"If your power transformer has a 6.3v center tap, instead of grounding it to the chassis you can elevate the heater circuit ground reference voltage by connecting the 6.3v center tap to the tube side of the power tube cathode resistor. This elevates the heater ground reference by the voltage on the cathode which is around 17 volts in the 5E3. The elevated heater ground reduces the voltage difference between the heater filaments and the tube cathodes which helps minimize 60Hz heater hum."

Heater elevation and grounding:
5e3_Deluxe_Amp_Optimized_Layout_small.png


New and improved, and corrected...:
5E3to6G3 CHASSIS Copy - Copy.png


Splitting the grounding will be easy to try...:
5E3to6G3 CHASSIS Copy - Copy SPLIT GROUNDING.png
 
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I’ve tried the elevated heaters but didn’t care for that. A lot of techs do it. Watched some Psionic videos and Lyle had some good info about AC noise. In my earlier builds I didn’t pay much attention to seperating the PT AC grounds (and the first reservoir cap ground, ) But these Fender biuilds really point out that need

Those last two where I had hum with some hiss, I tried everything then remember to isolate the AC grounds, now they are unbelievable quiet
 
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T-Rex said:
I’ve tried the elevated heaters but didn’t care for that. A lot of techs do it. Watched some Psionic videos and Lyle had some good info about AC noise. In my earlier builds I didn’t pay much attention to seperating the PT AC grounds (and the first reservoir cap ground, ) But these Fender biuilds really point out that need

Those last two where I had hum with some hiss, I tried everything then remember to isolate the AC grounds, now they are unbelievable quiet
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Thanks, Terry. Plenty of food for thought. To be honest, I’ll probably wire up the grounds in the manner that I have shown. If when this build is complete and there are noisy gremlins related to the grounding, it will be easy to change things up by drilling two or three extra screw holes for more separate grounding points, and some minor rewiring too.

Anyways… Some parts should arrive within the next couple of days, and I might be able to get a start on the eyelet board. But the chassis, trannies, and filter caps are coming from Modulus Amplification (United Kingdom), which I’m not expecting for two to three more weeks. I’ll probably start a new thread when the build is happening.
 
T-Rex said:
Watched some Psionic videos and Lyle had some good info about AC noise.
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I just got through following up the subject on grounding by watching the three part series of videos from Psionic Audio. Very interesting and very well explained. I also noticed that Lyle Caldwell has another three part grounding video series just on the early 80's JCM800's only, and I'm definitely going to watch those too. So, for reference, I'm posting the videos that I just watched... Cool stuff!!





 
T-Rex said:
I’ve tried the elevated heaters but didn’t care for that.
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Sorry, Terry... Just one more...

If I did away with the elevated heaters and followed the "Larry & Lyle" grounding, is the following what you would expect?

5E3to6G3 CHASSIS Larry and Lyle Grounding.png
 
Am away and can’t see much on my phone, will reply back by Monday. Lyle can be a bit pretentious but does explain his take on things where a viewer can understand the idea behind the thought
 
syscokid said:
Sorry, Terry... Just one more...

If I did away with the elevated heaters and followed the "Larry & Lyle" grounding, is the following what you would expect?

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This is how I would wire the grounds up, but remember what the hey do I know about anything. The AC grounds of the PT center tap and the Heater center tap (the heater is the worse) are the two most AC ripple wires in an amp, along with the reservoir filter node that feeds the screen grids. If you isolate those grounds from inducing noise into the signal chain, the amp stays pretty dang quiet most times. Plese pardon the crappy paint drawing adjustment areas in the red circles.


 
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T-Rex said:
This is how I would wire the grounds up, but remember what the hey do I know about anything. The AC grounds of the PT center tap and the Heater center tap (the heater is the worse) are the two most AC ripple wires in an amp, along with the reservoir filter node that feeds the screen grids. If you isolate those grounds from inducing noise into the signal chain, the amp stays pretty dang quiet most times. Plese pardon the crappy paint drawing adjustment areas in the red circles.


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Sweet! Thanks, Terry. But looking at the input area, the four Switchcraft-style input jacks are already grounded to the chassis. They are not insulated like the speaker jacks will be. So technically there are two grounds in the input area. Any chance of a counterproductive ground loop here?
 
Sorry about adding that grounding tab, but I just don't trust those jack nuts to stay tight. I know, too stuck in my old ways.

As you have it drawn there should be no ground loop, as everything is spidered out.
 
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