Apex/Nady Power Supply for G7-grounding

[craigmorris74]

I'm about to start on building my G7, and I have 3 Chinese power supplies lying around. They've all put out about +160/+6.3 after modification.

After reading every post about the G7, I'm still confusted how I should connect it to the Apex/Nady PSU. Specifically, I don't know what to do about the grounds. It seem that the China PSU has 2 grounds coming from 1 source, while Jakob's G7 supply has 2 separate grounds, 1 for the B+ and one for the heater. How do I connect the grounds of the mic to the power supply? Here's a diagram showing what I understand up until now.

Any help will be greatly appreciated. Thanks,

Craig

 

[vertiges]

... and here is the schematic of the Chinese PSU :

Note : the values of the components may differ (the voltages too of course), but it's the same circuit.
eD

 

[craigmorris74]

Should pads should the 0V/GND and heater 0V both be connected to pins 4 and 7 on the connector from the China PSU? I ask this because I read where Jakob mentioned in another thread about the 0V/GND and heater 0V not being connected until the tube section of the PCB.

Craig

 

[beatpoet]

I'm wondering if Zener and Regulator regulation are worth the harmonics that they inject?

 

[Gus]

The China built supplies do not seem to have a noise issue stock.
The China microphones often have another RC in the microphone for the B+. Also look at all the RC stages in the B+ part.

That posted I do change some things in the supply

I have found the heater supply to be important than the B+ in tube microphone builds.

 

[craigmorris74]

Right, I've got the heater supply at 6.3V in all my China power supplies.

My question involves the how to properly connect the 0V/GND and heater 0V of the G7 to the two ground pins of the China PSU.

Thanks,

Craig

 

[vertiges]

[quote author="craigmorris74"]Right, I've got the heater supply at 6.3V in all my China power supplies.

My question involves the how to properly connect the 0V/GND and heater 0V of the G7 to the two ground pins of the China PSU.

Thanks,

Craig[/quote]

Please someone correct me if I'm wrong :

Is the 0V for the B+ in the G7 PSU not a 'zero floating potential' reference (PIN 1 G7 PSU) ? Versus the 'real ground' ? I mean the "earth"- chassis - body given by the PIN 7 (G7 PSU)... :?:

By the way, I like the idea of the LM317 with the variable resitor. It can be useful for figuring out the "sweetest" heater voltage.


eD

 

[craigmorris74]

Giving this one bump to see if anyone knows the answer to my grounding question for sure.

Thanks,

Craig

 

[rodabod]

Craig, as Ed says, the G7 PSU grounds are isolated between the HT voltage and the heater. This can be easily done with this PSU since it uses two mains transformers which provide isolation and allow you to "lift" the earth.

Now, the Chinese PSUs do not do this, and don't even attempt to float the voltages from mains earth at all. All of the earths are tide together.

I use two of the typical Chinese PSUs and these have not had any ground loop or hum problems as they are, so my advice is to use them as they are, and if you find that you have a hum issue, then mod them later.

 

[craigmorris74]

Thanks eD and rodabod for the advice. I'm getting my parts order together today.

Craig