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EHHA Rev A - Interest Thread - Page 106

post #1576 of 1733
Quote:
I believe SG is Signal Ground.

Star Ground is the designator of the topology where grounds are 'tied' together at a single point to ensure there is no potential difference between any of the grounds.

Correct.

post #1577 of 1733

...and another point just crosses my mind looking at the last pic... (now big ;)).

Isn't the GLB supposed to be put between chassis and Mains Ground?

Not sure since I never used one...

post #1578 of 1733

Hi All;

 

Your mains ground should be connected to earth, thus, for this conversation, they are about the same thing.  Your mains ground should then be connected directly to the chassis. Star ground is a common point for grounding as UKToecutter points out.  This common point may be tied directly to chassis ground or "lifted" through a ground loop breaker.  Meaning all the wires are connected at a common point, run through the breaker (there are several types) and then to the chassis.

My heater and power supply lines are connected directly to the amp board with twisted pairs.  Ground lines are not routed to star ground first.

The only common point or star ground I used was to run 1 wire from SG on each board (located on the input connector) to my ground loop breaker and from there to chassis ground.  SG probably means signal ground in relation to this connector.

 

Stixx asked "Isn't the GLB supposed to be put between chassis and Mains Ground?"  I have seen people posting builds done both ways. On this one, I use it between the amp boards and chassis. I don't like the idea of directly connecting any of my electronics to a wire that plugs into the wall.

 

One tip I read in a post a year or so ago was to construct a GLB with a longish pigtail wire attached.  Connect one end to chassis ground and use the pigtail to "probe" different grounding spots while listening for a reduction in noise.  This is how I traced down my problem.

 

I hope this helps.

Jim

post #1579 of 1733

Hi All;

 

Your mains ground should be connected to earth, thus, for this conversation, they are about the same thing.  Your mains ground should be connected directly to the chassis. Star ground is a common point for grounding as UKToecutter points out.  This common point may be tied directly to chassis ground or "lifted" through a ground loop breaker.  Meaning all the wires are connected at a common point, run through the breaker (there are several types) and then to the chassis.

My heater and power supply lines are connected directly to the amp board.  Ground lines are not routed to star ground first.

The only common point or star ground I used was to run 1 wire from SG on each board (located on the input connector) to my ground loop breaker and from there to chassis ground.  SG probably means signal ground in relation to this connector.

 

Stixx asked "Isn't the GLB supposed to be put between chassis and Mains Ground?"  I have seen people posting builds done both ways. On this one, I use it between the amp boards and chassis. I don't like the idea of directly connecting any of my electronics to a wire that plugs into the wall.

 

One tip I read in a post a year or so ago was to construct a GLB with a longish pigtail wire attached.  Connect one end to chassis ground and use the pigtail to "probe" different grounding spots while listening for a reduction in noise.  This is how I traced down my problem.

 

I hope this helps.

Jim

post #1580 of 1733

Ok, I will now start to test.

 

For the first point, I directly wired ground of amp ps and amp board.

Since the ground wires coming from the ps are soldered below the

board I just left them floating. (Dismounting the boards is a huge effort...)

 

That actually brought me back to the state before.

Loud hum on the left channel and more quiet on the right. :confused:

 

When I attach the ground of the left amp PS to star ground, the hum

gets a bit more quiet.

 

muskyhuntr:

As far as I see in the Pictures, your heater-ps grounds are not connected to anything?

post #1581 of 1733

Hi All;

 

You are right,  plus/minus from the power supplies to plus/minus on the amp boards. This goes for both the heater supply and the amp supply.

 

Jim

post #1582 of 1733

But have you wired ground from the amp ps and ground of the amp board?

 

 

I just reconnected amp ps ground to star ground and disconnected

the heater ps ground from star ground:

 

Gives me same hum on both channels, louder than with heater ps

ground attached to star ground, but not as loud as the hum that

comes on the left channel when amp ps ground is not connected to

star ground, but to amp board ground.

 

This is so damn confusing!

post #1583 of 1733

Hi All;

 

The rail supply board has a connector with 3 outputs, +30, 0, -30.  With 0 considered as ground.  The amp board has a connector for 4 connections, +30, ground, out, and -30.  On mine, I have the +30 connected to the +30 on the amp board, the -30 connected to -30 on the amp board and the 0 connected to ground which is next to the +30 on the amp board.  Additionally, on the rail power supply board, I  have 2 wires connected to the +30 and the -30 going to the E12.  On the amp board I have 2 additional wires going from out and ground to my E12.  Each channel is wired the same.  As noted earlier, the EHHA requires 2 E12's because there are 2 power supplies.  The ground from each E12 is combined at the output jack.  The jack, BTW, is isolated from the chassis.  Nowhere are wires run from either the rail supply or the heater supply to a star ground. 

 

Hope this helps

Jim

post #1584 of 1733
Quote:
 Nowhere are wires run from either the rail supply or the heater supply to a star ground. 

Sorry Jim,

but isn't this misleading? When I look at my breadboard as well as on both wiring schemes there are wires from

either heater supply and rail supply to Star Ground...

post #1585 of 1733

Hi All;

 

From Stixx:  "Sorry Jim, but isn't this misleading? When I look at my breadboard as well as on both wiring schemes there are wires from

either heater supply and rail supply to Star Ground..."

 

You are right.  I was referring to my build in that statement and should have been more clear.  I probably should have stated this from the beginning that I did not follow Cavalli's wiring scheme.  My intention was to make the absolute minimum connections needed for operation (heater supply, rail supply, input, and output) and then, if there was a hum problem, go from there.  My one criticism of this amp is that there are too many connections to and from the boards.  I wanted to eliminate as many as possible.  I was lucky in that I only needed the two from SG.

 

I'm sorry if I was misleading, I hope this clears it up. 

 

Jim

post #1586 of 1733
Having a go at this again...

I had a close look at your first image (post # 1552) and it seems correct to me, except that the pot
is not connected. Both channels of the pot have to be connected with their ground pins to ground
or there will be hum!

You seem to have wired all psu grounds and heater grounds to star ground. Amp board and psu
board are connected. RCA's (isolated) and the pot are connected to Star Ground as well as the
output jack. Doing so should result in no hum...?

I did exactly so on my breadboard. As Jim pointed out you can “lift” the Ground via a Ground Loop
Breaker that goes between your Star Point and Earth (at the IEC connector).

Have you checked the pot? Both channels connected to star ground…? (my last hope)
post #1587 of 1733

I was wondering if i could use 12au7?  The plate voltage is limited to 30V only but there are good souding amp like project sunrise only run at 13.5V plate

post #1588 of 1733
Quote:
Originally Posted by muskyhuntr View Post

Hi All;

The rail supply board has a connector with 3 outputs, +30, 0, -30.  With 0 considered as ground.  The amp board has a connector for 4 connections, +30, ground, out, and -30.  On mine, I have the +30 connected to the +30 on the amp board, the -30 connected to -30 on the amp board and the 0 connected to ground which is next to the +30 on the amp board.  Additionally, on the rail power supply board, I  have 2 wires connected to the +30 and the -30 going to the E12.  On the amp board I have 2 additional wires going from out and ground to my E12.  Each channel is wired the same.  As noted earlier, the EHHA requires 2 E12's because there are 2 power supplies.  The ground from each E12 is combined at the output jack.  The jack, BTW, is isolated from the chassis.  Nowhere are wires run from either the rail supply or the heater supply to a star ground. 

Hope this helps
Jim

You connected the center tap of your transformer to what ground???
post #1589 of 1733
Quote:
Originally Posted by Sathimas View Post

But have you wired ground from the amp ps and ground of the amp board?


I just reconnected amp ps ground to star ground and disconnected
the heater ps ground from star ground:

Gives me same hum on both channels, louder than with heater ps
ground attached to star ground, but not as loud as the hum that
comes on the left channel when amp ps ground is not connected to
star ground, but to amp board ground.

This is so damn confusing!

You are not the only one confused.

Did you follow the alternate grounding scheme or not?

Follow the alternate grounding scheme and establish a reference. In this configuration, which channel exhibits a hum?
post #1590 of 1733

Hi All;

 

jdkJake asks: "You connected the center tap of your transformer to what ground???"

Nowhere in any posting have I even suggested that I connected the center tap of my transformer to any ground connection.

 

Jim

Sathimus you have mail 

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