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Old 28th June 2012, 01:32 AM   #1611
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Hi,

when I am near the amp (premium kit) and I have the Iphone in my pocket I also occasionally hear the typical buzz of cell phone interference but at low level and when I sit back on the armchair the buzz stops.

Renato
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Old 9th August 2012, 03:10 PM   #1612
johnm is offline johnm  United Kingdom
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Forgive me for asking a question which is probably answered somewhere in the labyrinth of Gainclone posts (I tried a search too to no avail). What's the best earthing arrangement for a true dual-mono (two transformers & rectifier boards) Gainclone in the same chassis?

Many thanks!

- John
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Old 9th August 2012, 09:50 PM   #1613
johnm is offline johnm  United Kingdom
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Quote:
Originally Posted by johnm View Post
Forgive me for asking a question which is probably answered somewhere in the labyrinth of Gainclone posts (I tried a search too to no avail). What's the best earthing arrangement for a true dual-mono (two transformers & rectifier boards) Gainclone in the same chassis?

Many thanks!

- John
Found what I needed here post 714: Commercial Gainclone kit- building instructions

And post 73: Commercial Gainclone kit- building instructions

Might be an idea to add both of these to the sticky for others using stereo and/or dual mono setups in same chassis?

Last edited by johnm; 9th August 2012 at 09:54 PM.
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Old 10th August 2012, 09:11 AM   #1614
AndrewT is online now AndrewT  Scotland
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Try asking Peter D. to add then as an index (or similar) to post1.
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Old 19th August 2012, 01:28 AM   #1615
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Just to make things clearer for anyone building a true dual-mono Gainclone, but housed in the same chassis, Peter says:

"In case of dual mono, I would connect AC Earth ground directly to chassis first and then run CHG from each amp board to that point through 10R resistors each."
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Old 19th August 2012, 10:14 AM   #1616
AndrewT is online now AndrewT  Scotland
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That advice is potentially dangerous.
I'll explain why, because Peter takes exception to me posting on this commercial sector of the Forum.

Here's the scenario:
The mains Live wire breaks, or the mains transformer breaks and this failure results in a mains connection to some part of the secondary side of the amplifier. The audio side shorts out that high AC voltage to any route it can find back to mains Neutral.
That route will be via the PE wire in the mains cable.

How does the faulty mains voltage get to PE?
Via whatever secondary side connections to chassis that exist. Most of the amplifier is insulated from chassis. The Main Audio Ground is connected to chassis via PD's proposed 10r resistor.

The next part becomes the problem:
Mains voltage is trying to return to Neutral via PE and through that 10r resistor. 230Vac across 10r is ~ 5.3kW and could be >32Apk.
The resistor almost instantaneously overheats and then goes on to "frazzle" itself. This sequence of resistor failing to open takes just a few microseconds. This period is too short to reliably rupture the fuse fitted in the equipment nor to open the circuit breaker back at the distribution board.

Now the potentially FATAL part of the scenario:
The mains fuse is not open.
The Main Audio Ground to Chassis resistor is open.
The faulty mains connection to the secondary side makes all the internal components LIVE.

Those LIVE parts can be connected to other double insulated equipment.

Both the faulty amplifier and all the other (connected) ClassII equipment now have Mains voltage on the LV side.
Touching any conductive part of the LIVE equipment will kill you, or your child.

The Main Audio Ground Must be connected to Chassis by a route that can pass Mains Fault Current to PE and this route MUST survive long enough to ensure that the Mains Fuse ruptures and the arc extinguishes.

If PD only mentions that 10r resistor and makes no mention of the other "Fault Current" route components then he is wrong in advising only a resistor. A plain wire is safer.

But any Member should help themselves by reading all/some/many of the other Threads that discuss this topic and read the ESP site about this same subject.

Summary
The Main Audio Ground of mains powered equipment MUST be connected to Chassis.
This "Connection" MUST be capable of passing "Fault Current".

There are no exceptions in ClassI equipment, (all diy audio builds using mains power).
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Last edited by AndrewT; 19th August 2012 at 10:34 AM. Reason: Note that from posting @ 1014 to final editing @ 1033 I spent 19 minutes checking this post.
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Old 21st August 2012, 11:57 AM   #1617
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Thanks for the above advice Andrew - I attached the main audio grounds direct to the chasss earth point, without the 10R resistors. Fortunately absolutely no hum that I can decern, otherwise I guess one then needs to implement the disconnecting network shown on ESPs website.

Extremely pleased with the end result - stunned in fact. These little chips really are quite something!

Thanks for your help Andrew.

John.
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Old 29th August 2012, 02:54 PM   #1618
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Perhaps a dumb question but I am not sure. I will change my gainclone tomorrow to a dual mono amp. But I am not sure how to wire the stargrounding. Only CHG from chipboard or also from the rectifier board (I now have grounding from CHG and pg+ and PG-)? My guess is the only grounding needs to be from CHG grom both chipboards.

Last edited by Dracoplasm; 29th August 2012 at 03:12 PM.
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Old 29th August 2012, 03:11 PM   #1619
Marra is online now Marra  United Kingdom
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Like johnm I ran both chg to the chassis without any 10R resistors and had no bproblem with hum.No connection to the chassis from the power supply only to the amp board.
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Old 29th August 2012, 03:12 PM   #1620
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There's no common ground on rectifier boards (separate grounds for each rail which connect on amp board), so in your case just the wires from CHG for stargrounding.
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