Author Topic: Grounding: asking advice/tips for valve amps  (Read 271 times)

Online vinyljan

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Grounding: asking advice/tips for valve amps
« on: November 06, 2017, 09:55:42 PM »
When it comes to chassis ground, house ground, signal ground, star ground, earth rail etc.  Which of these should be directly connected, and which "indirectly" via caps etc :thinking:.   Also, should RCA jacks be isolated from the chassis routinely?  Trying to sort out a "humm" on one channel of a valve phono amp. It is only noticeable between songs but still quite annoying :headbanger:  Any advice appreciated
In a maximum bank turn in a normal category airplane, like a typical Cessna, everything is fine until you turn across your own wake

Offline King_Julian_S

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Re: Grounding: asking advice/tips for valve amps
« Reply #1 on: November 06, 2017, 10:00:29 PM »
I had that as well somewhere canít recall and recently guilaume commented on the fact that open tonearm wires are not shielded .. so I am sure it would cause a human if close enough to ?  What ? Iím not sure.
Also found a him due to my shitty soldering of a RCA connector ...

Moral of the story .. I donít know but have you tried other interconnects as a elimination method ..


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Non audiophile music lover...

Offline gavinbirss

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Re: Grounding: asking advice/tips for valve amps
« Reply #2 on: November 06, 2017, 10:03:36 PM »
Don't exclude magnetized tubes.

Fellow forum member sent me checklist and this includes checking for the phenomenon.

Offline Hi-Phibian

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Re: Grounding: asking advice/tips for valve amps
« Reply #3 on: November 06, 2017, 10:11:34 PM »
Itís good to isolate rca sockets from chassis as it gives you the freedom to try independent signal ground and joint signal ground. and not isolated. 
Also to eliminate external influence a battery powered headphone amp and headphones are of great value so you can listen for hum while switching everything else on and off. 
I would start by isolating the rca sockets and removing the lid off the case. 
Is the transformer in the same enclosure and if so is it nearer the humming channel or the other. 







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Offline Hi-Phibian

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Re: Grounding: asking advice/tips for valve amps
« Reply #4 on: November 06, 2017, 10:12:40 PM »
Does it hum with rca plugs with 1k resistors plugged in rather than the turntable/arm or is there any difference with other arms or tables. 







[Anyone who thinks that wealth is measured in money is blind and narrow minded.  Wealth is obviously measured in turntables and records.]
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Offline Hi-Phibian

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Re: Grounding: asking advice/tips for valve amps
« Reply #5 on: November 06, 2017, 10:13:03 PM »
I can demag your tubes by the way. 







[Anyone who thinks that wealth is measured in money is blind and narrow minded.  Wealth is obviously measured in turntables and records.]
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Online vinyljan

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Re: Grounding: asking advice/tips for valve amps
« Reply #6 on: November 06, 2017, 10:22:59 PM »
I should actually open it up and spend quality time on it.......usually just fiddling while busy with something else.  Swopped arms and also swopped valves between channels but it is always same channel.  More of a soft hissing sound, but it is definitely the channel closest to the transformer, so that's where I'll start  :thumbs:. Will also try the 1k resistors.
In a maximum bank turn in a normal category airplane, like a typical Cessna, everything is fine until you turn across your own wake

Offline gavinbirss

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Re: Grounding: asking advice/tips for valve amps
« Reply #7 on: November 07, 2017, 07:23:19 AM »
I can demag your tubes by the way. 

Can I bring all my tubes?
 :be:

Offline Ampdog

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Re: Grounding: asking advice/tips for valve amps
« Reply #8 on: November 14, 2017, 03:35:12 AM »
Vinyljan,

Yes - this can be a devil. Other than the above suggestions, is this a phenomenon that started at a time, not having been there before? Otherwise I would start with replacing the cartridge inputs with the mentioned 1K resistors or similar. Next, if the heaters are ac, one could 'disengage' those. A simple way is by putting the heater feed from the transformer on a fly-lead which could be held down by hand. Have it on until the valves have properly heated, then removing it will keep the valwes working for a few seconds, long enough to detect a difference. But primarily one needs to know whether it is a 'new' fault.

Regarding where to earth in general, the safest is to use some sort of 'star' earth, and connect that to the enclosure at one perticular point. But I have built many amplifiers where I earthed all indicted components at a point near each - all over the place; no problem. [I must point out that my chasses were aluminium. Steel chassis: I never had a quiet amplifier using any of the systems - guess steel (magnetic conductivity) and I am not friends, although most commercial ampliers use steel chasses.]

Connecting to the mains is somewhat easier. As long as no loops exist matters should be fine. [A loop is where there are connections to the mains from more than one place separate from each other, so as to create a physical loop through which induced fields could act, as in e.g. earthing each separate ancilliary through its three-core mains lead.]  But occasionally induced hum could be a bugger.  It is also helpful to determine at an early stage whether the hum is 50 Hz or 100 Hz, denoting different origins. Not to go much further, but an oscilloscope can be a great help in tracing interference of any kind.
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Offline JimGore

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Re: Grounding: asking advice/tips for valve amps
« Reply #9 on: November 14, 2017, 09:56:12 AM »
Grounding is a very interesting topic, and can cause quite a bit of headache when Murphy is working against you.

I am sure you know about this, but just in-case anyone out there doesn't - this article by Rod Elliott is a very good primer on the subject:  http://sound.whsites.net/earthing.htm

Best of luck with your troubleshooting.

Kind regards,
Ian.

Offline Ingvar Ahlberg

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Re: Grounding: asking advice/tips for valve amps
« Reply #10 on: November 14, 2017, 08:11:28 PM »
There is only one real way to grounding in an electronic/electric device.

One ground point, period.

Lots of ground wires, lots of work, but the only way, if chassis is grounded, only way is one wire from chassis to ground point, nothing else connected to chassis.

All other methods will produce ground loops, bad. There are no electronic devices that are classed as life support systems ( also reffered to as class3 electronics) that use anything other than one point ground.
Some aircraft electronics have been designed other ways, with not very satisfactory results, short airtime (but on the other hand, low fuel cost).

This above is a good way to approach grounding in music equipment, pls note, star ground designs on PCB and in wiring is just this, in my years in the industry and with my own equipment i have never had a hum problem that wasīnt caused by bad grounding, never caused by components.

For finding source of hum in the PU-phono stage- amp  remove all grounding wires, just keep signal cables connected and then start with first touching the outher (ground) surface of one channel connector from PU to phono amp input, probably hum will be gone or lowered, keep testin different connection points for the grounding wire untill quiet, if not found grounding problem is within phonoamp.

If this is incomprehensible, not unusual in my ramblings, drop me a PM and i will guide further.

Ingvar
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Re: Grounding: asking advice/tips for valve amps
« Reply #11 on: November 14, 2017, 09:45:29 PM »
Thanks for the advice so far  :thumbs:., will try some of it this weekend if all goes well.

If I remove the chassis/wallplug earth connection on the phono amp (but PCB is still connected to chassis) and the phono amp is connected via the interconnects to an integrated amp that is connected to house earth.....is there any danger in this :thinking:
In a maximum bank turn in a normal category airplane, like a typical Cessna, everything is fine until you turn across your own wake

Offline Ingvar Ahlberg

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Re: Grounding: asking advice/tips for valve amps
« Reply #12 on: November 14, 2017, 09:57:42 PM »
Dont remove/dissconect any power grounds/earth, has nothing to do with the hum, only ground wires in interconnections tonearm-phonoamp-amp, and we dont want fried forum friends, smell bad.

Ingvar
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Responsible for H.A.D Halland Audio Design and The vacuumed cat Company.

Online vinyljan

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Re: Grounding: asking advice/tips for valve amps
« Reply #13 on: November 14, 2017, 10:19:37 PM »
 :
...... power grounds/earth, has nothing to do with the hum.....

Ingvar
2thumbs:...my initial question was also regarding  the function of the different types of ground /earth :thinking:
In a maximum bank turn in a normal category airplane, like a typical Cessna, everything is fine until you turn across your own wake

Offline Ingvar Ahlberg

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Re: Grounding: asking advice/tips for valve amps
« Reply #14 on: November 14, 2017, 10:38:21 PM »
Sorry, unclear and maybe even not read entire thread carefully. Protective ground/earth is an entirely different thing than the ground we are trying to find problem point causing hum. Protective earth/mains grounding is allways the same thing, no matter if power (live wire) supplying equipment comes from different phases of incomming power, protective ground is the same.

This can be connected to ground/signal ground in some music equipment, in that case the in/output connectors will surely be insulated from chassis, otherwise uncorrect designed.

If You describe system layout i can try to guide the hum killing project a bit better.

Ingvar
A senile Swedish loudspeakermanufacturer, ponytail and all, why is he here?

Responsible for H.A.D Halland Audio Design and The vacuumed cat Company.