My Gainclone is now a day old, still sprawled across my living room floor, but producing nice sounds ! The tweaker in me has now started to kick in, and my attention now turns to earthing. With no input, I get a slight hum from my speakers, quite normal, I believe, for a Gainclone (especially a naked Gainclone !). As an experiment I connected the power ground star point to mains earth and the hum quietened to virtually nil. Now, my NAD CD player is not earthed, it has a two core mains lead, so it just "floats". I have measured the chassis voltage of the CD player at about 50V AC, the Gainclone ground is also about the same (with the CD player disconnected). This volatge is obviously just "leakage" , so no harm in connecting to earth, or is there ? I would of thought that earthing the amp (and eventually, the metal case of the amp) would "shield" the circuitry from RF interference, a good thing ? However, I`m concerened about problems that I may get when I eventally connect my Satellite Decoder, Television and XBOX. These appliances have switch mode power supplies with chassis grounds that do carry a little more "oomph" ie. their grounds float at a higher voltage with respect to earth, and can actually provide a little current if connected to earth. Should I avoid earthing anything, or is there an advantage in doing so ? Maybe I could connect to earth through a resistor and/or capacitor. Can anyone with any knowledge on this matter please advise ?
Search on "ground loops".
The best way to deal with a ground loop is to eliminate it if you can implement a single-wire-ground situation, where removing 1 wire would isolate you from your mains ground.
In your case, that get difficult because of your satellite receiver. I have personally used resistors to limit the current flow in the ground loop as a successful crutch, so keep that in your pocket if you need it.
The best way to deal with a ground loop is to eliminate it if you can implement a single-wire-ground situation, where removing 1 wire would isolate you from your mains ground.
In your case, that get difficult because of your satellite receiver. I have personally used resistors to limit the current flow in the ground loop as a successful crutch, so keep that in your pocket if you need it.
Prof said:
An actual earth ground has no particular relevance to your audio equipment.
Neither the amp nor the case require any earth ground connection in order to be effective at shielding. If that were the case, then the sensitive instrumentation on aircraft and spacecraft could never be effectively shielded. At least not without a REAAAAAALLY long extension cord.
The only reason you'd want to connect to the earth ground (i.e. the safety ground) is for safety reasons. That's basically its only purpose.
se
mothman said:
What exactly do you mean by "stray voltages"? Stray voltages from what? And what's the reference point for the voltages (seeing as a voltage is just the potential difference between two points)?
The earth connection really only functions as a drain as it regards such things as lightning. That's basically all it's there for so that if lightning happens to strike the power lines, it provides a path to ground seeing as lightning is due to opposing static charges between the earth and the clouds.
se
I do understand the 'safety ground' function and it having nothing to do with the 'amp ground'and I guess 'stray voltage' is a term flung around to confuse novice guys like me.I thought airborn or a connected component could channel nasties into the amp circuit or maybe it was reading too many of Jonathan Skull's columns that corrupted me.
Seriously though assuming my amp is properly grounded(and I believe it is)and my case is connected to 'Earth Safety Ground'is directly connecting 'Amp Ground' to this point,to get the shielding benefit of the case OK?..You don't really wanna leave the amp floating do you?
Seriously though assuming my amp is properly grounded(and I believe it is)and my case is connected to 'Earth Safety Ground'is directly connecting 'Amp Ground' to this point,to get the shielding benefit of the case OK?..You don't really wanna leave the amp floating do you?
mothman said:
Hehehe. J10's cool. He and I go back to the old The Audiophile Network BBS (a.k.a. TAN) back in the mid-80s (that's where JA recruited him from to write for Stereophile, along with several other TAN members). But alas he's sold his soul to Monster Cable.
Floating with respect to the chassis? Not really. Technically you're better off making the chassis part of the amp's reference ground. Just that once you bring the safety ground into the picture, you open yourself up to ground loop and other problems.
So basically you trade a margin of safety for a margin of potential noise problems.
Of course you can use a line level input transformer and just eliminate any ground loop and interchassis current problems altogether. That's what I've been doing for years.
se
Prof,
I suppose that laying on the floor you have one transformer (you don't specify if one or two) and the two channels of your GC.
Join the two channels together (get them close) and run a wire from the star ground of left channel to the star ground of the right channel.
This wire must be very short, so you have to get the two cannels toguether.
Then, from a middle point of this wire, connect to the ground wire of your transformer (or if you use two bridges, the ground point).
For now, forget the mains earth.
Turn it on and listen.
Silent?
If not, you have a problem with ground loops on your implementation.
You can try also connecting only one channel and see how does it behave.
If there's noise with only one channel connected, you have a ground loop.
If it's silent and the noise only appears whent both channels are connected, it's because you have long wires to the ground point, and you easilly solve this as I describe above.
I hope this helps.
I suppose that laying on the floor you have one transformer (you don't specify if one or two) and the two channels of your GC.
Join the two channels together (get them close) and run a wire from the star ground of left channel to the star ground of the right channel.
This wire must be very short, so you have to get the two cannels toguether.
Then, from a middle point of this wire, connect to the ground wire of your transformer (or if you use two bridges, the ground point).
For now, forget the mains earth.
Turn it on and listen.
Silent?
If not, you have a problem with ground loops on your implementation.
You can try also connecting only one channel and see how does it behave.
If there's noise with only one channel connected, you have a ground loop.
If it's silent and the noise only appears whent both channels are connected, it's because you have long wires to the ground point, and you easilly solve this as I describe above.
I hope this helps.
Prof,
I would always recommend connecting a metal chassis to earth/ground for safety - even with 'double isolated' electronics - as you should not discount the possibility of the case coming into contact with mains/live (externally) - with an earth connection it should at least blow a fuse / open an RCD somewhere !!
The real question is do you connect the 'center tap' of your PSU to earch as well ? If you do not you risk some other piece of connected equipment raising the potential of this point WRT ground and generally swinging it around !! My choice would be to connect to ground (through a resistor ?) but not to make it to difficult to change, if, and when, nessesary ...
My most recent experience of 'ground loops' occured after my cable TV intallation was upgraded with a cable modem. This resulted in severe interferance breaking through the shields from a DVD and PC (no problems prior to modem). Nothing I tried could eliminate this totally (ferrites/earthing/un-earthing/messin' with the cable TV shield/hasselling the cable co/etc/etc) and I eventually had to resort to optical links
. Sometimes no amount of fiddling with earthing will fix a problem ....
Dave
I would always recommend connecting a metal chassis to earth/ground for safety - even with 'double isolated' electronics - as you should not discount the possibility of the case coming into contact with mains/live (externally) - with an earth connection it should at least blow a fuse / open an RCD somewhere !!
The real question is do you connect the 'center tap' of your PSU to earch as well ? If you do not you risk some other piece of connected equipment raising the potential of this point WRT ground and generally swinging it around !! My choice would be to connect to ground (through a resistor ?) but not to make it to difficult to change, if, and when, nessesary ...
My most recent experience of 'ground loops' occured after my cable TV intallation was upgraded with a cable modem. This resulted in severe interferance breaking through the shields from a DVD and PC (no problems prior to modem). Nothing I tried could eliminate this totally (ferrites/earthing/un-earthing/messin' with the cable TV shield/hasselling the cable co/etc/etc) and I eventually had to resort to optical links
. Sometimes no amount of fiddling with earthing will fix a problem ....Dave
DRC said:
My most recent experience of 'ground loops' occured after my cable TV intallation was upgraded with a cable modem. This resulted in severe interferance breaking through the shields from a DVD and PC (no problems prior to modem). Nothing I tried could eliminate this totally (ferrites/earthing/un-earthing/messin' with the cable TV shield/hasselling the cable co/etc/etc) and I eventually had to resort to optical links
Dave
You gan stop that ground loop with a 1:1 isolation transformer.
Nuuk said:
On my basement I discovered a nice little 2x20v toroid from an old Nokia modem I sent to the dust bin some years ago.
I always keep the nice things...
That little toroid has an earth connection too.
I'm using it on my new preamp (it's playing, but it doesn't have a box yet, it's laying on the floor).
Hey Nuuk, fantastic sound I'm getting with my new preamp + Gainclone!
OPA627 + BUF634 = Ultra-high-end.
Deam, now I have to listen to all those CDs again.
Nuuk said:
Nuuk, the BUF634 is a buffer (unity gain) capable of 250 ma current output.
You use that in the feedback loop of an op-amp and you can have the power amp on the other end of your house!
Use the op-amp to get the gain you whant, and the BUF634 to get more current.
Go to www.ti.com, search for BUF634, and dowload the datasheet.
I made a preamp "based" on the schematic on the datasheet for an headphone amp.
Man, this is high-end, I can tell you.
Impressive.
I haven't made a box for it yet, as soon as I have it done I'll post some photos.
High-end preamp
Nuuk, in fact I'm making a standalone preamp.
With a gain of 2.4.
It will wave 6 line-ins, 3 buffered tape loops (again, with OPA627) and 2 pre outs.
It's much more useful to me to have a standalone preamp.
I wont put anything inside my Gainclone, I don't see any advantage.
With my standalone preamp I can even think of (later) biamplification of my Epos speakers.
I tell you, the preamp is laying on the floor, on my room, connected to my main system and it just sounds glorious.
The boards are all done.
What is missing is to complete it with a nice box.
Nuuk said:
Nuuk, in fact I'm making a standalone preamp.
With a gain of 2.4.
It will wave 6 line-ins, 3 buffered tape loops (again, with OPA627) and 2 pre outs.
It's much more useful to me to have a standalone preamp.
I wont put anything inside my Gainclone, I don't see any advantage.
With my standalone preamp I can even think of (later) biamplification of my Epos speakers.
I tell you, the preamp is laying on the floor, on my room, connected to my main system and it just sounds glorious.
The boards are all done.
What is missing is to complete it with a nice box.
Oh, just a budget model then Carlos
I hope you get the OPA627's cheaper than we do in the UK!My current preamp has two tape buffers but I only ever use one, and then only once a week to record a late night/early morning radio programme while I get my beauty sleep and dream about Gainclones
I'm thinking of taking the 'bare minimum' approach with just a pot between source and (buffered?) GC's. I'm not even sure if I will use a selector switch and mayjust rely on plugging and unplugging to select the source.
Even if your preamp is separate from the GC's, you could still invert the signal so compensate for the inverting mode of the GC's!
Nuuk said:
You can at least use one of those little double up-down metallic switches.
I have found they are very good for signal.
Some time ago I made a little amp for my son, for it's bedroom, with only two line-ins, with one of these switches.
With one device playing, I switch to the other line-in, take the volume to the maximum and I can't hear anything!
Absolutely no crosstalk.
Well, I prefer the non-inverting topology for preamps.
Gainclones are different animals.
Anyway, as I have the positive speaker terminal connected to the star ground, it's not inverted again!
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