Regarding earthing/common, products without uk plugs don't even have EARTH wire. This philips amp I've got certainly doesn't, it only has neutral and live.
How can earth/common be possibly devised without tapping into the 'power supply' common as nigel is suggesting?
On the linkwitz riley PCBs there are ''GND' terminals.
I'm told I cannot connect them to power supply ground.
What other choice do I have?
How can earth/common be possibly devised without tapping into the 'power supply' common as nigel is suggesting?
On the linkwitz riley PCBs there are ''GND' terminals.
I'm told I cannot connect them to power supply ground.
What other choice do I have?
Ordinary retailed equipment is only available in two standards:
Class11
Double insulated with the concentric squares symbol and a guarantee that even after they have been dropped and thoroughly abused they won't give you a lethal shock. All have 2pins operative. The earth pin (maybe all plastic) is only there to open the safety shutters in the wall socket.
Class1
Fitted with a PE protected chassis. The chassis could be internal (inside a plastic casing). All have a 3pin plug with an operative Earth Wire.
There are "not ordinary" products. eg. A mains powered electric shaver and others that operate from special supplies.
Can you tell Class1 and Class11 apart?
Confirm !
Class11
Double insulated with the concentric squares symbol and a guarantee that even after they have been dropped and thoroughly abused they won't give you a lethal shock. All have 2pins operative. The earth pin (maybe all plastic) is only there to open the safety shutters in the wall socket.
Class1
Fitted with a PE protected chassis. The chassis could be internal (inside a plastic casing). All have a 3pin plug with an operative Earth Wire.
There are "not ordinary" products. eg. A mains powered electric shaver and others that operate from special supplies.
Can you tell Class1 and Class11 apart?
Confirm !
Andrew, the insulation classes are in Roman Numerals.
Appliance classes - Wikipedia, the free encyclopedia
Appliance classes - Wikipedia, the free encyclopedia
I changed just a couple of weeks ago.
I saw a site that seemed to show that 1 & 11 were the correct symbols.
Wiki obviously thinks otherwise.
Maybe I should revert to what I used to use: I & II
Thanks for relieving my doubt.
**
Also, perhaps i'm misunderstanding the purpose of common...
I know the difference between class one and class two.
But you'd think, in a good design both common and earth should be connected (making it a class one).
I don't see the point in common existing at all otherwise, other than maybe 'stabilizing' imbalances throughout a design...
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Common is short for common voltage reference, at least in my head.
Safety Earth and it's connection to the PE wire has nothing to do with audio.
The voltage reference in the audio amplifier (pre-amp, source or poweramp) is there so that different circuits operate with the same voltage reference. These circuits are isolated from Mains power by the isolating transformer.
None of these circuits NEED a connection to PE. None of these circuits NEED a connection to Chassis.
All of these circuits will operate without a Chassis and thus without a Safety Earth connection to PE.
Safety Earth and it's connection to the PE wire has nothing to do with audio.
The voltage reference in the audio amplifier (pre-amp, source or poweramp) is there so that different circuits operate with the same voltage reference. These circuits are isolated from Mains power by the isolating transformer.
None of these circuits NEED a connection to PE. None of these circuits NEED a connection to Chassis.
All of these circuits will operate without a Chassis and thus without a Safety Earth connection to PE.
If I connect signal return to common as suggested, then this joins multiple commons together (i.e.other external device) via interconnect.
So going by this, if you have a hifi consisting of three amps and a 3-way crossover/hpf design (like the one on this thread) and providing common is connected to signal return, then technically all common throughout the entire system are joined.
This means one amplifier has the potential to throw the rest off balance via any analog processing circuit between. Surely this can't be a good thing(?)
I'm therefor guessing reference voltage must be 0v at all times.
So going by this, if you have a hifi consisting of three amps and a 3-way crossover/hpf design (like the one on this thread) and providing common is connected to signal return, then technically all common throughout the entire system are joined.
This means one amplifier has the potential to throw the rest off balance via any analog processing circuit between. Surely this can't be a good thing(?)
I'm therefor guessing reference voltage must be 0v at all times.
FIRST !!!!!
connect all your modules together using TWO WIRE Flow and Return connections.
The only exception is a dual polarity PSU. It needs a THREE WIRE connection to each module it supplies.
ALL of these connections MUST be twisted pairs (or twisted triplet).
AFTER you have done that consider whether any voltage reference connection is missing. There may be none in which case you are ready to start testing.
You may have to connect the Signal Return to the Output Return.
You may have to connect the Zero Volts to the Output Return.
Unfortunately looking at the schematic is not helpful. They use a "GND" symbol for everything and that is most unhelpful !
I have seen one schematic from quite a few years ago and it was done by one of our Members, it showed every signal pair as a pair.
It showed every return going along it's matching Flow route back to Source.
I wish I had printed it out. I would now know where to find it and who posted it. Thinking about it it was in an article, who did the amp series of articles?
connect all your modules together using TWO WIRE Flow and Return connections.
The only exception is a dual polarity PSU. It needs a THREE WIRE connection to each module it supplies.
ALL of these connections MUST be twisted pairs (or twisted triplet).
AFTER you have done that consider whether any voltage reference connection is missing. There may be none in which case you are ready to start testing.
You may have to connect the Signal Return to the Output Return.
You may have to connect the Zero Volts to the Output Return.
Unfortunately looking at the schematic is not helpful. They use a "GND" symbol for everything and that is most unhelpful !
I have seen one schematic from quite a few years ago and it was done by one of our Members, it showed every signal pair as a pair.
It showed every return going along it's matching Flow route back to Source.
I wish I had printed it out. I would now know where to find it and who posted it. Thinking about it it was in an article, who did the amp series of articles?
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hi again dA, back with update:
I've connected hpf circuit to jacks as illustrated below, following instructions from quote above.
However I'm getting an odd sound through the hpf section. I doubt it's PSU related because it is not present in the XO circuits (including 0hz-87hz crossover band).
Meaning the hum is strictly limited to HPF circuit- it largely resembles the sound of a guitar amp when the jack is absent (?)... drrrrrrr droning sound (if that rings a bell).
It may well be ground loop.
I'm confused because I was advised the simpest solution would be to remove the one (or more) connection(s) from outer ring (of jack) to the internal circuits common - but this contradicts speed skaters post quote above. So I'm after some re-assurance please...
This is the current configuration.
Many Thanks
, of each pair of C1's to ground which will kill any signal. Try the last opamp stage first. Make the short to the correct ground point. You should have silence. If you have then do the same for the first pair.
Hi mooley, I'm unsure what you mean exactly, here is my guess?
I noticed my circuit lacks the provision I think exists on all amplifiers/ line level devices. (example below), where an additional cap is in place separating common from circuit. So would adding caps to common line help (unless this is what you're already suggesting)? a 10nF ceramic disc is all I have here.
I'm sure this is very trivial to most peeps on here, tbt I have no idea..
I noticed my circuit lacks the provision I think exists on all amplifiers/ line level devices. (example below), where an additional cap is in place separating common from circuit. So would adding caps to common line help (unless this is what you're already suggesting)? a 10nF ceramic disc is all I have here.
I'm sure this is very trivial to most peeps on here, tbt I have no idea..
It was yes. You just have to try and find where the problem is. You could also try lifting (might be a better option) the cap directly after the first opamp to isolate the signal chain.
The caps are very application specific and tbh its something I've never done on anything of mine. It would have no effect for ground loop issues, more for RF problems.
The caps are very application specific and tbh its something I've never done on anything of mine. It would have no effect for ground loop issues, more for RF problems.
Ah
Because the HPF circuit has an op amp with + and - pins - I assumed and connected it up as if it were a dual polarity circuit. :doh:
The neg pin of the op-amp is currently connected to the negative terminal of the PSU - it should be connected to the 0v of the PSU, i think...
I will amend and return with feedback - no web access at home.
Because the HPF circuit has an op amp with + and - pins - I assumed and connected it up as if it were a dual polarity circuit. :doh:
The neg pin of the op-amp is currently connected to the negative terminal of the PSU - it should be connected to the 0v of the PSU, i think...
I will amend and return with feedback - no web access at home.
Hi all back once more with some R&D...lol
unfortunately re arranging the hpf to single polarity did not eliminate humming problem i'm experiencing.
The hum is still present when the whole project is OFF (no mains input) and while both signal returns are isolated - I think this is a feedback issue.
The test amp i'm using to detect the hum is definitely not the source of hum,
The interconnect protruding from the test amp, when unconnected causes no hum while test amp is on, I switch test amp off - connect rca to HPF out-jack and switch test amp on, hum is present.
The hum is present on both IN and OUT jacks.
I find this strange because the signal return of both jacks are separated from hpf circuit - a loop is impossible, yet hum still occurs.
Anybody seen this before? As I said definitely not PSU issue because, a)PSU voltage readings are spot on and b) the crossover section works splendidly with no hum what so ever.
unfortunately re arranging the hpf to single polarity did not eliminate humming problem i'm experiencing.
The hum is still present when the whole project is OFF (no mains input) and while both signal returns are isolated - I think this is a feedback issue.
The test amp i'm using to detect the hum is definitely not the source of hum,
The interconnect protruding from the test amp, when unconnected causes no hum while test amp is on, I switch test amp off - connect rca to HPF out-jack and switch test amp on, hum is present.
The hum is present on both IN and OUT jacks.
I find this strange because the signal return of both jacks are separated from hpf circuit - a loop is impossible, yet hum still occurs.
Anybody seen this before? As I said definitely not PSU issue because, a)PSU voltage readings are spot on and b) the crossover section works splendidly with no hum what so ever.
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