Hi,
I am looking for advice about the best way to implement a 1KVA iso trans into my system (it has 0-220V in and out and one earth connection on the input side). Mains here is 220V AC. The system is 2 class-T amps for bi-amping (100VA trans for each), a pre-amp/crossover (80VA), two DACs and a few sources (maybe 100VA total) so about 400VA absolute max load.
I have some objectives - eliminate DC, reduce or eliminate transformer buzz, remove smps noise from other devices in the flat, stop the ocassional crackle when a strip light turns on, etc - ultimately to improve sq of course.
I also have some 140uH 5A toroids and a whole bunch of 275V y-rated caps and some 630V metallised poly caps too.
If anyone can direct me to circuits / methods they've tried and know work well I'd be very grateful !
Thanks to all.
I am looking for advice about the best way to implement a 1KVA iso trans into my system (it has 0-220V in and out and one earth connection on the input side). Mains here is 220V AC. The system is 2 class-T amps for bi-amping (100VA trans for each), a pre-amp/crossover (80VA), two DACs and a few sources (maybe 100VA total) so about 400VA absolute max load.
I have some objectives - eliminate DC, reduce or eliminate transformer buzz, remove smps noise from other devices in the flat, stop the ocassional crackle when a strip light turns on, etc - ultimately to improve sq of course.
I also have some 140uH 5A toroids and a whole bunch of 275V y-rated caps and some 630V metallised poly caps too.
If anyone can direct me to circuits / methods they've tried and know work well I'd be very grateful !
Thanks to all.
Last edited:
Hi,
Thanks for the replies. Here is a picture :
The input dc resistance is ~1 ohm and the earth reads open circuit to either/both input (and chassis) so it isn't a centre tap. Static shield seems more likely but I'm not sure...
Croatian site looks interesting - I was thinking of using a filter (LCLC) on the output and just some small value caps on the input but I don't know if this would achieve my aims ?
cheers
Tom
Thanks for the replies. Here is a picture :
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The input dc resistance is ~1 ohm and the earth reads open circuit to either/both input (and chassis) so it isn't a centre tap. Static shield seems more likely but I'm not sure...
Croatian site looks interesting - I was thinking of using a filter (LCLC) on the output and just some small value caps on the input but I don't know if this would achieve my aims ?
cheers
Tom
Last edited:
Hi,
Thanks for the help guys. A screen is good news and it can also serve as a star earth.
I already have filters on the individual gear and interconnects, and the power and pre-amps also have their iso trans but still the crackles and noise can come through. I've tried using a surge suppressor normally used for PC supplies but that still lets the odd one through too. I'm hoping a big iso trans will free the other trans of DC and reduce buzz (already inaudible but I can feel it through the case), and adding a filter will clean up the supply.
I'll have a closer look at the parts I've got and do a schematic so you can see what I'm planning. I think putting the filter on the input side is a better idea to avoid losses on the output.
I'd rather get some comments before I build anything so it isn't a complete ****-up.
Thanks again
Thanks for the help guys. A screen is good news and it can also serve as a star earth.
I already have filters on the individual gear and interconnects, and the power and pre-amps also have their iso trans but still the crackles and noise can come through. I've tried using a surge suppressor normally used for PC supplies but that still lets the odd one through too. I'm hoping a big iso trans will free the other trans of DC and reduce buzz (already inaudible but I can feel it through the case), and adding a filter will clean up the supply.
I'll have a closer look at the parts I've got and do a schematic so you can see what I'm planning. I think putting the filter on the input side is a better idea to avoid losses on the output.
I'd rather get some comments before I build anything so it isn't a complete ****-up.
Thanks again
That's what I thought - so can you explain your previous message that I can't tie the shield to earth ? Surely I must tie it to earth (because I must tie it to the chassis and of course the chassis is earthed) and best practice is to create a star earth - one centralised point for all earth connections - so why not use the shield connection point on the trans as the star earth ?
Your star earth implied, by my interpretation, an audio reference point required by all amplifiers to work properly as a pieces of Audio Equipment.
The Safety Earth and the PE and the chassis connection to the third wire are all solely to do with Safety. They have nothing to do with Audio signal processing.
This confusion all comes from the common use of the word "ground" for many quite different parts of the circuit. I interpreted your reference to earth as a beginners' error in mis-naming ground.
The Safety Earth and the PE and the chassis connection to the third wire are all solely to do with Safety. They have nothing to do with Audio signal processing.
This confusion all comes from the common use of the word "ground" for many quite different parts of the circuit. I interpreted your reference to earth as a beginners' error in mis-naming ground.
No problem.
I just remembered I have an unused toroid transformer - Talema 50VA 12V - any idea what the Henries might be for the secondaries wired in parallel ? I think this could work well as part of a CLC output-side filter - but of course I need to estimate the Henries so I can select suitable cap sizes. Any guesses ?
Data sheet doesn't help much except advise that the secondaries in parallel are gonna be about 0.2 ohms dc resistance.
http://www.talema.net/en/products/pdf/0050P1_1001.pdf
Any ballpark guesses anyone ? There's a calculator here :
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/indtor.html
but I have no idea how many turns. Say 100 turns, toroid radius 5.2cm, coil radius 4cm, iron permability 200... would give 40mH. Seem reasonable ?
I just remembered I have an unused toroid transformer - Talema 50VA 12V - any idea what the Henries might be for the secondaries wired in parallel ? I think this could work well as part of a CLC output-side filter - but of course I need to estimate the Henries so I can select suitable cap sizes. Any guesses ?
Data sheet doesn't help much except advise that the secondaries in parallel are gonna be about 0.2 ohms dc resistance.
http://www.talema.net/en/products/pdf/0050P1_1001.pdf
Any ballpark guesses anyone ? There's a calculator here :
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/indtor.html
but I have no idea how many turns. Say 100 turns, toroid radius 5.2cm, coil radius 4cm, iron permability 200... would give 40mH. Seem reasonable ?
Last edited:
- Status
- Not open for further replies.