Hi all. I have toroid trans (230v in) with TWO RED wires which label indicates as " IN 230v ...RED-RED " ; then it has " OUT 2x 20v ...BLACK-WHITE " referring to TWO WHITE and just ONE BLACK.
I was advised to NOT CONNECT THE BLACK TO ANYTHING AT ALL....Just to connect the two whites to the pos and neg terminals on the phono preamp board's input.. After several months of trying to eliminate the HUM problems I put it all away ! Now I am going to try yet again to sort this out.
If you have ANY thoughts at all which may help me out I'd be eternally grateful.
Cheers 🙂
I was advised to NOT CONNECT THE BLACK TO ANYTHING AT ALL....Just to connect the two whites to the pos and neg terminals on the phono preamp board's input.. After several months of trying to eliminate the HUM problems I put it all away ! Now I am going to try yet again to sort this out.
If you have ANY thoughts at all which may help me out I'd be eternally grateful.
Cheers 🙂
Whom you ask? Advised by a member of another site which is more of an audio enthusiasts site than electronics techies...
As for more details I really can't add much..except to say that the Phono preamp was a kit style of high quality and it runs just fine if I power it using 2x 9v batteries in series...but they don't last very long and so I bought a ready-made regulated psu from circuitsUSA.com and a toroid transformer. So using the psu when powered by the trans it has an earth-loop or some-such hum. I still wonder if I should have used the black lead from trans to the ground term on psu card?
As for more details I really can't add much..except to say that the Phono preamp was a kit style of high quality and it runs just fine if I power it using 2x 9v batteries in series...but they don't last very long and so I bought a ready-made regulated psu from circuitsUSA.com and a toroid transformer. So using the psu when powered by the trans it has an earth-loop or some-such hum. I still wonder if I should have used the black lead from trans to the ground term on psu card?
if the transformer has only 3 wires on the secondary (White , Black , White) then it can"t be 2 x 20v , it is probably a 20v 0v 20v ....
Can you fill us in on what the power requirements are for your preamp , like what voltage it runs on (a 20v 0v 20v transformer would a bit on the high side for most preamps) ?? Does it have 2 places to connect the Transformer or 3 places ?? Most higher end preamps run on a dual supply which uses 3 wires from the transformer ....
Maybe a picture ??
Can you fill us in on what the power requirements are for your preamp , like what voltage it runs on (a 20v 0v 20v transformer would a bit on the high side for most preamps) ?? Does it have 2 places to connect the Transformer or 3 places ?? Most higher end preamps run on a dual supply which uses 3 wires from the transformer ....
Maybe a picture ??
Thanks guys..yeah I will try again to upload the pics as the site rejected my pics due to some " sort of security certification " not available. I'll try reducing them...meanwhile it's a firm YES to fact the tranny has only TWO white and one black output.
That 20v gets reduced by two vari resistors on the psu board and the phono preamp can run on 6v to 18v-so I have that fed by 10v from the psu.
That 20v gets reduced by two vari resistors on the psu board and the phono preamp can run on 6v to 18v-so I have that fed by 10v from the psu.
It runs fine on 2 x 9V batteries but hums with a transformer.
Have you connected an AC supply to a board designed for DC ?
Have you connected an AC supply to a board designed for DC ?
Well if you are using the two white wires and not the black one then you are feeding your preamp 40v AC (which is about 55v DC) which is probably too high for your preamp ....
And Katieanddad is right , your preamp boards probably runs off of DC not ac ... A transformer put out AC and batteries are DC , unless your Preamp has an onboard rectifier then you are not powering it correctly ....
yes , pics would help .....
And Katieanddad is right , your preamp boards probably runs off of DC not ac ... A transformer put out AC and batteries are DC , unless your Preamp has an onboard rectifier then you are not powering it correctly ....
yes , pics would help .....
RE😛HOTOS -TRANSF & PSU CIRCUIT HELP PLEASE
Guys this is hopefully going to help obliterate my "hum" issue......
Guys this is hopefully going to help obliterate my "hum" issue......
RE😛HOTOS -TRANSF & PSU CIRCUIT HELP PLEASE
View attachment 368892
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Guys this is hopefully going to help obliterate my "hum" issue......
View attachment 368892
View attachment 368893
View attachment 368894
View attachment 368895
Guys this is hopefully going to help obliterate my "hum" issue......
with that board you need to use all 3 wires from your transformer , so white on the 2 outer lugs and the black on the center .....
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