I'm getting a buzz rom my midrange speakers that is precisely the same frequency (by ear) as my transformer is buzzing at. Hmmm. Any ideas on how to resolve this?
I'm pretty sure it's not a signal earthing problem. The R-core transformer is as follows:
Primaries 115x2 = 4 cables (weirdly, linking two inner cables to make 230 supply is fine, but mains supply trip-switch goes if I connect joined centre to earth, so I have them isolated. There is a dedicated earth cable coming out with the secondaries. Is this normal?
Secondaries 18x2 = 4 cables and 12x2 = 4 cables and (never seen it before) EARTH cable.
I do hope it's not just a **** transformer.
Many thanks
Lucas
I'm pretty sure it's not a signal earthing problem. The R-core transformer is as follows:
Primaries 115x2 = 4 cables (weirdly, linking two inner cables to make 230 supply is fine, but mains supply trip-switch goes if I connect joined centre to earth, so I have them isolated. There is a dedicated earth cable coming out with the secondaries. Is this normal?
Secondaries 18x2 = 4 cables and 12x2 = 4 cables and (never seen it before) EARTH cable.
I do hope it's not just a **** transformer.
Many thanks
Lucas
The amp sounds wonderful, if I turn it up enough to drown out the buzz. It's not excessive from the transformer or the speakers, about the same volume in each, but I'd sure like to get the speakers silent. Any ideas? Anybody?
Also, I realise that Andrew T was very right about the delay circuit earthing - I should have done the mod to earth it before switch-on. At the moment I get 10 seconds of filth before it clicks in - not the desired effect!
Also, I realise that Andrew T was very right about the delay circuit earthing - I should have done the mod to earth it before switch-on. At the moment I get 10 seconds of filth before it clicks in - not the desired effect!
Are you certain that cable is not a 'screen' connection? I.e. a grounded shield for the output windings? (I may have not used the correct terminology)
Ryan
It's green and yellow, labelled "EARTH" on the label, thicker than all the others and makes the circuit quieter when soldered to the star ground. I think it's an earth. Why it comes out of the secondaries side is my mystery. Also, why can't the primary 115/115 centre tap be put to GND without tripping my house out?
The primary centre tap as you call it turns the dual 115V into a 230V connection !! Sleeve and isolate.
Have you used a CL60 from centre connection on the pcb to chassis ground?
Yes I am on a 230vAC supply (actually 240 here in the UK).
I have connected the central wires together, as ever to create a 230v primary, but normally that central cable is connected to the IEC socket. On this one, that causes a power trip, so I've sleeved and isolated it.
So should the central GND on the DCB1 PCB be connected to Chassis GND by a CL60 thermistor? If so I shall do so - right now it's just a wire.
Many thanks
I have connected the central wires together, as ever to create a 230v primary, but normally that central cable is connected to the IEC socket. On this one, that causes a power trip, so I've sleeved and isolated it.
So should the central GND on the DCB1 PCB be connected to Chassis GND by a CL60 thermistor? If so I shall do so - right now it's just a wire.
Many thanks
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Yea, I hated the clicky clack of the stepped attenuator I had in before, and wanted a nice smooth volume pot, but didn't want to put my signal through carbon after going to such lengths to keep it short, simple, clean. The LDR solution is the answer, and of course allows a remote control to be fitted that is completely isolated from the circuit. So, yeah, it is an ideal combination I think. Sound wise, I can't say it's any improvement, but then I wouldn't expect an improvement over a pair of quality resistors - that's also pretty clean.
Don't think it matters its just that its how I wired mine and its so quiet I sometimes think I've forgotten to turn it on....and then the music starts
I have a thought - the main comes in to the power amp, and is then linked through to the pre-amp. Perhaps separate IEC cables to the sockets will sort it - I'll go check now!
Hi,
The primaries of the transformer are "LIVE".
Do not connect any of them to Earth, nor Ground, nor anything else.
The extra secondary could be an "Earth" from the transformer core. The transformer core is exposed and you don't want that becoming "Live" in event of a primary winding failure.
Connect the secondary Earth to Chassis.
The primaries of the transformer are "LIVE".
Do not connect any of them to Earth, nor Ground, nor anything else.
The extra secondary could be an "Earth" from the transformer core. The transformer core is exposed and you don't want that becoming "Live" in event of a primary winding failure.
Connect the secondary Earth to Chassis.
OK, I get that Andrew. So, this buzz that comes from the transformer and into my speakers, gets into the signal GND because they are both linked to the star GND at the IEC EARTH terminal. Where do I use a CL60 to provide a degree of isolation for the signal GND? Do I connect the signal star GND to the mains GND via a CL60, or what?
Many thanks
Lucas
By the way, did you get your remote volume working yet? I found the supplied pot terminals to be ridiculous, so I swapped it out and Frankensteined the motor onto another alps pot. None of the terminals needs to go to the remote board - only the two motor terminals.
Sorted it with 3x CL60s
The first between the two centre tap wire of the transformer (as I saw in a Nelson Pass power supply schematic)
The second between the pre-amp signal and IEC Earth connection. Still buzzing at 50Hz!!!
OK, opened the power amp and CL60ed the signal to Earth in there too. Sorted! Silent as the dead of night! It was transformer buzz going through the inter-connects.
The first between the two centre tap wire of the transformer (as I saw in a Nelson Pass power supply schematic)
The second between the pre-amp signal and IEC Earth connection. Still buzzing at 50Hz!!!
OK, opened the power amp and CL60ed the signal to Earth in there too. Sorted! Silent as the dead of night! It was transformer buzz going through the inter-connects.
Thank-you Salas.
I will add another basic regulator circuit with a 78 series regulator.
The buffer worked with only one half of the transformer 2ndary connected - all leds nice and bright!. I suppose that 21v AC when 1/2 rectified with those large PS caps was enough to five decent +/- DC output. it even sounded good!
just ruined my 12mm thick alu front panel with a wrong router setting, so will have to wait b4 I can complete the pre-amp and put it in my system.
Brad
