..........John
Researching for a dual PSU schematic I found a 1985 Patent by onkyo:
Rectified and smoothed DC supplying circuitry - Patent 4555751
They invented a smoothing circuit between the transformer's center tab and the rail where the smoothing caps are tied together. This circuit - #11 in the attached figure - is made from two antiparallel diodes D1 and D2.
I've never seen a schematic that include this simple device. Does it make sence? What type of diodes are the best for this job?
Rectified and smoothed DC supplying circuitry - Patent 4555751
They invented a smoothing circuit between the transformer's center tab and the rail where the smoothing caps are tied together. This circuit - #11 in the attached figure - is made from two antiparallel diodes D1 and D2.
I've never seen a schematic that include this simple device. Does it make sence? What type of diodes are the best for this job?
Attachments
The link in johnalexwarren's first post
Power Supply for Power Amplifiers
also shows a ground loop circuit with two antiparallel diodes.
What is new with the 1985 onkyo patent is the triangular layout they suggest as an improvement. Has anyone tried this?
Power Supply for Power Amplifiers
also shows a ground loop circuit with two antiparallel diodes.
What is new with the 1985 onkyo patent is the triangular layout they suggest as an improvement. Has anyone tried this?
Attachments
Dual secondaries driving separate BR & filter banks
After reading thru this thread several times and studying the diagrams I feel ready to plug in my soldering iron and get busy. I hope to use that copper bus idea.
I have two Belles 1 power amps. I'm sure the 25+ year old filtering could stand some "freshening." While I'm at it kick the PS performance up a notch or two. I think my power amp has dual secondaries.
Do the above:
w/a bit more capacitance
2 bridge rectifiers, one for each channel
4 filter caps, 2 for each channel
better filter caps.
I welcome your input for new filters-skinny caps w/screw tops please.
I'd like your opinion on whether I'm on the right track. Please take a look at my crude drawings (attachments). I apologize for not drawing diode bias.
Attachment 1 is the existing PS* for both channels using 2 Mallory 33Kuf 50V 65V surge filters w/ the no-load rail voltage per DMM. Near as I can tell its NOT center tapped. Yeah that's it. 2 Huge** filter caps & transformer; 1 bridge rectifier.
* add'l filtering on PCB, unknown. Belles won't release schematics
** huge compared to Hafler's
Attachment 2 are the mods. BTW I want to get the big stuff right first. I drew in early a few small improvements. Will add more bypass caps and an RC network.
Later replace the single transformer with 2 toroidals each w/dual secondaries &, if space permits, add 2 more bridge rectifiers & more filtering.
2 other items: the amps have 2 prong plugs; the chassis is grounded to the PS. Something from Simon's post (#31) I'm unclear if should disconnect the chassis ground from the PS, change the power cord to 3 prong, & ground the chassis to the 3rd prong.
This work will serve as a "warm-up" for my other brand of amps
thanks for your inspiration and help tony
After reading thru this thread several times and studying the diagrams I feel ready to plug in my soldering iron and get busy. I hope to use that copper bus idea.
I have two Belles 1 power amps. I'm sure the 25+ year old filtering could stand some "freshening." While I'm at it kick the PS performance up a notch or two. I think my power amp has dual secondaries.
Do the above:
w/a bit more capacitance
2 bridge rectifiers, one for each channel
4 filter caps, 2 for each channel
better filter caps.
I welcome your input for new filters-skinny caps w/screw tops please.
I'd like your opinion on whether I'm on the right track. Please take a look at my crude drawings (attachments). I apologize for not drawing diode bias.
Attachment 1 is the existing PS* for both channels using 2 Mallory 33Kuf 50V 65V surge filters w/ the no-load rail voltage per DMM. Near as I can tell its NOT center tapped. Yeah that's it. 2 Huge** filter caps & transformer; 1 bridge rectifier.
* add'l filtering on PCB, unknown. Belles won't release schematics
** huge compared to Hafler's
Attachment 2 are the mods. BTW I want to get the big stuff right first. I drew in early a few small improvements. Will add more bypass caps and an RC network.
Later replace the single transformer with 2 toroidals each w/dual secondaries &, if space permits, add 2 more bridge rectifiers & more filtering.
2 other items: the amps have 2 prong plugs; the chassis is grounded to the PS. Something from Simon's post (#31) I'm unclear if should disconnect the chassis ground from the PS, change the power cord to 3 prong, & ground the chassis to the 3rd prong.
This work will serve as a "warm-up" for my other brand of amps
thanks for your inspiration and help tony
Attachments
Hi,
you cannot use a bridge rectifier to create a dual polarity supply from one secondary winding.
a.) If you have a centre tapped transformer you can use a single bridge to create a dual polarity supply.
If you have a dual secondary, you have two ways to create a dual polarity supply.
b.) convert the dual secondary to centre tapped and proceed as in a above.
c.) create a single polarity supply from one secondary winding using a single bridge.
create a second single polarity supply from the other secondary using a single bridge.
Connect the two single polarity supplies in series to creat your dual polarity supply.
you cannot use a bridge rectifier to create a dual polarity supply from one secondary winding.
a.) If you have a centre tapped transformer you can use a single bridge to create a dual polarity supply.
If you have a dual secondary, you have two ways to create a dual polarity supply.
b.) convert the dual secondary to centre tapped and proceed as in a above.
c.) create a single polarity supply from one secondary winding using a single bridge.
create a second single polarity supply from the other secondary using a single bridge.
Connect the two single polarity supplies in series to creat your dual polarity supply.
Spliting the load: in-rush current & new filters
Ok. A lot of PS expertise replying to this thead.
This in reference to my previous post about 2 25 year-old amps of which I've since learned much.
Would two* smaller toroidals* have lower in-rush current issues than one large toroidal?
* totaling the same VA rating
Also is it a big deal that most of the PS related caps* have 50V ratings? ...w/rail** voltages** about 55-56V? I plan to replace them w/ higher rated caps regardless.
* includes 4 on driver boards,
** I'd like to lower the voltage to finals to about 50V
I welcome input for replacement caps:
Size-currently 3"X4" want "2*" X 4"
*can be smaller
Current Capacitance: total 66Kuf. Want 4-6 per channel providing 80K-100Kuf total.
Finally what brand cap?
Saw some Nippon ChemiCon 22Kuf on ebay for about $40/pr. Some like Nichicon.
Merry Christmas, thnx tony
Ok. A lot of PS expertise replying to this thead.
This in reference to my previous post about 2 25 year-old amps of which I've since learned much.
Would two* smaller toroidals* have lower in-rush current issues than one large toroidal?
* totaling the same VA rating
Also is it a big deal that most of the PS related caps* have 50V ratings? ...w/rail** voltages** about 55-56V? I plan to replace them w/ higher rated caps regardless.
* includes 4 on driver boards,
** I'd like to lower the voltage to finals to about 50V
I welcome input for replacement caps:
Size-currently 3"X4" want "2*" X 4"
*can be smaller
Current Capacitance: total 66Kuf. Want 4-6 per channel providing 80K-100Kuf total.
Finally what brand cap?
Saw some Nippon ChemiCon 22Kuf on ebay for about $40/pr. Some like Nichicon.
Merry Christmas, thnx tony
Not likely.
It is at least strange, because they should be rated higher than the rails to be on the safe side. If they have held for 25 years however, your question is answered.
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