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goldenreference low voltage power supply


kevin gilmore
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12 hours ago, kevin gilmore said:

coming soon, synchronous diode bridge using lt4320 and power fets

lower dropout voltage, much less switching noise

Can you keep the physical size and standoff hole placement same to GRLV with RS402L (goldenreference6d.zip)?

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someone needs to check this, works as single rectifier with center tapped transformer, or a pair with dual secondaries. Up to 72vdc, perfect for GRLV

caps are 100v rated, 1uf is 0805 size, 10uf is 2220 size

I can certainly do a bigger version with different fets for higher currents and lower voltages. .9 x 1.1 inches

 

syncrectifier.jpg

 

syncrectifier.zip

Edited by kevin gilmore
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  • 7 months later...

Kevin,

I have just built 3 of the synchronous rectifiers, I built a little test setup with just the + side of a spare golden reference LV board and used  a single non centre tap AC ionput.  (LV board set to +14VDC output transformer known good). I found all 3 rectifiers to produce rectified output with some 100hz ripple by scoping the + terminal output of the synch rec and the scope ground on the ground of the LV board. Testing drawing from 0mA to 300mA using a DC electronic load from the LV board produced a stable, non drifting clean output - I expected 14V and got 14.014V. The output voltage dropped by about 3mV when comparing the 0mA draw to 300mA which seems reasonable. My conclusion was the sync rec boards where correctly soldered and working. 

I then desoldered the traditional bridge rect from my well tested and fully working blue hawaii gold ref LV board (which uses a centre tap transformer for it AC input) I replaced the bridge with the synch rec, brought the amp up slowly on a variac and immediately noticed a buzzing sound coming from the golden ref board and only the + side of the board got to 15V and stable with both leds lit and the neg side could not get past about -10V and the second led did not light on the neg side... this was with the gold ref lv connected to the blue hawaii amp boards and drawing current but before the delay circuit activated the B+ lines. I immediately pulled the power before the B+ came up to protect the amp.

I repeated the experiment with no load i.e. the blue hawaii not connected to the gold ref LV and still got the same behaviour.  I tried all 3 sync rec and got the same result. Thinking I had damaged the LV board I put back the original bridge rect and both the  - and +15V both were fine and measured exactly as before I removed the original rect. 

regards

James

Update,

Looking at the diy forum,  https://www.diyaudio.com/forums/group-buys/333844-ideal-bridge-rectifier-gb-23.htmll they also say the LT4320 will not work correctly on a centre tapped transformer.... the two AC outputs of the transformer must be in phase with each other and most centre tapped transformers are out of phase...

I have successfully got the synch rectifier working with the golden reference LV power supply. but only using transformers that have dual secondary windings. I cant not get centre tapped to work correctly.

Update I am convinced the synchronous rectifiers only work with non centre tapped transformers.

 

 

 

 

 

 

Edited by jamesmking
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  • 2 months later...

The regulated output voltage is:

for V+: ((R8 + R7) / R7) x 10 (reference voltage of D5 - LT1021-10)

for V-: ((R9 + R10) / R10) x 10 (reference voltage of D7 - LT1021-10)

On the goldenreference4 board silkscreen, R7, R8, R9 R10 are all 1.5K. R7 and R8 are connected and R9 and R10 are connected. R8 and R9 are the 1.5K resistors closer to the DN2540 on each side of the board.   

The 10R is for ground connection ( from iec input ground to power suppy ground) and is optional. I personally never populated it on all the GRLV I've built.

Edited by mwl168
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Only change R8 for positive rail and R9 for negative, don't change R7 and R10 unless you have to. If you keep R7 amd R10 as stock 1.5K then

+ output required    value of R8 

20V                                         1.5K

15V                                         750ohm

12V                                         300ohm

For negative rail output adjustment change R9.

The two resistors NOT to change (R7 and R10) are the ones directly connected to the ground rail.

with R7 and R10 fixed:

R8 in ohms = ( (voltage you want in volts / 10) - 1 ) * 1500

if R7 and R10 are not stock

R8 in ohms = ( (voltage you want in volts / 10) - 1 ) * R7

 

Edited by jamesmking
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Can I use 40V caps for the large 4700 uf 50V caps?  I think those see the rectified unregulated voltage.  The transformer I'm using would be 15 VAC with primary at 115V.  My mains usually run at 120 so maybe output would be 16VAC,  16 x 1.4 would  put the unregulated voltage at 22.4 VDC.  That's still ok right?

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These values should be noted on the silkscreen to make it easier for anyone who wants to fool around with different output voltages. [emoji4]

I just have a calculator built into my BOM spreadsheet with a few of the voltages I normally use available.


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Can I use 40V caps for the large 4700 uf 50V caps?  I think those see the rectified unregulated voltage.  The transformer I'm using would be 15 VAC with primary at 115V.  My mains usually run at 120 so maybe output would be 16VAC,  16 x 1.4 would  put the unregulated voltage at 22.4 VDC.  That's still ok right?

Should be fine as that would be the highest voltage seen, more or less. 40V caps? Seems like an odd value, at least for people used to Panasonics...


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Mundorf makes a cap that'll fit and it's rated at 40V.  It's probably not gonna make much difference but this one's going to power the output stage in my DAC and all the other PSU caps are mundorf so I was just trying to keep them all the same.

Edited by sbelyo
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  • 3 weeks later...

Hi, I've a few questions regarding the mini GRHV/LV, if this is the right thread to ask in.

1. Since the base board only has a single cap per unregulated voltage, I suppose the highest voltage secondaries for the HV section that can be used is 350VAC? Around 90% of a 550VDC cap's rating? Assuming that is the highest voltage rating I can get on a 680uF board, which it should.

2. Is there a BOM for the base board? Have been comparing the diagram with the GRHV and LV and figured out most of it, but not quite sure if I got it right, especially the delay circuit. Found another diagram here on it, but it was on 12V rather than 5V, and I'm not sure if the relays would even open on 5V with the same values. 

3. And, lastly, what's the trimmer R21 for? Bias adjustment, I assume? It's not on the GRHV boards, or I'm blind and/or looking at the wrong ones.

It's a lot to ask for so, thanks for reading!

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  • 2 months later...

Starting to gather parts for a GRLV and found a pair of 4700uf 63V nichicon UKW capacitors. They are leaded not snap in. Any issue with using these in the PSU? 

Comparing to regular snap in caps I get higher ripple current but rated only for 2000h vs 3000h.

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Another one lives...  This one is powering the IVY III output stage of my DAC.  I populated all the resistors with the trim pots.  I get -14.96 and +14.96

I noticed that when I adjusted the pots there was no change.  I read that my 4.5 digit meter will not have the resolution to display what's being adjusted when I adjust the pot.  Is that why I see no adjustment?

 

IMG_1224.JPG

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On 1/30/2020 at 7:09 AM, HatIsMyFriend said:

Hi, I've a few questions regarding the mini GRHV/LV, if this is the right thread to ask in.

1. Since the base board only has a single cap per unregulated voltage, I suppose the highest voltage secondaries for the HV section that can be used is 350VAC? Around 90% of a 550VDC cap's rating? Assuming that is the highest voltage rating I can get on a 680uF board, which it should.

2. Is there a BOM for the base board? Have been comparing the diagram with the GRHV and LV and figured out most of it, but not quite sure if I got it right, especially the delay circuit. Found another diagram here on it, but it was on 12V rather than 5V, and I'm not sure if the relays would even open on 5V with the same values. 

3. And, lastly, what's the trimmer R21 for? Bias adjustment, I assume? It's not on the GRHV boards, or I'm blind and/or looking at the wrong ones.

It's a lot to ask for so, thanks for reading!

Sorry, just seeing this now.

  1. Not sure, but that sounds about right.
  2. See attached for the BOM I have for each. In the GRLV BOM, ignore the Schottky rectifiers  (yellow shading).
  3. I only see an R21 500R resistor feeding the + input of the - rail opamp on the GRLV. All of the pots are labeled RV# in the schematic that I have.

 

goldenreference LV schematic.pdf GR HV BOM_Sep26.xlsx

On 4/13/2020 at 10:26 AM, sbelyo said:

Another one lives...  This one is powering the IVY III output stage of my DAC.  I populated all the resistors with the trim pots.  I get -14.96 and +14.96

I noticed that when I adjusted the pots there was no change.  I read that my 4.5 digit meter will not have the resolution to display what's being adjusted when I adjust the pot.  Is that why I see no adjustment?

Steve,

I hadn't read that regarding a 4.5 digit DMM, but I would assume you would be able to see something? I've never used the trimpots for adjusting the voltages (I usually use either matched resistors using my HP bench meter, or 0.1% resistors and live with the results.)

GR LV BOM_Sep26.xls

Edited by Pars
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1 hour ago, sbelyo said:

I noticed that when I adjusted the pots there was no change.  I read that my 4.5 digit meter will not have the resolution to display what's being adjusted when I adjust the pot.  Is that why I see no adjustment?

Judging by the photo you should definitely see output voltage change as you adjust the pots. If not, I would first check to see if the pins of the pot are soldered in correctly - is it possible you soldered pin 1 and 3 of the pots to the fixed resistor positions?

 

Edited by mwl168
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