Replaced Q10 ZTX450. In hindsight, it should have been my first port of call. Now going perfectly, particularly with the caps broken in.
What Value R to use in Power Supply
I've collected nearly all the parts for my Pearl II and the rest should be here next week.
Only waiting on some Mundorf caps which were supposed to be in stock but turns out were not.
I am using an Antek 5022 transformer with the Universal PSU board from the DIY store.
The DIY UPSU is a CRC supply and I am trying to properly size the R in the CRC
Does anyone know how much current the Pearl draws from a +/- 22Vac supply ?
I recall seeing 50 mA somewhere but can't seem to find it again.
Also, does anyone know how to pick an optimum R value for the DIY UPSU.
I read the build thread but this was based on a power amp build not a phono preamp build.
I ran some simulations using PSU designer but it does not seem to be able to show me how the variation in R changes the ripple on the output (input to the regulators).
I've collected nearly all the parts for my Pearl II and the rest should be here next week.
Only waiting on some Mundorf caps which were supposed to be in stock but turns out were not.
I am using an Antek 5022 transformer with the Universal PSU board from the DIY store.
The DIY UPSU is a CRC supply and I am trying to properly size the R in the CRC
Does anyone know how much current the Pearl draws from a +/- 22Vac supply ?
I recall seeing 50 mA somewhere but can't seem to find it again.
Also, does anyone know how to pick an optimum R value for the DIY UPSU.
I read the build thread but this was based on a power amp build not a phono preamp build.
I ran some simulations using PSU designer but it does not seem to be able to show me how the variation in R changes the ripple on the output (input to the regulators).
Series R or snubber R?
The series use 10 ohm or so. The negative rail draws a bit more than the positive.
The snubber R needs to be measured with a quasimodo jig or something similar. It varies from transformer to transformer.
Use the v3 PSU if you've already got it.
The series use 10 ohm or so. The negative rail draws a bit more than the positive.
The snubber R needs to be measured with a quasimodo jig or something similar. It varies from transformer to transformer.
Use the v3 PSU if you've already got it.
Pass DIY Addict
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I was just measuring my pearl power supply last nght (I'm interested in putting in a pair of Salas BiB regs). Both Pearl boards are fed with a shared CRCRC filter. The last resistors in each rail are 10R and the positive rail drops about 0.83v and the negative rail drops about 0.43v.
Thus, the draw for each board is about 42mA on the positive rail and about 22mA on the negative rail.
Thus, the draw for each board is about 42mA on the positive rail and about 22mA on the negative rail.
I think I've got a set of Salas LV shunts (BiB) laying around for that very reason... Always wanted to try a shunt reg in a project like this.
Then again, I have enough projects on hand to last me a decade at my current rate. 🙂
Then again, I have enough projects on hand to last me a decade at my current rate. 🙂
Pass DIY Addict
Joined 2000
Paid Member
Just finished with my measurements of voltage, current, and AC ripple noise for each PCB:
Regulated positive voltage to Pearl II circuit (output of R3/R4) is 24.3v, 0.0mV ripple, -75db to -83dB noise (constant fluctuation).
Regulated negative voltage to Pearl II circuit (output of R31/R33) is -23.9v, 0.0mV ripple, -82dB to -84dB noise (constant fluctuation).
My meter is only able to measure down to -87.6dB with the probes shorted. I do not know what noise levels Salas' BiB shunt regulator is able to achieve, though I suspect it might be closer to -100dB.
Regulated positive voltage to Pearl II circuit (output of R3/R4) is 24.3v, 0.0mV ripple, -75db to -83dB noise (constant fluctuation).
Regulated negative voltage to Pearl II circuit (output of R31/R33) is -23.9v, 0.0mV ripple, -82dB to -84dB noise (constant fluctuation).
My meter is only able to measure down to -87.6dB with the probes shorted. I do not know what noise levels Salas' BiB shunt regulator is able to achieve, though I suspect it might be closer to -100dB.
Mouser Bill-of-materials for Pearl II
As I mentioned in an earlier post I've been collecting parts for a Pearl II build and now have everything here or on order for delivery next week.
A huge thank you to 6L6 who helped me with component selection.
I decided to start with a single enclosure build due to significant space limitations in my equipment rack.
I based the Power Supply on the Universal PSU boards from DIY Audio Store (I had a spare set of boards from an earlier project)
Jim (6l6) has told me repeatedly an outboard supply is the only way to make it quiet but I figured I would give it a try ala the XP-15 due to space limitations.
I used a shielded Antek transformer and plan on shielding all the AC wiring inside the box.
I will try a mu metal box shielded "box within a box" if it is still too noisy.
I purchased most of the parts from Mouser and some specialty resistors and caps from Parts Connexion.
I prefer Mouser's Website to Digikey's especially when you are trying to compare parts or choose a particular part from many choices. (I have no commercial interest in either).
Since the other BOM I found here in the thread was based on Digikey and a bit outdated, I thought I would post my updated Mouser BOMs here to save anyone else some trouble.
It is an exel file in the attached ZP file.
I color coded the cells with Orange for alternate parts and Grey for parts not purchased from Mouser.
There are sheets for the Pearl II, the PSU, and some resistor sheets as well.
I went for higher end parts and an "as Wayne designed it" build.
You could certainly build it for less but, as my wife says, the delta on parts cost is minimal when you average it over years of use.
I did go a bit crazy with some Mundorf caps for the Pearl II board and some TX-2575 resistors but who is counting.
I also attached a progress photo showing the chassis with boards mounted but mostly unstuffed.
I did start stuffing the PSU boards but am waiting for the heatsinks to arrive later this week to finish and test the PSU.
I'll post some more pics as the project progresses.
As I mentioned in an earlier post I've been collecting parts for a Pearl II build and now have everything here or on order for delivery next week.
A huge thank you to 6L6 who helped me with component selection.
I decided to start with a single enclosure build due to significant space limitations in my equipment rack.
I based the Power Supply on the Universal PSU boards from DIY Audio Store (I had a spare set of boards from an earlier project)
Jim (6l6) has told me repeatedly an outboard supply is the only way to make it quiet but I figured I would give it a try ala the XP-15 due to space limitations.
I used a shielded Antek transformer and plan on shielding all the AC wiring inside the box.
I will try a mu metal box shielded "box within a box" if it is still too noisy.
I purchased most of the parts from Mouser and some specialty resistors and caps from Parts Connexion.
I prefer Mouser's Website to Digikey's especially when you are trying to compare parts or choose a particular part from many choices. (I have no commercial interest in either).
Since the other BOM I found here in the thread was based on Digikey and a bit outdated, I thought I would post my updated Mouser BOMs here to save anyone else some trouble.
It is an exel file in the attached ZP file.
I color coded the cells with Orange for alternate parts and Grey for parts not purchased from Mouser.
There are sheets for the Pearl II, the PSU, and some resistor sheets as well.
I went for higher end parts and an "as Wayne designed it" build.
You could certainly build it for less but, as my wife says, the delta on parts cost is minimal when you average it over years of use.
I did go a bit crazy with some Mundorf caps for the Pearl II board and some TX-2575 resistors but who is counting.
I also attached a progress photo showing the chassis with boards mounted but mostly unstuffed.
I did start stuffing the PSU boards but am waiting for the heatsinks to arrive later this week to finish and test the PSU.
I'll post some more pics as the project progresses.
Attachments
![IMG_0693[2].jpg](/community/data/attachments/558/558008-6250f0d96ed6c8674a3ca7d4a3909668.jpg?hash=YlDw2W7WyG)
Hi Berd,
Are you going to run a shield down the centre of the chassis? That will help with hum.
-Chris
Are you going to run a shield down the centre of the chassis? That will help with hum.
-Chris
Chris:
Thanks for the suggestion. I might give that a try.
I was thinking of trying it without anything down the middle then, if the hum is too loud (I expect it to be), build a shielded box within a box.
The inner shielded box would contain the AC input jack, the transformer and the UPSU.
- Berd
Thanks for the suggestion. I might give that a try.
I was thinking of trying it without anything down the middle then, if the hum is too loud (I expect it to be), build a shielded box within a box.
The inner shielded box would contain the AC input jack, the transformer and the UPSU.
- Berd
Hi Berd,
If it comes right down to it, you might have to do both. Trial is the only way to know. See if you can insulate the inner box from the chassis while you're at it. The better test equipment is / was built like that.
-Chris
If it comes right down to it, you might have to do both. Trial is the only way to know. See if you can insulate the inner box from the chassis while you're at it. The better test equipment is / was built like that.
-Chris
I was thinking of a one box setup but was advised by 6L6 that's not the way to go. I ended up with a two box solution. The Transformers and caps (in my setup) in one box the Pearl II boards in another, which has to be at least 700mm away from the Pearl II boards to keep it hum free.
Definitely a two box solution. I had to move mine away from my pre to avoid hum, I cant imagine with the supply in the same box. I may be mistaken, but most if not all? of the builds I have seen of Pearl 2 were two box.
In fact, in separate boxes I couldn't set one on top of the other...w/o hum.
Russellc
This is best done in two boxes since the transformers are an unknown.
We have some new ones that are very quiet and you can even stack the supply and phono but best still to separate.
We have some new ones that are very quiet and you can even stack the supply and phono but best still to separate.
Hi Everyone,
Just got my Pearl 2 Boards and matched transistors. About to start gathering up parts. I'll probably build the external supply before I start on the Pearl boards. I'll need lots of help as this is my most advanced build in years and my mind will need some refreshing. 6L6 helped me a few years back with mods to my SL1200MK2 TT and it's still going strong. I'll probably build the power supply based on the one in his thread as it worked great for the TT and was used as a guide for my line stage power supply built a few years back. I don't have the room to keep it 3 feet or more away (my listening area is fairly small) but I'm hoping 1.5 feet will work out. I'll put the PS in a steel case and use a cap over the transformer. It worked for the line stage which is only 1.5 feet away. Of course the phono stage is much lower output but since some have been able to put the supply in the same case, I'm hoping to make it work. I've already been through this thread and the 6L6 thread a couple of times and took lots of notes. Hope that helps me get it right. Thanks Berd for the updated BOM for Mouser. I'll use it as a guide. I also prefer Mouser for parts. Just started 2 new projects on their website, one for the power supply and one for Pearl 2 Boards. I've been thinking of using the LGU Nichicons in the power supply and for the 10KuF on the board. The Mundorfs are a bit out of my price range. I have a 22v x 22v 200 VA shielded Antek transformer that I bought 4 or 5 years ago and never used. Kind of big for this project but I might use it to save $ on having to buy something, as I doubt it will ever get used if I don't use it here. I live about an hour from Antek and Par Metal, so I use them for transformers and cases. I plan on using an Audio Technica OC9ml2 (.4mv output) that was given to me as a gift. Expensive gift, as now I need a new phono stage for MC to us it. But building this allows me to spread out the cost and build slowly. My line stage has 20 db gain, so I figure the stock 55 db build should hopefully be enough gain. Looking forward to getting started.
Just got my Pearl 2 Boards and matched transistors. About to start gathering up parts. I'll probably build the external supply before I start on the Pearl boards. I'll need lots of help as this is my most advanced build in years and my mind will need some refreshing. 6L6 helped me a few years back with mods to my SL1200MK2 TT and it's still going strong. I'll probably build the power supply based on the one in his thread as it worked great for the TT and was used as a guide for my line stage power supply built a few years back. I don't have the room to keep it 3 feet or more away (my listening area is fairly small) but I'm hoping 1.5 feet will work out. I'll put the PS in a steel case and use a cap over the transformer. It worked for the line stage which is only 1.5 feet away. Of course the phono stage is much lower output but since some have been able to put the supply in the same case, I'm hoping to make it work. I've already been through this thread and the 6L6 thread a couple of times and took lots of notes. Hope that helps me get it right. Thanks Berd for the updated BOM for Mouser. I'll use it as a guide. I also prefer Mouser for parts. Just started 2 new projects on their website, one for the power supply and one for Pearl 2 Boards. I've been thinking of using the LGU Nichicons in the power supply and for the 10KuF on the board. The Mundorfs are a bit out of my price range. I have a 22v x 22v 200 VA shielded Antek transformer that I bought 4 or 5 years ago and never used. Kind of big for this project but I might use it to save $ on having to buy something, as I doubt it will ever get used if I don't use it here. I live about an hour from Antek and Par Metal, so I use them for transformers and cases. I plan on using an Audio Technica OC9ml2 (.4mv output) that was given to me as a gift. Expensive gift, as now I need a new phono stage for MC to us it. But building this allows me to spread out the cost and build slowly. My line stage has 20 db gain, so I figure the stock 55 db build should hopefully be enough gain. Looking forward to getting started.
I also use a .4mv LOMC cartridge, the standard setting of 55db worked fine with an F5 (15db gain) and speakers rated at 91db.
It's really not too tough of a build, you'll be fine.
It's really not too tough of a build, you'll be fine.
In Post# 2665 I show my Pearl Two which I built in one chassis and did not get any hum. But I did about everything I could to avoid hum in it, Antek shielded xfrmer, input as far away from the xfrmer as possible, shielded cables low, etc., which by using the emf meter, I could tell was reducing the effects from the power supply. If I had room though, I would have just built it in 2 chassis to avoid the chance of hum. BTW, it still sounds beautiful after using it for a about a year.
To u1022: a 25VA Antek is cheap and less likely to throw out interference than a 200 VA.
To u1022: a 25VA Antek is cheap and less likely to throw out interference than a 200 VA.
I decided I'm going to proceed with the single chassis Pearl II build with the Antek 5022 shielded transformer.
I was over at a friend's house today and he is a long time electrical engineer with lots of experience in instrumentation and measurement.
He suggested I build it and then do FFT plots of the output to show the 60/120 Hz noise component with inputs shorted.
He has a PC based DAS / analyzer that can do 24 bits at 200k samples/sec/channel which ought to do the trick.
I'll do one measurement with the transformer plugged in and then another one immediately after turning it off (plug strip).
I have 40k uF in each rail of the UPSU plus the 10 kuF per rail on the Pearl II boards before the regulators.
There should be plenty of capacitance to be able to make a measurement with the AC off but before the caps bleed down.
This should give me a good idea of how much 60/120 Hz hum caused by having the transformer and diodes in the box, i.e. Switched off = no AC = no hum.
Assuming there is noticeable / measurable hum I can do a couple of more things and measure the hum at each point along the way.
1) Baseline AC on and off
2) Mu metal shielded transformer can.
3) Mu metal shielded box-within-a-box around Pearl II boards
4) Outboard transformer only (diode bridges still inside)
5) Output transformer and diode bridges (DC only inside box)
I'll post results as we go along and hopefully it will provide some good quantitative data for discussion.
Now if only those last few back ordered parts from Parts Connexion and Mouser would arrive...
I was over at a friend's house today and he is a long time electrical engineer with lots of experience in instrumentation and measurement.
He suggested I build it and then do FFT plots of the output to show the 60/120 Hz noise component with inputs shorted.
He has a PC based DAS / analyzer that can do 24 bits at 200k samples/sec/channel which ought to do the trick.
I'll do one measurement with the transformer plugged in and then another one immediately after turning it off (plug strip).
I have 40k uF in each rail of the UPSU plus the 10 kuF per rail on the Pearl II boards before the regulators.
There should be plenty of capacitance to be able to make a measurement with the AC off but before the caps bleed down.
This should give me a good idea of how much 60/120 Hz hum caused by having the transformer and diodes in the box, i.e. Switched off = no AC = no hum.
Assuming there is noticeable / measurable hum I can do a couple of more things and measure the hum at each point along the way.
1) Baseline AC on and off
2) Mu metal shielded transformer can.
3) Mu metal shielded box-within-a-box around Pearl II boards
4) Outboard transformer only (diode bridges still inside)
5) Output transformer and diode bridges (DC only inside box)
I'll post results as we go along and hopefully it will provide some good quantitative data for discussion.
Now if only those last few back ordered parts from Parts Connexion and Mouser would arrive...
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Thanks everyone for the encouraging words. I'll be ordering the parts for the external power supply and the on board power supplies for the 2 boards in the coming week. I think I'll go with the Nichicon caps I mentioned. They're snap-ins with a 10 mm lead spacing. For the 4 - .1 uF caps used to bypass the power pins of the regulators to ground on each board, would multi-layer ceramics be better or should I just use some polypropylene's? I've used the multi layer ceramics for that purpose in older builds as I was told they were great for that purpose. It's nice to hear that the stock build with 55 db gain will work. I think I'll try it 1st with the transformer I have. I'll put it on the side of the case that's furthest away from the phono and see how it works. If it's a problem, I can always swap it out later. I have a steel cap that goes over the transformer and I'll line the cap on the inside with some copper tape I have. The transformer would end up around 2.5 feet from the Pearl 2 at the far end of the case.