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Post by zleepy on Jan 24, 2021 18:10:17 GMT
Hi! I need help with choosing a transformer for a Walt Jung PSU I bought from the bay. I know Oliver has used this PSU in his preamp so I thought I might get some advice from here? I am currently collecting parts for a Wyn Palmer phono stage (if interested you can find lots of info about it on AudioKarma) and I thought I would try to utilize the Walt Jung PSU for this build. For this phono stage I need dual voltage -15V +15V, max current draw 1A per channel. My problem is I don't have any instructions other than what can be read in the eBay listing: www.ebay.com/itm/HiFi-Walt-Jung-Super-Regulator-DC-Power-Supply-Board-Linear-PSU-Audio-DAC-Preamp/264513334594?hash=item3d96392d42:g:~MgAAOSw5B9dtk5sI guess I should choose a trafo with secondaries of one or a couple of volts over required regulated output voltage and 30 VA? Can anyone help me out with the trafo specs? Also, I assume the trim pots are there to adjust the output voltage? Does anyone have experience with those? What if they are way off from the start, might that not cause damage to the components? Very grateful for any help. |
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Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,398
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Post by Bigman80 on Jan 24, 2021 18:56:40 GMT
Hi! I need help with choosing a transformer for a Walt Jung PSU I bought from the bay. I know Oliver has used this PSU in his preamp so I thought I might get some advice from here? I am currently collecting parts for a Wyn Palmer phono stage (if interested you can find lots of info about it on AudioKarma) and I thought I would try to utilize the Walt Jung PSU for this build. For this phono stage I need dual voltage -15V +15V, max current draw 1A per channel. My problem is I don't have any instructions other than what can be read in the eBay listing: www.ebay.com/itm/HiFi-Walt-Jung-Super-Regulator-DC-Power-Supply-Board-Linear-PSU-Audio-DAC-Preamp/264513334594?hash=item3d96392d42:g:~MgAAOSw5B9dtk5sI guess I should choose a trafo with secondaries of one or a couple of volts over required regulated output voltage and 30 VA? Can anyone help me out with the trafo specs? Also, I assume the trim pots are there to adjust the output voltage? Does anyone have experience with those? What if they are way off from the start, might that not cause damage to the components? Very grateful for any help. Because you have the trim pots, I'd suggest around 18v 30va Traffo for your build. However, I'd await a professional opinion from either sq225917, misterc or firebottle |
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Post by misterc on Jan 24, 2021 20:21:37 GMT
Pretty straightforward Zleepy
Remember that converting ac《》dc you will use the 1.41 rule for conversion
Take into account forward bias on the diodes usualky between 0.45-0.7vdc depending on diode type
Next current draw followed by voltage
For example if i was looking for 12vdc @ 1.25amps to ensure enough headroom to cope with the drop across the diodes and current draw.
I would suggest a tx with 12Vac secondaries this will give you a raw unregulated ac voltage before the full bridge rectifier of around 17Vac depending on how good TX regulation is
Just make sure the heat sink on the regulator has a good c/w ratio
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Post by firebottle on Jan 24, 2021 20:31:31 GMT
You also need more than 30VA as there are losses associated with transformer utilisation.
A rule of thumb would be 70%, so 1/0.7 = 1.428.
30 x 1.428 = 42.8VA
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Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,398
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Post by Bigman80 on Jan 24, 2021 21:22:47 GMT
You also need more than 30VA as there are losses associated with transformer utilisation. A rule of thumb would be 70%, so 1/0.7 = 1.428. 30 x 1.428 = 42.8VA So what spec should he look for? |
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Post by zleepy on Jan 24, 2021 22:09:46 GMT
Pretty straightforward Zleepy Remember that converting ac《》dc you will use the 1.41 rule for conversion Take into account forward bias on the diodes usualky between 0.45-0.7vdc depending on diode type Next current draw followed by voltage For example if i was looking for 12vdc @ 1.25amps to ensure enough headroom to cope with the drop across the diodes and current draw. I would suggest a tx with 12Vac secondaries this will give you a raw unregulated ac voltage before the full bridge rectifier of around 17Vac depending on how good TX regulation is Just make sure the heat sink on the regulator has a good c/w ratio Thanks for info but I'm afraid I do not understand your example: "I would suggest a tx with 12Vac secondaries this will give you a raw unregulated ac voltage before the full bridge rectifier of around 17Vac depending on how good TX regulation is " How does 12Vac secondaries transform to ~17Vac before rectifier? And in my situation where I need the PSU to output regulated -15V and +15V? Do I multiply 15V with 1.41? That's 21,15V which seems high to me..? I feel really uneducated right now... |
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Post by zleepy on Jan 24, 2021 22:12:32 GMT
You also need more than 30VA as there are losses associated with transformer utilisation. A rule of thumb would be 70%, so 1/0.7 = 1.428. 30 x 1.428 = 42.8VA Thanks, this I can understand, I guess that means I should look for 50VA if 40VA is not enough as I doubt there's many sizes in between? |
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Post by zleepy on Jan 24, 2021 22:13:45 GMT
You also need more than 30VA as there are losses associated with transformer utilisation. A rule of thumb would be 70%, so 1/0.7 = 1.428. 30 x 1.428 = 42.8VA So what spec should he look for? +1  |
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Post by misterc on Jan 25, 2021 8:20:35 GMT
Pretty straightforward Zleepy Remember that converting ac《》dc you will use the 1.41 rule for conversion Take into account forward bias on the diodes usualky between 0.45-0.7vdc depending on diode type Next current draw followed by voltage For example if i was looking for 12vdc @ 1.25amps to ensure enough headroom to cope with the drop across the diodes and current draw. I would suggest a tx with 12Vac secondaries this will give you a raw unregulated ac voltage before the full bridge rectifier of around 17Vac depending on how good TX regulation is Just make sure the heat sink on the regulator has a good c/  w ratio Thanks for info but I'm afraid I do not understand your example: "I would suggest a tx with 12Vac secondaries this will give you a raw unregulated ac voltage before the full bridge rectifier of around 17Vac depending on how good TX regulation is " How does 12Vac secondaries transform to ~17Vac before rectifier? And in my situation where I need the PSU to output regulated -15V and +15V? Do I multiply 15V with 1.41? That's 21,15V which seems high to me..? I feel really uneducated right now... Sorry Zleepy Should have read raw unregulated DC after the bridge rectifier too much vintage cider yesterday I have one of those basic regs I will sim it for you are you looking for a constant 1 amp @ 15vdc? |
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Post by zleepy on Jan 25, 2021 10:27:03 GMT
Ah, ok, then your example makes sense . No, the current draw will probably be significantly less than 1A constantly. This phono stage is not only a phono stage. It has many features like a warp filter with optional +10dB gain, a line stage, and a headphone amp. All these modules are using the same PSU. It is only when all of them are used at the same time that the max current draw will get anywhere close to 1A. Originally the selected PSU by the designer is a smps + filter board. That smps (Mean Well pd-2515) is rated at 24W or 0,8A @ 15V per channel and that is enough to cover the current draw for all modules. Br, Karl |
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Post by misterc on Jan 25, 2021 12:04:25 GMT
Hello Karl
I would say that for 350-500ma per rail you should be fine with the MW you could for tighter rail control and ripple noise improvement use the Walt Jung copy as a pre regulator and add some LT3045's.
If you have space personally I would use a encapsulated SM Tx on a small board or a small 50/80va toroidal though appreciated if it is a kit then understand you may wish to just get it up and running.
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Post by zleepy on Jan 25, 2021 15:01:24 GMT
Thanks for info! The problem here is that I cannot get the MW smps to EU for sensible money. Digikey and Mouser will not ship it to EU because it is an open frame smps... Stupid EU nannystate regulations.
That's why I changed plans regarding the smps.
I am pretty sure the WJ regulator does not need any additions. It should perform well enough on its own.
Based on this info I will order a 50VA -15V +15V TX, either toroidal or O-core.
Many thanks for your help! I really appreciate it!
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Post by misterc on Jan 25, 2021 16:34:37 GMT
I am pretty sure the WJ regulator does not need any additions. It should perform well enough on its own. Hi Zleep the WJ is a good design but it's a 20+ year old concept and has been plagiarized many times to both good and bad implementations , but can be improved pretty well, possibly a project for the future maybe |
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Post by sq225917 on Jan 25, 2021 18:19:19 GMT
If I was going to use a wj supereg, I'd want to make sure it was the genuine circuit. It's very easy to build them marginally stable by mistake and I'd be weary of Chinese parts in this instance.
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Post by zleepy on Jan 25, 2021 19:34:46 GMT
Hmm, geting second thoughts here... Any safe recommendations for a quality regulator with my desired output?
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Post by misterc on Jan 25, 2021 20:00:42 GMT
If I was going to use a wj supereg, I'd want to make sure it was the genuine circuit. It's very easy to build them marginally stable by mistake and I'd be weary of Chinese parts in this instance. Absolutely Simon 100% a few of the Chinese variants I have been asked to fit crap out around 780ma and are quite noisy using the fitted pot imho is not obtaining the best form the original design |
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Post by sq225917 on Jan 25, 2021 22:28:26 GMT
Yeh, like any reg it has its place, great on digital rails in dacs and as a clock supply.
I have a couple of pos/ neg pcbs lying round from an approved group buy years ago, must dig them out and try them on my dac stack at some point.
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w ratio