low noise Pre-Amp / DAC power supply MJE15034 TL072 Regulator based on STUDER 900

For anyone buying one of the above kits from ebay / Hongkong /audiophonics (where I bought for 45€) the following problems and solutions may be interesting:

- Problem: I need +/- 12V dc from the supply, however when the jumper was soldered to the middle M position I hit the end of the potentiometer at 12.6V. Solution: also connect the H position together with the M position (both 33kOhm and 14 kOhm resistors are in parallel then - this is safe because the low L position reseistor would be even smaller at 3.3kOhm). In that way, the adjustment range goes below 12V :)

-Problem: I did not read the description properly and ordered a -12/0/+12 transformer. However this supply board needs two primary coils not a center tapped coil. Solution: Luckily my transformer had two coils that were connected, and digging into the connectors where the two coils where connected, I could separate them :)

PS: here is the exact description of the item on ebay:
MJE15034 TL072 Regulator Power Supply Kits based on STUDER900 for Pre AMP DAC
on audiophonics:
Linear Dual Power Supply board MJE15034G Low Noise 5V à 24V 2A
my transformer, which is not the correct choise but could be fixed:
Transformer R-CORE 30VA 12-0-12V + 1x9V
 
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Hi, there

I am thinking of buying this board, but I cannot get any answer from the vendor on how to connect the jumpers for H, M or L in order to get the voltage range I want. Can you show me using a picture and drawing the connections? Thank you very much for your help in advance.

Regards,
 
Thanks! Unfortunately, I am not sure how close these vendors follow the original circuit. I do not have the full version of Adobe to convert the PDF to a word document which can be translated with Google Translate. But I do find a block diagram that show how a series of resistor is use to provide different voltage output. Not sure whether this will be applicable to the board we are talking about.

Regards,
 
voltage choice

You can turn the potentiometer (the part marked with MEXICO in the image) until the voltage matches your desired value. As the tuning range does not cover the full voltage range, you either put solder across the pads marked L, M, or H to be able to get the right voltage. As stated above, in my case the desired 12V were just outside the M range, which only went down to 12,5V. So I also connected H in addition to M and voila the potentiometer range was enough for 12 V (see image).
The nominal voltage ranges are:
L (Low voltage) : 5v - 9v.
M (Middle voltage ) : Sortie 12 à 18v. (Vendu dans cette position initale).
H (High voltage) : 20 à 24V.
 

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Hi Yoshisoakland, I cam across yor post while searching for info on this PSU. I have just put one together, but unfortunately it doesn't work properlyn no regulation.

I have checked and double checked my assembly and can't see anything I've done wrong.

I noticed there are 2 empty pads on each half of the pcb, have you got these on your pcb? are they supposed to be linked across?

I am using split secondary 18 0 18 Transformer, want to obtain 15 0 15 supply.

Output sitting at 26 0 26 at the moment with no sign of adjusting.

Any assistance would be very much appreciated.

Thanks
 
I recently bought one of these "Studer 900" PSUs, and surprisingly, it made a very big difference in the sound quality in my system. I used it to power the Sotm sMS-200ultra endpoint renderer at 9V DC. It was surprising because I was comparing it to my Uptone Audio Ultracap LPS-1 that is "energized" by a 12V linear PSU, and the Studer 900 PSU improved the clarity and detail of the SQ of everything by a big margin, similar to how the LPS-1 improved the SQ when I moved from a regular LPS (based on the sigma 22 design) originally powering the sMS-200ultra.

I was stunned by this, and I can't explain it. I also changed the energizing PSU of the LPS-1 to the original Meanwell SMPS that came with it, and it made no difference. The Studer 900 was still clearly better.

I am running Roon Core from a SonicTransporter i5 and the sMS-200ultra is the Roon client connected to a Denafrips Terminator DAC.

I can't find a schematic of the "Studer 900" PSU anywhere, and it's not in the Service Manual of the Studer 900 series Audio Console, at least not similar to these "Studer 900" PSUs. Anyone knows where to source for the actual schematic of this PSU based on the MJE15034G and TL072?

Thanks
 
It was also a big surprise for me, while testing this "studer 900" power supply. This seems to me a great design, although I'm completely unable to understand this design, how it works.

I am currently playing arround my cheap AK4495 DAC board ( Weiliang) where - after a lot of tweakings - close to everything has been replaced/desactivated except the dac chip itself. Onboard power supplies have progressively been replaced by external ones. A lot of caps replaced, including some ceramic arround DAC chip. Op amp replaced by Burson V5.

I few days ago I compared the Reflektor-D supply with one "studer 900" like bought at Audiophonics on analog pins VDDL/R of this AK4495 chip. And like fibonacci1618 said, the studer gave a so much better sound on that specific place. Sound clarity, dynamic, bass level, there is not a small difference but a big one. I was very surprised and switched several times, and even made the JFET R6 mod on Reflektor in order to be really sure. But in any configuration this studer power supply gave best sound.

Now my power supplies setup arround this DAC is following :
- 1 Reflektor-D on digital 3.3V DVDD with r-core transformer
- 1 Reflektor-D on digital 5V feeding KALI with same r-core
- 1 Studer900 on analog 7V VDDL/R and VREFL/R with toroidal transformer
- 1 Studer900 symetric on analog +/-15V feeding Burson op amp with toroidal transformer

And the sound has never been so good :D

There is maybe some improvement potential on analog 3.3V AVDD currently fed by digital 3.3V DVDD with ferrite bead.
I have no opinion on removing the bead and placing there a 3rd Reflektor-D will bring something or not.

Regards
 
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Thanks for confirming my observations, @greinedo, about the huge jump in sound quality this amazing "Studer 900" PSU makes. I took a much closer look through the original Studer 900 service manual and I think I found the original schematics that this particular PSU is based on. It is in Section 8 of the manual and is entitled "Phantom / 24V Stabilizer 1.915.107".

Reading further on the Web, I believe phantom stabilizers are traditionally used to power electret condenser microphones, and since mics are very sensitive to electrical noise , the PSUs powering them have to be very low noise PSUs.

I am making a wild guess here, that part of the reason why it gives a huge jump in SQ is that the PSU has no output capacitors, or at least no electrolytic caps. I'm not sure if this is true but that's what I see in the original Studer 900 schematic, see around page 498 of the PDF file of the original manual.

Another thing I am guessing that could be responsible for the high SQ is a very low output impedance.

Perhaps someone else who is technically qualified to analyze the schematic could help to explain how this PSU is so good.

Thanks!
 
I recently purchased one o these supplies and have been impressed with the results. Unfortunately there is very little information available on the power requirements of the board. I tested the board with a 230V/15VAC toroid that supplied 17VAC unloaded. The board has a trimpot for voltage adjustment along with three jumper connections H<M and L. My board came with H and M jumpered. With the transformer connected to the board, I got 13.2VDC - 9.7VDC unloaded. With only M connected, 17.1VDC - 12.7VDC no load and 14.5VDC loaded. With only H connected, 23VDC no load and 14.3VDC loaded. Power requirements seem similar to those for Sigma11. Currently using as above to power Auralic Aries. Heatsink only slightly warm to touch powered 24/7. Also noticed this board for sale at Audiophonics. Their explanation regarding the jumpers is not correct. I would only connect jumper for the voltage range required and fine tune with trimpot.
 
I purchased one of these dual supplies, intending to use it to power my Allo Kali reclocker and ApplePi DAC, both at 5V. It powers the Kali OK but seems unable to supply the 0.6A at 5V that the DAC requires. I'm using a 9V AC 30VA transformer.
I thought it would have no trouble supplying up to 1A at 5V. Has anyone encountered similar issues with this board?
There's a noticeable improvement in the sound with it powering Kali so I'm very much hoping to get it to power the DAC too. Any ideas please?
MJE15034 TL072 Regulator Power Supply Board For Pre AMP DAC Based on STUDER900 699956878803 | eBay
 
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I believe there could be a kind of inconsistency. A few questions:

Your regulator board is for symmetrical “+”/”-” output voltages. Such normally uses a transformer with center-tap. Does your 9V AC 30VA transformer have a 9V-0-9V secondary winding?

You only want to use one rail (possibly the positive) to give you a 5V output, right?
 
It sounds like the board is designed with two (probably identical) positive voltage regulators. With two floating secondary windings, you can stack the two regulator output voltages to form a symmetrical supply or use them as two individual positive supplies.
I would then only experiment with one regulator such that interference can be excluded.
One secondary transformer winding connected to one board power input and the ApplePI connected to that output (set to 5V), what happens? Does the output voltage collapse such that the voltage is significantly below 5V?
 
Yes, that's the problem.

And the voltage at the buffer capacitors before the regulator remains above 9V?

A silly question, would you happen to have a circuit diagram of the regulator? I see no reason why such a circuit should not be able to handle 1A. They use a 350V series transistor (MJE15034) for some obscure reason.

I found a board that seems to be made by the same manufacturer: TL072 Regulated Power Supply DIY Kits based on STUDER900 For Pre AMP DAC | eBay. For that board I have a schematic. This circuit uses a current limiter set to some 1.5A (set by 0.4R). Perhaps your board has got a similar current limiter.
Can you see if pin 3 (the right-most pin) on the MJE15034 is connected to a resistor wit a value below 2.2 Ohm? That may be the resistor setting the current limit.