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low noise Pre-Amp / DAC power supply MJE15034 TL072 Regulator based on STUDER 900
low noise Pre-Amp / DAC power supply MJE15034 TL072 Regulator based on STUDER 900
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Old 5th April 2019, 01:36 PM   #131
bButcher is offline bButcher
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@adrian
Yes, blue led is noisier than red, but the low pass RC filter's cutoff freq. is set at ~0.34Hz, so most of its high freq noise won't reach to error opamp's input, it should be O.K. To be honest, LM4040 or LM336 isn't that expensive, and much more stable under temperature and line voltage variation.


If you plan to use 6/7VAC input, than change R104 to 3.3k will give you ~6.5V op rail voltage. And also change R102 to 1K to maintain the proper zener current. But the problem is at high current (>1A), MJE15034's hfe will drop significantly so OPA2134 need more than 6.5V to supply the needed driving current. The solution is change it to some higher rating power transistor like D44H11.


6V transformer is kind of risky, you must consider rated lowest line voltage is 94%*230V.
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Old 6th April 2019, 07:29 AM   #132
adrian311 is offline adrian311  United Kingdom
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@bButcher
Thanks again. It looks a lot more straightforward sticking with the 9v solution for the 5v feeds, and using more heatsinking. I'll go with one dual board for the +/- 12-15v supply for the DAC output (12v trafo), and one dual board for the separate 5v feeds for the RPi and the isolator board. I'll do a few of the mods you suggest (R107 to 5k and the cleaner feed for Vref) for these, but I'll probably buy another board to try the other bigger changes later.
Regards Adrian
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Old 17th May 2019, 02:21 PM   #133
stereo247 is offline stereo247  South Africa
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Thanks to everyone who's contributed so far - Ive learnt a lot and have have also ordered a STUDER for a RPI3B+ Digione Signature build.

Really interested to see what comes from the opamp experiments and maybe trying my hand at the remote sensing mod.

How would one float the OP power supply from the output voltage? I have a spare tap on my smallest 9V-3.5Va transformer.
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Old 30th May 2019, 01:09 PM   #134
Dinolobe is offline Dinolobe  Canada
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Could you guys tell me what transformer secondary voltage I would need to get a regulated output of about 18-20V ? I don’t find voltage drop specs and don’t want my power supply to dissipate too much power if the input voltage is too high. Thanks !
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Old 30th May 2019, 10:03 PM   #135
jonners is offline jonners  United Kingdom
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@Dinolobe
My experience of using a 15V AC transformer to give a 15V DC supply would suggest that a secondary of around 18-20V AC should be OK in your case.
If @bButcher is around he could probably give you a definitive answer.
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Old 31st May 2019, 05:55 AM   #136
CallMeMike is offline CallMeMike  United Kingdom
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Quote:
Originally Posted by Dinolobe View Post
Could you guys tell me what transformer secondary voltage I would need to get a regulated output of about 18-20V ? I donít find voltage drop specs and donít want my power supply to dissipate too much power if the input voltage is too high. Thanks !
...it would be useful to know what is the current consumption of the device you are intending to use your 'Studer' PSU with...
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Old 31st May 2019, 07:55 AM   #137
danny_66 is offline danny_66  Belgium
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Here's a general rule from bButcher:

For moderate load current (<=500mA), use 9V AC for 9V DC output or below, use xV AC for xV DC output for x >= 9.
You need at least 9V AC bc opamps need 10V dc to operate properly.
For best result, keep Vce of pass transistor > 2V under worst condition, please refer to post #97 part (2) for more detail calculation
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Old 4th June 2019, 02:16 PM   #138
Dinolobe is offline Dinolobe  Canada
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Quote:
Originally Posted by CallMeMike View Post
...it would be useful to know what is the current consumption of the device you are intending to use your 'Studer' PSU with...
It will be used in a phono preamp wich, according to the seller, has a max current consumption of 100mA.
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Old 11th June 2019, 10:55 PM   #139
Dinolobe is offline Dinolobe  Canada
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Could someone confirm the values of R30, R31 and R32 ? They are not on the schematics that I can find online and in this thread. They are the resistors next to the L, M and H solder pads. Thanks !
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Old 11th June 2019, 11:51 PM   #140
Dinolobe is offline Dinolobe  Canada
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Originally Posted by Dinolobe View Post
Could someone confirm the values of R30, R31 and R32 ? They are not on the schematics that I can find online and in this thread. They are the resistors next to the L, M and H solder pads. Thanks !
Never mind. Just found the answer in the product description on ebay. Lol
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