Walrus

Re: DIY 500 Series Lunch Box
« Reply #20 on: August 24, 2019, 01:37:15 PM »
Seems the MW LR35-36 is a 35W 36 V single output power supply.
Going to be hard work getting +- 16v let alone 48v from it!!
Kevin.


Re: DIY 500 Series Lunch Box
« Reply #21 on: August 24, 2019, 01:48:14 PM »
Sorry, but what is a MW LRS-35-36

Normally better to use a tl783 for phantom power it is more capable with regards to the difference between input & output voltage.  This makes it more reliable in this application.

Hi,

I look into that, thanks alot.

The MW is a closed power-supply for internal use with an output of 36V @35W. That way I wouldn't have to to fiddle with the mains myself.

Rob Flinn

Re: DIY 500 Series Lunch Box
« Reply #22 on: August 25, 2019, 04:51:36 AM »
Personally I wouldn't use an smps for this application as I have had problems with these cheaper ones for audio in the past.   Although I have also seen some SMPS work quite well for audio but these were quite expensive ones and not cheap cartridge types.

Also you wouldn't be able to use the LM317/337 combination with this particular PSU to get + & - 16v because I think the regulators have to drop at least 3v to do their job, but you can verify this on the relevant data sheets.
regards Rob

Re: DIY 500 Series Lunch Box
« Reply #23 on: August 25, 2019, 10:24:22 AM »
Personally I wouldn't use an smps for this application as I have had problems with these cheaper ones for audio in the past.   Although I have also seen some SMPS work quite well for audio but these were quite expensive ones and not cheap cartridge types.

Also you wouldn't be able to use the LM317/337 combination with this particular PSU to get + & - 16v because I think the regulators have to drop at least 3v to do their job, but you can verify this on the relevant data sheets.

Hi Rob,

the output of the PSU is 36V,  and lets say this PSU would power the LM317/337. The LM317/337 is able to regulate the voltages +/- 37V, lets say 35, for safety.

What's wrong with that? I'm more curious.

Thanks again :).

P.S. Maybe I should stay with programming and buy a Midas L6, which is only €169 here.

Rob Flinn

Re: DIY 500 Series Lunch Box
« Reply #24 on: August 25, 2019, 02:48:26 PM »
The regulators do their job by burning off voltage in terms of heat.    Each regulator needs 3v across it to do it's job, so if you need + & - 16v you would neeed to feed each reg with at least + or -19v to regulate to + or -16v.  2x 19 is 38v.   

Also the more voltage you drop across it the less current it will deliver.   so if you had 20v being burnt off by the reg the current capability would be significantly less than the 1.5A these regs are specced at.  This is shown as a graph on the data sheet.     I tend to use maybe a 2x 15v or 2x 18v transformer.     The rectified voltage is 1.4x the specced r.m.s a.c voltage of the transformer.    Therfore 15v a.c becomes 1.4x15v once rectified, therefor you have you bit in hand for the reg to burn up.      I normally bolt the regs to the case (with insulating mounting kit) to keep them cool.

Looking at the data sheet will help you understand these devices.
regards Rob

Re: DIY 500 Series Lunch Box
« Reply #25 on: August 25, 2019, 03:14:14 PM »
The regulators do their job by burning off voltage in terms of heat.    Each regulator needs 3v across it to do it's job, so if you need + & - 16v you would neeed to feed each reg with at least + or -19v to regulate to + or -16v.  2x 19 is 38v.   

Also the more voltage you drop across it the less current it will deliver.   so if you had 20v being burnt off by the reg the current capability would be significantly less than the 1.5A these regs are specced at.  This is shown as a graph on the data sheet.     I tend to use maybe a 2x 15v or 2x 18v transformer.     The rectified voltage is 1.4x the specced r.m.s a.c voltage of the transformer.    Therfore 15v a.c becomes 1.4x15v once rectified, therefor you have you bit in hand for the reg to burn up.      I normally bolt the regs to the case (with insulating mounting kit) to keep them cool.

Looking at the data sheet will help you understand these devices.

Thank you ever so much! I really appreciate your kind help.