Inexpensive Bi-Polar Power Supply for Gilmore Amps

Now the Gilmore Lite MK1 (aka Dynalo) aps and the the Lite MKII need 15V bipoloar DC power supplies. Meaning a +15V rail, a ground or 0V reference, and -15V - all DC current. The stock SMPS supply only puts out 0.24A per output, so that is 0.48 amps total, or 14.4 watts.

Now you can get the upgraded power supply from HeadAmp for $200, and that is a highly regulated and filtered power supply with some assitance from MeanWell, and and excellent choice. I wanted to see if I could make or build one myself from a kit or something.

Someone suggested I look at the Acopian Mini Encapsulated LPS's. They sell new for around $200, but I was able to get one off ebay for less than $40. Score! Now just a box to protect all the wires, an LED power indicator, and 5-pin DIN power out. I picked up a small case off ebay, only had to drill holes for the switch and 5-Pin DIN in the back, and one in the center for the LED.



The aluminum project box already came standard with the IEC cut out and connector. The Acopian DB series has four holes in the bottom (or back) for securing the wall or other device. I used those screw holes to secure it to the box from the bottom. The LED was hooked up AC mains with a resistor given the voltage drop with and LED calculator. I was able to use the existing power supply to figure out the pin-out.

All that was needed after this was a cable. You can use any 5-pin DIN or MIDI cable. I custom made one from MIDI connectors and Canre star quad mic cable, because, why not?



Was it an improvement, yes, yes, yes! The stock power supply is slow, hazy, muddy, noisy. There is just no comparison, the new power supply wins everytime. Better definition, blacker background, and better separation of instruments.



Now I made a couple of more changes to the Gilmore MK1 to make it closer to my Gilmore clone, which was simply:

1. Change the TL071 DC coupling cap to a OPA604? That op amp was chosen after experimented with a few different single channel op amps and using the one that is in the MKII. It really brings out the best in the Gilmore and some say a DC coupling cap should not change the sound, I beg to differ. It is true that it will not shape the sound like a true op amp in the audio path, but it can change it in the immediacy and change the character of the amp just slightly. The OPA604 is a winner in this amp.
2. Add two caps to the voltage rails. You can never add enough. The ones here are just Panasonic 330uf.

It makes for one helluva package with an amp that is just slightly bigger than the Magni, that is an all Class A discrete design that is warm, dynamic, punchy, without crispy top end. I will say, the MKI is not quite the level my clone is. Mine has an Alps RK50 volume pot, and more caps on the power rails (really much more that it could ever need, and a super low noise LPS). In switching, it is really hard to tell the difference between the two. Mine is slightly wider and deeper in sound and the MKI has super similar timbre, just maybe not as wide and slightly mids pushed up some. Some say mine is more U-shaped, and in comparison, that makes sense. Both are killer though.


You can see the Sys at the top to get the scale. I was actually A/B'ing two DAC's and just feeding the Dynalo with the split output on the MKI.

I think this MKI is going back to the original owner as I don't need two as I am not going back to the office and remote forever. Hopefully he likes the changes.

 

For a DIY approach I'd highly recommend Pete Millett's filament boards for a bipolar PSU as shown in his page: http://www.pmillett.com/DC_filament_supply.htm
I have these boards, it was a breeze to solder and they're excellent performers.

 

That board is for tube heater filaments if you want to drive with bi-polar DC. The LT1084T is limited to 5V.

There are other DIY bipolar power supplies out there. The one I have for my Dyanalo is based on a Studer 900 console power supply that is highly regulated.



The board says "Ultimate Mini Regulator", but I can hardly find any information about them online, and of course they are not made anymore. However, there are a few Studer D900 clone power boards out there. You just have to be careful, some of the Studer 900 PS's are single ended output.