Powering a Regen cascade - one possibility (a 65VA eBay LPSU), including the 12V dilemma
by, 02-05-2016 at 12:57 PM (1129 Views)
Note: I started writing up this project in early October 2015, as I was assembling the parts, but it has taken all this time to complete and refine the text for publication (it was not my highest priority, but worth completing).
1) The Regen cascade
My USB cleanup cascade is made up of two UpTone Audio Regens connected in series between my Apple Mac Mini and Benchmark DAC2, with both powered by a Chinese linear PSU.
I was lucky to get one of the last of the first batch of Regens (the 'Green's), and later decided (like every other 1st batch buyer !) to upgrade to an 'Amber' circuit board, when UpTone made that available for a very small and fair fee. My original 'Green' Regen circuit board then went on a tour to some of my local audio friends so they could hear the benefits of this new device. I know of at least three new orders that came from that exposure.
Once my 'Green' came back home it was time to try a 'cascade' of the two devices with the old Regen feeding through the original hard adapter to the new 'Amber' Regen, which then plugs into the back of my DAC with a little bit longer hard adapter to clear the AC cable. The two Regens are now powered by a 5mm splitter cable connected to a Ultra Low Noise LPSU I got through eBay, it is a temporary supply until I get a LPSU that's better suited to the Regens and use the 65VA for my Mac Mini. The cascade is fed by a Supra .7m cable from my 2010 Mac Mini. The Mini and my DAC share an acrylic platform (with vibration isolation devices), so there are a lot of dense cabling behind the two, and the cascade has to fit in there too, with some Velcro straps to keep things floating nicely.
2) The Linear Power Supply
An "Ultra Low Noise" regulator that does 4+ amps at 12 volts, for about $100 (with free shipping), sounded pretty good to me. Contrasted with the great UpTone Audio JS-2 at $925, the price was right, plus it has an R-core transformer, high speed diodes, lots of complicated regulation circuitry ( :) ), and that nice little "Ultra Low Noise" designation ! This LPSU is certainly over powered for a couple of UTA Regens, but I really intend it for my Mac Mini when I get an MMK for it. But for now it should do fine for the Regen cascade, and let me get rid of the original Meanwell SWPS, which I suspected of adding a little haze to my system (probably RF back through the AC lines).
Note that this LPSU's voltage is not adjustable - you must declare the voltage you want set at the factory (probably a zener diode), and your AC line voltage, when you order. I ordered 120VAC/12VDC. I went to eBay and did a 'Buy It Now', and the package appeared on my doorstep about a week later. I opened up the top of the PSU case and checked out the devices, took a few pix, discovered, and removed, a 1/2" long thin metal whisker (clipped component lead?) that was stuck under a resistor, or something, on the PCB. (QC :( )
12 volt, 4.2 amp , $95-125 from various sellers on eBay. "Finished 65VA Ultra Low Noise Linear Power Supply", eBay search
I know some of you are interested in what is inside the box, so here is a list of the active device numbers (read off the actual devices):
4 - U860 - ON Semiconductor ULTRA FAST DIODE (25 and 50 Nanosecond Recovery Time) (8A 600V) TO220
2 - 2SC5200 - Toshiba High power NPN epitaxial planar bipolar transistor (15A, 230V) TO-3
3 - BD140 - medium-power PNP transistor (1.5 A, 80V) TO-225
1 - (2S) K30a - Silicon N-channel junction FET (.01A, 50V) TO-92
1 - LM336-2.5 - Shunt Regulator Diode Voltage Reference (2.49V) TO-92
1 - NE5534 - Low Noise Operational Amplifier
I have not found a circuit schematic for this unit. Anyone ?
I wanted a stand to get the LPSU box off the carpeted floor, so, armed with the dimensions and keeping my eyes peeled, I discovered a closeout "Backyard Grill - Jalapeno Pepper Cooker" at Walmart. I think it was about $6. Now the big black PSU box is nested upside-down on top of a jalapeno roaster, sitting on the carpet, behind my equipment rack ! (upside-down so the AC cord doesn't cross the low voltage DC cable)
2.5) The 12 Volt decision...
You probably wonder why I choose to use 12 volts, rather then the more conventional 7.5v or 9v to power these Regens. I Initially thought that I could set the LPSU to 9 volts for powering the Regens, then switch it to 12v to power my Mac Mini, once the UpTone 'mystery' power regulator became available. BUT, a closer look at this PSU revealed that it is set for a voltage at the factory, and there are no switches or potentiometers for a user adjustable voltage setting. That got me looking into the possibility of using 12 volts temporarily with the Regen, since I would need it later at 12v for my Mac Mini. There were words of warning about using 12v power, but reading the FAQ section "long answer" on the UpTone website very carefully, convinced me that I could get away with the higher voltage with a couple of caveats.
a) DAC current draw:
The big question for 12 volt option was how much current do my Regens draw. If it was too much, the heat generated in the 5v regulator chips could lead to failure.
One could purchase a special tool that once inserted in the USB chain, lets you see the actual current draw on the Vcc line happening at the moment. They are not that expensive, but I couldn't see another use for it, and decided to save my money. The only other option for me to get the current data wasApple's "System Information/Profiler" app (also "More Info" from the "About this Mac" window). Select the USB section, and follow the chain to the Regen devices, that look like hubs here. At the bottom of the list of values should be a line for "Current Available (mA):", and another for "Current Required (mA):". Odd that there isn't one for "Current Used", but I suspect that these numbers come from reading control blocks hard-coded inside the end-point devices, and not from measuring electron flow.
My in service Regens show a "Current Required" value of 2ma each, no big deal there, but my DAC (Benchmark HGC) shows a "Current Required" of 500ma (!!), for a total of 0.504 Amps.
I know that my DAC requires +5v on the USB input to work, but I suspect that the 500ma "Required" has been coded into the DAC by the manufacturer, and may well be less in actuality.
b) Heat sinks:
So, I may be on the edge, or even a little over the line, of safe performance of the 5volt regulator on my 2nd Regen, due to the potential load from the DAC's PHY. The problem is one of heat dissipation, and can be addressed by getting rid of heat, as well as not generating it in the first place, so I thought of adding more heat sinking to the +5 regulator chip on both Regens, through the last one is the most important since it's the only one supplying significant +5v current.
I found some bent strips of thin phosphor-bronze in my parts bins*, that were about the right size to fit on top of the regulator chips and extend over to the output USB connector shield, for addition heat sinking beyond the direct radiation from the strips. I bent them carefully to fit between the chip and connector (roughly a 'Z' shape), chemically blackened them, and 'attached' them with small amounts of white thermal compound paste (Wakefield 120-2). The thermal paste is sticky enough to hold the light metal strips in place, but only barely. They should be adhered some other way too, if not safely inside the case, or avoid any light contact that might shift them. I used a small piece of electrical tape. The thermal paste is a horrible mess to cleanup and seems to get everywhere, so be very careful with it.
* An alternative metal strip would be 1/64" x 3/16" K&S brass strip which should be available in better hardware stores, or online.
c) Temp readings:
I recently bought one of those IR laser thermometers from Harbor Freight for about $25 on sale. It is very easy to use by just pointing the device's laser beam at a spot on the surface to be measured. Not only can this cool tool show me how hot my electronic devices are running, but all kinds of other household appliances, motors, and whatever :)
1) The 1st Regen in my cascade, the old 'Green' without case reads 90˚ on my little heat sink. It is not providing any +5v downstream, so no problems expected.
2) The 2nd, 'Amber', Regen reads 105˚ on the top rear of the case. Warmer, but not enough to concern me, aside from the fact that it has been working fine for a couple of months now :)
3) The 65VA LPSU is just coasting along at 75-77˚ on the bottom of the upside-down case right where the active devices heat pads are bolted to the case. No surprise here either, since it is running well below capacity.
4) My HGC DAC registers about 98-99˚ on the top of the case, which I find interesting since it runs 24/7. I have measured it at 87˚ at an early occasion, and I recall that shortly after I got it, it ran so hot I didn't want to leave my hand on the case for very long. It seemed to cool down after I placed a 2"x2"x1" steel block on top (for weight distribution). I have no idea what is going on here - burn-in, line voltage changes , ???
5) The 2010 Mac Mini runs at 87-94˚ across the top of the case.
I don't yet have much experience with digital temperature readings of my audio gear, which will come with time and more use of this fun tool, but, at least, now I don't have any strong concerns about possible heat problems with the current system !
3) The wiring
a) AC and DC power:
1 foot AC to IEC cable (stolen from the Regens Meanwell PSU - thank you, Alex C :)
eBay LPSU supplied cable with screw-in lock connector to 5mm x 2.1mm barrel power plug,
then a 5mm x 2.1 mm splitter cable from Amazon to feed the two Regens power.
To prevent the AC cord and power cable from crossing each other, I turned the unit upside-down. The active devices inside are bolted to the case floor for heat sinking, so I'm not concerned about this orientation.
b) USB cabling components:
A Supra .7m cable from an unused high-speed port on my 2010 Mac Mini (pin 1 taped over on Mac side), to the 1st Regen (green), and suspended by some Velcro strips and a rubber band, hung from clamps on the back of my equip racks upper shelf.
UpTone supplied hard adapter between the two Regens,
A slightly longer hard USB adapter found on eBay (with a little surgery) to clear the IEC bulge on the Benchmark power cord.
I don't think there are any issues with using the same PSU for the two separate Regen devices, through I not sure how I could tell such a very subtle problem. There are certainly no hums in the system, and all my digital front-end components are plugged into the same, RFI filtered, power strip.
As much as I might like to, I just can't afford a set of the Curious (or similar high SQ) USB cables. I hope that someday, someone looks inside the better sounding USB cables and identifies the conductor-insulator-configuration details that make the SQ differences, so some of us can do our own DIY knock offs ! (Hint, Hint !!)
4) The results
At first I didn't notice much of any change… (WTF ??) So, I just let it just play, 24 x 7 streaming radio*, background level or muted. This went on for many days while I attended to other aspects of my life. After a week or two I started to listen to some familiar tracks and noticed that the sound was getting better. Bass was regaining its clarity and visceral-ness, above that transparency returned, through it took longer. But cymbals, bells and such, while fully 'present and accounted for', lacked air, reality, beauty. I think the the poor showing in the highs is partly due to my old heavily modded Audio Research D-52d amplifier that is doing temp duty for my broken Marsh A400s. Thus, I am hearing through to other problems in my system, and indirectly putting a positive light on this upgrade. The 'haze' from the old Meanwell switcher is gone, and there does seem to be an increase in the 'Regen' effect, but difficult to tell after all the time that went by. Others might want to put the old PSU back in place to check, but not me. I'm happy with where I am at now (all things considered) :)
My very first exposure to the Regen SQ was a revelation. The improvement in SQ was a little subtle at first, but unquestionable once I noticed my ability to follow different instruments 'lines' through the music, and hear distinct sounds that were previously masked in a general wash of sound. I don't recall a burn in period with the 'green', but that was a long time ago.
* For the last 3 weeks or so, my radio streaming no longer runs 24/7, but now won't even last through the night ! I haven't made any changes to the system, or my network, so it must be upstream in modem, AT&T, or the streaming company (somafm.com). A quick search didn't uncover any clues :(I'm baffled and a bit pissed, since it has been recently discovered that a continuous flow of music bits through the DAC contributes to a better SQ !)
1 - 65VA eBay LPSU interior
2 - 65VA LPSU setup
3 - Regen heatsinks and hard adapters
4 - Regens heatsink application tools
5 - Regen cascade
6 - Regen cascade in service with Velco cable sling