MX-VYNL Analog Power Supply – Upgrade
UPDATED: 8/28/2021.
During my original review of the MX-VYNL phono pre-amplifier I discovered that its external, inexpensive switched mode supply, caused noise problems which I improved with the addition of a couple of ferrite beads on the DC power supply cord feeding the pre-amp. I was never happy with this power supply solution, so I decided to replace it with a low noise analog toroidal power supply.
One of the more popular analog audiophile power supplies is the SBooster but I found its price of $399.00 rather excessive, no matter how well designed or manufactured. I therefore turned to Little Green Computer who sell several low noise analog toroidal supplies from 5V to 12V at 25Watts or 100watts at a more reasonable price.
Little Green Computer is probably better known for its range of Music servers, streamers and players. However, in order to provide their clients with upgrades to improve the musical performance of their hardware line they sell a range of linear power supplies, clearly acknowledging the audible improvements that analog power supplies bring over switched mode power supplies.
The supplies arrived just a couple of days after placing the order and were well packaged. They are well built and mounted in very solid extruded aluminum black anodized cases with a front, very bright, blue LED display that shows the output voltage. One advantage of using an all metal case is that it becomes the heat sink for the power regulator, really helping to keep it cool and improving reliability. Secondly the all aluminum case provides significant electrical screening. The 25VA model contains an internal AC power fuse, the 100 watt model has the AC power fuse mounted within the rear IEC power connector. They come with a short IEC AC power cord and a short DC power cord that has ferrite bead(s) to reduce RF and noise, plus a set of DC plug adapters to fit a wide range of DC input sockets.
The two I tested were the 25watt and 100watt 5V/7V/9V & 12Volt supplies. Just a brief word of warning here; while the 25watt version can provide a low noise 12volt output, it can only support a maximum current of 0.8amp (800mA or <10watts) at that voltage due to the low secondary transformer voltage (See update below). The 12volt 100W supply can deliver approximately 8amps if required. In either case I would not use these supplies at more than 50% of their rated wattage. Also the 100 watt supply is almost double the physical size of the 25watt supply: 25 watt-100mmx50mmx150mm, 100watt-130mmx50mmx250mm (WxHxD).
25 Watt Power Supply
100 Watt Power Supply
The 25 watt arrived set to 7volts but adjusting it to 12VDC is very easy using the front LED voltage display and rear voltage adjustment screw. The 100 watt supply came set to 12Volts. If adjustment is required removing the top cover gives access to the multi-turn potentiometer (see image above) that you use to set the required voltage. Both of these supplies can have their output voltage set to anything between 5volts and 12volts. With the 100 watt supply going above 16 volts depending upon current draw.
Due to the much higher current capability of the 100 watt supply its rear connector is an Arospace type GX12-2.
Checking the output voltages using both digital and analog voltmeters against the display showed that both were accurate at all voltages between 5V and 12V.
While monitoring each supplies output on an oscilloscope and AC millivoltmeter, the supplies were loaded to 800mA (25watt) and 4 amp (100watt) with no visible increase in output noise or significant drop in voltage. The noise level of the 25 watt supply was below 2mV peak to peak, the 100 watt supply 6mV peak to peak. The noise spectrum of BOTH power supplies showed a pulsating, irregular “saw tooth” shaped spiky noise pattern. This turned out to be from the powers supplies digital LED display(s). If the displays were disconnected the power supplies noise spectrum was primarily extremely low level 120Hz ripple. The 25VA supply showing 0.14mV RMS, the 100VA supply showing 0.07mV RMS.
I tested both supplies, being hyper attentive to any background noise issues. Either supply would easily power the MX-VYNL (12volts @ 500mA). Ultimately I decide to use the 25watt supply due to the low current requirements. The 100 watt supply was used to replace my turntables 15VDC 1 amp switched mode supply whose low level radiation I had noted during its original installation – see here.
Both supplies DC outputs are fully floating from the AC power ground and the case, so cannot create a ground hum loop.
So were there any audible improvements when I replaced the MX-VYNL noisy switched mode supply?….Read on.
For these listening tests the MX-VYNL was tested in two modes:
- Balanced MC mode, RIAA EQ, +6dB gain, 400 ohm load. Listening volume set to 0dB.
- Unbalanced MM mode, RIAA EQ, 0dB gain, 50pF load plus my Lentek head amplifier. Listening volume set to -6dB as this pairing creates +6dB more gain.
Initially I used the 25watt supply and then swapped to the 100watt supply to see if I noted any changes. There was only one. The background noise level at my receivers maximum gain of +18dB was very slightly higher with the 100 watt supply, but there were absolutely no differences in hum level. At normal listening levels any noise at the MLP was barely audible. Either supply provides the same ‘musical’ audible improvements described below, with the 25watt saving the user almost $100.00.
My noise issues with the MX-VYNL switched mode supply are quite obvious, have been documented in earlier posts and are easy to replicate and hear, so I left it up to my ears to determine any improvements, rather than setup a whole barrage of measurements, which readers may not necessarily understand or want to read about.
The BIG question is; were there any audible improvements? A RESOUNDING YES. (These are not psychological improvements just because I had spent the money!)
For my listening tests I used the following three vinyl albums:
- Dire Straits – Brothers In Arms – Mobile Fidelity -45RPM
- The Sheffield Track Record – Lab 20
- Harry James – The King James Version – Sheffield Lab 3
To summarize this is what I heard or didn’t hear for BOTH test modes listed above:
- All hum and noise that was associated with the left channel were completely gone and movement of the MC cartridge phono cables entering the pre-amp no longer injected any hum or noise based upon their location.
- Overall background noise was lower and there was no audible hum at any gain.
- The bass was sightly more solid.
- The mid-range slightly more open.
- The sound “felt” more dynamic.
- The top end was slightly more detailed.
NOTE: The level of hum and noise from the Lentek head amp now dominates anything generated by the MX-VYNL. However, the above noted ‘musical’ improvements are still audible AND I still prefer the musical sound of the MX-VYNL/LENTEK pairing despite its slightly higher hum and noise levels which are barely audible at the MLP at my normal listening volume setting of -6dB.
Other than the drop in noise and hum these improvements are not dramatic, but they are worthwhile and audible, realizing the full potential of this phono pre-amp.
Upgrading your cheap switched mode supplies to low noise toroidal analog power supplies is highly recommended to ALL users of the MX-VYNL and probably any other phono and turntable related hardware.
Available from Little Green Computer.
MSRP:
- 25watt – $189.00 (5v > 9v adjustable) – (10W @ 12VDC)
- 100watt – $285.00 (5v > 16+v adjustable)
UPDATE 1: 25watt PSU Modification
I decided to modify the 25watt supply by upgrading the transformer to 25watt 12VAC. This then allowed a current draw of 1.0 amp at 12 volts while still maintaining the same low-level noise. The Talema replacement toroidal transformer, model 70062K, was purchased from Digi-Key, part number 1295-1021-ND, cost $23.28. If you are handy with a soldering iron and solder sucker its exchange is fairly easy as both transformers are physically identical and have identical mechanical mounting requirements. REMEMBER this will VOID your warranty.
Upgraded 25VA Power Supply with Talema Toroid
As expected, there were no audible changes to the musical sound or noise levels, but I now felt more confident with the power supplies improved power headroom.
UPDATE 2: Display Switches
Due to the high switching noise created by the digital LED voltage displays, both power supplies have now had switches added to the rear panel that allow me to turn the LED display OFF in normal use. This notably improves the noise of both power supplies, in particular the 100 VA design (see upcoming post).
Associated posts:
