I've managed to put together a low price, high performance power supply for the SL1200 for under $50 parts cost. Its centered around the Mean Well LRS 50-24 SMPS.
This supply is very well built, using United Chemicon capacitors, a well laid out chassis and a high quality PCB design - pretty good for a $14 power supply. Output shows very little noise and ripple with more than enough current (max 2.2 amps) to feed the turntable.
The output voltage is adjustable via a small pot in a very wide range of 20 - 31V. It also has a soft start and a nice status LED. This can be extended out to the chassis for an external power indicator. The SMD series resistor on the bottom of the PCB can be changed to suit the current needed to run other LEDs.
With this PS you can turn the output voltage all the way down to 20V for a direct application, bypassing the stock reg or instead of a 3 pin based circuit. You can also turn it up to supply enough voltage to accommodate the drop of the stock reg or your 3 pin based reg of choice.
The SMPS regulation is very tight and I'd feel very comfortable using this straight into the supply rail of the SL1200's motor PCB. I would however fuse the main B+ rail into the TT if I chose to do this. Its just as a precaution against an eventual fault or failed component inside the TT to protect the main PCB from burning up any traces.
I configure the front panel to include a ground lift switch in case of noise issues due to grounding. Coming out of the PS I chose a typical 4 pin screw lock connector used in many low voltage applications. I left an extra pin available to shield the umbilical cable going into the turntable.
A KAB 3 pin reg board was used inside the TT instead of the stock reg. Honestly, the OE Technics setup is more than adequate for the job as long as the filter caps are all in good shape. Of you need to replace them, I'd recommend the Panasonic EB series caps. They're inexpensive for being rated at 105 deg C along with excellent ripple current capability.
The chassis I used was an enclosure made by Context Engineering, part number 4006. I had it in stock already, as this is an enclosure I use for many projects. I don't know if these are still being made, but I'm sure there still are other suitable enclosures being sold for this purpose.
This supply is very well built, using United Chemicon capacitors, a well laid out chassis and a high quality PCB design - pretty good for a $14 power supply. Output shows very little noise and ripple with more than enough current (max 2.2 amps) to feed the turntable.
The output voltage is adjustable via a small pot in a very wide range of 20 - 31V. It also has a soft start and a nice status LED. This can be extended out to the chassis for an external power indicator. The SMD series resistor on the bottom of the PCB can be changed to suit the current needed to run other LEDs.
With this PS you can turn the output voltage all the way down to 20V for a direct application, bypassing the stock reg or instead of a 3 pin based circuit. You can also turn it up to supply enough voltage to accommodate the drop of the stock reg or your 3 pin based reg of choice.
The SMPS regulation is very tight and I'd feel very comfortable using this straight into the supply rail of the SL1200's motor PCB. I would however fuse the main B+ rail into the TT if I chose to do this. Its just as a precaution against an eventual fault or failed component inside the TT to protect the main PCB from burning up any traces.
I configure the front panel to include a ground lift switch in case of noise issues due to grounding. Coming out of the PS I chose a typical 4 pin screw lock connector used in many low voltage applications. I left an extra pin available to shield the umbilical cable going into the turntable.
A KAB 3 pin reg board was used inside the TT instead of the stock reg. Honestly, the OE Technics setup is more than adequate for the job as long as the filter caps are all in good shape. Of you need to replace them, I'd recommend the Panasonic EB series caps. They're inexpensive for being rated at 105 deg C along with excellent ripple current capability.
The chassis I used was an enclosure made by Context Engineering, part number 4006. I had it in stock already, as this is an enclosure I use for many projects. I don't know if these are still being made, but I'm sure there still are other suitable enclosures being sold for this purpose.
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Maybe a consideration: An outdoor Meanwell supply. I have bought a 20V 90W OWA-90E-20, which has an IP-rated enclosure, a mains plug and a DC plug (Neutrik 4pin) already installed. Ripple 150mV is probably not worse than the built in PSU; and I measured the 20V output voltage at 19.99V. Price is about the same as your solution, but it's more or less ready-to-run.
Very nice!
Externalizing the PSU is such an improvement to the stock deck. I cannot recommend it enough, it makes a large improvement to the turntable, mainly by removing the source of 60Hz hum in the table itself. (The conventional EI transformer.) Although the stock transformer is soft-mounted and metal-shielded, removing it from the chassis is always beneficial.
This appears to be a wonderful solution, very well done.
Externalizing the PSU is such an improvement to the stock deck. I cannot recommend it enough, it makes a large improvement to the turntable, mainly by removing the source of 60Hz hum in the table itself. (The conventional EI transformer.) Although the stock transformer is soft-mounted and metal-shielded, removing it from the chassis is always beneficial.
This appears to be a wonderful solution, very well done.
@6L6 So far, I haven't found a better regulated commercially available SMPS than this one regardless of price. It solves many smaller problems which the stock supply doesn't address.
I haven't always been a big fan of SMPS used in audio applications, but the overall performance of the LRS 50-24 is quite remarkable for the money. Residual output noise was more than 90 dB down. Ripple @ 50% current draw measured well under 5 mV peak. For some extra insurance, a ferrite HF choke can be put onto the cable, but is completely unnecessary. Once the platter is in place, you won't see any visible junk on the DC rail.
The caps they used in these supplies are United Chemicon UKW series along with quality brands of semiconductors. That's actually unheard of at this price point.
A massive design feature is the adjustable DC output, ranging from about 20 - 30V. That means you can use it in front of or after the on board reg in the SL1200. I'd even venture to say it can be installed directly in place of the stock transformer inside the TT. It would be a tight fit, but would work with some trimming of the supply chassis and a little RF shielding for extra peace of mind. That's at least better than having mechanical hum. I just left the stock transformer in place mainly for more mass, but also convenience just in case.
I actually bought two of these supplies to torture test one - $14 isn't alot of money for peace of mind when using it on a 4 figure priced piece of gear. I tested the SMPS durability by direct shorting the output a few times and also by getting it good and hot to the point it became too hot to touch by fingers for longer than 10 - 15 seconds (roughly 140 degrees F). It survived all that with flying colors.
Operating in the un-vented enclosure, it didn't show any problems temperature wise. The supply didn't even get warm to the touch under load. Being in an all-aluminum case, it was able to shed any heat by conducting and radiating it. It still has an on board fuse, a thermal sensor and an AC line fuse along with a grounded mains connection, so its completely safe.
For $50 you won't find a better deal anywhere for this quality.
I haven't always been a big fan of SMPS used in audio applications, but the overall performance of the LRS 50-24 is quite remarkable for the money. Residual output noise was more than 90 dB down. Ripple @ 50% current draw measured well under 5 mV peak. For some extra insurance, a ferrite HF choke can be put onto the cable, but is completely unnecessary. Once the platter is in place, you won't see any visible junk on the DC rail.
The caps they used in these supplies are United Chemicon UKW series along with quality brands of semiconductors. That's actually unheard of at this price point.
A massive design feature is the adjustable DC output, ranging from about 20 - 30V. That means you can use it in front of or after the on board reg in the SL1200. I'd even venture to say it can be installed directly in place of the stock transformer inside the TT. It would be a tight fit, but would work with some trimming of the supply chassis and a little RF shielding for extra peace of mind. That's at least better than having mechanical hum. I just left the stock transformer in place mainly for more mass, but also convenience just in case.
I actually bought two of these supplies to torture test one - $14 isn't alot of money for peace of mind when using it on a 4 figure priced piece of gear. I tested the SMPS durability by direct shorting the output a few times and also by getting it good and hot to the point it became too hot to touch by fingers for longer than 10 - 15 seconds (roughly 140 degrees F). It survived all that with flying colors.
Operating in the un-vented enclosure, it didn't show any problems temperature wise. The supply didn't even get warm to the touch under load. Being in an all-aluminum case, it was able to shed any heat by conducting and radiating it. It still has an on board fuse, a thermal sensor and an AC line fuse along with a grounded mains connection, so its completely safe.
For $50 you won't find a better deal anywhere for this quality.