SL-1200 DC Power Supply DIY

[dimkasta]

I'm honestly a bit disappointed to hear that the tracking prereg didn't make very much difference over the referenced 317, but not entirely surprised either... The short-term wall variance is being well handled by the 'big, dumb' approach of the huge caps and filter resistance in the PSU box.

Well I guess diminishing returns had to kick in at some point...

[337alant]

When I built that power supply for the DAC I tried a standard LM317, a TPR1, a TPR2 and a Super Teddy Reg
The STR and the TPR2 was clearly better to me and I ended up using the Avondale TPR2 as it was a bit cleaner.
I would expect a DAC to be far more sensitive to tweeks in the power supply than a turntable ?

Alan

[dimkasta]

Difficult to quantify...

[dimkasta]

By the way, what also made a very distinct improvement was removing the old reg parts.

R1 – 5K6
R2 – 6K8
R3 – 2K7
R4 – 470R
R5 – 470R

Q2 – 2SD637
Q3 – 2SD637

C2 – 33uf 25V

D3 – 5v1 Zener diode

These parts are in parallel to the reg/load and even if they do not perform any function any more, they still mess with impedances, produce noise and who knows what else.

Removing them gave a far softer sound... but not in a bad way... more like less harsh.

[6L6]

You pulled all those items? Cool.

I was going to at least remove the silicon the next time I opened everything up. It's good to hear that there's a benefit.

[dimkasta]

OK next step is complete.

I removed R304 and D301 and in the zener's place I installed an extra LM317 psu with two red leds as a reference for 4,95V output.

I don' t know where to begin describing the size of the improvement...

Instrument positioning (width and depth) and separation is boosted tremendously. At the same time, all instruments have their own quite distinct harmonics, cracklings, textures and whatever else you can imagine. You can just select which one you want to follow, hearing every little movement of the player, and you can do it effortlessly as it intertwines with the rest of them.

At the same time, timing has also been improved very much. Bass lines are very clear and they have a very distinct kick timing. You can very specifically hear if and when the players were synchronized or if one missed it for a split second joining in just a bit after the bass drum.

Voices also have very deep and detailed textures. I never had noticed that Knopfler had such a textured and awesomely rough voice.

Overall just a WOW moment for the SL1200
So happy I am part of this

[dimkasta]

The next step is ready too. I have a 317 with 150R biasing 4 green leds as the reference, giving a steady 9.37V for IC301.

I will not install it right away though. I will leave it a few days like that to settle first. I need some time to get used to the sound too...

[dimkasta]

I also installed the 9.4V reg for IC301

It did not make any significant improvement. Rather borderline psychological. But I have to say that this spot is supposed to need super stable regulation, so I might have to add the tracking prereg too.

[dimkasta]

I like the reg so much that I decided to make some pcbs too.

Here are the prototype images... I hope to have them in less than a month...

The reg
Please note the sense ground terminal, which will allow the connection of the reference directly to the load, allowing the reg to compensate for the effects of the output cables too (parasitic resistance, capacitance etc)
reg.jpg

the tracking prereg, which is designed to sit next to the reg if required.
tpr.jpg

If there are no issues, the final pcbs will be about half this size, to allow mounting them in really confined spaces, like... I don' t know... below a platter?

[6L6]

Dimmy - Beautiful!!!

When you get another run of those made, make an extra set for me, I'll gladly pay your cost and shipping. I would love to have some compact PCB like that.