SL-1200 DC Power Supply DIY

[Co&]

Trying to reduce the reg count !
I already have a dedicated reg supplying only the 6675.
Havent used a LM431 Ill have a look as soon as I get time. What are the advantages of constant current to a Zener over a low noise voltage stabilizer for the Cmos Chip IC302?

Shunt reg vs series regulator. The shunt reg (CCS + zener) kind of splits the line regulation from the load regulation. They are simpler to design and can have excellent properties. I just used it because I had one lying around. I can swap the 317 CCS into a 5V series reg and see it this matters. One point where I think it matters is that the OSC is at a frequency where a pedestrian 317 doesn't operate anymore, but the 431 will.

I'm having difficulty " hearing" the effects of additional tweaks. Any way we can measure the platter rotational accuracy and stability?
Would a 1K tone from a test record into a spectrum analyser help as LF and HF speed variations should show up as sidebands ?
I have ARTA and a pico scope and access to an unmodified Techie

Probably, but I don't think you will get much wiser because it is about the dynamics of the control loop. So if you have a record with pulses or square waves you might be able to learn more. Anyway my main system is stashed away because of the house painter. I'm listening though a headphone (AGK 701) and have no problems identifying changes in the sound as result of the tweaks (that is if the change matters to the sound). I have developed the habit to let everything settle down before judging whether the changes are for the better or worse. Changes that do not work for sound can be identified right away, but for others I take a few days. Lots of tweaks on the 1200 worked but not without adaptations that I made afterwards.

[dimkasta]

Good point. Chip series regs are terrible at high frequencies.

A capacitor multiplier might be another option there. Quite slower though and with higher output impedance. Perhaps a combination?

By the way, I have also designed a cap multiplier pcb to go with my snubbered filter/rectifier. I just have to test other stuff first before I finalize it and sent it for a test run and eventually test it with sl1200

[Co&]

Hah the gyrator! Components are gathering dust somewhere, seemed a good idea for a 'prereg' at the xformer location. This was thought to be a cap multiplier with a triple darlington config. In the day the choke input filter allready delivered the goods, I wonder what I think of it today....Sound on my headphones is allready at a higher level than I ever had.

[Ianmac]

Ive started looking at the possibility of gaining more info with measurements
Playing a test record on an unmodified deck is shown in the blue display[IMG][/IMG]
Playing the same record on a modified deck is shown in the red display[IMG][/IMG]
Both deck phono outputs were fed diredly into a Pico Scope
On the red display some of the reduction in amplitude is due to my having one of my own bearings in the modded deck, they typical improve LF noise by 7-8db but the peak amplitude difference here between blue and red is closer to 10db.
Perhaps the most important indicator of the effectiveness of the PSU mods is the width of the pulse at 1Khz. Interpreting the pulse shape is a bit of a learning curve so I have some reading to do.

Ill repeat this attempt at getting some indicators with my ARTA software as soon as I get time.
I think i have an old techie bearing I can put into my modded deck to ensure a true like for like comparison.

[Co&]

Interesting! The sideband on the right is intriguing. Is the measurement at 1 KHz or is it a normalized scale (linear?)? Looks like some 50Hz AC power modulation... (100 Hz peak on the far left still visible)

[dimkasta]

Hmmm

Try attaching the ground wire to the - line if you did not already

[Ianmac]

Gnd wire wire was connected to equipment Gnd.
There is no mains cable running into my modded Technics the other deck was absolutely standard Technics. Both used the same Pick Up.
Laptop was Battery/ SMPS and Picoscope is USB from Laptop
Test record was High Fi Sound stereo Test Record HFS69, Side 2 Test 1

Sideband to the right of the 1K ref is 1.050Khz. Small + 6db SB to the far left is 50hz.
The 1.050K is quite dominant. I must try and establish where this is coming from.

I have a new Cardas frequency sweep and 1khz tone test record here now. I will continue and introduce ARTA software running on a barebones PC/soundcard with both Linear and SMPS supplies available.
Its interesting and I might learn a little more about the effects of the PSU mods.
There is obviously a fair bit more work to do.

[dimkasta]

If nothing weird comes up from work, I will try to get an FFT of my TT using the HIFI News record.

[Ianmac]

Sideband at 1.050Khz is ex the Hi Fi News record.
Cardas 1Khz is OK.

[dimkasta]

Which track of the Hifi news record are you using?

If I remember correctly there is no clean 1KHz tone. Only some 300Hz torture tracks to test the tracking and bias settings.