In SW england, we have the worst of both worlds. Especially in Bristol as it never snows! It just rains. Hohum.
A preregulator will help split the voltage drop, so to speak, but you're still wasting heat by such a large drop, just between two devices. I guess its better to use a more suitable voltage tap from the transformer if possible.
I've no idea if the larger voltage drop makes life harder for the regulator, and thus upset its performance. I suspect its probably better to make life easier for it.
Of course, preregulation does have other advantages, so if you can do it, you should try it
Why not add a separate tx Simon? I did this and it brought another jump forward in sound quality, I assume from the effect of isolating the SAA "noise" even further. And I'd also make sure you use at least a 220uF cap at the chips supply input. Anything smaller and I've found the sound quality to be very held back.
Does your player have the SAA7210 also?
Cheers, Lee.
edit: it never snows here either
Does your player have the SAA7210 also?
Cheers, Lee.
edit: it never snows here either
I got mine back up and running this evening. I installed a 30VA toroid, schottky bridge, 10000uF smoother, LM317T pre-regulator (10V drop!), and then a 7805CT for the SAA7220.
I've only listened to some Kate Bush so far but wow, this sounds poor! I hope I didn't damage the chip by overheating the Super Reg.
I think I can see how the reg died - the output device (D-Pak SMT thing) has actually de-soldered itself from the little PCB!!
To cool the 7805 better I've made two improvements - the heatsink is now actually bolted to the reg, and interfaced with thermal goo. Secondly, instead of the existing 12V supply it's being fed from 9.6V, which comes from a new LM317 I put together. The 317 is fed by 20V or so, and it has to be on a pretty large heatsink!!
Each 'sink hurts to touch for more than a few seconds or so.
Simon
I've only listened to some Kate Bush so far but wow, this sounds poor! I hope I didn't damage the chip by overheating the Super Reg.
I think I can see how the reg died - the output device (D-Pak SMT thing) has actually de-soldered itself from the little PCB!!
To cool the 7805 better I've made two improvements - the heatsink is now actually bolted to the reg, and interfaced with thermal goo. Secondly, instead of the existing 12V supply it's being fed from 9.6V, which comes from a new LM317 I put together. The 317 is fed by 20V or so, and it has to be on a pretty large heatsink!!
Each 'sink hurts to touch for more than a few seconds or so.
Simon
Here's another angle. You can see I'm using tantalum caps on the LM317. You can also sort of see where I had to slice off a piece of plastic to flush-mount the transformer to the chassis. I also sliced the palm of my hand with my sharp craft knife 
This really does sound flat and bland compared to how it was with the super reg. The treble has gone shy and the image seems to have caved in. The ultimate test will be to hear it with a good reg back in place running off the new PSU. For now I'll just use the 7805 and give it a good cooking, see what blows up etc..
Also, crucially, it can come up to full, stable temperature. And, although this is madness-talk, it will need to "settle" for some hours before I can expect the best sound.
Simon
This really does sound flat and bland compared to how it was with the super reg. The treble has gone shy and the image seems to have caved in. The ultimate test will be to hear it with a good reg back in place running off the new PSU. For now I'll just use the 7805 and give it a good cooking, see what blows up etc..
Also, crucially, it can come up to full, stable temperature. And, although this is madness-talk, it will need to "settle" for some hours before I can expect the best sound.
Simon
Attachments
Luke said:
The red one is something to do with the processor. The one off to the side that I chopped in half is the display power supply mainly.
tubee said:
I might try this, but I'll need to buy parts, so it won't happen any time soon.
I was too quick to judge the sound last night, it certainly needed time to warm up, bed in, settle down, black magic / voodoo to occur etc.... it's excellent today, probably as good as before. There is still some grain we could lose but no doubt that'll come with additional power supplies and more, better regulators.
Simon
'black magic', 'voodoo', 'madness-talk' - LOL
Odd how we perceive things isn't it? I read your first point, and was convinced I'll see an improvement with better regs, to discover it may not be so drastically different after all (although, it will obviously be an improvement to use better regs).
I suppose, for you, the acid test must be Norah Jones.
Odd how we perceive things isn't it? I read your first point, and was convinced I'll see an improvement with better regs, to discover it may not be so drastically different after all (although, it will obviously be an improvement to use better regs).
I suppose, for you, the acid test must be Norah Jones.
It's an extra analog out, which is extra filtered. Don't you guys have a manual or the schematics....?
Just rebuild the powersupply on a veroboard and remove this pcb.
Another picture to show how, i put the heatsink outside the case. Less warmth inside.
An earlier incarnation of my player, experimenting with nos dac with two 1541's.
Just rebuild the powersupply on a veroboard and remove this pcb.
Another picture to show how, i put the heatsink outside the case. Less warmth inside.
An earlier incarnation of my player, experimenting with nos dac with two 1541's.
