Superclock in SL-1210

[UV101]

I'm much more familiar with the effect of clocking digital circuits in CD players and I'm not sure if there would be any audible improvement adding better clocking to the techie.

No harm in trying.

I've been following progress on a discrete clock design that is based on a standard type xtal and runs 2 oscillators out of phase with each other which should give better PSU supply noise rejection (don't ask me how cos I really don't know!!!) . Its similar to the clocking that has evolved in the "EC Design TDA1541 NOS" thead on diy audio.

Hopefully I should be getting a couple of PCB's to try and I thought as the techie has an odd freq and there is only a std type xtal available it might be worth trying.

[MartinT]

That's pretty much it, Andy. As you know, regulating the power supplies with Paul's on-board regs has gone some way to helping that along. I guess (and it's only a supposition until I can hear the results) a highly stable clock would help to get even cleaner drive current into the motor windings.

[nat8808]

How does the drive current fuzzyness translate into sound?

Wouldn't their be a fair old smoothing of speed due to the innertia of the deck compared to fast adjustments of drive current?

Must also depend on how the servo type thing works - are different currents used to vary the turning force or is it down to timing of the currents to the coils?

If the servo opperates via changing the amount of current to each coil (i.e. turning force at each point) then the timing of that delivery would stay constant and only determine absolute speed accuracy and the speed slider circuit quality might have a much much higher order of magnitude of effect (or removing it might be better). It might not to be to do with anything in the servo loop.

That 4MHz seems familiar as if it is the same value used in the Pink Triangle Too PSU. The Too PSU uses logic to recreate an AC drive to the same Premotec motor as used in the Linn.

[Reid Malenfant]

1. How does the drive current fuzzyness translate into sound?

2. Wouldn't their be a fair old smoothing of speed due to the innertia of the deck compared to fast adjustments of drive current?

3. Must also depend on how the servo type thing works - are different currents used to vary the turning force or is it down to timing of the currents to the coils?

4. If the servo opperates via changing the amount of current to each coil (i.e. turning force at each point) then the timing of that delivery would stay constant and only determine absolute speed accuracy and the speed slider circuit quality might have a much much higher order of magnitude of effect (or removing it might be better). It might not to be to do with anything in the servo loop.

That 4MHz seems familiar as if it is the same value used in the Pink Triangle Too PSU. The Too PSU uses logic to recreate an AC drive to the same Premotec motor as used in the Linn.

Apologies for being lazy, adding numbers makes things a tad easier.

1. We don't know, but it'll be fun finding out.

2. Once the platter is spinning there shouldn't be much of any difference in the current fed to the stator coils.

3. The Technics has a PWM feed to the coils (Pulse Width Modulation) at a fixed frequency by the crystal. The time that the coils are powered is varied & thus the current is varied. Most current will be used at startup as this is when the most torque is needed. The PWM circuit simply turns each coil on for longer & as a consequence more current is drawn & more torque is generated. As it gets up to speed the pulse width fed to each coil will reduce until some kind of near equilibrium will be reached.

4. You are assuming the timing stays constant, but I'm assuming that it may not well be so, this is why a more accurate clock & better timing might improve things on a fully fettled deck

But what do I know

[MartinT]

Jitter in the motor drive could translate as rotational jitter in the platter spin. I'm not saying it will be audible, but it could be. After all, no-one thought that jitter in the clocking circuit of a CD player would be audible - how wrong they were.

[sq225917]

I'm surprised that they use a XO to create three lagged motor drive phases, that's a very odd way of doing things when two capacitors would give exactly the same effect. Are we sure it's implemented that way?

Time would likely be far better spent on a better compensation mechanism to remove their tendency to hunt and overshoot.

[nat8808]

Jitter in the motor drive could translate as rotational jitter in the platter spin. I'm not saying it will be audible, but it could be. After all, no-one thought that jitter in the clocking circuit of a CD player would be audible - how wrong they were.

There's jitter and jitter and jitter.. The same term gets used to relate to very different things.

I'm not entirely convinced that jitter in the clock crystal per se is a cause of "jitter" in a CDP although the whole clock circuit and how it interacts with the chip (Dac or whatever) may have an effect. There are many accomplished digital designers out there who do make final judgement of their work on sound who would dispute the effect of a superclock being to improve the sound of a player with an already well designed clock (not just a white paper circuit copy). It may subtly change the sound but not necessarily improve it.

With a turntable, the sound is coming from the cartridge and the arm is probably the strongest influence on that cart. The TT itself is a combo of drive, plinth resonances, bearing quality and platter interaction with the vinyl with perhaps the drive being the lesser of those. Then on a well designed drive system is the eccentricity of a record causing more pitch instability than the drive system? The 1210 does have a well designed drive system even if there are still faults and compromises that can be sorted out with upgrades. Probably a drive system has more of an effect on a belt driven tt.

Then there's the amount of smoothing of servo mechanism effects by simple physics . Many bad servos out there are quite crude yet, whilst they might lack drive and pace in the sound on a cheap deck, we don't hear the much finer detail of the fast working adjustments that the servo is making - it's masked by the momentum of the platter.

So you cannot compare the two (CDP players and turntables), even if the same word "jitter" is used.

IMO changing one component on the drive circuit without changing the whole design for an even better one might just be a too miniscule a change to warrent both the cost and effort..

Still, I would never tell someone not to give it a go. So give it a go and see what happens.

[ar-t]

If you have a discrete design for use with the original crystal in mind, count me in.

With the crystal you have, the design won't matter. All will perform the same.

When you get one that costs $50-100, then you can get picky on the design.

[ar-t]

Jitter in the motor drive could translate as rotational jitter in the platter spin. I'm not saying it will be audible, but it could be. After all, no-one thought that jitter in the clocking circuit of a CD player would be audible - how wrong they were.

Don't know if any made it across the pond, but in the late 80s to early 90s, there was a product called the IsoDrive, that was a plastic doo-hickey that went on top of the CD, in Philips drives. It made a significant difference, and the difference was identical to the one lower clock jitter made. The guy who made it didn't know why it affected the sound the way it did, just that increasing rotational stability had to be good.

[UV101]

With the crystal you have, the design won't matter. All will perform the same.

When you get one that costs $50-100, then you can get picky on the design.

Are you saying that the limiting factor will be the xtal?

With the various clocks I've had and built for CDP's I've definitely found that the power supply makes a difference. I realise that better oscillators with real interesting parameters quoted like phase noise will ultimately out perform something like the eBay oscillators with nonsense performance figures quoted. I would say that the quality and suitability of the supply rail will allow an oscillator to perform optimally.

What I'm proposing here really is a suck it and see approach. The simple circuit would be very cheap to implement and if it doesn't work out to be any improvement, I'll use the PCB's in CD upgrades.....simples