New!!!!! NVA CD players

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Lurcher300b
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Re: New!!!!! NVA CD players

Unread post by Lurcher300b »

karatestu wrote: Mon Jan 20, 2020 10:12 am True. My thoughts and those of others on pfm (who were far more electronics aware than me) were that the inductive nature of the output of the regulator needed a bit of resistance (provided by the extra wiring) to prevent oscillation with the low esr caps that are decoupling at the input of the opamps.
Maybe, but that would make me question the stability of the regulator. More likely I would have thought was the inductance of the wire having a effect. But if (say) 1cm was unstable, its hard to know if 10cm (for example) was only just stable, or fine, or still prone to problems, just not as obviously. I would have tried to check the theory by trying to see the problem on a scope or measuring distortion and then check the theory by adding a 1R resistor in the supply.

My point was you just have some hypothesis, but nothing certain. So all you have learnt is that you don't know for certain what happened.

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Re: New!!!!! NVA CD players

Unread post by karatestu »

:grin: You are of course correct Nick and your views are always welcome. I was relying on others who had done the same with the same cdp and regulator (which they knew inside out) and who had sillyscopes. This opamp based feedback regulator was well known to cause issues for the unwary especially if the remote sense was used. I don't use any of those regs anymore, all six of them are sat in a drawer collecting dust.

Maybe i should get a scope and learn how to use it properly. Too busy learning nothing though :grin: Anyway, as i have bypassed that anologue stage then i won't be going back to look closely at the issues.
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Lurcher300b
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Re: New!!!!! NVA CD players

Unread post by Lurcher300b »

karatestu wrote: Mon Jan 20, 2020 2:03 pm :grin: You are of course correct Nick and your views are always welcome. I was relying on others who had done the same with the same cdp and regulator (which they knew inside out) and who had sillyscopes. This opamp based feedback regulator was well known to cause issues for the unwary especially if the remote sense was used. I don't use any of those regs anymore, all six of them are sat in a drawer collecting dust.

Maybe i should get a scope and learn how to use it properly. Too busy learning nothing though :grin: Anyway, as i have bypassed that anologue stage then i won't be going back to look closely at the issues.
Fair enough. Power supplies are rarely simple and adding remote sensing will just make it more so. Op amps need a quiet supply not a exact one, and the bipass caps (preferably ceramic) should be what supplies the varying load requirements. Worth remembering that 0v is important or more so than the +ve or -ve rails and that can be hard to manage when adding an external regulator. Trying to make two feedback loops (the one in the regulator op amp and the one in the load op amp) control one thing is a recipe for disaster.

Analog design is a very deep pit of complexity, I figure I understand maybe 5% of what there is to know. And that's just based on what I know I don't know :-)

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Re: New!!!!! NVA CD players

Unread post by karatestu »

Thanks for your thoughts Nick. The decoupling caps were 0.1 uf wima film caps not ceramic. I tried other regs (LM3*7 based pre tracking regs with a cap multiplier in front) which sounded very good but at the time the ALWSR (Jung) was flavour of the month and i just went along with the flow :roll:

I also tried some capacitance multipliers (gyrators) both BJT and mosfet based that were very low noise and had output that varied with load that were very pleasant to listen to but sounded rather sat on or lacking in dynamics / life. I put that down to their relatively high output impedance.

You are definitely correct in saying that 0V is the most critical thing to get right. If you only understand about 5% of what there is to know then there is no hope for the rest of us :cry:
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Re: New!!!!! NVA CD players

Unread post by Lurcher300b »

This is a good paper on op amp decoupling, and it also shows why replacing op amps in a circuit can come with side effects.

https://www.analog.com/media/en/technic ... AN-202.pdf

Thius has some good words on cap choice.

https://www.analog.com/media/en/trainin ... MT-101.pdf

I know the audiophile in us wants to use film insted of ceramic, but it may not be the best choice:
Multilayer ceramic (MLCC) surface mount capacitors are increasingly popular for bypassing and filtering at 10 MHz or more, because their very low inductance design allows near optimum RF bypassing. In smaller values, ceramic chip caps have an operating frequency range to 1 GHz. For these and other capacitors for high frequency applications, a useful value can be ensured by selecting a capacitor which has a self-resonant frequency above the highest frequency of interest.

In general, film type capacitors are not useful in power supply decoupling applications because they are generally wound, which increases their inductance. They are more often used in audio applications where a very low capacitance vs. voltage coefficient is required.

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Re: New!!!!! NVA CD players

Unread post by karatestu »

Thanks for setting my homework for the week Nick :grin:

I did not some low value resistors (1 - 4 ohms) between the output of some of the internal lm317 regs and the chips they power especially in the digital side. A bit of damping i supected to calm things down and stop any inclination to rave off.
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Re: New!!!!! NVA CD players

Unread post by savvypaul »

Fretless wrote: Fri Jan 17, 2020 7:42 am Richard ended up looking at the Pro-ject CD Box S which is a slot-loader with a high quality transport, remote and external PSU.

But he was hesitant due to the higher price.

I tried out one of these and ended up with the Cambridge CXC which totally fulfills my CD needs. :grin:
We just picked up an 'open box' CXC for use at shows...
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Re: New!!!!! NVA CD players

Unread post by Fretless »

:grin: :guiness; :dance: :music-listening:

Upstairs:
Vinyl
Pro-Ject 1.2 + Grado Sig Jr + Cambridge Alva Duo
DigiVolumio PC + Kiss DP-500 + Sabaj A20d
NVA: P50sa - Cube2 - SSP - LS6+ Sabaj A10a (x2)
Downstairs:
Vinyl
Logic DM101 + Syrinx LE1 + Grado Sig MCX
DigiDenafrips Ares II + Volumio PC + Cambridge CXC
NVA: P50 - BMU+ Aiyima A07 MAX (x2) + Arcam One
HP: HifiBerry Digi+ PRO + Sabaj A10d
Office:
Allo DigiOne SIG + SMSL M300se + Douk G4 (x2)
Mission 760 + Monolith THX AAA 887
Headphones: German Maestro, Monolith & AQ

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Re: New!!!!! NVA CD players

Unread post by savvypaul »

Fretless wrote: Mon Jan 27, 2020 3:27 pm :grin: :guiness; :dance: :music-listening:
Tomasz is even happier - he gets to 'look after it' in the workshop system.
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Re: New!!!!! NVA CD players

Unread post by Ithilstone »

Its mine...
my preeeeeeciousssssss...
mine!
Nothing to see here...
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