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Have you ever considered removing the voltage regulator to improve PSU noise levels?
Have you ever considered removing the voltage regulator to improve PSU noise levels?
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Old 15th September 2017, 03:53 AM   #21
Markw4 is offline Markw4
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Join Date: Jul 2016
Originally Posted by VenusFly View Post
I'm considering using a transformer with two windings and putting the 50hz ripple out of phase with itself so that it cancels itself out. Any takers?
It is possible to reduce ripple with poly-phase rectifiers, such as a 3-phase, 12-pulse system (which requires a special transformer with two sets of out of phase secondaries which is called a delta-wye system). Used to use them frequently for some types of cyclotron power supplies.

But generating 3-phase from single-phase, and all the rest of it, is probably going to be more trouble than its worth.

In case you're still interested, here is a link with some info: http://www.idc-online.com/technical_...r_circuits.pdf

Last edited by Markw4; 15th September 2017 at 03:57 AM.
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Old 15th September 2017, 04:12 AM   #22
sumotan is offline sumotan  Indonesia
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Thomas Mayer the tube guru if I not mistaken has been using
poly phase supply for a long time. He should be able to shed
some light on this topic. Normally 3 phase is slated for industrial
use. Like you said Mark its a pita to generate from single phase

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Old 15th September 2017, 06:30 PM   #23
Ken Newton is offline Ken Newton  United States
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Location: Eastern Pennsylvania
As far as I know, there isn't a simple way of obtaining a three-phase output from a single-phase input. Obtaining a multiple-phased output would require utilizing some phase-splitting active circuit. Single phase can, however, be easily obtained from a three-phase transformer, but that doesn't help where three-phase wiring isn't already provided.

Often, the most troublesome noise sources will not include post-rectifier ripple, but will include higher frequency normal-mode noise from many different potential sources, and wide-band common-mode noise, also from different potential sources. Noise is, to my thinking, one of the classic 'slippery slope' parameters in audio. With such parameters, improvement is objectively superior, but are not relevant beyond some point. Harmonic distortion is another such parameter. Continued improvement on such parameters often becomes an exercise in overkill.

I feel that it's usually more productive to spend time and energy exploring which parameters make a subjective difference to one's ears, within one's system arrangement, at one's particular location. Then, spend time, energy and money on improving those system parameters. Unfortunately, this requires an in-depth learning of of the technical issues involved. Else, one must pray, or be lucky.
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Old 15th September 2017, 06:41 PM   #24
sumotan is offline sumotan  Indonesia
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Join Date: Sep 2016
Hi Ken
Totally agree with your statement. As far as whats coming out of the wall,
I guess the best that we can do is to have dedicated lines & proper earthing
just for our audio system. This is what I've done when building my house.
The rest perhaps is to add somekind of noise filter. As for the system yep
lots of tweaking , analyzing & slow deep thoughts. Diy is like a black hole,
there just never ending tweaks cause we're always looking to more out of
what we're building

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Old 15th September 2017, 11:46 PM   #25
Raj1 is offline Raj1  United Kingdom
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Join Date: Jan 2003
Location: UK
Originally Posted by VenusFly View Post
I just powered up the dac and I must say that this analogmetric pcb is complete garbage. It wasn't difficult with a small pencil iron to burn and melt the solder tabs off and around the holes, just by the mere act of heating them.

First CD was shakespeares sisters and it sounded glorious. However it did have some crackling going on, which is probably because I haven't yet broken the trace which gives the secondary AD797s a feedback loop. I also haven't put the 2200pF capacitors in the PCB as detailed in the schematic so its running too hot.

The two final AD797 op amps were running really warm but the first two from the dac were running cool so I turned it off. I checked the outputs for short circuits but none were found and the voltages were fine, so its got to be the feedback loop which is overdriving the op amps.

The amazingly sounding vocals were the first thing that I noticed.

But think I'll plan on ditching this shitty low quality PCB and get myself something better.
Could be oscillation. Ad797 opamps are quite sensitive to improper decoupling.
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