Hi Mike,
neat drawing, what are you using? How do you save/compress/send?
All your routes make sense, but I would like one alteration and one addition.
1. add in the decoupling/bypassing at the amplifier and show the common between them. Then connect this dirty common back to the central ground, this is the power ground on the amplifier.
2. the centre tap is shown as two separate wires connected to the central star. Instead consider connecting the two internal centre tap wires together and then a single wire to the central star. Most centre tap transformers are built this way and all dual secondaries CAN be wired this way.
Let's see if we can make this work.
If it's better to do it with dual secondaries and wire them separately as you have shown, will come out from the discussion and then that can be a conclusion. Do not pre-empt the discussion.
I would like to add a comment.
Since this PSU discussion has begun to revolve around grounding.
Can we add to the discussion the topic of where/when/why the input RCA barrel connection goes to?
neat drawing, what are you using? How do you save/compress/send?
All your routes make sense, but I would like one alteration and one addition.
1. add in the decoupling/bypassing at the amplifier and show the common between them. Then connect this dirty common back to the central ground, this is the power ground on the amplifier.
2. the centre tap is shown as two separate wires connected to the central star. Instead consider connecting the two internal centre tap wires together and then a single wire to the central star. Most centre tap transformers are built this way and all dual secondaries CAN be wired this way.
Let's see if we can make this work.
If it's better to do it with dual secondaries and wire them separately as you have shown, will come out from the discussion and then that can be a conclusion. Do not pre-empt the discussion.
I would like to add a comment.
Since this PSU discussion has begun to revolve around grounding.
Can we add to the discussion the topic of where/when/why the input RCA barrel connection goes to?
Wavebourn said:
I lost them going from a large bitmap to a JPEG... I always have problems with the file size and have been bit by this before. Is there a better approach to posting images to the site? My files always seem to exceed the, what is it, 125K allowed size?
That is an important part.
Regards, Mike.
Wavebourn said:
ilimzn said:
This all depends on how you look at it. By coming off of the cap you have the effect of the wiring to the cap coming into play during charging pulses, affecting the current supplied to the output stage.
I've found the the direct power from the rectifier being faster when it's conducting and supplying the current, not the cap. Also consider the speed differences between charging/discharging of the cap, this muddies the timing of the current draw across this connection. When the charge on the cap does deplete, it is slower to build back up, making this connection more of an issue. Look at the the charging curves of a 10K electrolytic in the last 5% of it's charge.
Truthfully these are very subtle differences unless your supply involves a lot of real-estate and the wiring gets long.
My preference is to source and return the power from what I perceive is it's true source, but it's just an approach I've evolved into doing it over the years.
This is all just food for thought.
Regards, Mike.
AndrewT said:
Hi Andrew,
For amplifier output stages I don't use decoupling/bypassing caps. I haven't experienced the need in years. My layouts place the output from the raw supply at the output stage. The best implementation I've noted is putting .1mfds to the chassis directly at the outputs and use the chassis as a low-Z return back to the centertap. But technically they are part of the supply loop and should return to the filtercap ground.
Where the high frquencies they pass do not become super-imposed of any other returns that way.
For bypassing of regulators, preamps, etc. I consider them to be part of the circuit they are bypassing and connect them as part of the that circuit's power return, which in the case of bypassing a plus and minus supply dictates a separate return loop for each. No common connection at the circuitry.
AndrewT said:
I've done that for years but with my experimenting indicating that the two halves of the supply are independent loops as far as the current to the load is concerned (the reason for an amps existance is to preform this one task) I tried bringing that summing point out to the main ground reference. I perceive an improvement in the main zero reference being cleaner. Implementing this: the common ground from ther speaker returns to this point and splits as needed to complete it's (Kirchoffs's) loop. The concept here is to not let the two independent (+/_) currents interact in the common return wire you suggest. It's reflected in the signal and feedback reference.
AndrewT said:
I'll continue the discussion as prompted, although I have come to realize that my approach requires the reader to have access to 30 years of my experimentiing, which is not possible. There is so much missing in any attempt I make to discribe what I'm getting at. On top of that I'm describing things conceptually with the same limitations just noted. Add to this the need for me to be more open to the feedback discussion; not so absolute in my convictions.
AndrewT said:
As you know from the past, my approach here is just as different. I take the input shield directly back to the main ground either through the chassis or, as of the past year or so through a flat copper buss. This bypasses any noise on the shield and currents circulating between components back to the main ground to be absorbed, so to speak.
This is all just food for thought, not anything absolute.
Regards, Mike.
Wavebourn said:
The best sonic example of the difference this part of the layout can make was the Audio research D110. Compared to amps of it's time it sounded noticably slow in the bottom end and monitoring the averaged power draw from the mains you could watch the rise and fall of the caps replenishing themselves after large low frequency program material.
Compared to faster sounding amps which were obviously drawing the power quickly from the secondaries.
A few simple changes to the rectifier/filter wiring brought the speed back.
Life is simple when the rules are layed out and not questioned.
Mike
MikeBettinger said:
Hm. Sorry but I cannot reconcile this with the laws discovered by a certain Kirchoff.
You could try to set this up with realistic wire resistances in a simulator. Or, better still, set it up for real and measure with a scope. IT should be a simple matter to see which approach gives you more hash on the power lines.
ilimzn said:
Maybe that's part of the problem here. My implementation is such that I doubt the wiring is a problem.
I'll try to shrink an image or two to a postable size.
From a measurement standpoint are you interested in the simply the noise on the rectifier outputs and on the filters? I doubt I'll take the time or my system down to rewire the supply but I have my main amps and a chip amp currently layed out this way. A snapshot of the noise would be easy one night this week.
Regards, Mike.
I'm going to test this.
I should be able to setup to watch the supplies ability to source current to the load both ways, from the rectifiers and from the cap, which is after all my focus on this part of the layout.
The supply output through a .1 ohm resistor and read across, for both connections while the amp is driving a 8 ohm load.
Any suggestions for what's considered a normal good layout as far as the raw supply is concerned would be appreciated. Otherwise I'll just scan the posted images on the site to see whay's considered best.
I should also be able to watch the noise spectrum under different loads as well.
I have all the pieces and parts , it just takes time.
Regards, Mike
I should be able to setup to watch the supplies ability to source current to the load both ways, from the rectifiers and from the cap, which is after all my focus on this part of the layout.
The supply output through a .1 ohm resistor and read across, for both connections while the amp is driving a 8 ohm load.
Any suggestions for what's considered a normal good layout as far as the raw supply is concerned would be appreciated. Otherwise I'll just scan the posted images on the site to see whay's considered best.
I should also be able to watch the noise spectrum under different loads as well.
I have all the pieces and parts , it just takes time.
Regards, Mike
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