Separating Power Supply

Ken · 1909

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Offline Ken

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on: March 20, 2023, 03:00:19 PM
Other than perhaps gaining some additional real estate, is there any practical benefit to be obtained from placing the power supply for the Afterglows I am reconstructing on a separate chassis plate on the same wooden base, like in the attached drawing?


"It is not that I am mad; it is just that my head is different from yours" - Diogenes of Sinope


Offline Paul Birkeland

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Reply #1 on: March 20, 2023, 03:01:23 PM
There isn't any benefit I can think of to doing this.  There are enormous disadvantages to using separated enclosures with an umbilical, but what you're proposing is less risky. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Ken

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Reply #2 on: March 20, 2023, 03:28:42 PM
Thanks Paul.  If there's no benefit, then there's really no reason to do it.

I did read about the risks/problems with high voltage through an umbilical and won't be doing that :)

"It is not that I am mad; it is just that my head is different from yours" - Diogenes of Sinope


Offline Karl5150

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Reply #3 on: March 21, 2023, 06:43:48 AM
Paul, if the cable and connectors were spect correctly, what would be the disadvantages to a separate PS? I know some 'high-end' commercial manufacturers (Woo Audio to name one) use them. I looked around on the inter-web and had little luck finding definitive info. Am I moving this more towards a Technical Topic? As always, thanks for your insight.
Karl

Karl
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Offline Doc B.

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Reply #4 on: March 21, 2023, 07:20:52 AM
The notion behind a separate power supply is to put distance between the power transformer and the rest of the circuit. That assumes that the power transformer has a magnetic field that needs to be kept away from the circuit. As PB implies, separate boxes and umbilicals carrying high voltage are a recipe for a fatigue induced disaster. Our newer transformers are designed to work fine close to the circuit and we take pains to mount them in a position that gives the lowest possible noise. That said, the Afterglow could benefit from playing around with the relative position of the power transformer, choke and outout transformer as our skills were not as well developed when we did that circuit almost 30 years ago. 

Looks to me that this separate power supply configuration creates a lack of continuity in the chassis ground plane. If the inductors are mounted such that they electrically isolated from the chassis to avoid the generation of eddy currents in the chassis and safety ground drain wires run from the inductors to a common safety ground (as we do) and, assuming that ground point for these drain wires to be on the power supply part of the chassis plane, you now have a second (amp) plane that is floating with respect to your power supply ground plane and inductors - a potential source of noise. The solution to that would be to connect the power supply chassis and the amp chassis planes together. Easiest way to do that is make one chassis rather than two.

My thought is to make one big chassis plate and put more energy into experimenting with the relative positions of all the inductors on a breadboarded circuit, keeping in mind the notion that rotating each inductors core 90 degrees relative to the other inductors and keeping those orientations centered on each inductor's axis usually minimizes magnetic coupling. We have found that this is an area where moving the iron and looking at the noise floor on a scope often shows the most optimal position and that sometimes the best spot doesn't perfectly match the theory.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline Ken

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Reply #5 on: March 21, 2023, 08:09:18 AM
Thanks for the very clear explanation Doc.

"It is not that I am mad; it is just that my head is different from yours" - Diogenes of Sinope


Offline Karl5150

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Reply #6 on: March 22, 2023, 02:08:59 AM
So possible noise and failure of the umbilical or connections. Neither sounds appealing. I work with both Magnetic Particle and Eddy Current inspections so I get the basics of current & magnetic field interactions. As Ken said thanks for the information, and for having done the homework on the kits.
Karl

Karl
Downstairs: Planar3>PH-16>Stereomour II>OB Betsy+
Upstairs: RP1>Eros/CD5004>Seductor (2x Monoblocks)>FH3
Office: Modi Uber 2/Sirius>SEX2.1.1>µFonken FF85WK + DC160 subs
BR: FiiO M6>SEX3.0.1>ScanSpeak 10F + TangBand W6 (Mono)/DT770Pro
Garage: X12 streamer>Quicksand>Minimus 77


Offline Paul Birkeland

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Reply #7 on: March 22, 2023, 05:37:26 AM
When I get a random piece of tube gear in for a repair with an umbilical, the first thing I always do is to check that the umbilical is working properly.  This means using a meter to check for continuity on every single pin, then measuring the DC voltage at each end of the umbilical while the component is plugged in and running to ensure that there aren't voltage drop issues. 

I have had one component in for repair with an umbilical that didn't have an issue with its umbilical.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline RPMac

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Reply #8 on: March 29, 2023, 02:27:37 PM
Any layouts for Paraglow/Parabee rebuilds you can share with us?



Offline Paul Birkeland

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Reply #9 on: March 29, 2023, 03:05:46 PM
Here are a few.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Karl5150

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Reply #10 on: March 30, 2023, 04:31:25 AM
I like your solution for dealing with that gynormous cap in the first example.
Karl

Karl
Downstairs: Planar3>PH-16>Stereomour II>OB Betsy+
Upstairs: RP1>Eros/CD5004>Seductor (2x Monoblocks)>FH3
Office: Modi Uber 2/Sirius>SEX2.1.1>µFonken FF85WK + DC160 subs
BR: FiiO M6>SEX3.0.1>ScanSpeak 10F + TangBand W6 (Mono)/DT770Pro
Garage: X12 streamer>Quicksand>Minimus 77