Balancing Ground And Mystery Problems

[silverfox]

Please refer to attached Delta v. Star DC Circuit.
If diagram one represents the various, (not shown are the capacitance values in parallel or series) load values for a power supply: Could subtle AC impedance mismatches in the pre-amp and other stages result in distortion, Ghost, or phase issues resulting in hard to diagnose problems? I just can't seem to make this amp sound right, or, Hum at different  control settings? Basically the mismatch between circuit and power supply  result in a band pass filter that equals an unsatisfactory sound in the finished product arising from the power supply. Hence the importance of power supply design.
An interesting study would be a voltage doubling circuit. What would it pass?

silverfox.

[PRR]

You are on the wrong track.

Stick to basics (solid connections, ample filtering) and don't go off into mysticism.

(That vid is teaching a useful concept, and not the concept I thought, but it has no use here.)

[Colas LeGrippa]

Right on !!!!!


First, make sure the only ground in the preamp section is the imput jack ground  in case the jack is not isolated. I m talking about gnd from grid leaks, cathode rrsistors and caps, and B+ caps. In one word all the caps.
Second, add grid stoppers wherever you can.
Third, add abypass cap to the cathode of the power tubes if cathpde biased.


Start doing that. Very often in my first builds I did not respect these rules .






Colas

[silverfox]

I didn't mean to refer to the video. I posted that image as I divined it would be a simple redraw of an unbalanced power supply. But thanks for the reply. What got me thinking along those lines was how in Delta-Wye distribution circuits,, imbalances due to motor and other loads seems as though it would cause the electrician problems. I get your point though.
silverfox.
 

[vampwizzard]

the 3rd order harmonics are the main reason you'd use a delta connection.. youd also want lower voltage higher current situations. Also useful for larger systems where you connect a bank of single phase transformers together.. you can remove a faulty single phase transformer and replace it without interrupting power (at 57% capacity). Most of the help line questions I had to handle were about Inrush current fault and "where to ground the delta" it doesnt work that way. By leaving out the ground you let the 3rd order harmonics dampen within the other phases vs entering into the ground of the attached system.

Most of that isnt applicable to single phase systems though. We use the phase relations of certain push-pull PI's to make tone cuts and master volume circuits work.. also NFB.. but thats just single phase interference

[shooter]

distortion, Ghost, or phase issues resulting in hard to diagnose problems?

I've built 10 xSE amps, everyone has exhibited that you describe.  On a few I made an extensive "study" with scope.  What I found were persistent very low freq oscillations running around below the noise floor.  typical amplitude <5mV, typical freq <8hz.  I could "fix" the issues from a musician standpoint - mostly with various signal or Ecaps, But the real issue could still be found lurking along the DC pathways.

Here's a reply from iirc HBP, or PRR on impedance mismatch (I think), it still hurts my brain reading it 
also a PS sketch I pieced together from those calc's, unfortunately I didn't make any notes on the sketch, anyway, FWIW

quote;
1. Calculate bass roll-off "going forward" of the audio circuit.

First place to look would be the cathode circuit of the gain stage. Simplify the calculation to assume the cathode resistor is the total resistance to be considered (the actual effective resistance is somewhat lower).
Use 1/(2*π*R*C) to find the -3dB point ("C" is in farads, so you'll need to add decimal places).
F-3dB = 1/(2*π*R*C) = 1/(2*π*1500Ω*0.000025F) = ~4Hz

Do the same R-C calculation for the coupling cap. However, "R" is all resistance between each of the cap's leads. That's a 1MΩ to ground on one leg, and a 100kΩ to a.c. ground, so the 2 are "in series" as far as the cap is concerned. (100kΩ is an approximation; the output impedance of the 12AX7 is the real number to use, which includes the tube's apparent internal resistance in parallel with the 100kΩ, for a lower total. But this moves the roll-off up a little, so our approximation is safe.)
F-3dB = 1/(2*π*R*C) = 1/(2*π*1.1MΩ*0.000000022F) = ~7Hz

sketch;

[jjasilli]

I'm having a hard time grasping the nature of the problem for which a solution is sought.  Can someone state it with clarity?


I do agree that the PS affects tone.  Bigger early stage B+ filter caps tend to make for better, clearer bass response.  Some amps, like Bassmans, seem to sound better with an 8uF cap in the last B+ filter stage.


As shooter says, the PS can have low frequency oscillations below the audible range.  This can cause intermodulation distortion in the audio range; maybe even "bloom" or "warble"  -- a tremolo-like effect.


However, at least for a guitar amp (as opposed to hi-fi), I don't see that these things go so far as to ruin the tone of an amp. 

[PRR]

> how in Delta-Wye distribution circuits,, imbalances due to motor and other loads

Yeah, well the video-clip you show is something else. Any three resistors across three points can be figured two different ways. While the theorem is general, I only think of one audio situation where we care.

In a transistor LTP input, we may want 22K tail resistor to set current and and 200r between emitters to limit the gain. Folks sometimes question if Y or Δ is better (though rarely in so many letters). If you do the math right, they are exactly the same.

[sluckey]

♫♫♫ Delta Wye, what's that flower you have on? ♪♪♪

[Ritchie200]

I open the door with a Who song and now look at you... 
Jim

[shooter]

play nice
I can't recall the system, the Electrician gave us 480 3phase, on my side was 480 6phase.  If they picked the wrong one, my side started hopin n jumpin. All I ever cared about was slappin the mains n saying, "um, guys"
I don't think that'll help Mr fox though

[Ritchie200]

I was just commenting on Sluckey's excessive amounts of free time to turn a song now that he is retired.    


Jim

[sluckey]

♫♫♫To everything (turn, turn, turn)♪♪♪

[shooter]

Let the bodies hit the floor, let the bodies hit the floor