I'd like to hear the science behind that. Are you saying that dropping the voltage is causing the change in sound or are you saying that the introduction of equipment is having an affect on the sound?
Stabilising Wall Voltage (Without Breaking the Bank)
- Thread starter Crang
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I'd like to hear the science behind that. Are you saying that dropping the voltage is causing the change in sound or are you saying that the introduction of equipment is having an affect on the sound?
whoaru99
Epic Member
The science is that anything increasing the impedance of the AC mains supply over what it was previously introduces some amount of added current limiting.
Of course, net result depends on how much the impedance increased and how much demand is placed on the circuit at any given time. If there is only a small current draw then even a large introduced impedance may have little or no net effect. However, if a large amp tries to draw many amps to cover a peak demand, then the net effect of the same introduced impedance will have greater relative significance.
whoaru99
Epic Member
The end to your question can't really be answered with a singular factor of just the amp size. The higher the additional impedance, the bigger the amp, and the harder the amp is pushed, the bigger is the effect. And that considers really just the measurable side. Throw in that some may be able to hear the effect at an earlier stange than others, well, it's one of those points that goes without an exacting answer. Rather, answered generally by the concept of the science.
In effect, every combination is essentially a unique use case (unless exactly the same conditions exist).
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As long as a big enough bucker or variac is used so that the voltage doesn't drop under load, it wouldn't make a difference. Overkill is good in this case. More importantly, so long as the voltage on the main caps doesn't dip, it won't matter.
whoaru99
Epic Member
I understand, but the point is there is no exact answer how that all comes together without examining the details of every use case.
After examining enough cases one may be able to make generalizations if considering similar enough gear and similar enough type of use is involved.
petehall347
the brandy coffee man
look up "line constant transformer"
one example https://www.alliedelec.com/m/d/6fd38ef7c6e277334cbde5520ee3a11f.pdf
one example https://www.alliedelec.com/m/d/6fd38ef7c6e277334cbde5520ee3a11f.pdf
chuckworkb
Super Member
Make a bucking transformer maybe. http://www.geofex.com/article_folders/vintvolt/vintvolt.htm
Morzh
Active Member
Tim
As Whoaru said, it is the extra impedance that comes with extra equipment. In the equivalent schematic it will just look as an extra resistor at the output. Same as if you decided to connect your speaker with much thinner wires.
Where the line in the sand is, only measurements plus listening could tell. Surely not every transformer would matter: your Mains after all comes from that transformer on the lighting pole near your house. Well, most of the time. It's not that big either.
Transformer has several effects. One is, as said before, the extra loss impedance due to sheer copper resistance in its windings. Then of course, the larger the current, the more it saturates and that also affects the output. Then there are eddy currents in the core, resulting in additional heat losses that also look like added impedance. And then there is stray inductance. That resists current changes.
As a result, as your amp tries to draw more current, larger power is lost. And if it is fast changing output, it changes slower than it would like to.
There are other effects. But the bigger the transformer, the less pronounced they will be.
As Whoaru said, it is the extra impedance that comes with extra equipment. In the equivalent schematic it will just look as an extra resistor at the output. Same as if you decided to connect your speaker with much thinner wires.
Where the line in the sand is, only measurements plus listening could tell. Surely not every transformer would matter: your Mains after all comes from that transformer on the lighting pole near your house. Well, most of the time. It's not that big either.
Transformer has several effects. One is, as said before, the extra loss impedance due to sheer copper resistance in its windings. Then of course, the larger the current, the more it saturates and that also affects the output. Then there are eddy currents in the core, resulting in additional heat losses that also look like added impedance. And then there is stray inductance. That resists current changes.
As a result, as your amp tries to draw more current, larger power is lost. And if it is fast changing output, it changes slower than it would like to.
There are other effects. But the bigger the transformer, the less pronounced they will be.
primosounds
Powered with pure tube sounds.
In my experiment i was using MFA M75 amps which are PP 6550, but i was using KT90 tubes . They were connected to Magnepan speakers. This set up is quite stunning to hear.
In the end the decision to apply band aids to the problem is certainly not an ideal situation. Knowing the wall voltage of your location and designing the amp to work with that ACV will yield the best performing amp. It would be less things to buy or set up, and less thing to go wrong and troubleshoot.
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Whoareyou99,
I'm speaking directly to current draw of the amp which is directly proportional to voltage drop across the external equipment. If the complaint is about the external equipment causing trouble then it must be dropping voltage.
Next, is the poster saying that the dynamics are hurt. Is that because the current draw is also dynamic? The reason I'm asking is that the power supply caps are supposed to level out the current draw and to provide a steady source of power to the internals of the amp. Is the external equipment seriously restricting the current draw to the point that the power supply just can't get enough? Maybe, but that affect will be much less with smaller amps than with bigger amps.
Morzh
Active Member
No, this is not the case at all. The power supply caps stabilize the power DC voltage. Not the current draw. The latter depends on the output signal. The external equipment mostly restrict 1) the current draw due to the active impedance (DC resistance) and 2) the speed of change of the current draw (dI/dt) due to the reactance (inductance) that occurs during fas transients in the output signal (sharp attack loud sounds).
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whoaru99
Epic Member
@Tim D
Most of your questions from post #56 have been already answered.
But, yes, amp power capability is certainly one of the factors.
If one's amp is 2wpc I'd opine that current limiting on the mains side is likely of little practical concern even if the mains impedance is raised by aforementioned devices.
On the other hand, even without any additional devices, impedance of the ac mains (at least the branch circuit) is a serious consideration with audio gear capable of ~9kW output as I have in my garage.
Most of your questions from post #56 have been already answered.
But, yes, amp power capability is certainly one of the factors.
If one's amp is 2wpc I'd opine that current limiting on the mains side is likely of little practical concern even if the mains impedance is raised by aforementioned devices.
On the other hand, even without any additional devices, impedance of the ac mains (at least the branch circuit) is a serious consideration with audio gear capable of ~9kW output as I have in my garage.
Morzh
Active Member
9kW.......what are you doing with it, changing the local weather by creating some wind in the whole block? 
Ever heard from the power company complaining about having to install third pole transformer in two years? 
It could have side benefits of being listened to during the winter months without having to pay for the heating. 
I bet it takes at least 220 VAC to power.
Ever heard from the power company complaining about having to install third pole transformer in two years? It could have side benefits of being listened to during the winter months without having to pay for the heating. I bet it takes at least 220 VAC to power.
I've measured the current draw on a few amps while playing music. They absolutely do vary what they draw according to what's played. However, the size of the main caps can help with this. When I was a kid, I used to take the big capacitors out of junk industrial computers, and put them in amplifiers. Like 20,000 mfd in a 50w amp. The difference in the bass was stunning, and the transformer actually ran cooler!
whoaru99
Epic Member
That is an interesting observation to me, considering the energy to produce every milliwatt of output must be supplied by the transformer regardless of capacitance.
It wasn't expected, that's why I was watching it in the first place. My theory is that the current spikes were heating it up. The main transistors got hotter though, which was expected. I mounted a large but quiet computer fan in the back of the entertainment center, and plugged it into the switched out.
Sorry for the slow response.
I'll give you that one. You are correct in that the PS caps stabilize the DC voltage and they do nothing to stabilize the DC current. The amp is going to draw what DC current it needs in an instantaneous manner. My meaning however was that it stabilizes the incoming AC current which would also stabilize any voltage drop preceding the PS. It was my mistake for not being clear.
whoaru99
Epic Member
The AC current exhibits related peaks too, since the caps have to be recharged in the relatively short period of time of diode conduction at the top & bottom of each cycle.
This is from a basic FWB simulation I ran in LtSpice.
Gold trace is the DC output after the capacitor
Blue trace is the load current
Green is the AC voltage to the FWB
Red is the AC current to the FWB
Of course, the specific values affect voltages, magnitudes, etc., etc., but the net effect is the same re. AC side definitely exhibits peak current demand that is different than the average AC demand.
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Morzh
Active Member
Whoaru,
Yes exactly.
Basically, any amp is a power conversion device. So, if the power demand grows at the output, it is reflected to the input in some form or another.
The caps at the output are there to stabilize the voltage when the current demand changes, but then they have to be recharged and this makes them draw more current at the input.
Roughly speaking, since both AC Mains and the output of the rectifier are voltage sources, it is the currents both at the input and the output that get changed, not stabilized.
Capacitor charging is not smooth, it occurs only when the rectifier bridge output V exceeds that of the capacitor and then it charges really fast with really large current which is pretty much dictated by ESR/ESL of the capacitor, and in a much smaller part by the output impedance of the power transformer (we could safely disregard the Mains impedanc unless dealing with multi-kilowatt amp). Hence the red current waveshape with sharp rising and the flattened Green input voltage waveshape (capacitor resists voltage change which is reflected back through the rectifier to the AC input), which BTW is the part that power companies hate (it creates harmonics, changes power factor and results in losses in the Grid).
Yes exactly.
Basically, any amp is a power conversion device. So, if the power demand grows at the output, it is reflected to the input in some form or another.
The caps at the output are there to stabilize the voltage when the current demand changes, but then they have to be recharged and this makes them draw more current at the input.
Roughly speaking, since both AC Mains and the output of the rectifier are voltage sources, it is the currents both at the input and the output that get changed, not stabilized.
Capacitor charging is not smooth, it occurs only when the rectifier bridge output V exceeds that of the capacitor and then it charges really fast with really large current which is pretty much dictated by ESR/ESL of the capacitor, and in a much smaller part by the output impedance of the power transformer (we could safely disregard the Mains impedanc unless dealing with multi-kilowatt amp). Hence the red current waveshape with sharp rising and the flattened Green input voltage waveshape (capacitor resists voltage change which is reflected back through the rectifier to the AC input), which BTW is the part that power companies hate (it creates harmonics, changes power factor and results in losses in the Grid).
