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| Author: | Cogito [ June 23rd, 2021, 11:19 am ] |
| Post subject: | Re: Impedance of you house |
Roscoe Primrose wrote: Waveform distortion can cause the average value to no longer be 0V..... Roscoe That only effects the DC offset of AC, but that does not mean there is actually DC current in the wires. Walt's question is valid IMO. |
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| Author: | Roscoe Primrose [ June 23rd, 2021, 11:24 am ] |
| Post subject: | Re: Impedance of you house |
Cogito wrote: Roscoe Primrose wrote: Waveform distortion can cause the average value to no longer be 0V..... Roscoe That only effects the DC offset of AC, but that does not mean there is actually DC current in the wires. Walt's question is valid IMO. Yes, it does. That's where toroidal transformers have problems, they're not at all happy with even small DC currents since most of them have no gap. Roscoe |
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| Author: | SoundMods [ June 23rd, 2021, 11:46 am ] |
| Post subject: | Re: Impedance of you house |
Roscoe Primrose wrote: Waveform distortion can cause the average value to no longer be 0V..... Roscoe The zero crossing point is the same whether or not the sine wave is distorted or not. So -- where does the DC come from if at all? |
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| Author: | DaveR [ June 23rd, 2021, 12:04 pm ] |
| Post subject: | Re: Impedance of you house |
Why wouldn't the average value settle to 0 VDC? |
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| Author: | Roscoe Primrose [ June 23rd, 2021, 12:13 pm ] |
| Post subject: | Re: Impedance of you house |
https://eprints.usq.edu.au/75/1/AshleyK ... -_2004.pdf |
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| Author: | FerdinandII [ June 23rd, 2021, 12:53 pm ] |
| Post subject: | Re: Impedance of you house |
If you integrate the positive and negative waveforms independently you will get results that are not equal. The difference between them will create a DC offset. Here's a wildly exaggerated example:  SoundMods wrote: Roscoe Primrose wrote: Waveform distortion can cause the average value to no longer be 0V..... Roscoe The zero crossing point is the same whether or not the sine wave is distorted or not. So -- where does the DC come from if at all? |
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| Author: | SoundMods [ June 23rd, 2021, 1:26 pm ] |
| Post subject: | Re: Impedance of you house |
Roscoe Primrose wrote: https://eprints.usq.edu.au/75/1/AshleyKarlZEIMER_-_2004.pdf OK. I read that kid's white paper and I get it. But when the electronics "see" DC from the smoothed full-wave bridge with storage caps smoothing out the ripple, and maybe, if you're lucky, a choke coil that takes it further, then you have shunt or series regulation that does its thing -- how on earth can that DC component even possibly have any impact on sound quality?  I mean -- WOW!-- This whole "DC thing" is right up there with UFO sightings. |
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| Author: | Pelliott321 [ June 23rd, 2021, 2:30 pm ] |
| Post subject: | Re: Impedance of you house |
Rod Elliott "ESP" Said the same thing DC blocker will have nothing to do with the sound quality on buzzing transformers I have mentioned this in other threads that once in a while I would come into my sound room and hear a tranny buzzing. I determined that it was the Toroid tranny in my isolation transformer for my line-level equipment. I would unplug the iso and a whole later plug it back in and the buzzing was gone, until the next time. Since I have been fooling around with DC blockers I have not had that problem. I have heard no changes to the music due to this. |
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| Author: | HAL [ June 23rd, 2021, 3:47 pm ] |
| Post subject: | Re: Impedance of you house |
In the case of toroidal power transformers, getting rid of the AC line DC eliminated the mechanical hum in my case by dropping the line distortion. Just about any amount of DC to the toroidal core saturates it as Roscoe said earlier and makes them mechanically hum. That gets rid of acoustical noise in the room. Important in a quiet room. |
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| Author: | dberning [ June 24th, 2021, 1:07 pm ] |
| Post subject: | Re: Impedance of you house |
A half-wave rectifier will put dc on the power line. Equipment that uses half-wave rectification has low power draw, so it would be small. Inductive loads, transformers, including the mains transformer will shunt most of this. Distortion is probably the bigger issue making transformers buzz. Of course a half-wave load will make distortion. Anything with a power factor less than 1 makes distortion too. I put power factor correction in my power amps for this reason. For preamps I don't bother because the power draw is low. |
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