ALW said:
Check out the toroidal medical isolation transformers from Plitron ('http://www.plitron.com/'). The 'type 1' transformer has an electrostatic shield, a magnetic shield, and an overtemp switch. They are available in HUGE capacities (up to 12.5KVA). They have dual 100-120 inputs and dual 115 outputs, so they can be used to convert 220V to 115V and vice versa. All things considered, they are fairly inexpensive.
Just one of these would be able to clean up the power for a complete stereo system
.Good luck.
Chicken or the egg?
I think we are looking at two issues here:
1. Diode (in this case) switching noise getting into the rest of the power supply
2. Diode (in this case) switching noise getting back out on the net and into another device.
I believe I have experienced both. You can test number 2 by putting a mains filter on a detachable power cord. Putting such a filter into my CD player (and covert it to detachable cord at the same time) is one of the bigger upbrades I have done (with the system I had at that time). My power amp sounded much better, but my Stax OTL headphone sounded no different. Whether this was diode induced or not is another matter.
Regardless of whether I was experiencing digititis or diode swiching noise, I am convinced that anything you do to remove HF ringing at it's source should be done.
Schottky diodes are not very expensive these days but get hot at high voltages.
Hexfred's or equivalent are not really that expensive either ....
At least one can put some caps onto the devices. I would suspect ceramics are the best (shame on me!) as noted by other(s) previously in this thread.
Petter
I think we are looking at two issues here:
1. Diode (in this case) switching noise getting into the rest of the power supply
2. Diode (in this case) switching noise getting back out on the net and into another device.
I believe I have experienced both. You can test number 2 by putting a mains filter on a detachable power cord. Putting such a filter into my CD player (and covert it to detachable cord at the same time) is one of the bigger upbrades I have done (with the system I had at that time). My power amp sounded much better, but my Stax OTL headphone sounded no different. Whether this was diode induced or not is another matter.
Regardless of whether I was experiencing digititis or diode swiching noise, I am convinced that anything you do to remove HF ringing at it's source should be done.
Schottky diodes are not very expensive these days but get hot at high voltages.
Hexfred's or equivalent are not really that expensive either ....
At least one can put some caps onto the devices. I would suspect ceramics are the best (shame on me!) as noted by other(s) previously in this thread.
Petter
Filters - yuck!
These filters (particularly the filtered IEC inlets) are commonly used, but some systems don't like them at all.
Just plugging in any item with common mode filtering and / or adding series inductance in the form of filters screws the tune of my system completely, even if the filtered item is switched off.
The series inductors in many filters cause a rise in mains impedance that my equipment doesn't like.
Personally I prefer to eliminate the noise at source within the PSU, and avoid it's generation, rather than attempt to filter it using brute force methods. It's a much more elegant solution.
Andy.
These filters (particularly the filtered IEC inlets) are commonly used, but some systems don't like them at all.
Just plugging in any item with common mode filtering and / or adding series inductance in the form of filters screws the tune of my system completely, even if the filtered item is switched off.
The series inductors in many filters cause a rise in mains impedance that my equipment doesn't like.
Personally I prefer to eliminate the noise at source within the PSU, and avoid it's generation, rather than attempt to filter it using brute force methods. It's a much more elegant solution.
Andy.
Geoff,
I haven't tried MOVs--the circuits I threw together were simply 1:1 toroid isolation transformers that I bought surplus, and a few other junk box odds & ends. They look like a train wreck (I used perf board to hold the little parts), but made a far larger difference in sound quality than their humble origins and parts would have led me to believe. One of these days, I'm going to take a more scientific (a word some folks probably don't expect me to use...) approach to the topic and rebuild the poor things as proper circuits.
Petter,
I don't have a decent CD player at present; I just 'borrow' the DVD player from my video system when I want to listen to CDs. However, I do try to keep the DVD player (a mid-line Sony--forget the model) isolated on it's own 'conditioner' so as to stop digital gremlins from sneaking back up the line and down into my other equipment.
Grey
I haven't tried MOVs--the circuits I threw together were simply 1:1 toroid isolation transformers that I bought surplus, and a few other junk box odds & ends. They look like a train wreck (I used perf board to hold the little parts), but made a far larger difference in sound quality than their humble origins and parts would have led me to believe. One of these days, I'm going to take a more scientific (a word some folks probably don't expect me to use...) approach to the topic and rebuild the poor things as proper circuits.
Petter,
I don't have a decent CD player at present; I just 'borrow' the DVD player from my video system when I want to listen to CDs. However, I do try to keep the DVD player (a mid-line Sony--forget the model) isolated on it's own 'conditioner' so as to stop digital gremlins from sneaking back up the line and down into my other equipment.
Grey
Dear Grey,
Thanks for your comments. You might be interested to hear the whole story.
My power supply to the valve pre-amp consists of a transformer, 4, 1N4007 as a bridge rectifier and of course condensers. I did not have caps across the diodes. The transformer failed most liekly due to under power since it was an old one from my spares. So, I bought a replacement and that one has a centre tapping. Since I am using the 4 diodes, I only used half of the secondary coil.
When I decided to change the rectifiers for the pre-amp (since the power amp proved successful), I used two ultra fast rectifiers and the centre tap (this is more economical to do) and the result was disappointing as descrbied previosuly. As I said, I could not figure out the reason behind it as both circuits used were full-wave rectification. Going back to theory, I read from a book explaining that the secondary coil would need to work twice as hard when using two rectifiers and the centre tap.
As suggested, I bought two more of the same ultra fast rectifiers to build a bridge and the expected result re-appear. Yes, this time it illustrates that the component brings improvement to one circuit, it does the same elsewhere. So, the explanation might be that my new transformer is not that powerful too.
Many thanks for you guys participating and commenting.
William, 27/7/2001
Thanks for your comments. You might be interested to hear the whole story.
My power supply to the valve pre-amp consists of a transformer, 4, 1N4007 as a bridge rectifier and of course condensers. I did not have caps across the diodes. The transformer failed most liekly due to under power since it was an old one from my spares. So, I bought a replacement and that one has a centre tapping. Since I am using the 4 diodes, I only used half of the secondary coil.
When I decided to change the rectifiers for the pre-amp (since the power amp proved successful), I used two ultra fast rectifiers and the centre tap (this is more economical to do) and the result was disappointing as descrbied previosuly. As I said, I could not figure out the reason behind it as both circuits used were full-wave rectification. Going back to theory, I read from a book explaining that the secondary coil would need to work twice as hard when using two rectifiers and the centre tap.
As suggested, I bought two more of the same ultra fast rectifiers to build a bridge and the expected result re-appear. Yes, this time it illustrates that the component brings improvement to one circuit, it does the same elsewhere. So, the explanation might be that my new transformer is not that powerful too.
Many thanks for you guys participating and commenting.
William, 27/7/2001
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Joined 2000
Paid Member
Screened toroids
Looks like I'm a little late to the discussion on shielding toriods... but I just got back an e-mail from someone at Plitron. Adding an electrostatic screen and magnetic shielding to their 300va toroid adds approximately $10 to the cost and increases lead time to about 4-5 weeks. If you're not in a hurry, it seems that it might be worth the extra cost.
Looks like I'm a little late to the discussion on shielding toriods... but I just got back an e-mail from someone at Plitron. Adding an electrostatic screen and magnetic shielding to their 300va toroid adds approximately $10 to the cost and increases lead time to about 4-5 weeks. If you're not in a hurry, it seems that it might be worth the extra cost.
Screened toroid
2 years ago I had a lengthy design process going with Plitron specifically for Audio transformers for power amplifiers. As you know, they are knowledgeable in this matter and manufacture units for companies such as BAT.
I figured and electrostatic screen would be a good thing. However, their chief designer said that he did not recommend it as it caused other "problems". I was on an international call and chose to pursue other detailed topics at that time.
However, I also note that renowned DIY'er Thorsten Loesch likes electrostatic screens. Now he is a tube man so his needs are different than transistor power amp units.
Now as far as magnetic shielding goes, I usually specify double normal thickness for toroids when I get custom units made.
Petter
[Edited by Petter on 07-27-2001 at 02:41 PM]
2 years ago I had a lengthy design process going with Plitron specifically for Audio transformers for power amplifiers. As you know, they are knowledgeable in this matter and manufacture units for companies such as BAT.
I figured and electrostatic screen would be a good thing. However, their chief designer said that he did not recommend it as it caused other "problems". I was on an international call and chose to pursue other detailed topics at that time.
However, I also note that renowned DIY'er Thorsten Loesch likes electrostatic screens. Now he is a tube man so his needs are different than transistor power amp units.
Now as far as magnetic shielding goes, I usually specify double normal thickness for toroids when I get custom units made.
Petter
[Edited by Petter on 07-27-2001 at 02:41 PM]
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Joined 2000
Paid Member
Hmmmm. Transformer screens and shields cause other problems? Sounds like this might be worth a phone call to talk to someone. I'll try to give them a call over the next few days and post a brief summary when I'm done. I just made the automatic assumption that adding both would be a good thing...
[Edited by Eric on 07-27-2001 at 02:50 PM]
[Edited by Eric on 07-27-2001 at 02:50 PM]
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William said:
Hi William,
There are two ways you can connect a center tapped transformer with two diodes. One way will end up with one full-wave rectified DC output of half the voltage you would get with a bridge rectifier, and the other way you will end up with half-rectified +/- DC outputs.
Bear with me, here come some really bad ASCII schematics.
Full-Wave Rectified single output supply
Diode
{-------|>|-------|-----|------0 + Supply
}.................|.....|
{.................|.....- Filter Cap
}--0 Center Tap...|.....-
{....Ground.......|.....|
}.................|.....|
{-------|>|-------|.....0 Ground
Diode
Half-Wave Rectified Dual +/- Supply
Diode
{-------|>|---|---0 + Supply
}.............|
{.............- Filter Cap
}.............-
{.............|
}-------------|---0 Center Tap, Ground
}.............|
{.............- Filter Cap
}.............-
{.............|
{-------|>|---|---0 - Supply
Diode
The only way you could have got the same results changing from a bridge rectifier to 2 diodes would be if you doubled the secondary voltage of the transformer and only needed one supply output. You will get a slightly higher output voltage than before since you are now only have one diode drop in the circuit instead of two.
If you have + and - supply outputs then what you did was change from full-wave rectified to half-wave rectified which means that your filter caps are now undersized for the amount of ripple they going to see.
Phil
Second try. Drat! That didn't work very well. The spaces in my ASCII schematics just collapsed down. I have revised it to use ... instead of spaces. Just ignore the ....'s in the drawing.
Phil
[Edited by haldor on 08-13-2001 at 08:51 PM]
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