Some general suggestions here.
"Old school" iron core transformers are superior to toroidals in terms of noise rejection. Toroidal designs do work, but are not as efficient in terms of total noise rejection.
Look for transformers that use the most iron for their cores and are rated the highest in terms of KVA. "Good" isolation transformers are phenomenally heavy and expensive. My bare 3KVA isolation transformers weigh over 100 lbs apiece. The cores are actually good for about 5KVA. As such, i might saturate the windings but i'd never saturate the core. The 1.8 KVA bare transformers that i have weigh 42 lbs apiece. I used to think that these had "healthy" cores until i picked up the 3 KVA units : ) The bare "little" .25 KVA transformers i have weigh 12 lbs apiece. Just the sheer shipping weight and cost of raw materials for these units might tell you why many manufacturers opt for lighter and less costly toroidal designs.
If you must share transformers between components, keep the digital separate from analogue and vice-versa. If using a transport and dac, further gains can be made by having an individual transformer for each unit. If possible, take that a step further and use individual isolation transformers for each component.
If you are going to use an isolation transformer on a power amp, the transformer should be rated quite a bit higher than what the amplifier would draw at the point of clipping. Otherwise, you might run into core saturation on the isolation transformer during momentary peaks or sustained low frequency passages.
Bare in mind that transformers produce a magnetic field around them. You will have to take steps to shield them if placed near the gear. Keep signal cabling FAR away from ANY type of power transformer.
Start with your digital gear and work your way down the line.
I've been told to stay away from Sola units as they supposedly do "bad things" sonically. Besides that, 3% distortion is pretty high. According to what i've read, the power coming off the grid is "supposed to be" less than 5% at any given time. If it is higher than that, your pole transformer is probably defective.
Short of purchasing a TRUE power regenerator ( expensive and in-efficient ), there is nothing that you can do to remove ALL of the noise coming in off of the line. Using good quality iron core isolation transformers will give you the most benefits with the least drawbacks, but they are sloppier and far less convenient to work with than commercial "audiophile" PLC's.
Keep in mind that this is just my take on the situation. Others will have varying opinions that are probably just as valid, maybe more-so. Sean
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Dennis: Dedicated lines simply separate the power lines for your audio gear from all of the other wiring in the house. This in itself can reduce noise within the AC feeding your A/V system, but you are still susceptible to the noise that is coming in from the outside line feeding your AC mains. As such, an "optimum" installation would be one with dedicated lines and either a very high current power regenerator or extensive isolation via low impedance filtering / isolation. If you wanted to get "really crazy", especially if you had BIG high powered amps, would be to bypass all of the AC completely and feed your system off of a bank of batteries. If i had a simple, low powered system, that is probably what i would do. Since i am not in that boat though, i've had to go the first route.
An isolation transformer "uncouples" or "isolates" the A/V components from the outside lines. It is basically a 1 to 1 transformer. In other words, if you put 120 volts into it, you get 120 volts out of it. Due to the indirect coupling via the transformers windings though, you end up losing the mass majority of noise that may have been riding on the line. This is a good thing in every aspect. As stated above, "old school" iron core transformers are more efficient at "electrically isolating" the AC signal from the noise, but a toroidal design can also be quite effective. As Francisco stated, i would not pass up a good deal on a legit isolation transformer just because it was toroidal based. While it may not work quite as well as an equivalent E-I or C core "old school" transformer, it would none the less reduce the noise on the line very drastically. The drawbacks to the reduced efficiency ( in terms of reducing noise ) that the toriodals may suffer from can more than be made up for by compact size and measurably less weight than if one were to make comparisons with standard transformers.
The drawbacks to using isolation transformers is that they can introduce losses into the AC system and play games with the phase of the signal being fed to components. In both cases, this is typically a side effect of trying to use too small of a transformer for too big of a job. If the core of an isolation transformer is getting physically hot, you can bet that it is not big enough for what you are using it for and "bad" side effects will result. It is not abnormal for any device that is passing a reasonable to large quantity of power to undergo some type of temperature rise, but a transformer should NOT get physically hot to the touch. If it is, the transformer is simply not up to the task or being pushed too close to its' limits on a steady state basis.
As such, that is why i recommended using transformers that were rated for well above the amount of power that you intend to pull through them. This minimizes the potential for thermal losses / phase shifts while allowing the system to obtain all of the benefits of such a design. The use of higher current rated transformers also helps to keep the line impedance down, which is always a good thing. The "filters" used in many PLC's are of somewhat higher impedance and this can introduce problems of a different nature.
Hope this helps and explains a few things. There are variations to what i've mentioned, but this should cover the basics. Sean
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Using a good quality isolation transformer or "less intrusive" PLC typically results in the following results. That is, so long as the transformers or filters are properly sized and do not restrict current.
1) Lower noise floor ( "blacker backgrounds" )
2) Less grain and glare ( digital sounds less digital )
3) Increased liquidity i.e. voices and instruments sound more natural. ( Many PLC's don't do well here as they they can tend to sound more "sterile". Many people are willing to live with this trade-off due to having some form of spike / surge suppression )
4) Increased separation of instruments and notes ( there is less noise to fill in the gaps that would normally be quiet )
5) Increased dynamic range ( due to lower noise floor )
6) More stable soundstage and imaging ( less noise "blurring" the actual spatial information / musical content of the recording )
I think that you get the idea. I must state that results will vary as AC varies from location to location quite a bit. Both the effectiveness and the results observed will vary with the types of filtration / isolation devices used, the quality of AC to begin with, the amount of filtration designed into each individual audio component, etc... My experience is that all systems will benefit from isolation transformers, so long as they capable of passing more than enough current than any individual component would need at any given time. As mentioned, it is best to isolate each component if possible or at least separate analogue from digital.
The most "bang for the buck" installation would make use of an isolation transformer for digital, one for analogue and one for the amp. Obviously, one need not use mega-watt devices for the digital and analogue gear unless those devices pull a lot of power. If all of your digital gear adds up to pulling 100 watts, shoot for an isolation transformer that can sustain 250 watts or .25 KVA. If all of your analogue gear pulls 400 watts, shoot for an isolation transformer of 1 - 1.2 KVA. In essence, you want to keep the load passing through the isolation transformer at around 40 - 60 percent of capacity. This pretty much guarantees that you will not saturate the core under any circumstances ( the one potential major drawback to this approach ) AND gives you some headroom in case you swap gear for something that is a little more "thirsty" for current in the future. As far as power amps go, especially big brutes, you can't have a big enough isolation transformer. Use the biggest one that you can find with the highest KVA and most massive iron core.
Someone that was shooting for the "ultimate" in noise reduction would use a properly sized isolation transformer for each individual component. This is obviously easier to do if you have a smaller system with less componentry.
I do not recommend using voltage stabilizers or regulators unless you have a problem with voltage in your area. Most of these devices produce / add distortion of their own. You may now have more stable voltage on the average, but you've substituted one problem for another. Obviously, there are a LOT of different products and ways to do this, so there are bound to be exceptions to what i've stated. Running dedicated heavy gauge lines directly back to the mains with clean connections and no breaks in the line will typically reduce voltage drops or "sagging" to a minimum. If you've got an over-voltage condition, that could be a problem that only voltage regulation could fix if the AC provider is unresponsive. To me, AC regulation would be a last resort but at that stage of the game, it might be a necessary one. Sean
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Z: That sounds like a very nice product. However, i would still bypass this device and run the amp direct to the wall. Otherwise, you're trying to pull enough current through one power cord to feed the entire system. As such, the amp WILL pull hard enough to create sag on the line for the other components being fed if hitting the volume control. Other than that, it sounds like it would be a very convenient and clutter free device. Sean
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You are right about transformers being "different". Not only are we talking about the design of the unit, but also the quantity and quality of materials used. The 3 KVA transformers that i have use as much iron as other 5 KVA units that i've seen. Obviously, the smaller one is built a LOT "beefier" than the other even though it is rated for only 60% as much power. Retail price on the 3KVA transformers when new was up around $3000 and i've seen them selling for appr $900 in electronic surplus outlets. The only reason that i can afford the things that i have is because i am a careful shopper and know what to look for. I would imagine than many of you here are in the same position, hence the perusal of Audiogon's used gear listings. As such, I picked up the two above mentioned transformers for $210 : ) Then again, shipping set me back another $130 due to the high ( 230 lbs ) weight : (
When it comes to looking at electrical specs with these types of transformers, the models with the lowest stray capacitance is typically going to do a better job of isolation. Increased capacitance will couple ( you've heard of "capacitively coupled" ??? ) the main side of the transformer to the secondary side in a more direct fashion. In effect, the higher the capacitance per winding, the more of a "leaky" isolation transformer. The end result is only partial isolation if using a transformer high in capacitance.
Think of the amount of leakage as being compared to a signal to noise ratio ( S/N ratio ). The greater the isolation, the less leakage and the less noise gets by. Just as a higher s/n ratio is rated at a higher number in terms of dB's, so is the isolation factor. An isolation transformer with 146 dB's of isolation is "better" or more isolated / less leaky than a transformer that is rated at 126 dB's. At the same time, a transformer with a bigger iron core can pass more current without saturation or distortion. If you can achieve these two things in a transformer, you are most of the way there.
One should also take into account that any transformer generates a magnetic field. If you have multiple transformers within the same chassis, it is possible for the magnetic field of one transformer to "modulate" or "super-impose" its' signal onto another transformer. This occurs because the fields inter-act with each other due to close proximity. This is the very same reason that we do not want signal cables near power cords, etc...
As such, transformers that have "end caps" or shields over the windings are normally preferred over those that are expose the windings. While it is true that toroidals do produce a smaller field around them, they are also not quite as efficient at reducing / isolating noise to begin with. As such, one must pick and choose their trade-offs accordingly. If you have limited space and want convenience while feeding several different components, one can shoot for one chassis with several toroidals or fully shielded yet smaller sized iron core transformers in it. While one stands the potential for greater inter-action between them, the benefits would typically far outweigh the drawbacks in terms of having to use several different chassis, taking up tons of space with the associated power cord nightmare, etc... This is especially true if pulling minimal power from the transformers i.e. to feed line level sources, a preamp, etc... It would be a different story if you had multiple large transformers with their bigger magnetic fields trying to feed power amps, etc.. Sean
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Zaikesman: I'm human and make mistakes too. Wanna see some threads and posts to prove it ? : )
As such, most of my comments are based on either first hand experience, common electrical / electronic theory, logical deductions and / or any combo of the above. With that in mind, nothing in audio is set in stone and one REALLY needs to try things out for themselves within the confines of their own system to see what works best. I have seen / heard components and cables sound like hell in one system and really compliment the performance of another system. You really don't know until you try it.
Having said that, i would be curious to see if the outlets that you plugged the amp into were on the same breaker and circuit that the line level gear was plugged into. Can you verify this and let us know ? It is possible that one set of outlets was on one leg of the circuit and the other outlet was on the other leg of the circuit. The fact that you have also introduced a completely new device and source of filtration into the system could also introduce another variable into the equation.
Is there any way to plug the amps directly into the same outlet as the line level gear is plugged into using one heavy duty extension cord with some type of outlet splitter ? I would be curious to see what happened in such a situation. Sean
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Reverse AC polarity within a system can play a lot of games. One may not realize these "problems" exist until the situation is corrected. Once that takes place, the "sonic haze" has been lifted and you can now hear things that were previously not noticed. I'm sure that you've seen this before, but take a look at this thread about Noise, Hum and AC Polarity to really sort through what's going on with your system. Don't forget that you have to remove ALL interconnects from the system as you can't have any of the component's chassis' tied together. Sean > |
