Because of usually it's impossible to change the inner construction of commercial amplifiers, change power transformers, add RFI filters, etc'.
Impossible? Physically no space for additional components do you mean? I've modified many a commercial amp and never considered that I'd done something particularly difficult. I'd say the limitation is just confidence/experience in electronics hardware and many audiophiles don't have the training for inner tweaking.
You are correct, Joshua, modifying existing audio equipment can be a hassle. For example, I have never modified my Sony projector TV, my Sony SACD player, my video recorder, or even my own power amplifier in my sound system. It is too difficult, and prone to mistakes, leading to breakdown of the actual component, in fact, rendering it useless. I certainly have done lots of external tweaking, including filters on both the power line, and audio inputs and outputs, etc. It is easier to TRY and note a difference, if any.
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RFI filters can be added, sometimes. Replacing toroid transformers with E-I core or R core ones is usually impossible.
What's your experience with balanced power via an isolation transformer ala Equi=Tech or similar design?
Hogwash !
Small toroids are easily replaced by split-bobbin EI's.
There's absolutely no need to swap R-cores for big toroidals in most cases, and decent EI transformers for power amp use are way to expensive for upgrading a consumer grade commercial amp.
The one I have has quite significant results. Of course it also provides a 5 volt boost to the output AC line which explains a lot. Because it has shielding from primary to secondary it reduces some of the line conducted noise, but it is really good at getting hum out of badly designed equipment.
A must if you are recording electric guitar's amplifiers or just about any musical instrument quality electronics.
If it's relevant to the topic at hand, I'm sure many of us would appreciate details/a link.
I suspect it depends on how noisy your power line is. On my test bench I have two sets of outlets for equipment under test one is current limited with about .2 ohms of source resistance when not limiting. The other is through a 10 amp medical isolation transformer without a voltage boost. My AC line runs about 126 volts. I perceived a difference when I switched the AC source for my Ampslab modified LM-60 amplifier used for my recent tests. I suspect this was not my imagination, as I was not expecting a change and it was a bit of a surprise so I tried the swap a few times.
However it has about 18ua of case to ground leakage current one way and 5ua with the AC plug the other. If you look at my plots from yesterday you can see the hum was about the level of the distortion. (Plugged in for minimum leakage!) So for the junk box transformer I used with the kit an isolation transformer provides a measurable benefit.
My conclusion, measure your leakage current! Oh for the bigger ground buss crowd a ten fold increase in buss size is expensive and would only yield a 20db improvement.
Assuming you're not facetious, I'll simply answer that no matter how hard I try, I'm (or the yutz with their back turned) unable to unsolder and resolder 4 connections in the 6 seconds (or unplug an plug), the time limit I consider necessary to make valid subjective comparison. I've even interchanged the 2 DUTs to see if that affected my subjective evaluations. Nor have I ever subjectively heard any effect of the switch intermediation, but thats certainly not within a time gap I consider valid, and console myself with the fact that at least both DUTs are subject to the switch contacts. Power filters are one of the few things that allow making SBTs reasonably easy. Powering a power amp with sufficient ps capacitance allows for it to ride through the switch without a hiccup. No level matching issues as the gain is set by feedback. I'm not seeking peer review, but a tool for my own use. For power cords, I've 2 identically modified DACs fed by a galvanically isolated splitter, but then again, the signal is subject to the humiliation of going through a toggle switch on my preamp.
I further invalidate my tests by using quick connects on the power filter DUTs.
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Jan,
Thank you for providing a brilliant insight into the goings on here.
John,
I take it you started listening to stereo as a toddler.
Sy,
For you it must have been at 10 to 12 years of age.
Steve,
I take it you you and a stereo are never parted.
Of course then I must have invented stereo!
!!!ES
Not at all and I appreciate the answer. Very often, rapid switching tests are denigrated because the switch contacts are claimed (without evidence) to totally invalidate any listening tests. This despite the number of switch and plug/jack contacts already in the signal path and even when high quality switches or relays are used. Once that excuse is discarded, there's no reason that any listening test should be done sighted- at least if one actually trusts their ears.
Again, thanks.
Sure I do. You read those trashy hobbyist magazines with their greatest speaker, amplifier, wire, or whatever in the world of the month reviews, you go to the boutique audio equipment stores where you compare their equipment (do any of you even bother to bring your own recordings?) and then you buy, buy, buy. You've hardly got your newest whizbang out of the box before you're shopping for its replacement.
Meanwhile while your new equipment disappoints, you can always hope it will "break in." But it invariably disappoints which is what keeps these high end equipment manufacturers, designers, retailers in business selling endless variants of the same idea.
Especially if you haven't got a clue as to how it actually works. Why would someone go to the trouble to design, manufacture, and market a fine and expensive amplifier or preamplifier if its performance was compromised by the limiting factor, the power cord supplied? I'm still waiting for someone to tell me that they changed the power cord on their turntable and that the improvement blew them away. The electrons in the wire go round round round....
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