I had a feeling that , when galvanic isolation isn't a must , I can squeeze simple AVC in both configs - SE and balanced
gnd doesn't need to be involved in attenuating path for balanced - you can route it (gnd) around xformer
Hi Dave,
The duration of the applied DC current may affect the possibility of core magnetization.
When the core is magnetized, a possible solution is to drive it for a while with high current (within the transformer's specifications) at 50 or 60Hz, if possible, even at lower frequency.
I thought this too some time ago but could never get it to work in spice. Got a sketch of your idea?
dave
I guess like I do with resistors: using cold signal in place of gnd, so gnd not connected at TVC: input gnd connected directly to output gnd.
You'd probably note attenuation of the low frequencies.
If in doubt, attach to the core a ferromagnetic object, like a screwdriver (a non-magnetized one) and see is it is being attracted to the core.
The 'scientific', or engineering, way is to measure the transformer's inductance and see if it's as it should be, according to the manufacturer's figure.
There aren't fixed figures that I'm aware of.
TVC or IVC may sound superb, or it may sound bad, depending on its' compatibility with any given setup; mainly the output impedance of the source(s) and the input impedance of the power amp. The compatibility to a given setup also depends on the transformer's inductance, the output level of the source(s) and the gain of the power amp.
I know of no safe way to ensure compatibility, other than to test it on one's setup, prior to actually purchasing it.
However, once the TVC or IVC is compatible with a given setup, it may sound better than any active preamp.
Since you own one, you should know how it does sound in your setup.
I'm not sure if it can be done with resistors.
The IVC I own is a SE one. All my sources are SE, while the power amp have both SE and balanced inputs; it sounds better when connected to the balanced input.
I converted the IVC's SE output to balanced by attaching a Lundahl line level transformer to the output of the IVC. Actually I use the transformer as an autotransformer, with half of the primary windings connected in series with half of the secondary windings as one section and the other halves as the second section. It sounds better than connecting the IVC without a transformer to the power amp's SE inputs.
That it sounds better this way on my setup may not necessarily be so on other setups.
If there is/are balanced source(s), the above wouldn't be applicable. In such a case it is necessary to use a balanced TVC or IVC, possibly with a transformer to convert the SE output of those source(s) that are only SE ones, to balanced.
Thomas is right sounds better with low impedance sources, for example Legato I/V SE outputs have an output impedance near 0 ohms and sounds superb but when I use Valve Itch MM phono pre with an output impedance of 800 ohms sounds better a ladder switch of resistors.
My cores aren't magnetized & measured inductance is ok: 20H
My cores aren't magnetized & measured inductance is ok: 20H
So you got your answers.
Indeed, 800 ohms output impedance is too high, at least in your setup, with your power amp's input impedance. 800 ohms output impedance may be too high in most setups.
The TVC or IVC is supposed to replace the preamp. I see no point in using both of them.
In any case, mute/silence can be attained with a dedicated witch.
For balanced in to balanced out, you need either balanced TVC or IVC, or, with SE TVC or IVC, two suitable transformers, one at the input and one at the output.
The sound quality will depend on both the quality of the TVC or IVC and on the quality of the transformers used to convert SE to balanced.
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