That may well be. However, setting the volume to a lower-than-unity level (as in 95% of normal listening situations) improves the impedance ratio such that the output of the transformer can deliver more current. This is desirable for driving low-impedance loads. From this perspective things improve at normal listening levels.
DC currents will tend to magnetically saturate the core. This is also true for high-amplitude / low-frequency signals. Magnetic saturation is a bit like an amplifier that is driven into clipping, because large (especially low-frequency) signals cause an overload that results in higher-frequency distortion of the audio signal. However, a well designed transformer (or autoformer) that is operated within its intended operating range will not cause any unexpected degradation to the audio signal.
Are you sure? Stray fields penetrating the autoformer/transformer windings would need to induce a current through the windings. If the windings are connected to a low-impedance source, this current would be essentially shortened. In other words, mutual induction would make the stray field stay outside of the transformer windings. In addition, magnetic shielding of the transformer can be used to further improved the immunity to stray fields. As a result, I have never observed any hum coming from a transformer in the audio signal (be it in a passive attenuator, as an interstage in an amplifier, or an output stage in a DAC).
Agreed. But the same can be said for 99% of commercial electronics. They buy cheap parts that do the job, stuff them together and sell it for a gazillion. That's their business.
I used to think like this, too, but I changed my mind when I thought about the time I used to design and build things. DIY is mainly about building things the way you want it, not the way some factory designer wanted it to be to optimize the company profits.
Cheers
mbrennwa
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audioroot – custom audio gear for you
At lower than unity settings the transformer can deliver more current but the leakage inductance of the transformer (attenuation setting dependent) does increase the output impedance which will cause a high frequency roll off when the setting are below unity. The Allegri doesn't specify the test conditions.
What is the Allegri low frequency performance? It isn't specified below 400 Hz.
The transformers will be suceptible to external magnetic fields. The windings are connected to a relatively low impedance source, probably, but it isn't zero. The audibility depend on many things so it may not be a problem. Sowter use a MuMetal screening can.
I agree about the DIY option, I use a pair of DIY speakers using Focal drive units.
What is the Allegri low frequency performance? It isn't specified below 400 Hz.
The transformers will be suceptible to external magnetic fields. The windings are connected to a relatively low impedance source, probably, but it isn't zero. The audibility depend on many things so it may not be a problem. Sowter use a MuMetal screening can.
I agree about the DIY option, I use a pair of DIY speakers using Focal drive units.
Yes, there are man problems with these kinds of volume controls. The transformer must be magnetically shielded, for example. The frequency response will vary with volume setting, etc.
Why not just buy a Sowter unit and connect a unity gain buffer on the output?
Sometimes, I just don't understand audiophiles who don't believe in the laws of physics.
Because sowters are expensive that is the main draw back for me. The sheilding and unity buffer seem doable !
Maybe Zeta4 could let us know if the The Allegri was tested below 400Hz ??
Sorry just had to post a picture of a 2017 model Warpspeed V4 here... I tried to buy it from him but he was worried about sending it to the UK :-(
I like the balance control on the hood almost looks like the sort of thing you might find on a combination safe - not that I'm a safe cracker or anything !
Maybe Zeta4 could let us know if the The Allegri was tested below 400Hz ??
Sorry just had to post a picture of a 2017 model Warpspeed V4 here... I tried to buy it from him but he was worried about sending it to the UK :-(
An externally hosted image should be here but it was not working when we last tested it.
I like the balance control on the hood almost looks like the sort of thing you might find on a combination safe - not that I'm a safe cracker or anything !
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There's a lot of interesting infomation getting posted here I apreciate it and am reading all the while and trying to make a decision on the best way forward but a lot of this stuff is out of the scope of my experience but I already learn't a lot here - mean while still working out how to build I2s cables with Cat 7 Cable so I can test a £30 Ansycrounous unit CM6631 from China that's in now in the post a students life is tough !
PS: Not sure if I could even tell if it works or not unless I had a second unit to play with or some way of measuring any ideas ?
PS: Not sure if I could even tell if it works or not unless I had a second unit to play with or some way of measuring any ideas ?
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