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Review and Measurements of XDuoo TA-01 and Schiit Fulla V2 DAC and Headphone Amp

rebbiputzmaker

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#61
The problem with valve power amps isn't just the valves it is the output transformer. There are probably no transformers which perform well over the entire audible frequency bandwidth since what is required for good performance at low frequencies may compromise the performance at high frequencies and give early roll off. Having written that, even solid state stuff with inter stage transformers can sound "nice" so maybe the distortion/ addition/ removal of some of the signal by a transformer is something people like????
It isn't high fidelity though.
Transformers can be beautiful devices and they have their place in audio. Through the chain, microphone, mixing, recording and various other locations we may find transformers. They are high fidelity, in fact, can be very high fidelity, it just all depends on the quality and understanding of the application.

Transformer design is a combination of Art and Science, sadly mostly lost in this day and age modern engineering. Most haven't the foggiest idea how to design or even understand transformer design. The height of classic transformer design was probably the fifties into the early 60s. Amazing high quality superb sonic qualities were the norm. The Peerless company part of Altec basically a child of Bell Labs and with research from the Golden Age of audio created some of the best audio transformers ever made. High-quality materials, sophisticated multiple winding schemes and exotic laminations, were just some of the features of these transformers. Frequency response was not an issue with these high-quality devices
 

έχω δίκιο

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#62
Through the chain, microphone, mixing, recording and various other locations we may find transformers. They are high fidelity, in fact, can be very high fidelity, it just all depends on the quality and understanding of the application.
Matching impedance between a mic and high impedance input circuitry, or simply floating the mic's ground, is a very different thing than trying to drive a multi-way speaker with 50 watts of power. With the mic, you don't have to worry about reactance or damping factor with the driven load.

Frequency response was not an issue with these high-quality devices
How did they keep the inductance and capacitance of those output transformers from reacting with speaker drivers and crossovers?
 

Frank Dernie

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#63
Transformers can be beautiful devices and they have their place in audio. Through the chain, microphone, mixing, recording and various other locations we may find transformers. They are high fidelity, in fact, can be very high fidelity, it just all depends on the quality and understanding of the application.

Transformer design is a combination of Art and Science, sadly mostly lost in this day and age modern engineering. Most haven't the foggiest idea how to design or even understand transformer design. The height of classic transformer design was probably the fifties into the early 60s. Amazing high quality superb sonic qualities were the norm. The Peerless company part of Altec basically a child of Bell Labs and with research from the Golden Age of audio created some of the best audio transformers ever made. High-quality materials, sophisticated multiple winding schemes and exotic laminations, were just some of the features of these transformers. Frequency response was not an issue with these high-quality devices
Yes considerable investment and effort was put into the design and manufacture of transformers when they were inevitable though better materials are perhaps available now.
Still not all that good at audio frequency extremes . Distortion at 1kHz can be pretty low though.
I rarely use my valve amps, they look nice on a shelf though and give a classic old fashioned sound through my horn speakers for a bit of fun now and again.
 

DonH56

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#64
I think I am missing some of the discussion but there are reactances with microphones too, though you do not have the power requirements that amplifiers driving speakers require. It is fairly trivial to show how a transformer-coupled output causes the frequency response to vary when presented with a reactive load, plus you have generally high output impedance (increasing load sensitivity) and things like transformer hysteresis and saturation to contend with in addition to the transformer's impedance itself. And transformers are big and bulky, and generally not required (nor desired) when the paradigm shifted to amplifiers as a voltage source and speakers were free to have wild(er) impedance excursions. Atmosphere, Audio Research, Bob Carver, and other tube amplifier vendors, plus Macintosh (though more of a balun than conventional transformer IIRC), probably a few others are still making their own output transformers and probably represent the state of the art, but can't get around fundamental issues (physics).

I loved my tube amps on Magnepans but the amps struggled a bit on deep bass and very high frequencies as the speaker's impedance varied (drops below 3 ohms at HF with the ribbon tweeter) or lower output impedance was needed (e.g. to better control panel modes in the bass frequencies). Most tube amps I felt got a bit harsh at HF extremes with ESLs where the impedance drops. And of course with very few exceptions most transformers struggle dipping deep into subwoofer territory. With a lot of speakers exhibiting pretty wide variations in impedance over frequency I've gotten away from any desire for output transformers in the past few years (OK, decades...)
 
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