[sunseeker888]

For a tube headphone amp to be compatible with the majority of the headsets on the market today, it should have a reasonably low output impedance, right? Well why not go OTL exclusively? I feel like the output transformer colors the sound too much, and while this may sound 'sweet' or pleasant with a speaker amp, there is a definite loss of detail on headphones, since they are much more intimate and most of the time, more revealing.

Of course, the designer must choose a power tube with suitable characteristics to drive the headphones. What do you guys prefer?

 

[manofmathematics]

In my opinion, output transformers are only good for impedance matching.

 

[Nick 214]

I think that all headamps should be OT, unless it's a 100 foot long headphone cable, or something (this may actually come about in high-end pro sound).

NK

 

[Roam]

The "transformer colourations" occur since the vast majority of tube headphone amplifiers use inferior transformers. Good transformers cost a lot of money, thus it's nearly impossible for an under $2000 amp to possess quality output transformers such as Lundahls, Tributes or MagneQuests. Winding a high quality transformer is costly in terms of materials and labour, as well as being a bit of a black art. Many variables such as primary inductance, wiring losses & resistance, interwinding capacitances, core geometry and many others have to be balanced and traded off against each other, and it's especially important in single-ended transformers.

Used properly, they allow for the use of simple designs using extremely linear & low distortion tubes, some of which would be nearly impossible to use in an OTL circuit. Along with the use of CCS's, they also allow optimized current loop control on all stages of the amplifier.

 

[wower]

Quote:

Originally Posted by Roam /img/forum/go_quote.gif The "transformer colourations" occur since the vast majority of tube headphone amplifiers use inferior transformers. Good transformers cost a lot of money, thus it's nearly impossible for an under $2000 amp to possess quality output transformers such as Lundahls, Tributes or MagneQuests. Winding a high quality transformer is costly in terms of materials and labour, as well as being a bit of a black art. Many variables such as primary inductance, wiring losses & resistance, interwinding capacitances, core geometry and many others have to be balanced and traded off against each other, and it's especially important in single-ended transformers.

I'm not picking on Roam becuase he makes all good points. It can be done; but isn't. No one complains about the yamamoto's transformer. According to my reading, it's wound in-shop by shige-san. But even myself aim for an OTL design in the future.