After living with this new line preamplifier for almost a month, it is time to write a bit about the sound impressions.
When I was confronted with the challenge to find ways to improve upon my single ended line stage, that was a tough one. I am very happy with that preamp and have not changed the design in many years. There are users of this line stage around the globe who gave the most positive feedback about it's sound. There was also a test recently in a webzine called hifistatement. Click here to read that report, which is now also available in english.
Many years ago I experimented with differential designs. Mostly in phono stages. The results were extremely good and the total lack of capacitor coloration has some intriguing qualities. But those phono stages were very big, heavy and costly. So after going commercial with audio I decided to scale back a little and stay with the single ended designs.
I always wanted to try the same differential approach which I applied in said phono stages to a line preamp with directly heated triodes. So this was the opportunity to revive this concept.
Is it worth the extra effort and cost? Yes, the difference is clearly audible. But not huge. Don't expect big steps in sound quality from such a high level. It is more of an evolutionary step than a revolution. And honestly I am glad that the basic sound character remains very similar, despite the different circuit topology. It just improves on the strengths of the single ended concept. Resolution and tone colours get further enhanced. These are already extreme strengths of the single ended line stage. Yet the differential one can improve on them without negative side effects which often occur with higher resolution (artificial, antiseptic sound). Especially the tone colours seem truer to the original. This is due to the lack of capacitors in the signal path. Even the best caps add their bit of coloration. It also adds upon the 'lifeliness' of the presentation. It gives an even better feeling of 'being there'.
This line stage becomes the top level of my offering. It will now be built in a very exclusive version using transformers which are silver wire on finemet cores. Based on the positive results with tho line stage the differential phono stages will also get revived as an alternative series. I am also thinking about power amps to complete this line. Stay tuned!