after having modified my amp something remarkable happened. i started to listen to the amp with the RFT DF97 - Philips DL92 combo and really was blown away because of the unbelievable precision, detail and micro detail, texture and a clearly increased soundstage width and especially depth.
at first i thought it must have been a result of the modification itself using the dl92 in power safe mode so resulting in a better separation between the df91 and the dl92 stage heating power lines.
after having spent two days of listening the amazing result was, that the RFT DF97 was responsible for this changes:
The RFT DF97 has an amazing level of detail and fine detail and a soundstage width and especially depth to dream of.
i then tried different dl92 or compatible tubes with the following results:
The RFT DF97 - Philips DL92 combo is the absolute dream set when it comes to soundstage, detail, bass and bass texture. i never heard something like that.
this combo has a level of resolving the music that is unbelievable. each single instrument, voice, string has its own dimension, soundstage ,attack, decay, space around up to a level you could measure the size and distance. the only problem of this combo and this is the only problem of the RFT DF97 that at high level the sound and the highs can get slightly harsh, but layering, imaging, bass, bass depth and texture are exceptional.
This combo is wonderfull for voices, strings, classical music, but also listening to pink floyd, the wall (i never heard this recording so 3D like and real) is pure fun. the presentation is so full of details that it really forces you a little bit to listen to, activ listening is needed, not relaxed sounding due to the attention needed, but in any other aspect a real step up on the ladder of sound quality.
i tested my usual dl92 standard tubes and while bass texture is best of best with the Philils DL92 one could classify the tubes as follows in combination with the RFT DF97:
Philips DL92 - great bass texture, slightly warmer sounding than the others, but not warm like the Mullard-Phillips Combo
Tung-Sol mil-spec DL92 - Just in the middle, neutral to slightly bright, slightly less soundstage especially width, exceptional detail and high resolving
Tesla 1L33 - more on the bright side of sound, moving all the properties more to the midrange and highs - higly analytical - depending on the music slightly harsh at high volume, less bass and bass texture
a very fine and detailed sounding combo is also the RFT DF97 - Siemens DL92 combo.
i testes also some 1s4 tubes with rather average results, but today i got two PHILCO 1S4:
The RFT DF97 - PHILCO 1S4 combo is a real dream set, because it has all the properties of the Mullard DF91 - Philips DL92 combo (slightly less bass texture) but is a warm sounding combo and at the same time the first warm, beautiful and relaxing sounding combo with nevertheless no missing detail, fine detail, bite, attack and sparkle / highs and this great soundstage width and especially depth.
to be on the safe side i bought in total now eight RFT DF97 and one additional PHILCO, now having three of them with this special cardbox with the old fashioned font used.
can't wait to listen to the RFT DF97 - Mullard DL92 combo!
Edited by GermanGuy - 8/28/13 at 5:07pm