I have been using tube preamps and passives in my system for decades, and always unfairly dismissed using solid state linestage use. I do have a PassDIY B1 buffer, but it is capacitor coupled (on both ends), and therefore have to deal with the sound of these components. However, recently, experimenting listening to my DAC (Chord DAVE) as a preamp revealed the colorations these can have. Also having a vinyl system complicates just using a digital only system, and I have been experimenting with digitizing vinyl on the fly using an ADC to limited success. However, it would be better to not go through the conversion if I can help it.
I picked up the Wayne's BA 2018 board and parts kit from the DIYAudioStore and finally built. Wayne Colburn, for those you do not know, is the preamp designer at Pass Labs. This was just a throwaway project to the DIY community, as both Wayne and Nelson Pass is prone to do. It is a DC coupled discrete opamp design, with JFET input (using Toshiba 2SK208 SMT JFETs), and BJTs for current sources and output stage. Just completed the build a couple days ago and it is breaking in on the system. It is possible to adjust the gain via the feedback resistor, the default is 3.7 with a 10K resistor, but I have set it at around 2.5 using a 22K resistor to better fit in with my overall gain structure (been using passive attenuators for years, all my amps have enough front end gain). I find the clarity and transparency to be better than my recent 12SN7 Aikido linestage, and the drive and control that the active gain stage results in my tube amplifiers sounding more solid and powerful. The problem I have found with passives is often a slight thinness or lack of body, although they can be very transparent. The new linestage is absolutely quiet and very detailed sounding, with an expansive soundstage and a hint of warmth (but not so much as to be a coloration).
I am using a bipolar +/-15V power regulated power supply from a Pete Millett LR Phono stage that I am not using currently, the preamp is cased in a spare Hammond extruded aluminum enclosure I had on hand. I started with a NOS Alps Black Beauty 50K conductive plastic stereo pot, but just received a pair of 50K Mono series attenuators from Hong Kong (Design by Mr.K) that are very nicely built, similar to the Khozmo, and they went into the preamp this morning.
Anyway, I am coming around to the sound of a low gain solid state linestage, finding it works really well with tube amps. I am already using a solid state phonostage (iFi iPhono3 Black Label) that I found is significantly better than all my DIY phonostages I have built over the years. So maybe there is something to this solid stage stuff after all. Still using tube amps (I have enough of them!).
Some gratuitous pics follow.
| Attachments: |
|
IMG_0022 Copy.jpg [ 1.2 MiB | Viewed 22033 times ] |
|
IMG_0021 Copy.jpg [ 490.35 KiB | Viewed 22033 times ] |
I replaced the output caps with bobbins and added test points to revisit the offset.
Probably make a decent headphone amp too (if you go for that kind of thing) 