Hoping that I am not hi-jacking this thread, I would like to contribute my experience with stepped attenuators, if I may.
There has been a lot of debate among fellow audiophiles about the comparison of passive and active preamps. Each side had certain advantages to propose. I have a top-of-the-line Croft preamp, the Micro 25RSLS (line only), upgraded by Glenn.
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But I took the plunge and purchased a passive Hattor dual-mono preamp (the higher-end brand that Arek Kallas, the owner of Khozmo, has on offer).
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My Hattor passive preamp uses Khozmo shunt attenuators with z-foil resistors. In comparison to the Croft preamp, the Hattor was more transparent, more detailed, but simultaneously somewhat "thinner" and smaller in body. The passive preamp sounded more neutral, more precise, whereby the Croft sounded more alive, with greater body and more realistic. I could not say that the one was better than the other one on all points. I liked several qualities in both preamps.
And then it dawned at me. What if I could combine the best of each preamp?
So, I decided to make a small experiment. More specifically I decided to bypass the low-cost pots of the Croft (Tocos) and use the Hattor as a volume control upstream the Croft. In other words, I connected all sources (phono stage and DAC) to the Hattor and then I connected the Hattor output to one of the Croft's inputs. Interconnect cables for that connection were Mark Grant HDX1. All other interconnects were Belden 8428.
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The result? REALLY, really interesting! The combined preamps gave me both the transparency, detail, body and dynamics. The realism of the sound was upgraded. And all that, taking into account that there were additional circuits, binding posts and an extra set of interconnects than before.
After this introduction, I am now seriously thinking of having two Khozmo attenuators with z-foil resistors (similar to the ones in the Hattor preamp) installed inside the Croft preamp. This will allow me to achieve a shorter signal path than what I currently have with my chained preamps. Hopefully a remote control will fit inside the Croft box as well.
I understand that other fellow members have tried Khozmo attenuators, and there seems to be a consensus that series attenuators are better than shunt. I have not had the chance to make such a comparison, but I've liked the shunt attenuators of the Hattor (having followed Arek's recommendation).
I know that commercial (vs. DIY) hi-fi gear is built to a price point, and I have the utmost respect to Croft gear. However, in my humble opinion, I believe that Croft's designs would perform significantly better with upgraded valves (NOS instead of new stock) and switched attenuators (than carbon pots). I hope my comments are not misunderstood, I am just speaking from personal experience.