Budget preamp with quality volume control

In-line attenutor is just a fixed output passive preamp as opposed to passive preamp with variable levels of attenuation. Not clear what "Indus" is but if Rothwell refers to their in-line attenuator, the output impedance is stated as 3750 ohms, a bit lower than the Schiit SYS (5k) but still high enough to reduce the impedance ratio (approx. 8.6) down below the desired 10. Note that the cable I was using is merely 12 inch long and my Parasound amp has a reasonably high 33k ohm input impedance. It is still likely the company’s in-line attenuator will impact on the sound quality as SYS does. As such, I have no longer considered the passive preamp or in-line attenutor option.

Some active (with gain) preamps also have attenuation function in addition to amplication, such as SPL Volume 2 (-4 dB) and some others. All the Schiit active preamps starts from a "amplication factor" (Schiit refers it as "gain") of 1 which gives no volume (dB) increase/decrease. The formula is 20*log(amplication factor). So amp. factor of 1 give 0 dB. When the amplication factor is less than 1, say, 0.63, change in volume is 20 log(0.63) = -4 dB (like SPL Volume 2 mentioned above) indicating that the preamp is actually performing attenuation. Those active preamps with gain is exactly what I am shooting for.

Every passive attenuator company says the same thing, Goldpoint, the LDR folks (i.e., Lightspeed and Tortuga), manufacturers that put attenuators in their DACs like Metrum and Sonnet, and more.  Some say it louder than others.  Hattor/Khozmo offer both options, as well as op-amp or tube active stages to follow their passives, if desired.  I have tried more than a few passives, and currently own 5 different passive units, Goldpoint, Khozmo, Hattor, Endler (attenuators that mount to your amplifiers), and an icOn 4PRO autoformer.  I have also owned the Metrum Adagio DAC, with a lossless volume control.

The ONLY one of those passive solutions that IME preserves the tone and drive to the same level of an active preamp (or active buffer), regardless of how short the ICs are, is the icOn 4PRO AVC preamp, which uses Slagle autoformers.  The autoformers (a type of transformer) have the ability to decrease the output impedance while performing attenuation.  I really like the sound of the 4PRO but I also have a custom, higher quality, Khozmo dual mono passive unit that I use in front of a SMc Audio solid state unity gain buffer, which results in a quite low impedance signal going to my amplifiers.  I like the sound of the Khozmo/SMc buffer combination a little bit better than the icOn 4PRO.  The buffer does not provide gain (above unity), but with the buffer in the path following one of the  passives, I hear improvements in bass, dynamics, tone, and drive, over using any of the passives (except for the icOn) without the buffer.  The icOn 4PRO does not suffer the losses described above that I hear from the other passives.

All that said, only you can decide what type of sound you like, and what you hear in your own room with the equipment you have.  There are many here who like having a passive attenuator, and are happy with the sound.  In the end, any of us here can describe what has worked for us but "try it for yourself" is the only answer that really means anything.

+1 @mitch2.  Thanks for the elaboration.

I did see the icOn 4PRO in action at an Audio Show - very impressive - and a very easy to use remote because it’s taking advantage of the Apple r/c.

I think that would be my choice if I were to go for anything. Helped further by your endorsement and experience with other passive preamps.

The other popular choice is the Music First - but the icOn has great convenience features in comparison.

Linear tube audio MZ2. Don’t think you can beat the quality for the price: https://www.lineartubeaudio.com/products/mz2mz2-s