Preamp suggestions, yes again

@markf31
Not sure if you are aware, it’s a common practice to run a tube preamp in front of the PASS / Firstwatt amplifiers. If you’ve not seen or tried it, look up Korg NuTube on the firstwatt site http://www.firstwatt.com/pdf/art_diy_nutube_preamp.pdf

A few reviewers and owners of FW and DIY amps also demoing these flat tube preamps past few years. When I was doing research on the early version ".8" Pass amps a few years ago, was quite surprised to learn from Nelson directly how many owners were already using my own Cary 6SN7 tube based preamp in front of Pass SS amps. He shared he has a "lot of customers using my same tube preamp with his amps". If you are truly looking for suggestions...

Your RP-600M and former RP160M predecessor speakers still tend to be a little bright and forward with the TracTrix. A few buddies with them use tube DACs and tube preamps in second systems, and softer input driver tubes. Folks are doing recent crossover updates on them now to help tame the RP-600Ms some more. A nice tube preamp in front of your Aleph SS amp can truly be an enjoyable way to go, fwiw.

Or, the AVA Vision SLR preamp you are considering has the switch:

• "High Filter - to tame excess brightness from low quality sources".

Best of luck on the preamp research and purchase.

Linear Tube Audio Micro ZOTL mz-2. I’ve paired it with a Pass XA-25 and it sounds wonderful. My Supratek Sauvignon is now sitting on a shelf. 

I upgraded from the Linear Tube Audio (LTA) MZ2 to the MZ3 and it was quite an improvement. Based upon recommended NOS tubes from Brent Jessee, the MZ3 provides tonality that really fits my requirements. The MZ3 drives either a tube LTA Ultralinear or upgraded solid-state SMc DNA-1.

Good luck on finding equipment that provides your tonality requirement!

If you can afford a bit more...

https://wyred4sound.com/products/pre-amps/stp-se

I absolutely love mine and I believe I'd have to spend a considerable amount more to get this sound (or lack thereof).

The exception may be the Benchmark LA4 Line at $2600.

I really love my Don Sachs Model 2.  Seems like every year he improves on the design in some small way...very smooth and revealing...and made to order.

Want to tailor for your current amp's input sensitivity and one for your next amp? No problem.  One for most SS amps and one for tube amps...just ask.  

Component matching is important...and you can build in the flexibility.  Just talk to him and he will build to your needs.