I have had the following sort of affordable preamps in the last 3 years:

- Schitt Freya+

- Topping pre90

- Benchmark LA4/HPA4

- Holo Serene

The Benchmark and Holo are better than anything at any price from my perspective of how a preamp should work. That is no noise on the speakers, no addition to the sound so all  you hear is the other gear, and a great volume control.

I am going to sell my LA4 because I want to get the HPA4 (again). I now have a way to use the headphone amp of the HPA4 with my RAAL phones. I could not before.

I forgot I also have a Schitt SYS, $49.

Schiit Audio: Audio Products Designed and Built in Texas and California

It is surprisingly good. I used it a few times with a FM tuner.

1+ on the LA4. I have been saying this for almost a decade now. I got laughed out of the "Best Amp" thread for saying this a few years ago. Using the LA4 or (Holo Serene preamp) with really great gear is not a mismatch.

Since we are excluding Shitt I will add that I got the new 

https://www.schiit.com/products/mjolnir-3

preamp/headphone amp. It has to mostly work as a preamp to my Schitt Aegir amp and then into my headphones. The integrated headphone output will be used with a second headphone I have.

I was thinking of getting the Benchmark HPA4 which has similar functionality (and more) to replace my Benchmark LA4 preamp. However, I decided to get 2 preamps and save my self the chance of accidently messing up my system using 1 preamp with 2 amps.

I have 15-days to decide if this Schitt can make me happy given my expectations from using the amazing LA4 preamp. The Schitt Freya+ was not as good for me as the LA4.

Back to Schitt again. This new preamp from them is the best I have heard from them (including Freya+).

Schiit Audio: Audio Products Designed and Built in Texas and California

MJOLNIR 3

CLASS A HEADPHONE AMP & PREAMP

As a headphone amp it fails my very demanding phones (but that is OK). Less demanding phones are likely great with it. As a preamp into 2 amps (used for headphones and 2-channel) this thing is great. On the headphones it is reference class via the 20-watt ’Class A’ Schitt Aegir amp. As 2-channel to my Magtech amp (500-watts) and Magnepan LRS+ it is really good.

The Aegir path is better than even my Benchmark LA4 or Holo Serene preamps. On the Magtech path I prefer the other 2 but most would likely prefer the Mojolnir.

This preamp is on a limited run by Schitt. I am sure the reviews will be great.