Hattor Audio preamps?

I was quite happy with my dual mono, balanced unit. Unfortunately, it presented an Impedance mismatch. He sells a buffer that would have resolved it, but I didn't want to risk installing myself. Extremely well made

I have a couple DIY preamps using fully balanced Khozmo stepped attenuators which I really like. Hattor is the brand used for complete preamps from the same company. I prefer an active output stage, which Hattor also offers. 

I have not tried the AMRG resistors, but have read good things about them.  My first build uses the Takman REX resistors in the shunt positions with a Vishay Z-foil series resistor. This combination sounds excellent with exceptional transparency. My other Khozmo use Takman REY shunt resistors and an Audio Note silver tantalum series resistor. I'm still working on tweaking this preamp which uses different power supplies and output buffers, so I'm not ready to say whether I like this combination better or not. 

My Don Sachs preamp had the Khozmo attenuator and it was really nice in it's operation.

I have a balanced version with the AMRG Trans resistors. I am using it with an ARC Ref 75SE at the moment. It is superbly well built and the remote works really well. It controls volume, input, balance and has a mute. Once set up I am not sure you need much else. The sound is superbly natural, not surprising given there are only 2 high-quality resistors in the path. The only thing to watch out for is impedance mis-matches and it sounds like you have that sussed. It has equalled some very expensive preamplifiers in naturalness and clarity. If you want to alter the sound then this is not for you but if you want a neutral preamp then the value is great. It comes in a flight case and is really well made. I ordered a buffer input and all it required was to add a board, job done.

Short answer is that yes, I actually own a Khozmo and two Hattor preamps, and the Hattor Active Tube Stage, and I really like them.

The longer answer is that I became acquainted with Hattor as way to remotely control the volume in my system.  I own a very nice sounding active, unity gain SMc Audio TLC-1 preamp, which has been upgraded to a similar sound quality as their VRE preamp.  Unfortunately, the onboard Shallco VC does not allow remote control of the volume.  I worked with Steve McCormack to modify the TLC-1 so it is now a unity gain buffer achieved by removing the VC from the circuit and replacing it with two large AN silver tantalum resistors. 

With the TLC-1 as a buffer, I still needed a method of controlling my system volume and gave Khozmo a try with one of their inexpensive passive units.  I really liked the sound and the interface/remote so when I saw a Hattor Big Preamp for sale used at an attractive price, I purchased that.  Some months later, I wanted to try their tube active stage and Arek (the owner/designer) gave me a good price on a package with a Big Preamp, which is how I came to own two of them.

In my main system, I use the Hattor Big Preamp in passive mode, which provides me with a system interface that is as good as I have had with any of the preamps I have previously owned.  With the Hattor Big Preamp, you get rca and XLR inputs/outputs, a large display in your choice of color, input selection, and selection of mute, volume, and balance, all controllable using the remote.  My unit has the optional NewClassD OPamp active stage, which provides your choice of 3/6/9 dB gain, also selectable by the remote control.

Sonically, the Hattor Big Preamp is great, IMO.  I have literally owned about 20 preamps with at least two costing north of $10K before I found the SMc unit I have now, and IMO the Hattor would hang with all of them, particularly in passive mode where it seems to have close to zero impact on the sound.  You do get your choice of resistors and I chose the Amtrans AMRG carbon film resistors, which are made in Japan by the former distributor for Riken resistors.  In my Khozmo unit, I had Takman REY shunt resistors with the Vishay Zfoils in the series position, and IMO the AMRG Trans resistors in the Hattor sound more musical.

Regarding gain, I could be happy with the sound of the discrete OPamp board in the Big Preamp.  I could also be happy with the Khozmo Active Tube Stage, which sounds very good (a bit more musical/natural than the OPamp board) and better than the Tortuga and Purity Audio tube buffers I have had (on loan) here in my system.  My unity gain SMc TLC-1 buffer sounds better than all of them to me, so that is what I use - with the Hattor in passive mode providing my system interface. 

I hope this helps.   I would be happy to answer any specific questions.