Hattor Audio preamps?

@toro3 

"I know you and @mitch2 have Aric Audio amps and Hattor preamps"

@ozzy62 has Aric Audio amps but not me.  I have a pair of 650wpc monoblocks made by SMc Audio using formerly McCormack DNA-1 amps as a starting point.  Actually, I believe the only parts used from the DNA-1s were the chassis and heatsinks!  Mine are the black pair at the bottom of the first grouping of pictures on the home page.  

Although my custom built Khozmo volume controller is passive, I send the signal thorugh a unity gain buffer based on SMc's VRE-1 preamp circuit.  My system is basically the opposite of Ozzy's system that uses high sensitivity speakers and tube amps.

No apology necessary.  Just wanted you to understand that what I hear in my system could be very different than what somebody hears in a system using low-powered tube amps with high efficiency speakers. 

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.

The impedance issue can be more involved than simply verifying a 1:10 ratio (which many consider a minimum with a more desirable number being 1:20 or higher).  For example, many preamps (and particularly tubed preamps) have output impedance that is significantly higher at frequency extremes (particularly at bass frequencies) than at 1K Hz which is the typical frequency where the output impedance is reported.  In those cases, the reported output impedance (i.e., at 1K ohms) can result in one ratio while the actual ratio at frequency extremes could be much different (i.e., lower).  JA at Stereophile used to regularly report about this in his measurements of (mostly tubed) preamps.  Below is an example from his review of the Lamm LL2 Deluxe:

The LL2's output impedance was a low 245 ohms in the midrange and treble, this rising to 3.3k ohms at 20Hz, presumably due to the finite size of the output coupling capacitor. As a result, the preamp's frequency response suffered from a premature low-frequency rolloff into the low 600-ohm load (fig.1, lower pair of traces). Into the higher 100k-ohm load (fig.1, top traces), the response is flat from 10Hz to 50kHz and just 1dB down at 200kHz. 

It also becomes important with passive volume controls (i.e., passive linestage) where the output impedance is dependent on the impedance value of the volume control, and where the IC cable impedance becomes more important without active circuitry (which is why most recommend very short cables when using passives).  

Regardless of what Paul says in the video, there are still solid state amplifiers with input impedance as low as 10K ohms.  This is rarely a problem when using active solid state preamps, which typically have output impedances in the range of 100-200K ohms, or lower.  However, amplifiers having low input impedances will not likely reach their full sonic potential when driven through a passive line stage.  For this reason, the sonic impact of using a buffer (i.e., active circuitry to address output impedance) between a passive preamp and an amplifier can vary significantly depending on the differences in input impedance between amplifiers.

@tnk1998 

I still own two of the Big Preamps and more recently had Arek make a custom Khozmo dual-mono passive using his best Amtrans AMRG resistors and volume control from the Hattor, upgraded connectors, and only a single input and output (i.e., no switching) that I use to remote control the volume and provide a display into my solid state, unity-gain buffer.

The Big Preamp is IMO hard to beat for the money and for what you get wrt the volume control, remote, display, balance, connectivity (RCA and XLR), flexibility (i.e., passive vs. active with variable/switchable gain), and of course sound quality.  I also owned the Hattor Tube Active Stage, which is quite nice as an option to their op-amp active stage (my Hattor preamps have the NewClassD op-amps).

Do you have specific questions?

@pioneerhip 

Not sure how I responded to the wrong member but my post below from earlier today was intended for you.  Hattor’s The Big Preamp is a very good sounding preamp and a great value.  Let us know if you have any specific questions.

Earlier this year, I owned the icOn 4PRO AVC balanced passive preamplifier that uses four Slagle autoformer volume control modules. It was seductive in how the music was presented with the warmth described by @ozzy62 coming from a dead quiet background. I really enjoyed listening to it, and the Django TVC, if at all similar, may be just the thing for you. Ultimately, I slightly preferred my Khozmo volume control/SMc Audio TLC Signature Buffer slightly better, so I sold the icOn AVC unit.

I have not spoken with Arek since earlier this year and I am a bit surprised to hear he would recommend the AMRT resistors over the AMRG version. Both are carbon film but the AMRG appears to be Amtrans Corp’s more upscale version based on their higher pricing, gold-plated OFC lead wire, and description as "High-end carbon resistor." The AMRG resistors sound better to me than the Takman REY metal film resisters I had in an earlier Khozmo passive volume control. I have not heard the Takman REX or AMRT resistors. I suggest doing some research and talking with Arek before deciding on resistors.

@pioneerhip 

In a different thread you asked about Hattor's Tube Active Stage and I said I would answer here in this current thread.  I have cut/pasted and slightly edited portions of a couple of my previous posts that I believe will answer your questions about the Tube Active Stage:

Active Buffers

The functional purpose of an active buffer is to improve impedance mismatches by reducing higher impedance inputs to lower impedance outputs.  This can be helpful when driving amplifiers with low input impedances, when using passive volume controls that do not actively buffer the signal, and/or when driving long interconnects.  The effect can be significant, even in cases of unity gain (i.e., no net voltage gain between input and output), and the change in sound is sometimes described as having more body, tonal color, and drive.   Active buffers can be either fully solid state or tubed.

Tube Active Stage

I use the Hattor Audio Big preamp in passive mode to control the volume of my system and it sounds significantly better to me when followed by my SMc Audio buffer (solid state and unity gain) that is based on their VRE-1 preamp.  I also have the Hattor Audio Tube Active Stage, which is a tube buffer that typically comes with 9dB gain (mine has 6dB).  It is basically a tube buffer stage without a volume control. I have tried the Tortuga Tube Buffer on one of their tours, so I had it in my system for about a week, and I also tried the Purity Audio tubed buffer in my system. 

IMO, and in my system, the Hattor Tube Active Stage sounds very good although it just doesn't provide quite the magic of my SMc Audio TLC Signature buffer, so it is currently sitting in a box.  However, if I didn't have the SMc buffer, I would be perfectly happy to substitute the Hattor after my passive volume control.  

The Hattor Big preamp also comes with an opamp active stage (mine has the NewClassD discrete opamp stage), which can be set to 3/6/9 dB gain.  I bypass the active stage to run the Hattor as a passive into the SMc buffer.   However, I have tried it through the discrete opamp stage and I also find that to be an improvement over running it passively.  Therefore, in ranking buffers (some with low gain) in my system, I would put the solid state SMc Audio buffer first and the Hattor Tube Active Stage second, both of which I would be happy to use.  Third would be the discrete NewClassD opamp stage in the Hattor Big preamp, which I would judge as just a small step below the first two, although others may reverse the order and prefer the opamp stage over the tubed stage - they are close.  Finally, I just did not like the sound of the Tortuga or the Purity Audio buffers in my system.

and, more thoughts...

As I remember it, I was impressed with the sound through the internal NewClassD op-amp active stage of Hattor’s The Big Preamp. The drive, dynamics, and clarity were very good.  My recollection is that I could live with either the tube stage or the internal op-amp stage. 

I don’t now why the normal rules wouldn’t apply - passives work best being fed a low input impedance signal (<200’ish ohms) then output to a high impedance amplifier input (>50K ohms) and being positioned so the output IC only needs to travel a short distance to the amplifier (<1.5M).

Even if you meet those guidelines, some (but not all) still find their passives lacking in tonal body and drive that active stages seem to provide.  The only passives I didn’t have that issue with were AVC types.

@bornagainaudio

"- is there a simple answer?"

Sort of. Two companies run by the same guy (Arek Kallas) from Warsaw Poland, offering a couple of different types of discrete resistor volume controls, but Hattor has the more upscale, complex products with better looking casework while Khozmo offers more simplistic solutions, at lower prices, in more basic looking casework.

Because Arek will customize the builds from either company, you really can have it your way. I use a Khozmo volume control in my main system, but it is made from two separate volume controls (i.e., dual mono operation), has a display and full remote control of L/R volume and mute, plus on/off and display illumination. The attenuators are Hattor/Khozmo’s best using Amtrans AMRG resistors. It is in a Khozmo metal/wood case and has no switching, only a single balanced input and a single balanced output with Furutech connectors.

So, it is a very well made Khozmo badged unit but also very simplistic and in modest but nice-looking casework. The sole purpose is to passively control the volume ahead of a unity-gain, solid-state buffer that feeds my amps, and to allow me to remotely operate volume/balance/mute for my system and to see the result on an easy-to-read display. I also own two Hatter "The Big" preamps, which are very nice sounding units with much more functionality than my Khozmo by providing various single-ended and balanced inputs and outputs, and both passive or active operation with switchable gain from 3 to 9 dB. I used to own their Tube Buffer, which was very nice sounding as well.

I believe they still offer SMD Vishay, Amtrans AMRT or AMRG, and Takeman REX (carbon) or REY (metal), at least in the Hattor line.  I suggest emailing Arek directly to discuss possibilities for your specific project. 

My first Khozmo passive had Takeman REY resistors and I later gravitated to AMRG resistors in my current Khozmo and two Hattor units. You may also want to look at this video and do some searches on resistors.