Kinki studio EX-M1, EX-M1+ differences... vs Denafrips Hestia/ Hyperion combo?

Ie… “When matching preamps to power amps, a general rule of thumb is for the load (amp) input impedance to be at least 10 times higher than the source (preamp) output impedance to provide a suitably flat frequency response. Many prefer using a minimum ratio closer to 20 to 1, or having an amp with input impedance 20 times or more greater than the preamp output impedance. 

With solid state preamps, this is generally not a problem since most have output impedance of only a few hundred ohms or less, while most SS amps have input impedance of at least 10K ohms. However, you must pay much closer attention when trying to match tubed preamps to SS amps, since many tubed preamps have an output impedance of several thousand ohms or greater. Another thing to watch is how the output impedance spec is reported, since it is sometimes limited to a measurement at a given frequency such as 1K Hz, while the actual output impedance may vary with frequency. It is not unusual for the output impedance of tubed preamps to rise significantly as the signal approaches a lower frequency of 20 Hz, because of the size of coupling capacitors used in the preamp. In these cases, a low frequency roll off can occur whereby, for the same power output, the lower frequencies drop in output compared to the rest of the frequency range, resulting in a loss of deep bass. 

The good news is that most tubed amps have sufficiently high input impedance to allow the use of most preamps, tubed or SS. Also, for SS power amps, input impedances of around 50K ohms and above are common and these amps should work well with the vast majority of tubed and SS preamps.

Only a couple of manufacturers make SS amps with input impedances of 10K ohms (e.g., McCormack DNA500), and a couple (such as Pass) make SS amps with input impedance of 20K ohms. These lower impedance amps would require careful matching with tubed preamps. If you are trying to match a preamp with one of these lower input impedance amps, you should try to find information on your preamp's output impedance throughout the entire frequency range. Some manufacturer's report this information and some do not.”

Finally, a manufacturer that bridges dac to amp with a unity gain design optimizes both impedance and voltage relationships.  The unity gain steps down the voltage and the voltage regulators are an essential function of the preamps.  The systems voicing has been carefully considered and designed for.  Dropping in a wildcard component will have unpredictable consequences.  Many audiophiles go thru myriad system configurations and never fully understand what or why, what effects what.  Play around with moving coil cartridges and SUT’s feeding into adjustable phono stages and one will get the idea of how complex and inter-related the system chain really is.  There are 100 ways to get it wrong, that’s the fun and the education.  Bottomless, always something else to learn.  By adding a sub into my system it is much easier to hear which output tap is optimal on a tube amp, in fact it changed my preference.  I’m certainly not saying the Denafrips products are end game but like Kinki, offer a high value, low relative cost, solution if the more organic sound of what tubes offer, is desirable in a ss configuration.  Of course speaker matching, source, ect. are still ‘make or break’, but if one wants to explore and play a bit on the ‘dark side’, the Denafrips product catalog is fully fleshed and well thought out with all the goodies at attainable, every guy/gal, pricing.  The niche they fill, they fill very well.  What your ‘absolute sound’ is, is for you to decide.  It is a hobby after all.

Here’s a final bit on the importance of voltage…

“If you think of your preamp as a source, and your power amp as a load, then you may consider that maximum power transfer can occur when the output impedance of the preamp matches the input impedance of the power amp. However, in high fidelity audio, it is typically considered optimum to have a source with low impedance connected to a load with high impedance. In that case, the power that can pass through the connection is limited by the higher impedance (so power transfer is not maximum), but the electrical voltage transfer is higher and less prone to corruption than if the impedances had been matched.”

To which almarg replies, “I'll just add a little emphasis to your mention in the first paragraph that power transfer is completely unimportant between preamp and power amp, as well as for any other line-level interfaces. What matters is transferring the signal VOLTAGE accurately”

Denafrips knows what function they need their preamps to provide to their amplifiers.  Unity gain, a constant, considered, regulated voltage to impart the optimal audio signal and attain their desired voicing performance, would suggest they don’t wish or require excessive voltage gain at the amps input.  If I connect the Benchmark Dac3 direct with 0 attenuation, I can begin to introduce a touch of distortion, a slight ‘digital glare’ that is why Benchmark usually suggest the 10 or 20db pads that yes changes the output impedance, but more important into the 22000k Hyperion, it’s 4V input voltage.  
 

@jackd 

The Verity's are driven by either the BHK 250 or the Kinki EX-M7 with the Supratek Chardonnay.

I noticed that, due to their amps being direct DC coupled, Kinki advise against using their power amps with tube preamps as DC offset could cause tics or pops through the speakers or even burn out voice coils.

Did you have any issues feeding the EX-M7 with the Supratek Chardonnay? I'm not sure if it matters but are you using SE or balanced cables betwen them?

I can't find any reviews or listening impressions where the EX-M7 (or B-7 monoblocks) have been fed by a tube pre-amp. I was hoping to feed my Herron VTSP3 tube preamp into an EX-M7 rather than go all solid state ... but now I'm a little apprehensive.

@dkerr 

I've used the EX-M7 with both the Supratek Chardonnay via XLR and the Don Sachs Model 2 via RCA and had no problems with either.  The problems that Srajen had when he tried both his Nagra and later his Vinnie Rossi preamps had to due with the type of tube regulated power supply they use.  You should have no issues with your preamp. The EX-M7 is a single ended amp and the XLR inputs are strictly convenience.  I use them so I don't have to swap cables out if I substitute in the BHK 250 which is fully balanced.  

Just an update on the Hyperion and Athena preamp.  This has been a really nice combo on several sets of speakers.  The Zu DW’s just gobble up the combo and the combo does jazz, rock, blues, folk and grunge with aplomb.  More surprisingly to me has been how a pr, of ProAc 1sc thrive with the pairing.  Really, these guys will make one rethink using tubes in a system.  Initially I thought the pairing too ‘dark’, but something happened.  Now it’s a really great combo.  I’m not sure if adding the Rel T9i or a solid 4 months of break n’, but just, wow!  Everything is done with such conviction, energy, and propulsion you can’t help but be pulled into a connection with the music.  The system has fleshy, colorful, textured, mids in a way a bunch of lit bottles are usually required to provide.  There’s meat on the bones of the musicians.  Visceral and quite addictive, I’ve attempted to roll back in my tube amp, but I keep coming back.  This setup is both beauty and beast.  Hyperion and Athena does everything well, which really makes it fun.  Fronted by a Benchmark Dac3 HGC it got depth, drive, dynamics and detail out the ying/yang.  Vinyl/tape fed thru the HGC’s analog input sound terrific also.  I can see how this could make a guy give up tubes.  There’s plenty of resolution and it’s all in the right places.  There is a dimensionality and richness along with authority down low.  Cymbals and vibes sound great to, lots of shimmer, bite, and decay. This would be a terrific combo with the new Soul 6, which I can’t afford.  At some point I need to try one of the Denafrips dacs, but why, when this is so darn good?