If You Were A Swine Looking To Choose Between 3 Preamps...

I’ve dealt with impedance matching for many years now, having the product that I have.

With impedance matching if one stays with the 1:10 or higher ratio you’ll have things covered. This goes for source to pre and from pre to amp/s

All you have to worry about then is if the "1" (source or pre) has an output coupling cap, (if they’re dc coupled no problems) and that cap is large enough to maintain that impedance 1:10 ratio flat from 20hz to 20khz you’ll have no problems

If not and it’s too small you may get a change in that ratio in the bass maybe down to 1:2, if this happens because of that coupling cap being too small then you’ll get a "voltage divider" scenario happening in the bass rolling it off too early, maybe at 50 or 100hz and giving a thinner sound with lack of perceived level in the bass.

Cheers George

dont ask a swine to pick a preamp
it dont work
and only annoys
the swine

@almarg 

Ah yes, I see what you are referencing. And Henrys other amps have nowhere as low input impedance, this one seems to be an outlier. It does indeed look like a SS preamp with low output impedance is in order. That changes things. I guess we will see how this Edge pre amp works when it arrives. It is another odd one, and I cannot find the output impedance on the Si-M1 either. So we will have to see how that works out. 

@neonknight

As far as I can see that review does not address the H2O Audio S250, in either the Signature or non-Signature version.

Here are two sources indicating an 8K input impedance. Note that at the first link the 8K number is stated by Mr. Ho himself, for the Signature version.  (The second link is for the non-Signature version):

https://www.audiogon.com/listings/solid-state-h2o-audio-s250-signature-analog-icepower-amp-2014-06-0...

https://www.gearogs.com/gear/83438-h2o-audio-s250

Regards,
-- Al

@almarg 

Are you sure about that number? In this review and comparison I found the input impeance of the amp listed at 100K. 

http://www.highfidelityreview.com/monarchy-audio-se-250-vs-h2o-audio-signature-100.html

@dbphd    Nearly all preamps will be able to handle a balanced input impedance of 100K with no problem. And that is certainly true in the case of the Ayre KX-5 Twenty, which per Stereophile's measurements has a balanced output impedance of about 156 ohms at all audible frequencies.

However, I see in those measurements that the Ayre provides essentially zero gain for its balanced output (and negative gain from its unbalanced input to its unbalanced output). While your JC2 BP provides 14 db of gain (with its volume control at max). So with the Ayre you will find yourself having to turn the volume control up to a significantly higher position than you are used to.

If the minimum setting of the volume control on the JC2 BP is around the 6:30 or 7 o'clock position, and the maximum setting is around the 5 or 5:30 o'clock position, a 14 db change probably corresponds to a little more than 90 degrees of rotation. If you presently use volume control settings in the top third or so of the range of the volume control on the JC2 BP, the Ayre's lack of gain would be a definite concern.

Best regards,
-- Al

almarg -  I appreciate your analytic advice.  I'm using Parasound JC 1 monoblocks (100 kΩ bal input) with a JC 2 BP preamp (60 Ω output). I'm trying to predict how well the JC 1s might pair with a Ayre KX-5 Twenty preamp, but Ayre doesn't include output impedance in the specs.  I'm currently using the Ayre preamp with a VX-5 Twenty (2MΩ bal input) stereo amp, but expect to consolidate two setups into one in the future.

db 

Swine - you don't mention price or budget.  A used Allnic will probably cost more than a new Herron Audio VTSP-360 and will likely NOT outperform the Herron.

P.S: I subsequently found the following output impedance spec for the Line Magnetic preamp:

Output impedance: 600kΩ balance output 600Ω (RCA)

The 600kΩ spec is nonsense, as the design wouldn’t work with that kind of output impedance. The 600Ω number is probably based on a mid-range frequency such as 1 kHz, but given that the preamp’s output is transformer coupled its output impedance probably doesn’t vary greatly at other frequencies (as it probably would if the output were capacitively coupled). So it **might** be marginally suitable for use with an 8K load.

Regards,
-- Al

Your amp has a very low specified input impedance of 8,000 ohms. Many tube-based preamps will not be able to drive such a low impedance with good results. I would expect that to certainly be the case with the TRV 4SE, which has a specified output impedance of 7,000 ohms, that might be even higher at some frequencies!

The Allnic would be fine in terms of impedance compatibility with the amp. Although you would want to verify that its relatively low input impedance (10K/20K unbalanced/balanced) would be a suitable load for your source component(s), especially if they are tube-based.

I couldn’t find an output impedance spec or measurement for the Line Magnetic, but I would have my doubts about how well it can drive 8K.

Good luck. Regards,
--Al

I have an Edge signature 1.1 se and it's  a fantastic pre. Also have an Allnic L3000 tube pre that I switch in an out. Both are top quality 
Preamp. Best wishes

Buy the Allnic. Nothing that is mentioned here even comes close if you want a flexible, well constructed piece of equipment. It produces a very
smooth and detailed sound with a large 3D sound stage. 

Save your money and continue to use the pre outs of the Musical Fidelity. That's an excellent sounding and built unit! Anything else is just a side-wise move!

    I haven't heard the three preamps you're looking at,however they all seem to come from very good manufacturers. The only thing that would make me shy away from the LM pre is having to use a step up transformer, but that's me. Best of luck with the search!

I would take a good look at deHavilland HiFi very affordable and excellent preamplifiers.