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

@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

@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

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