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Preamp shootout

Posted by morricab (S) on July 8, 2016 at 07:08:55

Some friends of mine and I had a preamp shootout recently. This was a great event for 4 friends to get together and do what we love best...listen to music and evaluate gear.

This time the plan was to compare some preamps in a "reference" system. So we converged on one friend's place that was the most convenient for doing the swapping and space for sitting an listening as well as the best for all to drive there.

That friend's system was the following:

Einstein "The Tube" preamp
Cayin 9084 845 monoblocks
Meitner MA-1 DAC
HMS cables
Thiel CS3.7 loudspeakers

We ended up replacing the Cayin monos with a KR Audio VA350 power amp that another friend brought "just in case" as it was the better overall amp for the speakers by consensus.

I brought with me two preamps: the PureSound L10 with Lundahl transformer upgrades and the NAT Plasma.

The host of course had his Einstein "The Tube" MkII.

The friend who brought the KR also brought his Silvaweld SWC1000R along for comparison.

The fourth friend didn't have a preamp to bring as he runs a Devialet.

We started off by using the Einstein as it was already in the system and selected a Pop/rock track with female vocals (I admit that I don't know what it was) and Hilary Hahn playing Bach. Later, we switched to some other tracks as we got a bit tired of hearing those same ones over and over.

The Einstein brings an amazing openness and transparency to the sound. Imaging and soundstage are precise and wide with good depth resolution as well. The soundstage is wider with this preamp than any of the others tested and in fact wider than any other preamp we have ever tried against it (there have been numerous other evaluations but with other amps and sources). Bass is articulate and powerful but with very good control. About the only area where this preamp merits some crticism is in the overall tonal balance, which is slightly lean in the mid or upper bass and the overall tilt is towards the upper frequencies. It resembles in a lot of ways the tonal character I recognize in OTL amplifiers. Overall though this preamp made a really strong showing...it usually does.

The first competitor to go was the NAT Plasma. This is an interesting preamp because it is fully dual mono and is tube rectified and tube regulated. The output stage uses 6 PCC88s per channel (I think in parallel but not sure). I have had this now for a couple of months and it sounds really great in my system at home. It has a very dynamic and powerful sound with high precision in the soundstage and imaging. Tonally, it is only slightly warm but this sounds quite natural and is IMO just an indicator of a robust midbass. At my friend's the sound was still dynamic but tonally not as natural (a bit grey) and the transparency not as "see through" as either the Einstein or at home. I was a bit disappointed with the performance, which while still good, other than a better overall tonal balance than the Einstein, lagged behind in other important areas...it nagged at me.

So, later on, I asked for a retest where we first warmed up the preamp for a good 30+ minutes before playing it as I suspected that what we were hearing was just a warmup issue and we had decided too quickly to move on. Once good an warmed up it was game on! The transparency was now superb as was the tonality, which is both natural and muscular. This preamp delivers real powerful sound to drive the amplifiers. The top end was extended but not spotlit. The only area now where it fell behind the Einstein was the width of soundstage and tonal balance was better. It turned out that the NAT is a quite worthy competitor and was likely one of the better audio bargains out there for a preamp when it was still available.

The second challenger was the PureSound L10. Now, after replacing the power supply caps and the output transformers with Lundahl C core transformers, the sound of this preamp has improved considerably. It is still somewhat on the warm/lush side of things but now the HF extension is better and it is no longer "darkish" sounding. So, we put it in and a lot of the dynamic punch and drive was not really there compared to the NAT and Einstein. Clarity is also a step lower and the soundstage not as well resolved. I have found that this preamp also needs a serious amount of warmup, so perhaps we didn't quite give it a fair shake. However, the basic character is one I recognized from home (although dynamics in my system were far better than represented at this shootout), so I did not really expect a winner here.

The final preamp we tested was the Silvaweld. This is a sophisticated design with all tube rectified and regulated power supply and a single gain stage coupled to expensive permalloy output transformers. I used to own one of these and I found it to be among the best I have heard when I owned it. We hooked it up and the sound was rich and dynamic but the soundstage was a bit small and the smallest details did not come through as well. The sound was really nice ot listen to but not as transparent or resolving as the NAT and Einstein. Since I know this preamp well, I suspect that this preamp is in need of a retube (both PS and circuit) and readjustment of the bias settings. So, while it fell behind the leaders, I don't think it put its best foot forward.

All-in-all, I would give a slight nod to the Einstein as the winner, unless your system is on the analytical side in which case I think the NAT is better balanced for normal to lean systems. The NAT, after sufficient warmup, was very good sounding being bold and tuneful. The PureSound did not sound bad but was not really in the same class sonically. The silvaweld was quite good but missing a bit of resolution that to me sounded like old tubes in need of replacement. I would really like to hear it again in fully optimized form.

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