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Lightspeed Attenuator - Best Preamp Ever?

The question is a bit rhetorical. No preamp is the best ever, and much depends on system context. I am starting this thread beacuase there is a lot of info on this preamp in a Music First Audio Passive...thread, an Slagle AVC Modules...thread and wanted to be sure that information on this amazing product did not get lost in those threads.

I suspect that many folks may give this preamp a try at $450, direct from Australia, so I thought it would be good for current owners and future owners to have a place to describe their experience with this preamp.

It is a passive preamp that uses light LEDs, rather than mechanical contacts, to alter resistance and thereby attenuation of the source signal. It has been extremely hot in the DIY community, since the maker of this preamp provided gernerously provided information on how to make one. The trick is that while there are few parts, getting it done right, the matching of the parts is time consuming and tricky, and to boot, most of use would solder our fingers together if we tried. At $450, don't bother. It is cased in a small chassis that is fully shielded alloy, it gets it's RF sink earth via the interconnects. Vibration doesn't come into it as there is nothing to get vibrated as it's passive, even the active led's are immune as they are gas element, no filaments. The feet I attach are soft silicon/sorbethane compound anyway just in case.

This is not audio jewelry with bling, but solidly made and there is little room (if any) for audionervosa or tweaking.

So is this the best preamp ever? It might be if you have a single source (though you could use a switch box), your source is 2v or higher, your IC from pre-amp to amp is less than 2m to keep capaitance low, your amp is 5kohm input or higher (most any tube amp), and your amp is relatively sensitive (1v input sensitivity or lower v would be just right). In other words, within a passive friendly system (you do have to give this some thought), this is the finest passive preamp I have ever heard, and I have has many ranging form resistor-based to TVCs and AVCs.

In my system, with my equipment, I think it is the best I have heard passive or active, but I lean towards prefering preamp neutrality and transparency, without loosing musicality, dynamics, or the handling of low bass and highs.

If you own one, what are your impressions versus anything you have heard?

Is it the best ever? I suspect for some it may be, and to say that for a $450 product makes it stupidgood.
pubul57
kevinzoe
163 posts
 
Hi Guys,
My Lightspeed was delivered today and it looks well made. I've fired it up but it's too early for any critical listening. So far, it sounds very good!
grannyring's avatar
grannyring
4,637 posts
 
I have one comment or concern that I see in this otherwise great thread. It seems when one person has a different experience or opinion on this preamp their comments are dismissed and marginalized very quickly by some.

The reason must be system match or how the amp was made etc…but rarely is it simply accepted that another actually preferred the other preamp in a side by side test.

I can tell you the Samson amps by TRL do have the input impedance spec mentioned already. I can tell you I tried the Lightspeed with Atmasphere Ma1’s that have an input impedance of 100K ohms. My comments match those of Knghifi very closely. Our fine tube units simply performed better to our ears with no other reason than our own ears and likes.

This is OK right? The Lightspeed is also a good preamp, but won’t win every a/b shootout right?

Your thoughts?
clio09
2,978 posts
 
This is OK right? The Lightspeed is also a good preamp, but won’t win every a/b shootout right?

Your thoughts?

Of course it's okay and I wouldn't expect it to win every shootout. The fact it can favorably compete with preamps that cost at a minimum 10x as much and in Knghifi's case significantly more is an extremely positive statement all by itself. Let's not forget that it beat out some great preamps too.

Just for the record, it's been stated numerous times in this thread that certain conditions must exist in order for the LSA to work optimally. I don't see any harm in questioning whether those conditions existed. It's critical to ensuring the LSA was evaluated properly. Assuming it was, and both Knghifi and I both verified as much by indicating the proper specs for the amp, then you're right, it comes down to preference.
pubul57 OP
3,712 posts
 
Who dismissed Knghfi's observation? But asking whether or not there was a good impedance match is a valid question given the problems any unbuffered passive would have without a good impedance match (and short cables, and high sensitivity amps for best perfromance). Not sure any one suggested that he does not prefer his VAC to the LSA, it is one of the finest tube linestages available, so why doubt it? The fact that someone accustomed to such a high quality linestage would be willing to use the LSA on hot months, speaks well enough for the LSA in my view. What I would say is that for $450, anyone following this thread should give the thing a try and decide for themselves, but I certainly respect any listener's preferences and observations.
georgehifi's avatar
georgehifi
4,966 posts
 
Clio09 mentioned that "Paul Weitzel told me he does not like FETs or MOSFET" so all I said was "being the Samson is all solid state, that if it's not fet or mosfet input it would have to be bipolar", and any tech will tell you that it's highly unlikely to be 100k input impedance with bi-polars on the input stage. Look at any bipolar input amp, most are below 47k usually 10k to 30k, as dc offset problem arise if higher than this with an open circuit input.
Cheers George
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