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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
milpai's avatar
milpai
2,452 posts
 
Dave,
I agree with you that with a resistor-based volume control, the extra voltage is discarded in the form of heat. In addition the more resistance that is applied by the volume pot, the more the signal is compromised – usually in the form of compressed dynamics.
It is important to note that the output voltage specification on a source component represents the maximum output level when playing a disc that is recorded at the very highest possible recording level. Nearly all CDs are recorded at a level where the musical peaks never reach the maximum signal level that can be recorded on the disc. As a result, very few discs will ever result in the CD player outputting its full 2V potential even when playing the loudest passages of music on that disc.
So I believe, even in case of Lightspeed a high output volt from the source is better for the sound quality. I mean, I would any day take 3.9V from source over 2.0V.
pubul57 OP
3,712 posts
 
Actually, the voltage is 2v and 3.6v unbalanced. THe manual says output impedance is 50ohm, the brochure says 150ohms unbalanced - whatever it is, it seems to have no problem driving the Lightspeed Attenuator. Seems that there seems to be no reason not to use the higher output setting, and theoretically a good reason, though it does not seem like they are using a voltage divider (but just in case).
intactaudio
304 posts
 
Milpai,

What is this CD you talk about? Is it some kind of new format?

Obviously recording levels are all over the map and ultimately it is up to the end user to educate themselves and see what works for them or be doomed to repeat the same mistakes.

These are all simple attenuators and they must exist in some form in every system. Who decides which box they go in and what they are termed is just a matter of semantics.

I say learn to think outside the box and get your gain, headroom and impedance structures inline then choose the attenuator that sounds best to you.

dave
fiddler
581 posts
 
I have to eat a little crow.

I posted earlier that I preferred my Supratek linestage to the LS due to an added dimensionality and warmth that tubes offer with all other thngs being equal between the two.

Well, reading this threat spurred me to put the LS back into my system for another listen. I'm glad I did.

The first time I compared the two I simply connected the LS to my system with it sitting on a cardboard box on the floor. This time I went to the trouble to take my Supratek out of my system and I put the LS on the same shelving and footers I use with my Supratek.

This time I must say the LS is slightly more transparent, with equal slam, warmth, tonality soundstage width, etc. The only area that may be up for grabs is on some recordings the soundstage is slightly more forward with the Supratek. I'm not saying that is a better thing, but rather a simple difference.

To be honest, the two are so close that I have to really, really, really try hard to tell the two apart. I listened to several recordings that I know exceedingly well and I swear had I not known that I took my Supratek out of my system, I don't think I would have noticed.

The biggest problem I have with my Supratek is getting good 6SN7's, both NOS & current production, that don't have issues at some point, i.e. microphonics, loud hissing (not typical tube noise), whistling, cracking & popping, etc.

I just purchased a pair of the new Shuguang Treasure CV181-Z to try. They sounded as good or better than any NOS 6SN7 I have ever tried, including TS RP and 52 Bad Boys. However, one went extremely microphonic between 30-40 hours. As much as I love tubes, they frustrate the crap out of me at times.

So, I am sticking with the LS for the time being. I tried to be as objective as I could between the two preamps and when comparing apples to apples (same shelving & isolation) I have come to the conclusion I don't think I could tell them apart in a blind test.

Thanks for an incredible product George at an unbelievable price.
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