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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
grannyring's avatar
grannyring
6,519 posts
 
Scott, that would only be in a small room with highly efficient speakers. I assume that combo won't play at 95db in a larger room with speakers under 90 db efficient?

I also assume that combo would never have the dynamic impact of a more formidable set-up. Say 300-500 watt monoblock amps and an active tube preamp with killer drive and scale.

I must say this thread is interesting as I read about folks letting go of $18,000 preamps and the like. I have heard the RM10 and passives with 90db efficient speakers and while it sounded musical and very good the system was certainly dynamically limited in a medium sized room. I would certainly say it did not come close to approaching the impact and scale of live music or systems costing $20,000 with different gear.

My $8000 amp and pre combo does in my large room.

I have a question for you owners of this exciting volume pot. Will it work well on speakers that are 87 db efficient like Soundlab speakers and other ESL's? I say this assuming the amps are very powerful and the spec criteria mentioned by the poster are meet by the source unit and amps.

Last, this LS volume pot has no sound of it's own so I assume you hear the amp speaker combo and it's particular sonic signature and synergy? If so, an active preamp may well act like the hub or heart of a system bringing everything together the way the owner likes. Perhaps the speaker/amp synergy is just a little shy of perfect to the owners ears, thus the active pre is the crowning jewel or the cherry on top.

Ok, be kind to me as I am only trying open this up to all views and experiences. You guys have my attention on this thread.
pubul57 OP
3,712 posts
 
I would think a room much larger than 12x18 would be too large for the RM10 with my Merlins which are 89db, the RM9s do have more scale (and 162 watts)so you would expect that, but they are closer than you expect, at 20% of the price of the RM9 Special Edition (not the standard RM9).

I'm not sure why the 87db would be an issue in terms of the LS, if the amp 60 watts or more tube, or 100+ SS, and if their input sensitivity is 1v for full output, the limit would seem to be the amp, not the LS in this situation, but perhaps George will chime in as I have not actually tried it:)
pubul57 OP
3,712 posts
 
Also, on the RM10, I'm driving Merlins with its 35 watts (actually 27 watts since I use the 4 ohm tap) so it's not really trying to move large bass drivers which might show up the RM10s limitations, don't know. I do know that Roger designs his amps with electorstatics in mind, so....
clio09
3,360 posts
 
Will it work well on speakers that are 87 db efficient like Soundlab speakers and other ESL's? I say this assuming the amps are very powerful and the spec criteria mentioned by the poster are meet by the source unit and amps.
Grannyring

I don't see why not, but I'll let George address this. I thought I recalled a conversation where the Lightspeed was being used in a system with Maggies.

However, my own personal opinion would be that the amp driving the speakers and the synergy between the two would be the more appropriate matching criteria when determining this since the spec criteria (source output voltage and output impedance/amp input impedance and sensitivity) is met.

Last, this LS volume pot has no sound of it's own so I assume you hear the amp speaker combo and it's particular sonic signature and synergy? If so, an active preamp may well act like the hub or heart of a system bringing everything together the way the owner likes. Perhaps the speaker/amp synergy is just a little shy of perfect to the owners ears, thus the active pre is the crowning jewel or the cherry on top.
Grannyring

As I said previously, an active preamp is a tone control, or in some systems a band aid.
georgehifi's avatar
georgehifi
10,312 posts
 
06-16-10:
Grannyring:I have a question for you owners of this exciting volume pot. Will it work well on speakers that are 87 db efficient like Soundlab speakers and other ESL's? I say this assuming the amps are very powerful and the spec criteria mentioned by the poster are meet by the source unit and amps.Grannyring:

My Martin Logan Monoliths ESL's are around 86db, I am never more than 11 o'clock for very very loud listening. I make it a point of asking customers with low efficiency speaker where the position of the volume control is for good loud level listening, and the worst was 82db speakers and he was still only at 1 to 2 o'clock for loud listening sessions.
You can gauge this for your self by putting your source directly into your poweramps to see if is loud enough for you, I bet not one person says they need more level even with 82db speakers and this is what the Lightspeed Attenuator will let through no more only less if you turn down the volume control.
:This next part is important to read:
There is no need with todays high output sources (cdp,dacs,phono stages) the need to preamplify, they have enough output to clip nearly all poweramps into any speaker on the market. So why would you want to amplify again (with a preamp)only to knock it back down again to below the original source output???.
Cheers George
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