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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
georgehifi's avatar
georgehifi
10,312 posts
 
06-16-10:
Koestner:George, Are you, or could you, consider making a fully balanced version with some sort of remote volume function?:Koestner

I'll put it up again, Paul got it almost all.
To do a balanced version takes exponentially more matching time and is exponentially more critical, then if that was achieved, to calibrate it would be exponentially more critical and then it will only stay in calibration a few days.
I have customers that have balanced systems they just use 4 x balanced to rca adaptors on the back of the Lightspeed Attenuator.

http://www.jaycar.com.au/productResults.asp?keywords=rca+to+XLR&keyform=KEYWORD&SUBMIT.x=18&SUBMIT.y=5

After all balanced is only needed if you run extra long interconnects, single ended actually sounds better because of the lack of opamps in the signal path to achieve the balanced signal, and in the end lets face it, the speaker is also only single ended as it run only a + and a - back to the amp and that negative on the back of the amp is at ground potential.

Cheers George
tradeontheweb
43 posts
 
"I agree Anthony, as enjoyable as several $10-$20,000 combos I had here over the past 5-7 years. With the right speakers, the LS-A/RM10 combo($2,400 list)is incredibly good and competitive with just about any pre/amp combo out there, at any price"

Just my 2 cents worth in agreement with the above. Having recently listened to the LS inserted into an expensive system with Halcro Monoblocks (approx AUD $60K)and both Wilson 7's and 8's, I can vouch for the LS's ability to play in any company and far exceed it's modest price/appearance.

Cheers

Scott
pubul57 OP
3,712 posts
 
Well we may never get to the point that we can say of any preamplifier (or volume control, if you will) that it is the best ever (a silly thought), but I feel pretty comfortable saying that this is by far and away the best such thing for the money, and not a poor man's option, but a true SOTA approach to volume control, in the right system.

Anthony, if you do give the Axiom a listen in your system, your thoughts would be welcome, not sure it would be better than a Goldpoint with the right value attenuator, or the Placette RVC for that matter, but I'm not sure what they are doing that might make a difference compared with those, even with the Caddock option (better than Vishay?).
grannyring's avatar
grannyring
6,517 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:)
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