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
@ Georgelofi, Hi, believe it or not, I have used the Ayon 2s volume control at the level you are speaking of plenty of times!, It just dont have the gain for me to get the power out of my amp that I would like to have, I would say, half the power of the amp is available, no matter the max volume I set!, I have the Krell fpb 700 cx amp, I have 6 oms speakers that ride mostly at 4 1/2 oms while playing music, still, I know what high power sounds like, since I was a life long musician!, and the speakers are 91 db sensativity!, I do not like most pre-amps out there because they add a veil over the music at hand, and they always add their sound signature to the sound as well!, then theres the cost of mutiple cables, which btw, my i/c retails for $14,950.00 a meter!, one of these is what I like to stick with considering the cost here!, I still want to buy your unit, I can always use it somewhere on the other systems I am building over the next few years, by having your unit already is a plus with doing this!,, cheers!
You will not gain anything by putting the Lightspeed into your system and I would'nt sell you one until this is sorted out.
As your Krell FPB700CX has balanced inputs and is 100kohm with 3.58v sensitivity, that is, it takes 3.58v in, to take it to full output just before clipping.
Your Ayon CD2s has balanced output of 300ohm with up to 5v out at full level.
So you can see your Ayon at full volume output has enough output to take your Krell beyond it's full output which will damage it, you have either done this and is the cause of your Krell's damage, or something else is misconscrewed.

Cheers George
Read the above carfully before reading this.
You have a switch on the back next to the output rca's and xlr's that can set the full output level at either 2.5v or 5v, I believe you have it at 2.5v from what you've been telling us.
Quote from a review:Besides the outputs there are also four switches. One selects the absolute phase – 0/180°, the second one controls the overall gain – maximum output voltage of 2.5V or 5V, the third one selects the analog output we use, XLR or RCA. End Quote.

Cheers George
Hi Geogelofi, You are correct, I only use the ayon 2s player on 2.5 volts, that way I will never clip the Krell balanced input!, As far as the amp goes, I have never, ever heard this amp clip!, Yes, I do have the Ayon set on xlr setting, o degrees on the phase setting, I have played with all the settings, To my amazement, they work to very good effect!, George, The Krell was damaged when I first moved into this house I am renting 13 months ago,The receptical had 220 on it, It blew my amp up!, I sent it back to the dealer that sold me the unit used, As good as their technicians were, The compexity of a $14,000.00 amp new was beyound their experience!, I had problems with the amps bias on the left channel, It got worse as time went by, to the point that the amp was getting so hot on the left channel, that it would shut its self to stand-by!, so, my lesson learned here is to never let any body work on a Krell amp that is this sophisticated as this Krell 700cx is!, the dealer was not a Krell dealer at all!, I know of only two places here in the u.s.a. that can work on this amp to great effect is the krell factory, and the company called, the service department home, steve is the owner of the service department home, He was the service manager there at krell for 20 years before he started his own company in 2009, he is also a certified service bussiness for Ayon audio!, He told me on the phone that the Ayon 2s is really a hybred player, since the signal leaves the out-put tubes and then goes to R-core transformers that is on each channel that their is no way ever that the Ayon 2s would propose a problem for the krell 700cx running direct to amp, the transformers is the buffers for eany and all d/c that may or may not come from the tubes!, so no, the Ayon 2s was never the problem!, the problem of the krell 700cx was prior to me buying the ayon player!, the dealer who attemted to fix the unit basically band-aided the amp up to finish the sell to me!, I cannot complain alot here, they attempted to fix it for free!, At the end of the day, they had no bussiness tring to fix the amp!, they should of sent it to Krell as I did!, and since the amp is there at Krell, I am requesting for the amp to be totally renewed rather it needed it or not, that way, there will be no worrys in the next 25 years!,, cheers!