2. amps-preamps
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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
clio09
3,369 posts
 
Yes, whether it was Bobby, Ralph Karsten, or Roger Modjeski, Paul appreciated designers who refined their original concepts and more importantly stood by their convictions. The first time I met Paul was RMAF and we agreed to meet up in the Merlin room. Sitting there with just Paul and Bobby I had the opportunity to really hear the Merlins properly set up for the first time. At future shows the Merlin room always received a good chunk of my time and always ended up on my top 5 list.

Like Audiodynamo I do not own a set of Merlin's, but not because I don't like them, I really do, but because like Paul's commitment to Merlin, I'm totally committed to my Audiokinesis speakers designed by Duke Lejeune. I recall on a number of occasions Paul indicating he needed to try a set, since he and I shared similar tastes and similar equipment. Sadly he never got the chance.

While Paul did enjoy his system, he enjoyed music much more. What I also learned from my brief time knowing him and from reading the memorials posted by his family and friends from his obituary is that he truly enjoyed life.
socrates7
77 posts
 
Ah, geez. Say it ain't so! Paul introduced me to Merlin, Bobby and tubes. Seems like a lifetime ago.

Godspeed, my friend!
banquo363
371 posts
 
I've been having issues with the sound out of my system and finally had some time to diagnose.

I've narrowed it down to the LSA or my tube amp (music reference rm10). The symptoms are the following. I'm getting diminished power/volume and muffled sound quality. Every other track or so the volume and sound quality will briefly return (the volume will suddenly shoot up) and then go back down after a few seconds or so. It's not isolated to one speaker or the other, so I'm ruling out an interconnect or wire issue. I've changed all the tubes on the amp and the problem persists. So I'm suspecting the LSA. I'm using a wall wart power supply and not battery pack. But what in the LSA could cause the symptoms I'm hearing? More importantly, how can it be fixed? Preferably without having to send back to Australia?

Help. Thanks.
clio09
3,369 posts
 
Are you able to try another preamp in the chain to see if the problem persists. Although it may not be tube related, there could be something else going on in the amp that could cause this issue. Trying another preamp will help you further isolate the problem. If you don't have another preamp let me know as I have a set of EVS attenuators I can loan you. I'll be in Newport Beach next week so you can pick them up in room 417 where I will be exhibiting.
banquo363
371 posts
 
Thanks, Clio09. I think I figured it out. I was premature in blaming the LSA. You are right. I opened up the rm10 and found that one of the wires to the fuse box is disconnected. Now if only I knew how to solder :).

That's cool that you'll be exhibiting. I'll be sure to swing by.
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