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
I got my TeraDak just a few minutes ago.
No special surprise footers, but the cord they sent to attach to the LSA looks very nice in a retro toatser cord type covering.

I'll probably get a lot of guffaws over this next revelation, but the power cord I will be using is a Shunyata Annaconda Helix,which was sitting here doing nothing but collecting dust.

I'll report back in a few hours with the initial impression, and no I won't be doing any power cord comparisons, just the sound I hear compared to the wallwart.

Getting back to that connecting cord from TeraDak.
This by itself is very reassuring compared to the wallwart.
I'll probably get a lot of guffaws over this next revelation, but the power cord I will be using is a Shunyata Annaconda Helix,which was sitting here doing nothing but collecting dust.

No guffaws from me, just envy: I wish I had stuff like that just lying around. :)
I've only listened for about 45mins,and just to my vinyl, but here are my intial impressions-

More slam,more dynamic, increased bass,increased treble(some sybilance on Graceland I never heard before),a no brainer for the money investment.Perhaps the sibilance has always been there on the Graceland LP,but I've just noticed now with the TerDak.

I think this unlocks the real potential of the LSA and anyone who is using a cheap wallwart isn't getting the full measure of their LSA investment.

Granted I use a Shunyata power cord and the unit is plugged into a Hydra 8 on dedicated 20 amp line.

Some may question the sanity of plugging an expensive power cord into the TeraDak,but until you do you'll never know for sure how much you maybe compromising its potential, just as you are compromising the LSA with a cheap wallwart.

I think sometimes the common sense of audiophiles can be a stumbling block.Accepted wisdom is that we should always spend the big bucks on the amps, pre amps etc, and shell out the small change on the stuff that shouldn't make a difference like power cords.

I think many a fine low cost upgrade is compromised by the use of even cheaper ancillaries.
I think the combination of the LSA powered by the TeraDak justifies something better than a generic cheap power cord.

I'll leave it to others to expereiment and post their findings, I'm over the hill with the sound of my set up as it is and have no desire to try somethingelse.
The pieces fit and please me more so than I had expected.

It's almost like I've added a solid state turbo charger to my tube Acoustat servo amps.

In fact I never heard them clip before on the Dafos lp, but clip they did on the big drum crash,eventhough I didn't have the volume any higher than normal, nor did it sound any louder.

I think more of the dynamic slam that is on this recording was unleashed for the first time ,so watch out if you have low powered SS amps that might not clip as harmlessly as my amps did.

If there is any downside so far it's back to that solid state attack that this power supply adds to my sound.
It's very clean,crisp, and fast ,perhaps I'll have less of this when I put the cd player into service and I've run a few days on the unit, so I'll report back then as I said I would.

But I would gladly trade this bit of edge if it doesn't go away for the increase in all the good things this unit has done for my sound.Easily worth the trade off, and perhaps just a sign that I need to fine tune my cartridge a bit more.
Did I mention the TeraDak is more revealing?
Well it is, so make sure your system is up to snuff, because you will not have those nasties buried in the muck a wallwart gives you.

That sounds harsh.
I really was quite pleased with the LSA and the wallwart.

Like most things in this hobby, it's only when you go outside the comfort zone of "good enough"that you find how good can go to great, and in this case, how such a small cash outlay($60.00 CDN)can make such a big improvement.

In my system the TeraDak ,cold out of the box,was better than I had anticipated, and I had anticipated an upgrade, but not to this extent.

Anyone with an LSA has not heard what their unit can really do if they are using a cheap wallwart.

Thanks for bringing this to my attention George,I would put this at the top of your list of power supply options for your volume control.

In fact, if I were you I would make it part of the package for North American consumers from you as a low cost option.

If you haven't tried it you should.
Lacee hi, are you in the US also, just wondering if your wall wart was smp or linear?

Cheers George
@ Wisnon: I had the LSA on my Job 225 for a little while. I thought the input Z of the Job might be borderline but it wasn't the case at all. The LSA sounded lovely with the Job. Complex orchestral passages played at high volumes didn't sound too congested. Moving up to the Bent TAP-X autoformer freed it up even more. If you want to eliminate input/output Z issues all together, consider an AVC or TVC. I will say this, at no time with the LSA did I feel the need to change to another preamp. I happened to come across a Bent TAP-X (again), and loved the first one so much I bought it. In the end, I preferred the TAP-X just on musical tastes alone. Throw in the remote volume/balance control and it was a no-brainer for me.