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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
b_limo's avatar
b_limo
2,290 posts
 
How is my battery pack comparing to these wal warts? I went with the battery pack because I thought it was better...

I'd prefer not to go to the teradak simply because the battery pack looks cleaner and I don't have to buy another powercord and I only have 2 components plugged into my ps audio quintet in different banks.

If the teradack is going to be an improvement over the battery pack, well of course I'll buy it, but it seems like you guys are comparing the teradack to the worst power supply (smp is the worst one, right?) and not the linear one. I read some comparisons between the linear power supply vs. the battery pack, and the battery pack supposedly sounded better...
georgehifi's avatar
georgehifi
10,312 posts
 
I believe the Teradac power supply (http://www.ab-system.hk/index.php?route=product/product&path=73&product_id=64 ) is a great linear power supply. And at a good price.

But from the Lightspeed owners in the US and Canada that have said it's far better than the wall wart, we really need to know if it was an SMP wall wart, they were comparing to. It is very hard to tell the difference visually between an SMP or Linear wall wart. The portable AM radio trick is the easiest way to tell.

Cheers George
lacee
811 posts
 
Maybe I missed it,but what are the sonic differences when one goes from an SMP to a linear wallwart?

If my wallwart was an SMP,and if most of the other North American wallwarts are SMP,then it's a no brainer to go for the TeraDak, because the improvement is well worth the little bit of extra pocket money.

If my wallwart was a linear one, then the TeraDak is still an improvement.

Just looking at the very thin and cheap wire that goes from the wall receptacle into the wallwart and the physical small size and most likely cheap construction of walwarts be they SMP or linear,compared to the TeraDak,there is quite a difference in build quality of the two, yet not much difference in price.
In fact some catelogue wallwarts that I researched from N.Am. charged way too much to process and ship.
Shipping charges from HK were 15 bucks.
So not much savings with a linear or SMP .

It would be nice to hear from someone who has compared a SWP, linear, battery and TeraDak so we can put this to rest.
George,you're the master, any of your fellow Aussies tried one of these yet?
georgehifi's avatar
georgehifi
10,312 posts
 
Lacee hi, first off I'll explain the Lightspeed Attenuator consumes around 50mA max, "you could almost power it by rubbing two sticks together".
A 300mA wall wart will power 6 x Lightspeeds. So it's not a question of power, thicker wires or getting more current to the Lightspeed.
It noise, and smp wall warts are noisy little buggers, go near them with an AM portable radio and it will squeal like a stuffed pig.

If your wall wart is a linear one then it should be a close comparison to the Teradac (without hearing myself) because a battery is the closest to the perfect power for the Lightspeed, and not many people can hear much difference from battery to a linear wall wart.

However a smp wall wart is rubbish for the Lightspeed, I've even seen the difference on the test bench. These smp wall warts will be bettered by a Teradac and or battery by a long way.

Cheers George
banquo363
371 posts
 
fwiw: after some more hours of testing, I've confirmed to my satisfaction my initial observations.

First, the appearance of a difference in volume persists. The wallwart renders the LSA brighter and moves the stage forward, and I believe this is, in addition to increase in distortions, what I'm interpreting as a difference in loudness. Depending on one's system, I can see how someone could favor the wallwart. It seems livelier. YMMV.

However, with respect to transient response and transparency, the TeraDak is the clear and obvious winner IMO. My wallwart blurs transients and obscures the rhythmic qualities across all genres of music I tested: jazz, rock, folk, and classical. Choral work is more articulate.

Keep in mind that the deficiencies I note are relative to a side by side comparison with the TeraDak. Which is to say, I certainly didn't notice them in the 3 years that I've used the wallwart with LSA. (Or perhaps I noted them, but blamed other parts of my system?)

At any rate, in the end I'm with Lacee: my wallwart days are over. The question whether a linear wallwart is as good as the TeraDak is of theoretic interest to me, but I'll leave those questions for people like George to answer.

For $60 shipped, I see little reason to not hold such theoretical questions in abeyance and see for oneself.
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