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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
 
Hi Lacee, I like the Teradac, that's why I posted it up for Lightspeed owners to try, as we are always wanting to try out different things.

An smp wall wart will not give noise that you can hear, but it can be seen on the ocilloscope as very high frequency rubbish, and it gets through every thing in the system. What this does to the sound is anyones guess.

What I want to get down too is if the Teradac power supply was compared to a smp wall wart or linear. So far no one has been able to say without question.

Cheers George
b_limo's avatar
b_limo
2,273 posts
 
Lacee and Banquo,
Come on guys, if you won't tell us, or find out, whether you were using an smp wall wart or linear, maybe you could tell us the brand and model number so we can look it up??

It's funny that I'm on the other side of the upgraded power supply debate on this one, because I upgrade all of my power supplies and power cords, but I just don't see how this teradak would be an upgrade over the battery pack. It just seems logical to me that if it's a linear power supply, and your power supply isn't introducing noise into your system, then you would'nt gain anything here.

George states "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. ".

I have been thinking about buying a wall wart to back up my battery for those times when I forget to shut off my battery pack, now I'll get a terra dak and compare it to my battery pack. I must say though, I don't like the idea of buying another upgraded power cord for the terra dak but whatever.
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banquo363
371 posts
 
B_limo: several posts ago, I already linked to the wall wart that I own. George speculated that it is an smp. I've searched and searched and there's no published info to confirm or deny. George suggests the AM radio test, but I'm not buying an AM radio just to do this test. To be blunt, I have little motivation, since the differences between my wall wart and the TeraDak are so clear. If, theoretically, there shouldn't (couldn't?) be much difference between linear power supplies, then the conclusion to draw is that I must own a smp wall wart. If someone wants a stronger argument then that, well, they can try it out for themselves--as you have suggested you will with your battery supply.

fyi: for my tests, I used a cheap hospital grade power cord. Whether one could do even better with a better cord, I'll leave that to those with deeper pockets than I to determine.
clio09
3,346 posts
 
Not all linear power supplies are created equally. B_limo makes a good point as to the LSA not requiring a lot of current, and the LSA has it's own regulation, but any power supply can introduce noise into a system. If this Teradac somehow reduces the noise level then it should be quite apparent as Banquo indicates.
b_limo's avatar
b_limo
2,273 posts
 
My bad Banquo, didn't see the link, didn'tknow you looked into it at all, let alone actually digging around a bit. I apologize. I'll check the link, but like I said, I'll probablyend up just buying the terradak to back up my battery pack and will report back.

George, two questions: does the lightspeed ever need to be recalibrated? It seems like my volume control may be adjusting in larger increments than before...

Question 2: is it okay to dress it up a bit? I was thinking about a small wooden case or having it professionally painted.
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