2. amps-preamps
  3. 1276356977

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
 
05-19-14: Erwann
The only limitations I can think of, have nothing to do with the sound: leaving the volume control half-way to extend the life of the optoisolators took some getting used to, and indeed the lowest setting lets will let some minimal signal through, which compared to my previous setup, however, is well within my tolerance, and greatly superior to my earlier direct CD to amp connection. The overall experience is far beyond my expectation. This is a product that I will not be parting with, period.
Erwann (Answers | This Thread)

Glad you like it so much Erwann, as for leaving it at 12o'clock when not listening, this is not set in stone, as the leds should last 10-20 years at full power, which I never run them at, and by leaving it at half volume should double or tripple this life.
PS don't forget to let us know how your $15K!!!! analogue source sounds through it when you get the chance, as analogue lovers have told me it's the best they have ever had their records sound.

Cheers George
erwann
6 posts
 
Hi George,

I just had a quick glance at the Audiogon thread to figure out whether I can find a better power supply than my decommissioned Prius auxiliary battery, and I fail to understand how a Teradak, with or without a fancy cord, could offer an improvement other than convenience. I guess the answer is that you haven't felt an overwhelming urge to try it yourself. Not being an exhibitionist, I personally think that my best audio component is my brain with ear input, which in addition to being portable and self-powered, doubles as the biggest sex organ, but I'm still burning it in at sixty-six, and it keeps improving.
lacee
811 posts
 
Please do try the LSA with your phono stage.
I run my Steelhead volume full out and the LSA under 12 with very good results.
In my system, the Terra dak with upgraded power cords in conjunction with dedicated lines is an improvement over the stock LSA and walwart.
No doubt your power supply is also much better than the stock walwart.

I use the Annaconda power cord only because it was a spare,but I would assume any upgraded power cord would work quite well with the LSA/TeraDAk combo.

However if you haven't been able to hear the differences power cords can make with other components, then by all means use whatever you have at hand.

It's not about one-upmanship,just being practical without selling it at a loss.

Besides what would I spend the extra dough on?
georgehifi's avatar
georgehifi
10,312 posts
 
05-09-14: Jult52
I compared the LSA with a switch-mode ps and the linear TeraDak 9v supply discussed earlier in this thread. I am going to report a null result: I could not reliably differentiate between the sound of the two. The TeraDak carried no benefits in my system.


Hi Julian, I noticed on another forum you did a comparison with the Lightspeed up against another clone, and mentioned the Lightspeed Attenuator had the better bass performance.
I believe there could one of 3 factors for this difference.

1: The main one I'm leaning towards may be that the Lightspeed has no contacts in the signal path, where I believe the clone has, as it has input switching. And the whole point of the Lightspeed when I first built the original in the 70's was to eliminate any switches or volume pot wiper contacts from the signal path.

2: I also use quad matched LED/LDR's in the Lightspeed, this keeps the i/o impedances more stable, and also gives a better logarithmic feel to the volume control, I believe the clone only uses 2 x matched pairs.

3: I use the more expensive NSL32SR2S, where the clone from what my spies told me does not.

Cheers George
georgehifi's avatar
georgehifi
10,312 posts
 
05-19-14: Erwann
Hi George,

I just had a quick glance at the Audiogon thread to figure out whether I can find a better power supply than my decommissioned Prius auxiliary battery, and I fail to understand how a Teradak, with or without a fancy cord, could offer an improvement other than convenience. I guess the answer is that you haven't felt an overwhelming urge to try it yourself. Not being an exhibitionist, I personally think that my best audio component is my brain with ear input, which in addition to being portable and self-powered, doubles as the biggest sex organ, but I'm still burning it in at sixty-six, and it keeps improving.


I strongly believe that battery is the "technically" the best form of dc supply for the Lightspeed Attenuator.
But sometimes I forget which is on mine, the battery or the linear wall wart, they're that close to each other.
Sam Tellig of Stereophile uses both battery or wall wart on his Lightspeed, and so does his guitar teaching son on his Lightspeed. And both can hear a slight difference but can't say what that difference is.
As for the Teradac power supply, if you technically want a very good mains powered supply for the Lightspeed that to me is total overkill, this is the one to get. And it's only $44.
Some here that have used it, swear it's the ultimate mains powered supply. I have never used one so I cannot comment on it, but on paper it's miles ahead of a linear wall wart, but to me technically battery is even better again.

Cheers George
More to discover