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
teajay
1,702 posts
 
Please Fiddler, accusation has such a negative and bombastic tone to it. The only example I will give of someone who has given so much to the DIY community is Nelson Pass, yet he has never on any post here on Audiogon marketed his wares or ever stated his opinions as the only veiwpoint regarding performance as the absolute truth as far as I can tell, like the man that you say I'm unfairly challanging.

I just shared my opinion regarding my impression of how George comes across to me on this thread, somewhat negatively towards any design that he deems not being totally true to the source, what ever that means, and secondly this not DIYaudio, but Audiogon were threads normally are not used by designers to sell products, and if they do they are rightly called out on it.

Finally, your statement regarding George's reason for posting have nothing to do with selling because he gave it away for free to the DIY community, hum, has not Nelson Pass done the same thing, yet has never pushed his products like George has on this thread.

Sorry, if my impressions regarding George's motivation comes across as a personal attack on the man to you. I don't know George, I'm not a member of the DIY community, and I don't want to jump this fine thread with this side bar discussion regarding George. I'm sure George is a good guy who makes a very good product at a very reasonable price.
clio09
3,360 posts
 
Nelson Pass indeed has given a lot to this community as is evidenced here:

Pass DIY

In fact, go to the projects section if you're inclined to see some of the ideas and schematics Nelson allows DIYers to use:

http://passdiy.com/projects.htm

If you look down the list just a few lines, you'll see an article on the B1 buffer. Nelson's version of a passive but with active JFETs for the buffer stage to control impedance matching. I like the way Nelson writes. He divides his articles up into sections analogous to LP sides. This article is no different and for those not inclined to go over there and read the article, here is an excerpt of Side A:

The First Watt B1 Buffer Preamp
Nelson Pass, June 2008
Side A

So here we are in the New Millennium, and thanks to Tom Holman and THX we’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!).

Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.

I suppose if I had to floor the accelerator to drive 55 mph, maybe I’d think the life was being sucked out of my driving. Then again, maybe I like 55. Nice and safe, good gas mileage…

He goes on to talk about impedance matching/mismatching as well before getting into the technical stuff. My point simply is he talks about some of the same things those of us who prefer passives and George talk about here.

I still think Nelson paid George a nice compliment by publishing his own LDR schematic based on George's work. The two certainly share similar opinions IMO.

Fiddler's point on Goerge's IP is pretty valid. If George wanted to make quite a few bucks off this it would have been pretty easy to do. Instead he's given his IP away. No he's not the first and he won't be the last, but he still did it. Now there are people out there, both DIYers and manufacturers, building their own versions of LDR preamps (using all or parts of George's ideas) or incorporating LDR volume controls in their active preamp designs. I'd say that's another compliment to George.
fiddler
581 posts
 
Teajay, you posted, "I have no historical awareness that Ralph or any other well known designer has ever pushed as hard to sell his product as George has, if you can remember someone please share."

You didn't just "share your opinion". In your own words you flat out accused George of pushing hard to “sell his product".

And the fact that Nelson Pass has given much to the DIY community has nothing to with this discussion other than to offer some misdirection and a weak attempt to justify your accusation after you were made aware George had given his IP away.

And in your last post your accusatory tone continues by saying, "...and secondly this not DIYaudio, but Audiogon were threads normally are not used by designers to sell products, and if they do they are rightly called out on it."

If anyone is being negative and bombastic here, it is you. We can both agree that designers should be called out here for shilling their products. I'm with you on that one. But it is my opinion that your accusations against George have been grossly unfair. Considering the fact that you haven't given a single, concrete example of where George has attempted to sell his product to anyone, combined with the fact that he freely gives his design away; it appears you are left with a rather untenable position.

Teajay, I will be the first to join in with you when someone is truly shilling here (and it happens often), but I think you may simply be misinterpreting George's defense of his baby as something more nefarious, especially in light of the fact he has given it all away.
teajay
1,702 posts
 
Fiddler, if you think I have been nefarious and bombastic towards George that's OK with me.

I gave him credit for sharing information on his design and for helping people who own it get the best performance possible in their systems, sounds nefarious to me so far.

Then when I gave my opinion in a respectful way that it seems to me George is a little full of himself regarding his perspective on what a linestage should offer sonicly and that for an Audiogon thread it started to seem to be somewhat of unpaid promotion forum, wow, that sounds bombastic and accusatory doesn't, then I became a SOB in your opinion.

Your weak attempt at being disingenuous towards what information I did share regarding the difference between someone like Nelson Pass who gives things away to the DIY community but does not use Audiogon threads to market his wares, does not negate your final silly statement,"that George has given it all away". Really, as far as I know he still charges money for his LDR, he does not build them and give them away for free.

Gee whiz, guys lighten up. I'm not attacking George personally, I gave his product and his pricing of it a postive comment and I'm entitled to my opinion about the other issues.

Finally, I apologize to Paul for influencing this thread away from the great discussion concerning passives vs active linestages that was very informative and interesting. I guess you have to be very careful about sharing your opinion, even though I thought I have been respectful, when it comes to certain people's friends or heros.
fiddler
581 posts
 
Teajay, I get the problem now. You aren't carefully reading the posts here .

I didn't say you were being nefarious. Re-read my post. "Nefarious" was related to George's "defense".

And you are still implying that George is marketing his wares, "difference between someone like Nelson Pass who gives things away to the DIY community but does not use Audiogon threads to market his wares..."

As I said before, you haven't given one example of George, "marketing his wares". You just keep twisting words to try to defend your position.

And when did I ever imply you were an SOB? More twisting of words.

And talk about being silly. You clearly know that when I said, "that George has given it all away", that I was talking about his IP. I even used "IP" and "design" in my posts. I think it is clear who is being disingenuous here.

"Gee whiz, guys lighten up."

Take a little of your own advice. Had you not accused George of "selling" here in the first place (once again, without one example to back the charge up) we wouldn't be having this conversation.

And BTW, George isn't a friend or hero. I've never met the man, seen the man or even talked to the man. I simply don't like to see people falsely accused without one speck of evidence being provided to back up the claim.

And I agree it is unfortunate that this thread got sidetracked from the OP's question which was offered with a lot of caveats:

"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."
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