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
georgehifi's avatar
georgehifi
10,312 posts
 
There are some instances where additional gain is needed
Yes that needs to be added to No.2
" 2: All passives (except tvc’s), if the system permits impedance/gain compatibility (most do)


Like our old friend pubul57 (Paul, RIP) who started this thread years ago
Yes we all miss him dearly.

Cheers George
Post removed 
t_ramey
632 posts
 
@cerberus79
I rarely post anything here. I did so this time because I had direct experience on the topic and reported it in a factual and non judgmental fashion. My reward was to be called a lier by one member and told I was in the wrong hobby by another ( I have been in this hobby for 49 years ). I am and always have been in this hobby for the enjoyment of music. I once got into a discussion with Geof Kait on the directionality of fuses and realized

You/we are lucky GK has disappeared (or been banned) he was a real comic piece of work but fitted in well in these types of threads, and his website is really out there https://www.machinadynamica.com/machina5.htm best one is the pebbles.

As for your Maggies I had quite a bit to do with them owning the big Tympanies also, before going on to big ESL’s.

cerberus79A few months ago I purchased a used pair of speakers from another Agon member. To my surprise all the fuses were Orange fuses. I listened to them and then to satisfy my curiosity I replaced them with ordinary buss fuses and could not hear a difference. I did this test with a bunch of friends and neither I or them could hear a difference.


As you stated no difference in sound whether 10cent Bussman fuses were in or $150 SR Orange were in, to yourself or when the guys were around to do the A/B with.

cerberus79
Has the purpose of a fuse been lost ? How it is designed to work ? By design there is no directionality in a fuse. it is simply designed to open in an overcurrent situation. If it was directional in relation to the current passing through it would be a diode


Same thing I say to them, if it’s directional then it’s trying to be a diode, and that NOT good in either direction!

But I can tell your Maggies will sound a touch better with just a piece of copper wire soldered lightly outside of the fuse clamps and no fuses. This makes them vulnerable to an amp blowing and going dc, as you know having electronic knowledge background, but no more so than any other speaker would have no dc protection either.

You could try one of these if you want to retain the protection soldered to the fuse clamps.
https://www.jaycar.com.au/5-amp-circuit-breaker/p/SF2254

t_ramey
632 posts
 
@cerberus79
I rarely post anything here. I did so this time because I had direct experience on the topic and reported it in a factual and non judgmental fashion. My reward was to be called a lier by one member and told I was in the wrong hobby by another ( I have been in this hobby for 49 years ). I am and always have been in this hobby for the enjoyment of music. I once got into a discussion with Geof Kait on the directionality of fuses and realized

You/we are lucky GK has disappeared (or been banned) he was a real comic piece of work but fitted in well in these types of threads, and his website is really out there https://www.machinadynamica.com/machina5.htm best one is the pebbles.

As for your Maggies I had quite a bit to do with them owning the big Tympanies also, before going on to big ESL’s.

cerberus79A few months ago I purchased a used pair of speakers from another Agon member. To my surprise all the fuses were Orange fuses. I listened to them and then to satisfy my curiosity I replaced them with ordinary buss fuses and could not hear a difference. I did this test with a bunch of friends and neither I or them could hear a difference.


As you stated no difference in sound whether 10cent Bussman fuses were in or $150 SR Orange were in, to yourself or when the guys were around to do the A/B with.

cerberus79
Has the purpose of a fuse been lost ? How it is designed to work ? By design there is no directionality in a fuse. it is simply designed to open in an overcurrent situation. If it was directional in relation to the current passing through it would be a diode


Same thing I say to them, if it’s directional then it’s trying to be a diode, and that NOT good in either direction!

But I can tell your Maggies will sound a touch better with just a piece of copper wire soldered lightly outside of the fuse clamps and no fuses. This makes them vulnerable to an amp blowing and going dc, as you know having electronic knowledge background, but no more so than any other speaker would have no dc protection either.

You could try one of these if you want to retain the protection soldered to the fuse clamps.
https://www.jaycar.com.au/5-amp-circuit-breaker/p/SF2254
tomic601's avatar
tomic601
12,744 posts
 
congrats on a great run George. Does the fng have plans for a remote ?

My proposed path; Herron phono pre >>>> Lightspeed >>>> RM-9

big fun
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