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.
J’ai mis une planche de bois sur le Light speed pour changer le look, que veut dire l’étiquette avec la lettre B.
Ah yes the letter "b" underneath is a batch ID letter when they go through getting made.

Cheers George
 Non c est bien un des vôtres c est moi qui est rajouté une plaque de bois de chêne pour changer le look, le son est vraiment superbe
Bien à vous
OK I understand, each to his own for the look.
I’m just glad it wasn’t another clone ripoff on the market, and even using the Lightspeed Attenuator front logo.

Cheers George
Bonjour George
J'ai mis une planche de bois sur le Light speed pour changer le look, que veut dire l'étiquette avec la lettre B.
Non c est bien un des vôtres c est moi qui est rajouté une plaque de bois de chêne pour changer le look, le son est vraiment superbe
Bien à vous 
Hi roddek6 From what I’ve been able to understand with the translator, you bought this used and are very happy with your sound.
What you purchased is not one of my production Lightspeed Attenuators, but looks to be diy unit that has been made that I posted how to do it many many years ago.
But it looks to be a close copy of my artwork logo, which makes me wince.

Cheers George
J ai l impression petit problème de traduction, je ne vends pas le lightspeed, je viens de l'acheter
Bonjour excusez mon anglais je viens d'acquérir un Lightspeed et j en suis ravi il est alimenté : 100VA Ultra faible Bruit LPS SALUT-FIN R-core Linéaire alimentation/100 w PSU pour audio DC12V En Option Avec affichage.
J écoute Qobuz Hi-res avec un bluesound node2, câbles rca maison argent, sur ampli classe D N-core, sur des klipsch Rf7 lll., j arrive difficilement à dépasser midi, les RF7 ont  100dB de sensibilité.
Un gars de Cassis en provence en France 
Post removed 
Your very welcome Rob, and thank you very much for the kind words. Glad you like it so much and how it sounds, you’ve said it like it is.

Are you going to try the 12v Li-Ion rechargeable battery to power the Lightspeed with? It will give a good week of listening before a recharge is needed.

Cheers George
I have now had a good listen to my dual mono version of the LSA.
To my ears (and friend's and family's) It has bettered the pre-amps i have had in this system so far, including ARC Ref5se (the Ref 5se was nice with the ARC amps i had previously, (perhaps at a disadvantage due to an impedance issue with ARC & Current SS amp ??). Among other great tube pres, I also compared an older SS Pass X2.5 and Bryston BP20.

George was extremely helpful; not just in confirming impedance compatibility with my current equipment, potential PSU upgrades, but also general audio advice and a friendly approach to my many questions.

My Current system is:
0.25mV MC Cart > Herron VTPH2 phono stage > LSA > Gryphon Antileon Signature > Wilson Sasha.

Herron is configured to lower gain 64dB.

Levels are fine, i am running at 12-2 o'clock, or just past half way for comfortable to strong levels. Although my room is not large, there is still plenty of gain available (not from the LSA of course).

I wont go into its sound too much other than to say it seems to have no sound, very neutral and balanced. When i placed other preamps back in to compare it became apparent what colourations those other pres contributed to the sound, some aspects of which were enjoyable of course but ultimately there was too much trade off. I prefer the clean, open, neutral, balanced sound I am getting with the LSA.

Perhaps eventually I will discover a Pre that betters the LSA in my current system, (I'm sure when i do it will be in excess of 20x the price) or i may change a component and find it an impedance mismatch with LSA. However at this stage, with my current setup it is very impressive and very good value sonically. 

Thank you George
Post removed 
To go remote, you need the remote, a receiver, the motorised pot and power supply for it.
You need a dual 100kohm Logerithmic pot, and this one is just that, you could use it in the Lightspeed. (no need to use the input board with the 6 relays, just the remote and motorised pot board with receiver)

I won’t use them myself because the reliability factor is not there, and with supply is not there either for me over a long period of time, but there’s nothing stopping owners from doing it themselves.

As for the used Lightspeed, I’ll PM the owner and see if it’s still for sale.

Glad a search led me to revisit this thread today, had not received notice of replies. Fortunately they had one left lol. Thank You @georgehifi for the info. I will mount it externally, use the same size or larger knob and a rubber band or belt without having to take the LSA out of the chain to work inside of it and risk losing the sound I have now.

Thanks to some feedback, I put an iTube 2 in front of the lightspeed a couple weeks ago and have to say I'm liking it so far! Switched to +9db pure tube buffer mode today and think I'm liking it more. I'm curious if it's best to use it before or after the LSA and if there is an ideal LSA volume position. Without the added gain, I varied between 11:00 and 2:00 for the most part.

Was not looking for another LSA but what a great offer. I use a Teradak LPS with mine, BTW.


Wow, your reference to my post is from the deep archives. I recall trying the Lightspeed schematic together with battery-powered monolithic Nat Semi buffers. I ended up (and still employ) the Lightspeed schematic as a volume control in a tweaked-out AtmaSphere MP-1 tube preamp. TX2575 series resistors and Silonex LDR shunts in a differential balanced circuit. It sounds fantastic relative to the stock Shallco series attenuator.

hat i don’t like is even more limitation with Lightspeed to have just ONE input.

It meant to be like that on purpose, because it eliminates the "source selector" switch which is another lightweight potential distortion causing contact taken out of the signal path. The Lightspeeds all about no contacts in the signal path.

As you can see if you follow the green signal path, the music goes from input to output through nothing but a fixed resistor, unlike other preamps which have many contacts (that are very light in contact weight) that the signal has to go through.

A couple of customers use these external "source selectors switches" if they want to switch multiple sources and couldn’t be bothered changing over interconnects for non serious listening.
That way they have the option of still hearing the best without it when they want or to impress their friends by going back to direct into the Lightspeed. with no source selector.

The Goldpoint one is the better, it also seems it has the option of bypassing the source selector switch (see they know), BUT!! with what? another contact inside, so they take the nasty away but replace it with a not so nasty pin plug jumpers?

Cheers George
Here is a picture of my opened B1, and this is another view on this beauty. Sadly, even 2 inputs is not enough for me as i normally use two turntables with 4 tonearms (different cartridges and phono stages). On my tube amp i got remote control, sadly there is no remote on B1, but dual volume control is a nice option to adjust the balance if needed.

Always a trade offs :( 

Yes, the input impedance of by First Watt F2J power amp is 50k Ohms. 

What i don't like is even more limitation with Lightspeed to have just ONE input. BUT has anyone with the same problem ever tried Luxman Line Input Selector AS-4III which is easy to upgrade ? 


Nelson designed a buffer for the Lightspeed Attenuator over 10 years ago on diyAudio so my Lightspeed customers could drive some of his low impedance (10kohm) amps with it, here it is. Later he called the B1 buffer.

If you have a high impedance amp (>30kohm) the buffer (B1) is not needed and the Lightspeed will sound better without it.
The best buffer is still no buffer.

Cheers George

I expected to hear sonic trade-offs, with the passive winning on treble resolution & overall sonic purity, and the active winning on dynamics and LF control. In actuality the hybrid buffered approach won on every point. As a result I opine that if the impedance match is anything less than perfect(and who really knows for certain what is perfect?), a passive would benefit by being equipped with an active buffer on an A/B switch. There are several simple & inexpensive buffer designs(including one contributed to the Lightspeed DIY thread by Nelson Pass) that will do justice to a top-quality passive. In this scenario the comparison of LSA to other preamps becomes more of a contest between volume controls-- which is a critical and oft-neglected determinant of a preamp's performance.

Hello, have you compared LSA to FW B1 ? 

Well I see no reason why either of those sources would pose a problem for the Lightspeed. Glad to see the JLTi is still around as well. Listened to one a while back and enjoyed it quite a bit. Great bang for the buck.
@georgehifi not sure how anyone can judge by the picture (and it’s a bit off topic), but the picture of WLM you have posted is unfinished unit.

1) This is the actual picture of my WLM Phonata made when i opened it to upgraded load resistors to Vishay Naked Foil 100k Ohm for MM input (i prefer 100k over 47k for nearly all MM cartridges):

Technical Data:
MC-Input Impedance Range: < 100 Ohm to 50kOhm
MM-Input Capacity: 100pF
THD (Total Harmonic Distortion) @ 1kHz: 0.01%
SNR (Signal to Noise Ratio) MC: >72dB
SNR (Signal to Noise Ratio) MM: >85dB
Max. Input Voltage for MC-cartridges (theoretical value): 1200mV @ <1% THD
High Performance, Professional Type Step-Up Transformers

The PHONATA offers utterly precise RIAA equalization:
• RIAA equalization is implemented across two amplification stages (within current amplification), providing a frequency expansion from 10Hz to 50kHz (Subsonic cut below 10Hz). Selected components (1% tolerance) are used.
• RIAA equalization can be selected from two positions with a switch at the back of the unit (position “high” for records produced before 1965 or to improve the performance of somewhat “darker” sounding cartridges at higher frequencies. This position provides +3dB equalization as from 5kHz and +6dB as from 10kHz.) • Position “low” for all other records.

The unique feature of PHONATA is automatic adjustment of Load-Impedance for MC cartridges, but i use this phono stage mainly for MM cartridges nowadays, sadly a few units were made before the company closed the business, WLM speakers were quite nice, their tube apms were made by Trafomatic Audio (and i have one of them - WLM Minueta).

2) Phonata has much better bass response than Joe’s JLTi phono stage, the difference is huge (but the price difference is also very big). I like JLTi phono stage too, RCA plug load resistors on the back is such a great feature! If you want to look at the JLTi you will see it’s even simplier and smaller. This is the actual picture of my JLTi (inside).

For LOMC cartridges i use ZYX CPP-1 Pre-Preamp favorited by Arthur Salvatore (his name has mentioned in this thread many times).

And Luxman AD8000 with 8030 silver SUT for LOMC with extremely low impedance.

None of the mentioned phono stages can handle LOMC as good as the LUX silver SUT or ZYX CPP-1 headamp. So for MC i use those phono stages as MM mainly to connect my SUT or Headamp.

P.S. I hope i will find the right phono stage or sut to handle my 0,05mV Ortofon MC2000 cartridge, maybe now when i have so much power with First Watt B1 + First Watt F2J i have to try it again with my existing phono stages. We will see.    

Australian JLTi
Funny, but the cabinet of my JLTi phono stage looks exactly like the cabinet of the Lightspeed device.

I know Joe very well, he used the same Hammond case after he saw my Lightspeed. The phono stage is a simple opamp riaa input and a opamp buffer output.

Also the WLM Phonata is even simpler just one riaa opamp with transformer coupled output could even have capacitor coupling as well seeing that black poly cap near the trany.

Out of the two, just from an eyeball view, I would say Joe’s JLTI would have it over the WLM.

Cheers George

I have various phono stages, but Austrian (out of production) WLM Phonata Reference and new Australian JLTi is what i use the most. Funny, but the cabinet of my JLTi prono stage looks exactly like the cabinet of the Lightspeed device.     
@chakster, what phono sources would you be using? I think this will have some bearing on the result. I have heard the B1 but have not been able to compare it to my Lightspeed. I have compared my Horn Shoppe Truth buffered preamp to the Lightspeed and there is a thread here that discusses the results. Quite frankly, of all passive, buffered, and unity gain devices I have tried, the Lightspeed is the one I still use. Your input impedance on the FW amp is on the cusp, but I have used my Lightspeed with a solid state amp with a similar input impedance and had no issues.
In the beggining of this thread @clipsal mentioned that First Watt B1 killed his Lightspeed Attenuator in terms of dynamics.

This could be true, in most systems the Lightspeed is a great match just like many tube pre's are, this could have been an instance where it or a tube pre's was not.
clio09 and the originator of this thread (rip) pubul57 asked clipsal what were the other components, alas he was never to be seen/heard  of again???

Cheers George
Great thread, i'm on it. 
Well, i want to read an opinions from the users of both products like First Watt B1 buffer preamp (original, not a clone) and Lightspeed Attenuator with analog source only (not digital). 

After years of using several tube pussh-pull integrated amps with vintage NOS tubes i put First Watt B1 buffer preamp with First Watt F2J (current source power amp) in my system last night. Now i have to learn more about deviced i have never heard before. 

The input inpedance of my First Watt F2J current source power amp is 50k Ohms, gain 15.6db.      

My speakers are Zu Audio Druid mk5 (101db) 

My source is MC and MM cartridges with different phono stages, headamps, suts. 

After my firs listening session with First Watt B1 and FW F2J   
i've noticed that i use 10% of the volume control on buffer preamp. I could live with only 20% of volume forever as it's already pretty lound for an evening sessions. 

In the beggining of this thread @clipsal mentioned that First Watt B1 killed his Lightspeed Attenuator in terms of dynamics. 

I hope someone else compared those two products, i hope to hear from you guys. 


You sent me a PM for info PDF's ect, but for some reason I can't return to you via Agon PM with my email address in the answer as this is the only way I can send you all the info. So you have to email me on [email protected]

Cheers George  
Now I just need to rig up a motor with remote control to control the volume knob externally with a belt. Has someone diy this before on anything?

To go remote, you need the remote, a receiver, the motorised pot and power supply for it.
You need a dual 100kohm Logerithmic pot, and this one is just that, you could use it in the Lightspeed. (no need to use the input board with the 6 relays, just the remote and motorised pot board with receiver)

I won’t use them myself because the reliability factor is not there, and with supply is not there either for me over a long period of time, but there’s nothing stopping owners from doing it themselves.

As for the used Lightspeed, I’ll PM the owner and see if it’s still for sale.

Cheers George
Lets just say it is and get on with our lives, what life we have left.
Seems to still be available, surprised this has not been snapped up. I love mine!

Now I just need to rig up a motor with remote control to control the volume knob externally with a belt. Has someone diy this before on anything?
Anyone who wants a used late model Lightspeed Attenuator, one has popped up very cheap here for $250aud which equates to $196usd and I know it only costs around $40 post to send as I send heaps to the US.

Cheers George

Just found a new cheap well made linear 12vdc power supply for you guys to power your Lightspeed Attenuators with. just make sure you tell him the mains voltage in your country.

It’s $58aud, this equates to around $45usd. It has the right voltage 12vdc has plenty of current, has the right size 2.1mm plug centre possitive and looks to be well made, with a sexy digital readout of the voltage.

Cheers George
Hi clio09, I've purchased two U9 Teradak power supplies from the same seller and link you posted.  They both work great with the two Lightspeeds that I've recently acquired.
If anyone gets the rechargeable Li-Ion battery pack, I'd be interested to know what difference/s you guys hear with it if you can post it up.
As It's getting harder and harder to find linear mains adaptors (smp's "switch modes" are taking over) and they make more noise.

 I could be forced one day to supply these li-ion batteries with the Lightspeed instead of the linear supply.

Cheers George    

"Just make sure with the seller, that it has a 2.1mm plug, and that centre is positive..."


If you already have the TeraDak, use the 2.1mm plug from it.

Batteries??? Yes as I measured above they are 20uV quieter on test bench, but you’d have to be a "super bat" to hear that sort of difference.

But all including myself hear something different that we can’t put a finger on, but we all prefer it (maybe physiological).

And for the money, $20 for a 12v rechargeable Li-Ion one that lasts a good two weeks before a recharge is needed, well worth having.
Here is the ebay links.
Just make sure with the seller, that it has a 2.1mm plug, and that centre is positive.(I like the black ones, as they look better.)

Cheers George

Thanks George, what about a battery PS.
Hi clio09 , that one you've linked to is not one I've seen before, as at just 8.5v it's close to the drop out voltage (7.5v) of the 5v regulated circuit inside the Lightspeed.
For $50 it's a good buy though, and should be fine.
The ones I used to link to, were 9v and I think you could adjust them to 12v inside, with a trimpot, maybe you can with this too.

Cheers George
I had some time to kill so I decided to re-red this entire thread (I sure do miss Paul). I'm not on Audiogon much anymore, but have to say that the Lightspeed is still with me and getting its fair share of use. I've been looking to upgrade the PS so went looking for a Teradak and found this one:

I assume it will work based on what I have seen in previous comments here. On the other hand, what's the best batter PS option these days?


I dug out some noise measurements for you guys I did on the noise floor of the output into 50kohm load.
It was on the absolute limit on my Tektronics test gear to measure down that low.

And with the Linear powersupply it was 50uV P/P (micro volts peak to peak ), this is around ten times lower that the best active preamps I’ve seen, which are sometimes in the mV (millivolts)

Then I did the same using a pure battery supply, and yes it did come down a touch from 50uV to 30uV, this could be the reason some of us hear something when using battery but can’t explain what?

But a difference of 20uV (micro volts) noise is practically nothing?? I can't point my finger at this and say this is what we're hearing though.

Cheers George
Man, that FR88 is a straight focal copy.. looks nice though.
 my speakers are Be-One, model: The One. No one has ever heard of them; well, not in the West. I heard them and bought them. I have only ever found one reference online, by a reviewer (an amateur, I think)
Wow these guys look to make some good stuff, a bit like Usher. Some of the speakers are very Sonus Faber influenced.

Cheers George
In answer to your question Georgehifi , my speakers are Be-One, model: The One. No one has ever heard of them; well, not in the West. I heard them and bought them. I have only ever found one reference online, by a reviewer (an amateur, I think), who had them as his reference speaker. The site where I read that seems to have died. The brand is Chinese, and have a website It often works. My speakers have been discontinued, and removed from the site. They most resemble the BO-8, which has one less driver per cabinet. I have never heard their amps, but they do look gorgeous! Hey, if you are ever in the Dandenongs ...
tradeontheweb thanks for the guidance.  I may try the battery option too as a fun experiment.  I've started out powering the Lightspeed with a Teradak power supply. 

I hadn't done any upgrades to my setup in about 10 years since I recapped my AR9LSi speakers with audio grade film caps.  I thought I was done, but started sensing something was holding me back recently.  I started researching what folks were saying about the components that I already had and discovered folks saying the Adcom GFP-565 was not very good.  Glad I found the Lightspeed.  It totally makes sense that putting  more active components between the music source and the amp risks adding more noise to the signal.  It would have been another long journey to buy and try a bunch of different active preamps.  The Lightspeed has also rekindled my audio bug too.  Will be looking  at further upgrades or mods to my other components, but the Lightspeed will remain at the core.
BTW: esmith904

You can also try to power it using rechargeable battery power, (links are somewhere here to get one on eBay).
Most (including me) say it’s better than the wall wart, but there’s not much in it, just a feeling.
As they can’t explain what’s better, but it’s definitely worth doing as they are cheap to get.
Welcome to the club esmith904 !
Your description kind of mirrors what I remember mine was, more than 10years ago now. I’d thought I was doing well with my system. Big Infinity Speakers, couple of Krell amps and a Cal CL-15 HDCD/CD player. I’d used a variety of solid state and valve preamps, including Musical Fidelity, Audio Research SP10 & 11 and most memorably, a very "microphonic" Supratek valve Pre. Some were great, some less so, but all imparted their own coloration to the sound.
I actually borrowed my first Lightspeed from a friend. On first sight, it wasn’t impressive at all compared to the monsters I’d used. But connecting and listening dispelled any concerns I’d had on the appearance. As you say, clarity, cleanliness and dynamics are there in spades. I don’t care what it looks like, I bought one there and then. At the price, it’s one of the real bargains in high end Audio and let’s face it - they’re few and far between!
I don’t know whether we’re in a "secret"club any longer, as I see more and more comments on it here and over at DiyAudio as well.
Anyway, nice to see another happy Lightspeed’er on here!
Sharing my new experience with the Lightspeed Attenuator. I've recently been researching what key upgrade I could make to my mid-fi Adcom setup (Cal Audio Labs Icon II CD, GDA-700 DAC, GFP-565 preamp, GFA-545 II amp, AR9LSi speakers) in an attempt to approach hi-fi sound. After much web searching and reading reviews, I determined replacing the Adcom GFP-565 preamp was where I'd get the most sound improvement. However, most of the recommendations I could find suggested I'd need to step up to $3K-4K active preamp or give a passive a try. Luckily, I stumbled across this thread with glowing reviews how the Lightspeed is as good or better than very expensive active preamps. My experience so far has blown me away. I didn't know recorded music could possibly sound this good. The sound is super clean, clear, more 3 dimensional, and has more bass at low volume. The music seems to have more impact from individual instrument sounds at moderate listening levels. Seems like I can feel the music more.   I can really tell a difference in the sound of cymbals now have a clear metallic shimmer vs. a fuzzy sizzle. Everything just sounds better across the spectrum. I'm buying another one for my office system. I feel like I've joined the secret Lightspeed club. It's hard to believe something this good is not that widely known.
 Just to test before shelling out, I plugged my passive Schiit Sys into the Halcro. The Schiit outputs up to 5K ohm (not dissimilar I believe to the most the Lightspeed puts out).
Hi Mick, thank you very much for the glowing review, especially with your equipment the Lightspeed is keeping company with. I've tried to Google these speakers but found very little on these 100kg beasts have you a link to them?

As for the slight impedance mismatch, the worse scenario output impedance for the Lightspeed is around 2.7kohm, if the Schiit Sys is a 10kohm volume pot this should be about the same.

And yes even 2.7kohm output impedance into your Halcro's very low! 10kohm input impedance, it will be at a slight disadvantage, this is why you liked the extra drive the X10-V3 a little more.

But if the Halcro had say 33kohm or higher input impedance, you would probably have preferred the sound without the buffer in circuit. As the best buffer is no buffer still if you don’t need it.

Cheers George

One with a switch for different sources would be nice.

Hi Todd.
Yes it would be, but here’s the problem I have. The Lightspeed is all about not have any light contacts in the signal path, this includes volume controls and yes input or output switching.

My prototype still measures and sounds as good as it did when new, but it has got two inputs with switching (WHAT!!! you say), it has the best switching/wiring possible, because I need to A/B dac I/V stage modifications which I also do on the side as well.

This this prototype Lightspeed is the benchmark test for all production Lightspeeds to be A/B’d against with before they are sent to customers, to make sure they all perform as expected.

From even when it was new everyone that has heard the A/B’s including me production ones vs the prototype, says that the production ones with only one input sounds just a little better
You can’t put your finger on what it is, but the productions ones have just a touch more ease/transparency to the music presentation than the prototype.
It’s a bit like when you hear the battery supply vs the mains supply, you have a feeling the battery is just a touch ahead of the mains.

This is the reason I don’t do input switching, as I want the production Lightspeed Attenuators to be as transparent as possible, without any compromises done in the manufacturing process.

Cheers George
One with a switch for different sources would be nice. I know I can put a switch ahead of it, but that would add another box, more Interconnects...


I’d been searching for a preamp, so for a giggle I Googled “best preamp ever audiogon” to see to see who had recommended what.

The top hit was for tube preamps, but I didn’t want to limit my search to tubes. The second-top hit was not it either – just preamps for sale.

But the third and fourth hits were more like it. They came from this very thread. I started reading. My reading extended over two nights. (Thanks guys!) My interest turned to intrigue when I twigged that the preamp – the Lightspeed Attenuator of course – was Australian (which is what I am and where I am).

What really kept me reading was seeing actual users were replacing expensive and much-loved amps – tubes even – with something straightforward and cheap (by comparison).

Now, the OP here (thank you Pubul57) had made it clear that the Lightspeed needs the right environment in which to work.  A source ouputting 2V or more, which is pretty much everything these days I believe, a short interconnect to the power amp (three metres or less), low capacitance interconnects – and a power amp whose input is preferably the industry standard of 47K ohms or more.

I checked the specs on my Halcro DM38. Only 10K ohms on the RCA input. The Lightspeed outputs RCA only. That might be a problem. But I wasn’t going to stop now, was I?

Just to test before shelling out, I plugged my passive Schiit Sys into the Halcro. The Schiit outputs up to 5K ohm (not dissimilar I believe to the most the Lightspeed puts out). So we are a long way from the ideal 1:10 ratio, which would have us up around the 47K standard. But the Schiit provided enough bass and volume to make me push ahead. It worked, at least. But I thought I was probably going to need a buffer, so as to fix the impedance mismatch between the Lightspeed and the Halcro.

And I should detail the rest of the system. Speakers are a massive pair – Be-One, The One. Five drivers per cabinet, about 100 kgs each, sensitivity 89db. Streaming via an Auralic Aries Mini, listening to 320 MPs, CD rips, hi-res files and DSD. Switching between DACs – the Aries, an Emotiva and an R2R Audio-GD 11. Preamps on hand for comparison were the Aries Mini again, a Xindak XB 8250, and a Geiseler preamp (another boutique Australian product) (and the pre-outs of a few integrated, including a Jungson JA-88D, Yamaha AS200, Harmon Kardon 990). There were two tube preamps around, an Audile using Jan Philips 5814a tubes, and a SoundMaster Mk 23 using 2A3, but the tubes were so different, I didn’t make comparisons with the Lightspeed. The room is roughly 30 foot long and 12 foot wide.

So the Lightspeed arrived. One great thing about it – no burn-in. Because there is nothing to burn it. That’s a relief. Just give it one minute to get warm. We’re off.

First impressions: this is good.

It was clear. Like water. There was no shortage of bass. Or volume. Highs were clear. Volume – more than enough. I had it playing around 2 o’clock to play it loud (90db, sitting four to five metres from the speakers.) There is no sweet spot on the volume dial – the sound is the same all the way. There was no channel imbalance.

That’s what it sounded like – which is to say, it had little sound of its own.

It was dead silent – which I suppose is a function of no gain and no mechanical parts to speak of. My room is very quiet, so that silence is impressive – and necessary.

Whenever I get a new component, I make a point of listening to it. By which I mean, not comparing, but listening. (And I only change one thing at a time – so I can be sure where the difference is coming from.)

So only after a few days did I start to compare – with a little bit of fear.

Comparison confirmed my suspicions: what the Lightspeed delivered was good, but insufficient. It was approaching the weaknesses commonly attributed to passive preamps. The attack on notes – be they guitar strings or piano notes or kick drums or electronic bass bombs – wasn’t quite there. That one thing amounted to the music losing life and shine.

But what was there was all good – it just felt the thing was struggling, pushing the music uphill. But it was clearly good enough that I had to know how it would sound given the right conditions. So let’s get a buffer.

I got a Musical Fidelity X10v3 (not XD.) It puts out just 33 ohms. It deploys two military-spec tubes – which Musical Fidelity says are designed to withstand the radiation of a nuclear war. Pity the rest of the system won’t survive.

And, voila. Now we’re talking.

If the taste was water before, it was water out of a plastic cup. Now it’s water out of quality glass. Transparent.

All the life and dynamics were there. Transients had zing. Slam had slam. If the recording has depth and height and placement (ie soundstage), so does its reproduction.

It just sounded like I was hearing the music – be it Billie Holiday, Kraftwerk, Crazy Horse or Chopin. The lack of distortion from both components is quite the treat.

So, there you go. This will be old news to some of you – but I had to share it, and the odd fact that I had to go so far afield to discover something in my own backyard.

This thing really is ingenious.  Theoretically, it seems to me the ideal preamp: adding nothing, subtracting nothing, with no touching moving parts and no noise, simply providing a channel through which the music can flow. Like straight wire with gain – except there’s no wire, only light dependent resistors, and no gain either.

That’s an impressive list of gear you have there hopkinstk

1: Two Spectron Musician III MKII in mono blocks
2: Usher BE-20 Diamond
3: VPI Prime turntable with Dynavector xx-2 MKII cartridge
4: Whest PS.30RDT SE Phono Stage

I have a buddy that also has the Usher BE20’s and wow they are very good and full range to boot, I couldn’t see that the Rel sub would be needed with them they go so low.
(maybe from 30hz down? if you listen to a lot of organ recitals)
I’m pleased you think so much so much of the Lightspeed Attenuator passive pre to keep it in that company.

Cheers George