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
miller65Thanks George the temperature variation in the power supply makes sense as it is more stable in line with a stable room temperature I also intend trying with a battery in the next few weeks.
As a next stage I am considering using my CD player as a transport and introducing a DAC into my system this will also enable me to include a network player at a later date. However having checked the output spec of the DAC Beresford Caiman mk11 I have a couple of questions in terms of how output impedance can effect the sound quality . The output voltage of the DAC is 2v which is in line with LSA recommendation but the output impedance is 1k ? appreciate it should be 200 ohms or less ideally . Iwill use with a very low capitance Stager silver solid i/c 0.5 metre length .
Does anyone have experience of using the LSA with output impedance this high and if so what if any effect can it have on the sound / volume control . I love the transparent dynamic sound the LSA currently gives me and wonder if this potential impedance mismatch would have any adverse effect on the sound quality or use of the volume control which
currently operates at 12 o clock , which is generally plenty loud enough

Hi, yes please post up what you think of the battery once you've listened to it.

Your Dac at 1kohm is fine still into the Lightspeed's 10kohm, but then your poweramp comes into play and series up with the 10kohm of the Lightspeed, I would say amps with over 47kohm all will still be fine.

As for interconnect cable capacitance, stay below 100pf (capacitance) per foot and 2mts max, good cables are usually below 100pf per foot.

Cheers George

dgarretson

Hi George, I'm thinking of an DIY LDR attenuator to replace the stock 10K Alps dual pot in a Sennheiser HEV70 energizer for HE60 electrostatic headphones. I need to step down from 25Vdc to 5V for this application. The chassis is cramped and there is little room inside for a heat sink on the down regulator. An LM2596 looks like an easy fit in terms of low heat dissipation and compactness.  Do you think this would compromise sonic performance relative to a LM7805 linear regulator? My concern about the LM7805 is overheating from the 20V step down.

Thanks,

Dave  

 

Hi Dave, as for sinking 20v on a 1amp 7805 this is too much and will get very hot, best of getting a 12vdc supply for it.

Cheers George  

Hi all, owners that like to try different ways of powering their Lightspeed Attenuator’s. May like to try something new that Stereophile gave some push for.

It’s the new iFi iPower supply dc wall wart, now before any of you say it, yes I didn’t like recommending smp (switch mode) wall warts. This was only because the ones I tested had a bit of noise, that couldn’t be heard, yet was measurable when compared to a linear wall wart.

This new iFi iPower supply wall wart is smp, yet it’s noise is very low.

http://www.stereophile.com/content/music-round-77#61wYlEfbAywkfiS2.97

http://ifi-audio.com/portfolio-view/accessory-ipower/

If you order one be sure to get the 12vdc one with 2.1mm X 5.5mm plug with centre positive.

Lets please hear a review from anyone that gets one, as I may change to these as supplied wall wart with the Lightspeed Attenuator, as they are multi world wide voltage usable.


Cheers George



This is what Kalman Rubinson of Stereophile heard when he used this new iFi iPower wall wart on a low powered dac when he compared it to a linear wall wart, it should/could do the same for the Lightspeed Attenuators sound.


"When I switched over from the stock supply, the DAC didn't seem quieter when there was no audio signal, but that's not the real test. Recordings with open, ambient soundstages sounded cleaner, and both instrumental and vocal music was more distinct. This was no major change that struck me every time I listened, but it did make all of my listening much more relaxing—perhaps because, subliminally, it required less effort to attend to individual sounds, particularly those far back on the soundstage."


It has some pretty impressive measured noise figures, of 1uV of noise, (that's microvolt not millivolt)!!!!!

This could be a deal breaker, and the end of linear wall warts for the Lightspeed Attenuator.

I tried to find advertised pricing of them, but couldn't get an exact figure, but it seems to be around $50-$100 which should be a great upgrade for that kind of low noise supply.


Cheers George  

The Stereophile 'push' is working: it's out of stock everywhere I've looked. fyi: it's US$50

Thanks banquo, $50 is a very good price if it does what's claimed, can you supply a link to where you got this price, I like to get one when they've replenished their stock.


Cheers George

Thanks for the links banquo, I looked at the "musicdirect" link and it seems they do do international shipping also, and $49 is a great price.

This supply could be a no brainer, as smp's are very good everywhere save for the noise most have, and this one seems to have addressed that and made it even quieter than linear supplies that are available. 

http://www.musicdirect.com/t-shipping.aspx


Cheers George

Post removed 
I just got my dual control Lightspeed.  It has a very wide soundstage, stunning detail and is absolutely quiet.  I am very pleased with it.  Seems to work well with my solid state gear

Associated gear

Emotival CD
Weiss DAC
First Watt B-5 crossover 18dB/ octave at 150 Hz
Newly Rebuilt Threshold 4000 (bass)
DIY Aleph J  (wideband)
Dual Plains Audio Altec in open baffle
Lowther DX 4 

Hi all. I thought i'd share my experience of adding a lightspeed to my system as this thread helped me decide to try one. I was sceptical that it would work because my poweramp has a 33kohm input impedance and my dac has a 1000ohm ouput impedance, so it's on the limit of what is recommended as suitable for use with a lightspeed. I had had my dac running directly into the poweramp and controled volume with either software (Audirvana) or a squeezebox touch, but it rarely sounded real. So i investiagted preamps and attenuators and settled on the lightspeed due to it's low price, simplicity and high praise.

Well, the lightspeed has been a revalation. Music has come alive. Without the lightspeed music is compressed, less dimensional and digital. With the lightspeed music is more coherent, instruments and voices have precise space, height and depth, the image is rock solid, there's more detail, deeper tighter bass, and more pleasing tone. I hear nuances that i couldn't with my previous setup. Music flows naturally and consequently i'm more engaged. It's a keeper for sure. Cheers!

First I’d like to thank Dave and Greig very much for their positive findings and review on how the Lightspeed Attenuator sounds in their systems, both of you are using the standard (linear Wall wart) power adaptor. I would like to hear from you what you think when it’s battery powered.

I’ve been recommending a nice cheap alternative in the way of 12vdc Lithium Ion rechargeable, some users have said even better sound with it, even Sam Tellig of Stereophile reported better sound with his Lightspeed Attenuator, and same went for his son. 

These are the ones needed, as you can see quite cheap, the 6800mmA one lasts for at least 24hrs before a recharge is needed. Just make sure with the seller that the plug is 2.1mm and centre is positive.

http://www.ebay.com/sch/i.html?_odkw=12v+rechargable+Li-Ion&_osacat=0&_from=R40&_trksid=p2045573.m570.l1311.R1.TR1.TRC0.A0.H0.X12v+rechargeable+Li-Ion.TRS0&_nkw=12v+rechargeable+li-ion+battery&_sacat=0

Cheers George

Hi Georgelofi, is it possible to use a light speed attenuator on a phono pre-amp?, I like being different and the first world wide to have such a scheme,  if not,  can you build me such an attenuator? 
audiolabyrinth

Hi Georgelofi, is it possible to use a light speed attenuator on a phono pre-amp?, I like being different and the first world wide to have such a scheme,  if not,  can you build me such an attenuator?
Yes it is, I have numerous owners that use it with their phono stages, which say they have never heard their LP's sound so good.
First what is the phono stage you are using as there are the odd ones that are not compatible?

Cheers George   

@audiolabyrinth

Sorry, but you won’t be the first in the world! I replaced the stock Shallco series attenuator with a differentially balanced LDR control in my AtmaSphere MP-1 phono preamp. It is a successful upgrade, though not quite viable for commercial purposes, as the LDRs drift a bit with the heat of all those tubes.

Yes I would never advise anyone to put a Lightspeed circuit inside any audio equipment, no matter who made it.
But I don't think @audiolabyrinth wants to do that. He says he want to put a Lightspeed Attenuator "on" his phono stage. 

The Lightspeed Attenuator circuit should be by itself, in it's own chassis, and with an outboard powersupply as I make and supply them.
That way the quad matched set of LED/LDR's stay matched, and don't give any trouble at all.
  
Some of these Lightspeed clones getting around with internal transformer power supplies and other heat generating circuits that give large heat swings are asking for trouble and giving it a bad reputation, careless and I don't advise it or them at all. 

Cheers George 
Hi Georgelofi,  thankyou,  the phono stage that I'm considering is the Vincent pho-700 with outboard power supply solid state/tube hybrid mc/mm phono pre-amp,  check it out for me George,  audio advisor sells it,  has the specifications on their site.
George, the specs are mm 47k, mc 100 ohms, 12au7 vacuum tube used in duel triode mode, thankyou 😀
audiolabyrinth

Hi Georgelofi,  thankyou,  the phono stage that I'm considering is the Vincent pho-700 with outboard power supply solid state/tube hybrid mc/mm phono pre-amp,  check it out for me George,  audio advisor sells it,  has the specifications on their site.

Yes thought it was, saw you posting about it in other threads about it. A very nice looking phono stage for the money, looks like they really did some homework designing this.
I found that it is 250ohms output impedance and it has 40db gain for the mm section and 60db gain for the MC section. This will be a great match with the Lightspeed Attenuator.
As some of my customers have the Dynavector 75 which has the similar gain structure and they are over the moon with what they are now getting from their LP's using the Lightspeed with it.

Cheers George  
Hi Georgelofi,  I talked to Joe there at audio advisor,  he said that the Vincent pho 700 does 8 volts max out put,  your unit is passive?, I may put  this on my modified krell 700cx to play with from time to time,  it's 100kohms, however,  it takes 3.35 volts to push,  as you know, I've been pushing that amp with 2 volts running directly from the digital player,  cheers 
Yes, that 700cx Krell has low sensitivity as stated by Krell at 3.58 Vrms to give it full output just before clipping Most amps are usuall 1-2v. Your lucky the phono stage has so much output 8v (which I think is peak/peak anyway) not rms.

Well even with 2v from your CDP's and you still get enough volume, all this speaks that you have no use for and active preamp/s with their even more gain and colourations.

Cheers George  
Post removed 
Thanks for bumping Glory, no not dead just resting.

I’ve been on an extended holiday from any production runs, as they can be very taxing/monotonous to produce, just quad matching all the led/ldr’s can do ones head in, as to keep this kind of pricing I run basically a one man show.

Got a few orders and half way through finishing off the next batch to go out.

You should maybe get some more happy owners posting their thoughts if they are members of Audiogon and frequent these pages after they’ve had a good listen, but then most of the next batch is going to Europe and Asia, I don’t know how wide spread Audiogon forums go outside of the US. They seem to have their own go to forums in these areas.

Cheers George
Please forgive a perhaps ignorant question, but would substituting a Lightspeed for my existing Jolida Tube DAC and using my Rotel 1072's existing B-B DAC to send a signal through the Lightspeed into my LSA Statement integrayed be a good idea? 
Hi simao, yes you can.

Seeing the LSA Statement Intergrated has a "main in" this is the input you would use to put the Lightspeed's output into. What you are doing is bypassing all the Statement’s preamp section and using it just as a poweramp.

Then you could use either dac you have to the input of the Lightspeed and use which sounds best with the Statement as a poweramp.

Cheers George
I’ve been using the Lightspeed for several months now. I purchased the dual volume control version to solve a balance problem in my room. It works great and is as transparent as advertised. I compared it to 2 other passive pre amps that I own, a Schiit Sys and a Tisbury passive. Swapping the 3 passives in and out, and running the source straight into the amp revealed that the 2 other pre’s altered the original sound ever so slightly. The Lightspeed sounds the same as the source going straight in. I still like the other 2 passives, but the Lightspeed won the transparency test. My Lightspeed is feeding a 47 kohm input impedance, no problems there. I really like the flexibility the dual volume controls give me, and the performance has lived up to what I have read about it.

I’ve tried the iFi 12v power supply and a cheaper Jameco linear 12v supply. The difference wasn’t very noticeable in my system, but mileage may vary. I doubt I could tell them apart in a blind test.
Hi mward, glad you like it, good that you gave it a few months before commenting on it. As for the " iFi 12v power supply "I think you are the first to try it, I had high hopes for this.
But as you say it's not that discernible from the standard wall wart. 
Sam Tellig (Stereophile) and myself found the same, even with pure battery power vs the standard wall wart. You sensed there was something different but couldn't say what, and you had buckley's telling the difference in a blind A/B.
PS: buckley's = Aussie slang for, "no way mate"

Cheers George 
Hey George, yeah the iFi just hasn't done much for my Lightspeed in my system. I feel like my system is resolving enough to pick out a bad recording pretty easily and to hear differences in cables, but I just couldn't spot the changes from this ultra quiet power supply if they exist. I almost felt like it made things a touch more reserved compared to the linear wall wart, but there is no way i could blind test prove it.  That was probably pyschological negativity toward a change on my part.  I like a lively system. I'm actually using the iFi right now and there is nothing wrong with it, just not a noticeable change for me.   My system doesn't have super sensitive speakers or a room designed for extremely critical listening though. I would be interested to hear about the iFi from someone with a very revealing system and dedicated room.  
Glad to read the iFi iPower DC supply being discussed. I’m interested in using it in place of the as-supplied Auralic Aries Mini wall wart. I wouldn’t call my system extremely resolving, though I can easily hear changes in cabling. I could not, however, hear a benefit using the Audioquest Jitterbug. But, for $49 bucks from Music Direct and given their 60 day return policy it might be worth trying the iPower device. More likely to spend $49 as opposed $299 for the Auralic LPS. Am wondering if anyone other than mward has tried it. Tried searching discussions, this Lightspeed Attenuator thread was one of only two that came up. Thanks in advance for any input.
This Lightspeed sounded open, relaxed and showed me all  musical info that I have been missing for a long time, a real game changer..AN Dac 3 fed by msb digital cd rom drive into lightspeed then the CAT JL2...endless power and dynamics and i have not even matched the
impedance between devices yet...
soundwise
endless power and dynamics and i have not even matched the
impedance between devices yet...
Hi Michael, looked at your source and amp impedance's, and you have a nice impedance match.

BTW: what speakers are you using, as the rest of your system looks very nice, though I'd hate to have to fork out for 12 x 6550's when time comes around.
The ones I used to love were the military NOS G.E. green label ones, who's glass seemed twice as thick as anything else, and they cost over $200 each if you can find them new in box in Australia.   

Cheers George
Verity Sarastro 2 ..they took the Raven Ribbon tweeter apart and added better magnetic parts and also shortened the ribbon surface to widen the dispersion pattern. These speakers with the cat amp are very nice together..best for acoustic instruments.
Hi soundwise (Michael) you asked in a pm,
What about he CAT output impedance any way to adjust that?
MS

Your Verity’s are an easy load for your Cat most of the time, but at 5khz there is a hard load of 4ohms in conjuction with around 50 degrees of negative phase angle. http://www.sonicflare.com/IMG_1966.jpg
http://www.stereophile.com/content/verity-audio-sarastro-ii-loudspeaker-measurements#Xb47wFP2V0w59G7...
But your Cat should be fine still at this frequency as well. As the Cat has only one speaker tap (no way to adjust the output impedance), but having a bit of negative feedback brings the output impedance low enough to handle this, and also there’s not much power needed at this frequency either.

Quote: Cat JL2
http://www.soundbysinger.com/UserFiles/image/JL2%20Sig%20resize.jpg
Circuitry
*Ultra-wide open loop in-circuit bandwidth of the output transformers enables operation of the amps closed loop response entirely within the open loop response, eliminating any requirement for the output stage to perform beyond its natural capability.
***Unprecedented stability into complex speaker loads.
I can see why your liking the sound of the Lightspeed in this very nice system you’ve put together.

Remember the mil spec GE6550’s with the green label I mentioned a few posts back, they are a "cracker" of a tube.


Cheers George
George,

wondering if you have tried to upgrade the parts, if it is possible, and if so, can the sound get even better than it already is!? Noticed that the stage is wider, and that you can hear outer edges if that makes any sense. Also, does dual volume control do anything? I have tried your preamp with same type of audio note dac with Vac music block 160s…also with def tech bp 7002 speakers…not as good as the other setup , but not bad..I will use 1 ohm resisters to tame the tweeter output , but these speakers are 800 used and they sound holographic like the MBL radialstraters which cost as much as a large benz….   imho, bipolar is a far superior design compared to regular speakers..
best,

I am looking forward to your next project!

Soundwise
Hi Soundwise, once again thanks for the praise you’ve given on the Lightspeed.
As it stands with me there’s not much that can make it sound better. Others here may give things they’ve tried.
1:Some say battery power, the best power you can give to the Lightspeed, then some (including me) say it’s virtually undetectable. you can try this using one of these rechargeable ones.
http://www.ebay.com/sch/i.html?_odkw=12v+rechargable+Li-Ion&_osacat=0&_from=R40&_trksid=...
2: Some owners have replaced the gold rca’s with more expensive ones??
3: As for the dual mono Lightspeed, 90% of owners that have both Lightspeeds (stereo and dual mono version), prefer the dual mono. I think maybe it’s because they can get perfect centre image due to system/room imbalances.

As for the Vac vs the Cat JL2 maybe the Cat is just a better amp, the Vat being a tube should also be a great match but I can’t find anything (specs wise) on the VAC Musicblock 160’s

Can you link us to anything (spec wise) on them, or can anyone else?

Cheers George
Hi George,

I thought I'd share my quest for audio nirvana and how the Lightspeed was the final piece of the puzzle.

Most of my setup is fairly standard gear - a Logitech Touch playing flac files over Cat6 cable from a Debian file server.  Its optically connected to a MiniDSP 2x4 HD, which provides a flat freq response and acts as a DAC.  Then a Cambridge Audio 651W power amp.  

The (less conventional) speakers are omnidirectional (from OmniAudio) with single Lowther DX4 drivers in each.  My wife and I love the ominidirectional sound but we've never been fully satisfied with the sound in our house. The MiniDSP was a big help to fix room issues and the CA amp added the power and control but something was still missing.  Or was something in the way?

When we added the Lightspeed attenuator the difference was obvious to us both.  Digital volume control (from either the Touch or MiniDSP) was actually getting in the way and also raised the noise floor (as you would expect).  Adding the Lightspeed gave us deeper bass, much wider soundstage, and transparency that finally took full advantage of the Lowther's speed.  Noise floor dropped into the black.  

We've been listening to the new setup over Xmas and we're both very impressed.  My wife keeps telling me she is hearing new things in the music.  I'm amazed it made such a difference to the soundstage and bass.

So nirvana has been achieved. The Romp by My Friend The Chocolate Cake, as one of our standard test tracks, was a special treat for our ears.

I'd also like to thank you George for your fabulous support and emails prior to getting the Lightspeed plugged in.  I really appreciated it.

Cheers Scott..

Thanks very much for the great rap osmium, much appreciated.

So nirvana has been achieved. The Romp by My Friend The Chocolate Cake, as one of our standard test tracks, was a special treat for our ears.
Great Aussie talent, so much of it here, undiscovered.
https://www.youtube.com/watch?v=We3HrsuqYJk


When we added the Lightspeed attenuator the difference was obvious to us both. Digital volume control (from either the Touch or MiniDSP) was actually getting in the way and also raised the noise floor (as you would expect). Adding the Lightspeed gave us deeper bass, much wider soundstage, and transparency that finally took full advantage of the Lowther’s speed. Noise floor dropped into the black.
Yes digital domain volume controls can be very good if near full up, they have to be used at or over 75%, this can be too loud for most systems. If under 75% they can actually reduce the digital resolution "Bit Stripping" to 14bit, 12bit, 10bit ect, and the lower you go, the less resolution you get.
This is why the Lightspeed Attenuator being so transparent/dynamic is great, set the digital volume at full, adjust the Lightspeed Attenuator to the loudest you want to ever hear, and then use the digital volume remote to lower the level as needed, that way your never under 75% with it, this way you'll never "Bit Strip"

Cheers George
Great clip George.  Captures what they're like live.

I figured I'd hear a difference with no bit stripping and the change in noise floor but I was really surprised by the spatial effect on the music.  The soundstage is far wider and deeper.   Very happy.

As the Lowther's are so sensitive, I was really cutting a lot digitally.  We rarely go over 50% on the Lightspeed (depends on music) and usually sit at about 1/3.  

Cheers,
Scott

Scott you could try 2 inexpensive different ways to power the Lightspeed Attenuator, that many say is an upgrade to the power pack that I use.

1: Pure dc, rechargeable Lithium battery these will last around 1-2 weeks of listening a couple of hours a day before a recharge is needed. Just make sure with the seller that it has a 2.1mm plug and centre is positive.
http://www.ebay.com.au/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.X12v+Li-Ion+rechargeable.TRS0&_nkw=12v+Li-Ion+rechargeable&_sacat=0

2: Very good mains supply, also quite cheap. (9v-15v is fine) again make sure the plug is 2.1mm, centre positive.
http://www.ab-system.hk/index.php?route=product/product&product_id=64

Cheers George

My system if a fi2A3, an Abbas DAC, and Klipsch Belle speakers so it seemed ideal for this type of attenuator.  I was expecting it to be fairly neutral since not much is being added but I was stunned by how much improved the clarity of my system was.  The quiet spaces in between the sounds are unbelievable.  I am very happy with this new addition.  
Post removed 
Glad you enjoy it so much Jeff, that is a very interesting system, low power purest, you need the efficiency of the Belle’s for those amps.
Can you give some info or links on the dac and amp/s as I’ve never come across these before, I take it the amps are SET 2a3’s at a couple of watts each channel?

I quickly couldn’t find much except this made by a Don Garber
http://www.6moons.com/audioreviews/jj2a3/hero_fi2.jpg

I had a 3w Softone SET 2A3 from Japan (no longer made) he makes his own R-core transformers, amps ugly as sin but so cheap, This 3w amp drove a pair of monstrous Goldmund Apologue effortlessly.
http://softone.a.la9.jp/english/

http://www.milliondollarstereos.com/pix100k/goldmund_apologue.jpg


Cheers George
Crazy looking speakers.  The Belles came first and the amp followed.  About 3w is about right and I listen with the Lightspeed at about 1/3 volume.  Very efficient.  The DAC is handmade with the following as some particulars. Very interesting though.

 DAC 2.0SE features:

1.Tube DEM clock (E180F, EAA91)
2.CS8414 SPDIF receiver 24/96
3.Shunt voltage regulators based on the germanuim transistors. The scheme has been improved and has a superior thermal stability.
4. Vintage and modern audio components are used:allen bradley,philips,telefunken,
Capacitors:Black Gate (2pc FK series,1pc PK series),panasonic pureism,Audio note standard (2pc) and Audio Note Kaisei(3pc) 220mfX160v,470mfx25v
5.Board covered with gold and a special varnish for best sound 
6.Stranded wires composed of vintage copper wires taken from klangfilm, telefunken, siemens sound equipment
7. I/U convertor based on the special gold plated low noise vintage transistor. Because of this fact, an excellent reproduction of quiet sounds, at -60.-80db level
8. PIO output capacitors HYDRA from 60th 
9. Shortest signal path, the tube output stage with the low output impedance (5687,EZ80).
10.NOS mode(non oversampling)
11.Genuine TDA1541R1 philips factory
12.Siemens film capacitors in the DEM cells
13.Spdif receiver voltage stabilizer based on unique powerful vintage transistor with a semiconductor crystal on a thin gold basis in the copper case.
14.Separate power transformers for digital and analog sections. Separate transformer for DEM clock.
15.Telefunken choke from 30th in the 5687 power supply.
 

�4����
Genuine TDA1541R1
Best way of reproducing pcm redbook cd, with R2R Mutibit converters. Man after my own heart.


This intrigues me, as I'm right into zero feedback I/V stages for current output dacs/. Any more info on this, circuit perhaps
I/V converter based on the special gold plated low noise vintage transistor

Cheers George

My review….. As an ex-owner of many hi-end audiophile hardware from speakers such as Kharma, Dynaudio, Vandersteen, Magnapan, Sonus Faber, to amplifier such as Audio Research, Plinus, Rogue, etc I am experience and qualify to review hifi component, up to S$50K if putting a value to a piece of hardware means anything to you.

Lightspeed is a product that appeal mostly to the diy community. By saying diy community I don't mean only those who seek to build an attenuator only but also those who are constantly searching for tweaks to their hardware such as Caps and tube roll or optimising an amplifier circuit. The writer is one such person.

LS did no active advertising and I chance upon the LDR circuitry in a diy forum only recently while seeking to improve my channel imbalance with the Alps variable resistor swipe type volume control. I assembled a 23 steps attenuator and realised my Alps variable resistor was indeed a bottleneck to my system. The 23 steps attenuator was like from winter to spring in my system. But I believe much can still be done to improve the performance.

Than came the LDR attenuator. A simple and logical concept of using an isolated LED light intensity circuitry to vary resistance in another circuit hence producing a clean signal through the amplifier circuit resulting in crisp, clear, smooth, transparent and quiet layers of music only limited by the quality of the equipment downstream to the LS. The use of the stereotype audiophile jargon such as soundstage height/width, imaging, timbre, etc... is to me irrelevant in describing the LS. I believe an attenuator's aim is not to have a sound but to vary the signal level and pass-through effortlessly and not impeding the potential of your equipment. Any improvement gain is due to your equipment and LS is just an enabler.

But I will certainly get bomb to claim the LS do not have a sound because the signals do run through some circuitry before it gets transmitted to your equipment. My point here is that if the LS produce a negative effects to your setup or swing towards certain attributes that is not to your liking, most likely the cause is a mismatch in impedance or you have a coloured attenuator and not the LS being inferior.

Is the LS a plug and play component? No and maybe. First you need to make sure you don't have an impedance mismatch issue which is rare but not impossible. I have also a tube pre and SS power system and I lost the much preferred "tube sound" by putting the LS in place of my tube pre. This is not to say that it is terrible but not my preferred sound. I have now bypass my tube pre 23 step attenuator and use it as an over glorified tube buffer. If you are using a passive preamp the LS is a no brainer upgrade. If you have and like your SS pre, you will likely like the LS in place of your SS pre. Comparing my Alps to the LS is like winter to summer. It doesn't sound thin or dry on the contrary to some who have reported their experience. I recommend it highly if it fits you bill.

A working LS circuit is available from a diy forum if you are a diy-er or are hell bend for saving up for other upgrade and only if you can find a match pair of LDR out of the many required for a project. I believe I can also make one from the available info from the internet but I choose to support the inventor who is passionate and generous enough to share his circuit and know how to the diy community in the numerous forum in the internet. His generosity proved that he is not a money grabbing person and in today's world such character is few and far between.

The LS is where I stop my search for a better alternative for now. Buy it if it fits your bill before you consider an interconnect upgrade, tube roll, power cord upgrade, component upgrade. Most likely it is cheaper than other conventional upgrade path. DIY if you want and George will throw you his float when you are drowning. I hope the Lightspeed reach commercial success in a huge way in the future not that George care if it did or not.

 PS: I am not affiliated to the Lightspeed product.

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Thanks for that in-depth review water111 .

If any reading who have the skills wish to construct one for themselves as water111 did, instead of purchasing the ready made Lightspeed Attenuator, my first original post is here to do it with.
http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp.html#post924390
PS: you may have to join to see all the attachments, circuit diagrams ect.
 
I’m always available on this Audiogon Lightspeed thread for any help you may need,
PS: I do not sell kits or parts as they are all available for diyers to get themselves.

Cheers George

This is my impression of the Light Speed Attenuator (LSA) in my system that consist of the following equipment:

  1. Amps:  Two Spectron Musician III MKII in mono block configuration with V-Cap Upgrade, Super-Effect Bybee Purifiers upgraded rail and power fuses to Synergistic Research BLACK Quantum Fuses (Outstanding fuse) driving 4 ohms. 

    The Spectron were chosen due to the following capabilities:  (What does the limitation in peak voltage mean? To illustrate, let’s take example of a CD player with typical output of 2.2V rms (i.e. peak 3V), and if you use XLR balanced output then its peak voltage is 6 volts. Let’s for simplicity assume that you are using passive preamp with gain set at this experiment to the unity i.e. 1.0, and finally, let’s take typical amplifier which has usually gain of 26 dB or x20. Thus, you must expect your amplifier to have output peak voltage: 6V x 1.0 x 20 = 120V. This means that when listening to the same music with most other amplifiers, particularly those without output transformers, the signal would be "clipped". These amplifiers would be unable to deliver the transient voltage to the speaker. The effect is that the music loses some of its lifelike qualities i.e. signal is distorted and dynamics is clearly compressed).  The above example represents situation when your preamplifier gain is unity i.e. with relatively efficient speakers. When your speakers (or music) demand your preamplifier to have gain more than 1.0, then even Spectron amplifiers might clip! Fortunately, Musician III MK2 is capable of operating both in stereo and mono (fully balanced) modes. While not necessarily an advantage for highly efficient speakers as described above, less efficient loads will benefit from the fully balanced operation that triples the power and doubles the headroom to  + 240 volts as well as staggering 7000 watts of peak power (and hold it for an extraordinary 500 msec) assuring that no matter what the speaker load, the amplifier will deliver the full dynamics of the original recording undistorted. Number of reviewers observed that Spectron Monobloc’s sound creates noticeably deeper bass, effortless presentation and powerful slam).

     

  2. Usher BE-20 diamond sensitivity: 90 dB @ 1 watt / 1m at 4 ohms

  3. VPI Prime with Dynavector xx-2 MKII cartridge with the Symposium Prime Footer Damping Insert kit on Mapleshade 24 x 24 x 4 Finished Maple Platform with Audience Au24e Low Z Phono cables.

  4. Whest 2017 version of the PS.30RDT SE with the 40 SE series wire loom and 40 SE input modules.

  5. Crystal Cable Reference Diamond Interconnects.

Previous setups:

I was using the Sonic Euphoria Passive Line Controller (PLC), the Sonic Euphoria PLC is a passive preamplifier using an autoformer attenuator. The Purist Audio IRD LLC-P Preamplifier, also the Axiom passive with modifications to the internal wiring with Mundorf sgw110wh wire, a mixture of Silver and 1% Gold.

The closest of the above passives that came close to achieving true non coloration of the sound and delivering only what was in the recording was the modified Axiom passive.

I researched the Light Speed Attenuator and found interesting comments from owners that ranged from outstanding to not a great fit for my system.  Due to prior passives having plenty of gain for my system, I contacted George and made the purchase.  It arrived in Texas within the two week period he stated he needed.  He provided outstanding technical support and even researched the problem I noticed with integrating my Rel R528 SE subwoofer into the system. For some reason using the Neutrik Speakon connector from my amp to the Rel caused issues with the LSA, which to me sounded like an impedance matching issue. (I do not miss the Rel with the LSA, there is plenty of deep articulate bass with my Ushers alone, but will be searching for a fix).

LSA Power Supply:

Adding the LSA to my system was everything I have been trying to achieve in my listening room.  I decided to power it with my HDPLEX 200W Linear Power Supply vs the wart linear power supply due to the fact that it has a dedicated XLR---5.5/2.1mm Connector Cable.  Perfect for the LSA and provides Top of the Line Hi-End Audio ELNA Capacitors, High Quality 200W Silent R-Core Transformer provides clean energy, Separated Ground for Each Output Rail, EMI/RFI Circuit to Prevent AC Grid Pollution, No Humming or Buzz noise for 50Hz and Peak load, 100% Silent, High Quality Neutrik XLR Connector for All Outputs, and Low ripple noise and void of high frequency noise.

LSA Addition to System Sound:

There are details in the midrange and treble that are just more obvious now. The treble seems more extended, but there was absolutely no change in tone from what is on the album.   Vocals are even more realistic, and everything has increased texture and is more palpable. But the best thing of all is the increased speed of transients. Everything has an immediacy to it. This even translates to the very deep articulate bass. Kick drums have speed and an authority that is impressive. The entire sound stage is one cohesive unit now in my system.

There is a tremendous amount of fast energy. This is consistent on all tracks played. The music has real life and intensity. It is extremely quiet, musical, and detailed with a large soundstage and is very well focused. I consider it an outstanding value for its price range.

The best I've heard in my system to date. I perceive no loss of dynamics at any volume. I can load my room adequately at around 9:30 or 10:00 on the dial. I have plenty of headroom and absolutely no distortion at insane volumes. The bass has never been as good and the separation and blackness are vastly improved. You feel the real image of the instrument’s size and acoustic quality with all analogue recordings I have played to date.

Advantages of the LSA:

With the LSA in my system, I have noticed that setting the proper VTA on the fly with the VPI Prime on each record to optimize playback is very easy and the changes are easily heard without the use of headphones for precise imaging.  From https://londonjazzcollector.wordpress.com/for-audiophiles/tonearm-vta-adjustment/ “Precise adjustment of the Vertical Tracking of your tonearm is one of the most significant improvements you can make to your listening experience. It is not as difficult as you may be thinking, and costs nothing. You have already paid for your equipment, and though the turntable may have been set up “perfectly.  In less than 15 minutes, the effect of adjusting, refining the adjustment, and eventually locating the “sweet spot” in VTA – just a turn of the adjuster, listen, turn a little more, listen, turn again until you finally locate it  – completely transformed the performance of the system. The stereo sound stage snapped into focus, the troubling bass lifted, harshness was replaced by sweetness, an extraordinary and unexpected experience.”

 

Please understand that this is my experience with the LSA with my equipment.

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