Passive Attenuator/Pre amp: EVA 2 LDR

edited May 2012 in Amplifiers

Time for a little play: I have an NVA power amp, so I have to use a

passive pre. That's fine, I like them in general & the NVA ones are
super. But in order to upgrade my P90 to the uber stepped attenuator
version I need to shell out over £300.....


I keep hearing whispers about another kind of passive pre: not
passive pot, not stepped attenuator, not TVC....Jason (Figlet108) first
mentioned LDR (light dependant resistor) passives a while back, and I
have been doing some research. The original is the 'lightspeed' - here:


http://members.optusnet.com.au/~georgehifi/
I've got hold of a cheaper model, from Malaysia. It has three inputs
(I only need one) and a remote control - in fact it uses the apple
remote!

I'll try & post some more tomorrow - perhaps I'll figure out how to post a picture!
«13

Comments

  • Now that looks interesting Alan.

    Have you got a link to where you got it from?  What was the cost if you don't mind saying?

    I JFGI'd it and there's a lot of info on the DIY boards - I'll have a read later.
  • Here's one identical to mine with a picture if you log in:

    http://www.hifiwigwam.com/showthread.php?48230-For-sale-EVA-II-LDR-passive-pre-amp

    This is the product page for version 1 & 2:

    http://diyparadise.com/shop/index.php?main_page=index&cPath=18

    I gave 200 squid for a minty one. The single input version is £150 new - when it is in stock.  George (of lightspeed) reckons the EVA is as good as his lightspeed mk I, but the newer version of his is far better. and about £350 delivered.
  • Very interesting technology.  I'll read further.

    Thanks Alan
  • That sounds very interesting!
  • I agree - I just hope it arrives before xmas.
  • Alan

    Great spot !

    These seem to tick all the required boxes for passives - ie very simple so nothing gets in the way. And a remote !

    Intrigued to hear how you get on.

    Mervyn

     

  • edited December 2010
    image
  • edited December 2010
    image
    The EVA I, which is exactly the same as EVA II but has only a single input. I would have rather had this - quite apart from anything else I like the wooden case, and they are a paltry £150 or so new - but they are made slowly so there is always demand.
  • Have read up a fair bit on this idea.  A lot of merit I reckon but I'm no expert at all.

    But it reminded me of two interesting ideas I've heard about.

    One guy I know builds and generally fiddles with valve amps.  Problem is he uses very un sensitive panel speakers so he often just hooks a low powered valve amp he's been working on up to his CDP and straight to the speakers - i.e. no preamp or attenuation at all.  Sounds amazingly clear, dynamic and just right but limited in volume.  The trick would be to get the right speakers and/or right amp output I suppose.

    Another guy has chosen 3 volume setting and measured the necessary resistance values and replaced the pot with high quality switches and very good resistors.  He makes do with with just 3 volume settings.  Haven't heard this but he reports that it's fantastic.
  • Interesting Jim.
    Jason has said he has hooked up the TFS direct into the amps cutting out the pre and reported good improvements. Easier with a PC of course where you can use the computer's own volume settings.
  • There's a chap on PFM who this week reported his father running iTunes into DAC into power amps, also no pre amp at all. He just uses the iTunes volume control.

    I think Dave should give that a go, being an iUglyTunes kind of guy.

    I don't see why this LDR attenuation shouldn't be built into a power amp - the only power source that is required is an LED, and my NVA has four of them, despite it's minimalist design ethos. I wouldn't be surprised to see an LDR in an NVA statement amp sometime soon, especially with Jason around.

    My EVA II Pre-amp arrived this morning, at 8am sharp! Well done parcelforce (for once) - it was only sent yesterday. There is another one on wigwam (or there was yesterday afternoon).

    It is ice cold, so it has been gently warming today. It may get it's first outing this evening after the children are in bed, if the mod so takes us. It's actually starting to feel like a slobby telly evening already though...
    (:|


  • I don't see why this LDR attenuation shouldn't be built into a power amp - the only power source that is required is an LED, and my NVA has four of them, despite it's minimalist design ethos. I wouldn't be surprised to see an LDR in an NVA statement amp sometime soon, especially with Jason around.

    Having re-read that, surely it would make more sense for Jason to build one into the analogue output of the TFS?

     I wasn't calling you Shirley...
  • edited December 2010
    There's a chap on PFM who this week reported his father running iTunes into DAC into power amps, also no pre amp at all. He just uses the iTunes volume control.

    I think Dave should give that a go, being an iUglyTunes kind of guy.


    The problem with running directly into the power amps is that I need the attenuation the vol controls give. I'd all be just too loud!

    I know I could use the 'master' volume control in OS X to set the overall level, but seems to me like asking for a problem if it should get moved or somehow reset itself (OS upgrade?).

    The final problem is that I have SMA connections on the power amps.

    When are you brining the pre-amp round to mine, so I can hear it? :-)
  • When you take off that red suit & stop asking me to sit on your lap....


    >:p


  • I don't see why this LDR attenuation shouldn't be built into a power amp - the only power source that is required is an LED, and my NVA has four of them, despite it's minimalist design ethos. I wouldn't be surprised to see an LDR in an NVA statement amp sometime soon, especially with Jason around.

    Having re-read that, surely it would make more sense for Jason to build one into the analogue output of the TFS?

     I wasn't calling you Shirley...

    Funny you should mention that Alan but there is a recent thread 'AP20' on the Subjectivist forum where Richard has asked someone to build an LDR circuit into the amp and let him know how it sounds !

    Interesting times ahead maybe ( or maybe not !)

  • ISTR there being an issue with using a digital volume control.  Apparently the bitrate is reduced as one lowers the volume.

    Now I may have:
    • dreamt that
    • misunderstood what ever it was I read
    • made it up
  • The usual argument is that it destroys the bit-perfectness of the output, not that it loses information, AFAIK.
  • OK, serious question as I don't know enough about this:

    Is not being bit-perfect the same as losing some information?
  • As far as I understand it, no. It's changing the bits, but not losing them. Or to put it another way, the bit rate stays the same, but the content of the bitstream changes.
  • I understand the dynamic range is truncated as the digital signal is attenuated. Or rather - I don't understand...that's where 'properly dithered' volume adjustment (as you get with Amarra & Weiss 202) comes in. I too, am a proper ditherer.

    Just got it in, with the usual NVA owners near heart attack on power-up....no smoke yet, watching telly through it now. I'll see if Mrs wants a bath later so I can have a listen...Interestingly, I had heard you can't fully mute the volume with LDR attenuation, but I can get it right down to nowt.
  • Don't leave us all dangling...

    Wossit sound like?
  • Not a lot, really....which is what you want, of course.



    My initial thoughts are that it loses nothing to my P90, so on convenience grounds (ie size, remote control, and frankly - coolness) it is a winner. Assuming Richard Dunn makes a decent passive pre to match his own amplifiers (a very safe assumption IMO), there shouldn't be a substantive difference as both pre's are designed to add nothing.


    My first concern had been the soundstaging & imaging, but in fact the soundstage was as wide as ever - even seeming slightly outside the speakers as before. I had half expected that a pre with a single stereo volume control rather than two single channel pots would impact this, but not at all. In fact it was a blessing to not have the ever present slight channel mis-match you get with twin controls...



    I had a nice session on Saturday evening, when I was convinced more low level detail was present, in a very non-forced way. In fact it was rather like having a new DAC (or so I imagine, Keith....), as the whole presentation was just slightly different. I enjoyed hearing some things I hadn't caught before - notably things like subtle acoustic rhythm guitar hiding near the bass. As I would expect from a passive, the timing of the music was spot on; I was enjoying that aspect more than usual, but I am not sure there is a real difference. I most certainly cannot be faffed to swap the two pre's in and out, what with these rigid interconnects!

    Sunday evening we had a few round, and surprisingly they wanted to skip through my music collection & hear the system. We played an eclectic mix & things were great, but I couldn't help feeling there was something missing; feeling the bass in my bones even at low volume, the liquid midrange, sparkling treble (see - I'm a HiFi reviewer mum!) - a cliché, but true. I haven't listened since, but there are two conclusions. Perhaps the quality of the unit isn't up to the NVA after all, what with the box design, the specific type of wiring Richard uses. Or, perhaps more likely, having so many bodies in the room sucked some of the life out of the rooms acoustics.

    There is more listening to be done for sure, and not so many opportunities with the three children off now. But I will keep you posted.
  • Hmm. Sounds like the jury is still out.

    Thanks for the extended review.
  • edited December 2010
    Jury's back after lengthy deliberation: Fine Mr A Brown some pounds for ever doubting little Eva!



    This is a bit of a heavyweight, this little box! Every doubt I had the other night has evaporated - the textural detail that has surfaced since putting the little LDR pre into the system is gorgeous, the timing is infectiously groovy at times, the staging & imaging has just slapped me around the chops!


    @-)

    I was listening to Prelude 'N Blues played by the Matt Catingub Band, which is a track I have literally grown up listening to on my Dad's system & my own - and I am suitably awe struck at the perception of the alto saxophonist standing 8-10 feet closer to the mic than the trombone player - just one example. Imaging has never been top priority for me, though I've always enjoyed it when it's been good - but this is rather excellent!

    I recommend further investigation!

    (*)
    I should be interested if anyone ever compares an LDR pre to a P90sa.
  • Phew !!! I was getting a bit worried Alan after your last post.
    It sounds like money well spent and to work so well with the TSS is a good omen.
    Is the remote user friendly ?

    Mervyn

    ps totally understand heart-stopping effects of plugging the amp in again after any system change especially with SSP interconnects. Lack of any on/off switch simply compounds the cardiac arrest potential !
  • edited December 2010
    Yes, it's the little apple remote, about £6 new on eBay.

    image
  • Hi Alan

    I am so glad that you are getting on very well with the my ex Eva. Since I took her out of my system and just using an integrated amp as it, the sound is very dull and lifeless. 

    I am still waiting for my LFD Zero integrated amp as a new replacement for my Eva / Tripath combo. I am pretty much expecting the LFD will be not as good as the previous rig. Since I am just so use to the wide sound stage that the Eva produces. But lets hope that I am wrong.

    When I saw the ad for the Eva 2 after I sent mine off  to you. I nearly buy it off the guy. Deep inside I knew it was a mistake that I sold  the Eva. In the end I was leaning towards having the exciting feeling of trying out gears that I have read so much about.

    Will let you know how I get on with the LFD. 
  • Sounds encouraging.

    Looks like I may even have to look into swapping out the SMA sockets on my TDSs. 
  • edited December 2010
    Hi Steve (macnugget), great to see you here! Box swapping is a strange addiction, isn't it? - I have teetered on the edge more times than I care to admit...but is it wrong to enjoy the gear almost as much as the music?

    Jerry is da man when it comes to swapping gear, he & others like him have helped me innumerably when trying to decide whether to act on a whim or not. He assuaged my doubts over both Beresford & NVA - about 4-5 years ago now, as I was procrastinating badly. My first forum postings were on wigwam asking whether I should consider NVA seriously.

    I think trying out loads of gear, and broadcasting your views in a balanced way can be helpful to the larger community, as awkward as I feel when I share my views. No-one's opinions should ever be taken too seriously (in particular mine) as tastes and systems are too different, but amateur reviews have their place on the net for sure.

    You never know, the LFD rig might offer something very special in it's own right. I find gear that is just different in character is often as good as gear that is an incremental upgrade.

    This little EVA is a gem, no doubt at all. I will try a lightspeed attenuator in the new year and if it yields an improvement I will move the EVA on, but I think I will be sticking with LDR passives for now.
  • Sounds encouraging.

    Looks like I may even have to look into swapping out the SMA sockets on my TDSs. 
    Maplins sell a SMA - BNC adapter for very little. They also sell a BNC - RCA adapter. I can't see that two adapters is a very satisfactory fix, even for a bodge, but you would be able to try other bits & bobs while keeping your cables.

    I have used the BNC - RCA adapter before & it was sonically 'invisible', but that was for a digital connection.
  •  ps totally understand heart-stopping effects of plugging the amp in again after any system change especially with SSP interconnects. Lack of any on/off switch simply compounds the cardiac arrest potential !
    You're telling me! When I was at Uglymusic's place swapping DACs, he would take one speaker cable out of each speaker, so that infernal noise wouldn't damage the speakers (or terrify us). Apparently the amps are tougher than they might seem when it comes to that sort of thing. I do that each time I change anything now, and avoid switching the amp off at all. The other speaker cable is semi permanently in the socket with heat shrink; this stops the children from playing...
  • edited December 2010
    Pictures now added further up the thread.

    This is the original lightspeed, now mkII: (this has no remote control).

    image
  • There  http://www.maplin.co.uk/Module.aspx?ModuleNo=32015

    & There.  http://www.maplin.co.uk/Module.aspx?ModuleNo=1593
    Thanks. That could be a stop-gap for when you bring your pre around  :-D
  • £15 quid just to try a whim - Oh, what rich company I keep!
    :-D
  • Of course  :-D
  • Loving this! I don't think I will be going back to conventional pre-amps again...

     

    I mentioned (slightly tongue in cheek) the "ever present slight channel mis-match" I get with twin volume pots on the P90, but funnily enough there is a slight mis-match with the EVA! It is apparently a labour intensive - and wasteful process - to match the LDRs that go into these units, and it isn't uncommon for there to be a slight balance issue. It is very slight though, just nit-picking really, but I do want to know if George (who builds the original Lightspeed) pays more attention to this aspect of QC than the folks who built my EVA.

     

    I can't help but think (dangerous - a subjectivist trying to understand why something might work....) that little EVA II is missing a trick by having three selectable inputs - and a mute funtion via remote. The whole idea as I understand it behind an LDR passive is to eliminate the contact points that potentiometers & input selector switches introduce to the signal path - these were previously unavoidable. My guess is the EVA I would be marginally better, and I would hope the Lightspeed attenuator would have tighter QC wrt LDR matching. It is also single inout, and doesn't have remote control (I think), so the hair shirt minimalist approach would then pervade my whole system.

     

    Is there a way to put a PDF up on the board here? Lightspeed sent me some info over email that I could put up if it's easy.

  • I e-mailed George yesterday about the Lightspeed. Partly because it seems more 'purist' and partly because I can get hold of one  ;)

    He sent me a PDF, so I'll see if I can put it up here.
  • OK. You have to upload the pdf to a server and then link to it.

    That's OK if you have access to web space and are happy to use FTP, but not much use to most people. I'll see if there's anything I can install that will make it easier.

    BTW, was that the pdf you wanted to upload, @Alan?
  • Yup - That's it. I think I too will order one in the new year. Shame really, I had hoped to flog the EVA to you!!!
    :-))
  • I still want to hear your EVA, if you can find some time to come round.
  • Absolutely I will - early in the new year if we can find a good time.

    On a related note, Keith is expecting the M2Tech DACs to arrive Monday or Tuesday, so I suspect we will have much to talk about.
    :)]
  • Fabbo!

    I'd better get my order in at Maplins.
  • If you want to confirm exactly what you need (the links I gave were guesstimates - I've not seen SMA connectors before) - I can pick the up for you before I come over.
    :)
  • Thanks for that. I'll take you up on it if I don't get into Brighton.
  • Bless me Audio Chewers for I have weakened. 

    Late last Saturday, I was aimlessly clicking through some of my hi-fi related bookmarks and ended up on the EVA page. There was one left for sale and I bought it.

    Well, bugger me if the thing arrived today! All the way from Malaysia. Thank you Mr Fed Ex.

    I've ordered the Maplins Bodge Connectors(TM) for delivery tomorrow, so I'll be trying out EVA RSN.
  • Well, this will be interesting. I hope the daisy chained connections stay out the way. Did you go for EVA I or II? (The I is single input in a nice wooden case, the II has three inputs in a black & silver one).

    I like mine a lot, and it seems happy with NVA, although the input impedance is just out of recommendation. I believe the lightspeed may be better, but it is dearer & has no remote. Now I have had a remote it is hard to imagine sacrificing it!
  • 'Tis a II. There were no Is for sale. Just one solitary II.

    I must say, the remote is certainly an attractive proposition, especially when Decibel spikes the OS X volume control.
  • Well, she works. And I've nobbled the IR receiver on my MacBook so I don't keep confusing the poor thing with Eva's remote. And buggered up my SSPs, as you may have seen from another discussion.

    With substandard interconnects, and the Maplins Bodge Connectors(TM) in place all is listenable, but lacking in low-level detail and depth of stereo image. Surprise, surprise.
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