Lightspeed Attenuator - Best Preamp Ever?
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Hi Unsound, On a post by Grannyring a few days ago on this thread he paraphrased the esscence of George's position. Anyone not in agreement with either his theoretical prespective or did not think his LSA sounded better then any passive or active linestage, if certain impedance conditions were meet, were the following: 1) Have a tin ear 2) like distortion. 3) in it for the money only 4)LSA is the absolutely the standard. If these don't come across as putting anyone down who disagrees with him, I would like your assumption regarding the nature of his remarks. Specifically, his remarks towards Mr. Tsuda that he gathered from his anonymous "tube gurus" that, "if you are serious about valves" you would never use them like Mr. Tsuda does in his CF-080 preamp implies that this world renowned designer is an idiot for not agreeing with good old George's " tube gurus". One of the oldest forms of knavery in a debate is to share very nasty implied information by saying that it was proposed by someone else, not the speaker, to get the dig in and than avoid the heat from the audience. I doubt if good old George would even discuss this with anyone, why should he, he already knows everything about any design flaw in any preamp in the world, which means if its not his LSA its inferior and a waste of money and time. |
Hi Charles1dad, Thanks for your comment. Really like the "pompous windbag" description about good old George! Mr. Tsuda is not only one of the highest regarded designers and builders of Japan, but is a total gentlemen on a personal level. I'm still waiting for what Tony's response is going to be to George's condescending remarks about Mr. Tsuda and the CF-080 preamp. I know that you have a friendship with him and great regard for this preamp, so what's your position now? Let us know. |
09-21-11: Agear: 1:George, is the diode effect measurable? What does it do of rather what does it distort? 2: Paul asked the million dollar question above: what are the effects of gain? Does it produce distortion? 3: I did try the LSA with a SS amp (TRL Samsons) with 68K input impedance and the sound staging flattened. I have experienced the same thing when running the amps directly with my source. What is this about George?:Agear 1: Diode effect is the very lightweight pin point touch contact of the metal wiper in a volume control on the resistive track in any volume control, and also on some switches, this creates the diode effect, which has a rectifying (change ac to dc)effect on the ac music signal trying to pass through it. Even Hervé Delétraz of the Dartzeel NHB-18ns also acknowledges it half way down the page here and he also uses the Lightspeed volume control in this preamp to eliminate it. http://www.stereophile.com/content/dartzeel-nhb-18ns-preamplifier-page-2 2: All active circuits produce distortion/colouration whether they have no gain or unity gain. 3:By going directly from your source to your poweramps you are not adding or subtracting anything to that source. The perfect "mythical" active preamp is "a straight wire with or without gain", it doesn't exist. If you insert a preamp that sounds different/better to your ears to this, you are introducing either a coloration or distortion that you prefer, which is a band aid fix, you should have a source that does not have to have this expensive band aid fix. Cheers George |
George, is the diode effect measureable? What does it do of rather what does it distort? Paul asked the million dollar question above: what are the effects of gain? Does it produce distortion? I did try the LSA with a SS amp (TRL Samsons) with 68K input impedance and the sound staging flattened. I have experienced the same thing when running the amps directly with my source. What is this about George? |
You have no constructive critisism Teajay, all you try to do is to get this thread shut down with your personal attack. Not once have I attacked you personally just questioned the Ohms Law compatibility of components in your system that have not been properly addressed in the specs they have presented, and the voodoo that surrounds them. |
Well Tony, You just got a taste of what I keep referring to as George's arrogant know it all attitude, this time towards a gentlemen we both respect, Mr. Masa Tsuda. The quote's from George's "tube gurus" particlarly the crack about, " you don't hang them horizontally at the back of the chassis" shows how ignorant he is about why Mr. Tsuda has them in that position to begin with. And this is the guy you would want to hang out with and enjoy his company? Well, let's see what your going to do now. Come up with another excuse or rationalization for George's put down of someone you know is a brilliant designer, builder and your friend or finally stand up to this know it all who's full of himself. |
I take what you've found out onboard Tony. I can safely say a cap on the output will not change the output impedance of the tube in the audio band for the better (lower). And a resistor would also not change it for a lower impedance, only for higher impedance. So there is something else we don't know, if what you were told is "5.2k ohms and 900 ohms" As I find it very disconcerting that the output impedance has not been included in the specs or design on the website. As just one of a few of the tube gurus I queried about cascode output said. And they all say basically the same thing. Quote" If you want 6 or 12dB gain, you don't use a cascode. If you want lowish output impedance, you don't use a cascode. (NB. in a preamp you will want low output impedance, unless you are incompetent). If you are serious about valves, you don't hang them out horizontally at the back of the chassis, even with fancy roll-bars. This is asking for poor contact as the valve slowly drops out of the socket.Quote" Cheers George |
And I assume Terry is using the XLR connection which is 30kohms on his amps input so it so match ok, assuming not too much time is spent at 5,2kohms. But this is theory and Terry is a pretty experienced listener, I have to assume the CF works very well in his system. Well, I guess that is enough on the CF sojourn.... |
I have just received some information regarding the output impedance of the Concert Fidelity CF-080 that should put the discussion to rest. According to the designer, the 33k ohm output impedance is an incorrect assumption. In addition to the tubes, the circuit design uses a capacitor and a resistor at the output to prevent harmful DC signal to be transmitted to the power amp. So the actual measured output impedance, which depends on the frequency of the CF-080, is between 5.2k ohms and 900 ohms as measured between various points within a frequency range of 20Hz to 20kHz. From this I would say that the CF-080 will match up just fine with most power amps out there. This includes the Concert Fidelity amps with 47k ohms input impedance. Not that this was ever in doubt from my perspective having heard the system multiple times and regarding it as one of the best I have heard. I fully trust this information as it came from the designer himself. As such I don't feel there should be further debate on the subject. |
Jdec, it may or may not be. Remember, the end sound from your speakers is the sum total of all the parts in the system. Every single footer, wire etc...has impact. No two systems will ever sound identical and the end result may or may not have more added coloration then another system. Like Sam said sometimes an active just helps a system sound more like natural music with wonderful tone and ease. Sometimes a passive does this also. More than one road to accurate music and a passive is not the ONLY road to this end. All systems and gear have a sonic personality within a given system - all gear with no exceptions. |
I agree, there is nothing wrong with folks liking coloration that please them. I would just say that on principle, I would want my preamp to offer as little as possible so I can use it with alot of different amps and speakers with different voices - that is, the more nuetral the preamp the more equipment it can work with sonically. That is just a philosophical decision and preference on my part. Interesting that Sam paid full price and then decided to get an LSA for his son. Not sure about Sam's wants, but he does NEED to be excited about new products if he wants to keep writing:) |
Pubul57 Agreed, Sam did not NEED and active, but WANTED one. He does not NEED the CJ Art pre, but would like/wanted one! No NEED for an active in terms of function many times, however some desire one for the resulting sound benefit they perceive in their system. This is a want, not need in many cases. |
Yes I too received it today, and I need to tell all, before any assumptions are made, that Sam Tellig (Tom) purchased one at full price over 2 years ago, before I had any idea that he was going to review it. And just a couple of weeks ago one was sent off to a classical guitar buff, in New York, his son David, again at full price. Cheers George |
I agree with Sam, when you need gain or have an impedance mismatch and long cables you need an active line stage, and I imagine when you need an active it is pretty obvious when comparing it to a passive. I agree that ultimately one must choose what fits their fancy, especially since it is "reproduction" we are talking about. When you need an active, a passive will not do. What we cannot do without is a great preamp, in whatever form is most suitable to our source/amp/cabling. |
I just received the October issue of Stereophile. Please read Sam's Space as I swear I could have written that piece! He does a nice job explaining why some like actives in his well written and balanced article on preamps. Nice job Sam! I could not possibly agree more or have said it more simply than Sam. He is not saying one is better, but just gives another perspective to consider. Yes, ALL devices (active & passive preamps) have a sound and they all impact a total system's sound. Pick the one that suites your fancy and sounds most like music to you. Great piece IMHO. |
Just ran into this thread. Seems another LDR attenuator has been making the rounds as a DIY kit. There is a balanced version available as well. Not sure technology wise what the differences are with the LSA, but thought some of you here might be curious to read about it anyway: http://www.diyaudio.com/forums/vendors-bazaar/176847-warpspeed-optocoupler-volume-control.html |
George, I'm not sure that Teajay's "LSA test" was with his own system, it might have be a group of audiophiles getting together, comparing notes - obviously testing the LSA with Pass gear would be far from optimal, like testing a 3 watt SET with a pair of Maggies - no way to fairly assess either the amp or speakers in that situation. Anthony, it will be interested to hear what Tsuda has to say, something does not seem right. |
Like I have always said Tony, it will work and sound ok with no damaging side effects. But the source should be at least 3 x or more lower output impedance than the the load. I imagine then it could have sounded even better. Now can you imagine what Teajay heard when he listened to the Lightspeed into a 15k load and drew his conclusions? Cheers George |
George, yes I saw that review and was aware of the other information. As I stated in my previous post, amps input impedance is 47k ohms. What I am having a difficult time with is why the designer would build a preamp circuit with 33k ohm output impedance (assuming this is accurate) to mate with amps that have not much more relative to input impedance. It makes little sense given I have spent approximately 150 hours or so listening to this system and it in no way sounds like a bad match to me. |
This is the output description "The 12AU7 tubes are on the back panel virtually bonded to the output connectors." This is where the solid state part is used "It uses a solid-state analogue switch for input switching and an analogue solid-state volume control selected for its sonic quality and tracking accuracy." All this can be read here, half way down. http://www.positive-feedback.com/Issue41/concert_fidelity.htm Cheers George |
33k ohm output impedance is rather high, especially given that the Concert Fidelity amps have an input impedance of 47k ohms. Is that 33k ohm constant or at a specific frequency or perhaps a range? Now I know Masa Tsuda personally and have been working the Concert Fidelity rooms at the last few CES/RMAF shows. I'm here to tell you Masa in my opinion is a great designer and the system of components he brings to the shows has incredible synergy and sound. I'm having a hard time getting my hands around this so I'm going to go straight to the source and find out more information. |
Paul one of the tube guru's on diyaudio said the solid state part is at the input, and it's even stated that the 12AU7 in cascode mode is directly attached to the rca outputs in the manufacturers blurbs on a website. I asked what other preamps used this cascode output stage, and he said Rouge Audio used to on their preamps but their poweramps are very high, the M120 monoblocks I had here were 1meg! input impedance. And also he said some early Lamm preamps were also cascode output. It is ok to have this high output impedance if you have over 100k or more on the poweramps, but you do get the problem of having to use low capacitance and short interconnects 1.5mt or less, just like with the Lightspeed. Cheers George |
Try to bear with me here and let it sink in. You see this impedance matching goes right through the whole system between components. EG: source to preamp, preamp to poweramp, and poweramp to speakers. Even the internal stages of the individual components should be impedance matched if the designer is worth his salt. eg: of a poweramp it's: input stage to voltage stage, voltage stage to driver stage, driver stage to output stage. Same for goes the pre and source. Hopefully they are done/designed right as the end user cannot do anything about these stages inside the individual components or check them. But at least the end user can make sure the components are themselves matched from each other. I specify with the Lightspeed Attenuator that it needs to see a poweramp with 47k or higher input impedance, I believe that tube preamp and tube dac/cdp manufacturers should be saying the same, this is why so many high output impedance tube pre's sound bad when they are mated to low impedance poweramps. Cheers George |
George, it just does not seem possible that there is a preamp on the market with 33kohm Zout - does it? It would be almost impossible to match with most any amp. Unfortunately, their website does not provide a Zout for the preamp, but as a hybrid design, you have to believe they are doing something to provide buffering for that 12au7. But anyway, clearly you and Terry will never be in agreement, no matter what the Zs say in or out - I think we can all agree on that. It does seem that the passive / active divide is even more divisive than tubes / SS:) I wonder why. |
You do have a bad match Teayjay with or without the use of the Bryston Xover, and what it shows is that when you said you tried the Lightspeed Attenuator you also put it into that same bad impedance matching situation. With or without the Bryston xover, the Lightspeed saw the 20k input of the Passlabs XA60.5 or it saw the 15k input of the Bryston xover, and your $60k preamp is in the same unfortunate mismatch. It is well documented that the Lightspeed Attenuator needs to see 47k or more load, and your preamp is even higher at 100k. You your self said you do not care or know about impedance matching components, yet you think you have cred by just throwing money at components and bagging them if they don't sound right. |
George, I'm sure by reading this thread you know my position on your posturing regarding blatant promoting of your piece along with your arrogant know it all attitude towards anyone who does not see the the light of the purity of your passive linestage. So, when you make another snide remark like,"needs to do their homework before spending the big bucks," it fits into what I would expect from you based on your past posts on this thread. I have no idea how you experience music or how well you hear. All I know is that your LSA for my ears' was no better or worse sonicly then other passives I have owned in the past and came no were near the the performance of my active preamp regardless of your comment regarding the concern over the impedance of the X-over. Finally, I have never asked for your advise or your opinion, your minions are quite happy to keep asking for it or you provide it on a on going basis to keep promoting on this thread, so thanks for your help, but I'll just keep limping along with my system the way it is. I will also never directly reply to any of your statements that might include me in the future because it would be a waste of my time. When Paul wrote that one possible position, that is quite rational, " that passives can sometimes be better than actives" a few posts ago I was in total agreement with one qualifier besides system synergy is personal taste. Yet, good old George tells me that I have a bad match and who am I to know better then him how my own system sounds. George you have convinced me, I have changed my mind I will sell off my CF-080 as soon as possible and either call or E-mail you with my order for your LSA masterpiece. |
Sorry George, You have two mistaken assumptions regarding my system. First, I use Pass Labs XA-60.5's and not the 100.5's. Secondly, and I think more importantly, since I biamp my system any preamp I use active or passive the signal is first directed to a Bryston X-over then to my two pairs of monoblocks to drive my MG-20's. Therefore, your premise regrading a bad impedance match is invalid in my situation. I have no idea regarding what the impedance rating is of this active X-over, just that your LSA did not play music in my system like CF-080 does regardless of the reasons why. |
09-17-11: Grannyring Actives also need to be well matched with the amp. My cuurent tube active was a poor match to the Sunfire Signature amp which has an input impedance of 24k ohms.Grannyring Yes Grannyring, tube output active preamps are just as susceptible to poweramp impedances as passives are. I looked at what Teajay is using. The output stage of his Concert Fidelity CF-080 is a 12AU7 in cascode configuration direct to the SE output rca's, I thought this is a high output impedance. So I checked with our tube gurus, they confirmed to me for this tube to be use in this configuration in it's best linear way, it's output impedance will be around 33K! And at best it will only give 10mA maximum output current. This is fine if it sees a poweramp with 100k or higher input impedance, but he is using it into a Pass Labs XA100.5 which has 20k SE input impedance??? Bad Match this one!! Cheers George |
Actives also need to be well matched with the amp. My cuurent tube active was a poor match to the Sunfire Signature amp which has an input impedance of 24k ohms. The bass was muted and highs were etched. The Sunfire amp does not sound this way at all nor do my speakers or pre. I inserted a modest SS amp with an 100K ohm input impedance and all was much better.My system is magic again. Impedance matching is also important for actives. I think most, if not all, of our opinions of actives vs passives are based on the synergy of the system they are placed in. It's the total system stupid:-) |
This is also very important. An active preamp will be needed if the amp's voltage need is higher then the source's output voltage. I used to think this too until I tried my LSA with my Atma-Sphere S-30. Source = 2V and S-30 = 2.8V - nearly 6V depending on how it was configured. In either case the source did just fine driving the amp via the LSA. |
In the Aleph L manual, NP goes on to say, "If you need gain, above the 3 o’clock position the volume control provides 2 dB of gain per step, for a maximum of 10 dB. In this region you will be listening to the active circuitry of the Aleph L. As an interesting experiment, you may want to try listening to the difference between the straight-through position and the next higher one, seeing how well you can discern the character of the active gain system." The tenor of his comments seem to speak of the effects o gain stage as producing flavors, granting that even straight through might have a signature too. It always brings me back to Ken Stevens design goals for his (CAT) preamps, he said he wants the "flavor" (his word) to be like water - in his mind, no flavor. As for gain, I an tell no difference between my 2v and 4v settings on my EMM player, other than I turn back the volume control a bit. So we are left with. Passives are.... 1. Always better than actives 2. Never better than actives 3. Sometimes better than actives No lover of passives in general or the LSA would argue 1. - that would be foolish and clearly not the case. It seems hard to argue 2, since some folks with a long history of fine active line stages of considerable merit hear things differently and prefer the passive, their judgment not swayed by a lack of resources or inability to have tried the options. It does seem 3 is the most likely case and it it raises the question -- if so, when? Under what circumstances. I think this thread has provided enough guidance as to when a passive, and possibly the LSA best of all, will provide a quality of sound comparable to the very best available - for a fraction of the cost - as long as it is not made in Switzerland or ensconced in a 2" inch aluminum case. |
09-17-11: Banquo363I should add: what else should we look at other than impedance matching concerns. If the impedances are right, nothing, so long as the dac or cdp has volts high enough to clip/overdrive the poweramp which nearly all have, and enough current which nearly all have, except some tube output dac's and cdp's. Look at any of the user manuals of the higher end dac's and cdp from Wadia going right back now to the late 80's that had digital domain volume controls in them. The manual states going direct into a poweramp with any of these units will yield a superior sound than going through any preamp, so long as the digital volume is in the top third so there will be no bit stripping. There are no preamps inside these top Wadia's I have personally seen inside a few of them they are just like all other dac's and cdp's on the market, with a current to voltage conversion stages after the dac chips then output buffers to the rca's. The Wadia's magic happens before the dac chips, in their propriety filtering techniques and receiver stage . Cheers George |
Need to look at the voltage output of the source compared to the voltage input needed for the amp - sensitivity rating. This is also very important. An active preamp will be needed if the amp's voltage need is higher then the source's output voltage. I also think current plays a role and can limit dynamics in some set-ups. |
I should add: what else should we look at other than impedance matching concerns, which concerns I assume Salvatore knew about and also are not enough to determine sufficiency. As Paul suggests, we are left with trying out different equipment. But unlike trying out the LSA, trying out different active preamps is typically an expensive proposition. |
George, I think we are in agreement, as Anthony is likely to be, and it might seem Nelson Pass is likely to be in agreement too, and yet we find many(?) audiophiles that still don't see it that way, and I respect their view as well, but I guess I am just comfortable with my own conclusions, theoretically and in actual listening - and whatever divergence of opinion we have seems like an uncrossable bridge, so we are left with try it and see what you think. But the argument is also between a $500 approach versus 5-20K approaches, so where do you go from there? I don't know. I can only recommend that folks try it and decide for themselves. |
From reading A. Salvatore's review of the Coincident Preamp, I get the idea that it is not trivial to discern whether the source can deliver sufficient current and volts to make an active preamp unnecessary. After all, for more than a decade he believed his source was sufficient but it turned out, by his standards, it was not. I take it then that if his observations are correct (a big 'if'), then one cannot merely look at a spec sheet to determine sufficiency. The question is, what more is there to look at? One can do the Bolero test, but Salvatore did it and it gave him the wrong answer and misled him for a long time. What then? |
Pubul57: Raises the question as to the the "effects" are, and when is gain "necessary". Pubul57: With today's sources, cdp, dacs, even phono stages, there is clearly no need for added gain in most systems. As what most sources can give out today in volts and current, they can easily overdrive (clip) most of today's amps. So all that's needed is a way to attenuate that source no need to give them more gain with the added colouration of what an extra gain circuit gives, only to reduce it back down again to below what the source originally gave out. Cheers George |
