Good to hear stanwal. Max Townsend's designs are for some inexplicable reason ignored in The States. His Rock turntable is genius, his Seismic isolation products State-Of-The-Art, and his speakers legendary, though perhaps too heavy to ship over. The Allegri is very well regarded by the UK press as well. His U.S. distributor (Dan Meinwald) does not seem to be very aggressive in promoting both Townshend and another excellent U.K. brand he represents, EAR-Yoshino, whose electronics are designed by tube and circuit design expert Tim de Paravicini. Hardly any dealers, low visibility, the usual.
All I want is The Truth, just gimme some truth...
I've always wanted to find a use for that line which comes from a John Lennon song entitled, "Gimme Some Truth." Turns out a little discourse on a preamp would provide the reason to use it.
Okay, those of you that know me or have followed my comments here know I have eschewed the use of active preamps in my system in favor of passive designs. I still own a couple active preamps, namely a Berning Micro ZOTL and a Silicon Arts Design Si2, but primarily listen to the passive units in my system. I have also owned some fine active preamps from Cary, Joule Electra, Jeff Rowland Design, and Tube Research Labs. It’s not that the active preamps don’t work in my system. It’s just the passives work better.
There has been lots of talk here lately about the Lightspeed attenuator that I own designed by George Stantschleff in Australia. He’s known on Audiogon as Georgelofi. If you haven’t heard about this attenuator here are a couple links for you to check out:
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1248137240&read&keyw&zzlightspeed
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1276356977&read&keyw&zzlightspeed
To recap, the Lightspeed attenuator is basically a resistive passive design with a twist. The uniqueness of the Lightspeed's design is that there are no contact points in the form of a "wiper", as is the case with other passive designs (resistive and transformer) that use a potentiometer or discrete stepped attenuator. The key component in the Lightspeed attenuator is the Silonex NSL-32SR2. The device is a sealed unit that consists of a high performance LED that shines on a light dependent resistor (LDR) thereby achieving proper attenuation.
There has also been lots of talk about the challenges in getting passive preamps to work optimally in ones system. Impedance matching, cable length, source output, and other factors all come into play. In fact, I feel it’s safe to say that achieving system synergy with a passive preamp is possibly one of the most difficult things to do. It’s not difficult to find out if your system is passive friendly. Here is a link to a good test one can easily perform:
http://www.high-endaudio.com/RC-Linestages.html
Just scroll down to the Bolero Test. However, just because a system is passive friendly doesn’t mean you might like what a passive preamp does in your system. Many use terms like lean, flat, and lifeless to describe the sound they heard when using passive preamps in their system. Whether this is because of a lack of synergy or personal preference is not relevant to this discussion, but nonetheless passive preamps do get unfairly characterized in my opinion. Of course I have my own opinions too on the subject;)
Okay, so why more blather on a topic that has been discussed at great length of late? A couple months ago I was having a discussion with Steve Eddy, known here on Audiogon as Simply_q. Steve is a designer and manufacturer of fine cables and other things audio. In our discussions I mentioned the LSA and he pointed me to a Stereophile article written by Corey Greenberg many years ago. You can click on the link and read it:
http://www.stereophile.com/solidpreamps/54/
The article discusses passive preamps and describes a means of building one using the Analog Designs BUF-03 buffers. Interestingly enough it’s been “rumored” that the person referred to as Elvis in the article is none other than Steve Eddy himself. So just maybe he deserves the credit for the design. In any event Steve Eddy referred me to Ed Schilling at The Horn Shoppe. It turns out that Ed makes a preamp using these same buffers, but with some new design ideas added to the mix, including the use of photo cells. Ed calls the preamp The Truth. Here is what he has to say about it:
It has an input impedance too high to measure, output impedance is a couple ohms, bandwidth is to 60Mhz, slew rate is a couple hundred V/microsecond.
There are no capacitors or resistors in the signal path. There is no potentiometer in the signal path.
It uses photo cells to control the volume. It does not use optocouplers.
It is an "active" device and suffers none of the "problems" that "passive volume control/pre amps" have. It can drive long (30 feet) cables with ease.
I've had parts of this circuit run for 10 years without failure.
As far as I know there is nothing like it available for any price.....I could be wrong but I doubt it. I looked "pretty hard and long".
The price in a nice natural aluminum enclosure is $825 shipping included. Extra input adds 40 bucks...a third adds 20 more. Anodized black adds $40. It's taking 2-3 weeks right now, this may increase.
You can also go to The Horn Shoppe forum on their web site to read more about this preamp:
http://thehornshoppe.websitetoolbox.com/?forum=161088
Now, getting back to The Truth. First off, you’ll note that Corey Greenberg refers to his DIY build as a buffered passive preamp. However, I believe Ed Schilling has more accurately described a circuit that uses buffers as an “active” device. Buffers aren’t new to preamp designs and have been used by the likes of John Chapman, Nelson Pass, and I believe Guy Hammel among others. In essence the use of buffers in the circuit, if designed correctly, eliminates all the potential system matching issues normally associated with using a passive preamp in your system. As Ed Schilling mentions, cable length is no longer an issue. In addition, the output impedance remains fixed at each point in the volume control.
However, The Truth goes a few steps farther in keeping the circuit very simple and like the LSA design, eliminating the potentiometer from the signal path. In my opinion, one of the keys why these two preamps sound the way they do.
So by now you’ve probably figured out that I bought The Truth. I’ve had it in my system for a few weeks and have swapped it back and forth with the LSA. I’ve recently lent the LSA to a friend for evaluation and The Truth is now being used exclusively. I have hooked it up to both my VAC Auricle Musicblocs and Atma-Sphere S-30 driving Audiokinesis Jazz Module speakers. Sources are a CEC TL-51X/Lessloss DAC 2004 MkII digital front end and Galibier Design Serac/Colin Engineering Groove Master Phonostage analog front end. All running single-ended as unfortunately The Truth is not available in a balanced version.
Before getting around to describing my thoughts on the sound I would like to mention a couple things about The Truth. First off, using the volume control might be a little tricky for some folks. You will notice that even though you are rotating it, no music may be heard until you’re pretty far around the dial. In my case this was true regardless of the amps input sensitivity, which are quite different between the VAC (1V) and Atma-Sphere (2.83V). It wasn’t until about 1 o’clock that I started to faintly hear the music. However, once you reach that point, the sound level will rise pretty rapidly even with the smallest increments on the non-stepped volume control. Normal listening volume for me is around 3 or 4 o’clock depending on the amp. According to Ed Schilling, one of the benefits of using this much of the volume control is that The Truth operates quieter the further around the dial you go. Not that it’s a noisy preamp at lower levels, at least not to my ears anyway. I find like my LSA that The Truth is overall extremely quiet.
Secondly, The Truth does not use an on/off switch. Once plugged in it stays on all the time. No worries here as it does not run hot. However, even though it remains on constantly, Ed Schilling advised that it still takes about 10 – 15 minutes to sound optimal after music has been playing. Unfortunately I can’t recall Ed’s explanation as to why this is the case.
Now that that’s out of the way you might be curious as to the sound. Upon first impression the sound with The Truth in my system reminded me of the Wadia digital house sound. It was very fast, detailed, unforgiving, with a little edginess on the top. In fact in a conversation with another audiophile friend who purchased a unit right after me, and who also owns an LSA, we were discussing the possibility that the buffers were adding some coloration/artifact to the mix. Well as it turns out, my unit had a glitch that I stumbled on by accident and was indeed negatively affecting the sound. Upon inspection of a photo of the circuit I sent to Ed Schilling he immediate identified the issue and walked me through the simple procedure to remedy it. One thing I learned about Ed through this process is his customer service is impeccable. With the situation resolved the edginess was gone and The Truth began revealing itself.
Again, The Truth provides a very fast and detailed sound with plenty of dynamics. It is very transparent. Background is black and The Truth presents a nice 3-D sound stage (assuming it’s there in the recording to begin with). It will not hide flaws in recordings, or your other components for that matter. It gets out of the way and is quite enjoyable. I’ve found I can listen for extended periods with no fatigue. At its price point you can make the argument that it is a true bargain. For those of you into audio jewelry The Truth isn’t going to win any beauty pageants but it is well built in a nice aluminum chassis. The captive power cord may turn off some, but works for me as it does what it is intended to do. I have no desire to switch it out for an IEC.
For those wondering how it compares to the LSA I hate to disappoint but I won’t be making any comparisons. Both units are affordably priced and easy to obtain so try them for yourselves. The Truth is offered on a trial basis so in my opinion it’s a no-brainer and worth a listen. I will say three things. First, I do have an opinion on which one I like better. Second, both are staying with me. Third, The Truth provides all the benefits of a well designed passive without the need to worry about system matching issues associated with passive designs. Those who are hesitant to go down the passive road because of potential system matching issues, or their systems may not be passive friendly in general, can find a great no compromise solution with The Truth.
Okay, those of you that know me or have followed my comments here know I have eschewed the use of active preamps in my system in favor of passive designs. I still own a couple active preamps, namely a Berning Micro ZOTL and a Silicon Arts Design Si2, but primarily listen to the passive units in my system. I have also owned some fine active preamps from Cary, Joule Electra, Jeff Rowland Design, and Tube Research Labs. It’s not that the active preamps don’t work in my system. It’s just the passives work better.
There has been lots of talk here lately about the Lightspeed attenuator that I own designed by George Stantschleff in Australia. He’s known on Audiogon as Georgelofi. If you haven’t heard about this attenuator here are a couple links for you to check out:
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1248137240&read&keyw&zzlightspeed
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1276356977&read&keyw&zzlightspeed
To recap, the Lightspeed attenuator is basically a resistive passive design with a twist. The uniqueness of the Lightspeed's design is that there are no contact points in the form of a "wiper", as is the case with other passive designs (resistive and transformer) that use a potentiometer or discrete stepped attenuator. The key component in the Lightspeed attenuator is the Silonex NSL-32SR2. The device is a sealed unit that consists of a high performance LED that shines on a light dependent resistor (LDR) thereby achieving proper attenuation.
There has also been lots of talk about the challenges in getting passive preamps to work optimally in ones system. Impedance matching, cable length, source output, and other factors all come into play. In fact, I feel it’s safe to say that achieving system synergy with a passive preamp is possibly one of the most difficult things to do. It’s not difficult to find out if your system is passive friendly. Here is a link to a good test one can easily perform:
http://www.high-endaudio.com/RC-Linestages.html
Just scroll down to the Bolero Test. However, just because a system is passive friendly doesn’t mean you might like what a passive preamp does in your system. Many use terms like lean, flat, and lifeless to describe the sound they heard when using passive preamps in their system. Whether this is because of a lack of synergy or personal preference is not relevant to this discussion, but nonetheless passive preamps do get unfairly characterized in my opinion. Of course I have my own opinions too on the subject;)
Okay, so why more blather on a topic that has been discussed at great length of late? A couple months ago I was having a discussion with Steve Eddy, known here on Audiogon as Simply_q. Steve is a designer and manufacturer of fine cables and other things audio. In our discussions I mentioned the LSA and he pointed me to a Stereophile article written by Corey Greenberg many years ago. You can click on the link and read it:
http://www.stereophile.com/solidpreamps/54/
The article discusses passive preamps and describes a means of building one using the Analog Designs BUF-03 buffers. Interestingly enough it’s been “rumored” that the person referred to as Elvis in the article is none other than Steve Eddy himself. So just maybe he deserves the credit for the design. In any event Steve Eddy referred me to Ed Schilling at The Horn Shoppe. It turns out that Ed makes a preamp using these same buffers, but with some new design ideas added to the mix, including the use of photo cells. Ed calls the preamp The Truth. Here is what he has to say about it:
It has an input impedance too high to measure, output impedance is a couple ohms, bandwidth is to 60Mhz, slew rate is a couple hundred V/microsecond.
There are no capacitors or resistors in the signal path. There is no potentiometer in the signal path.
It uses photo cells to control the volume. It does not use optocouplers.
It is an "active" device and suffers none of the "problems" that "passive volume control/pre amps" have. It can drive long (30 feet) cables with ease.
I've had parts of this circuit run for 10 years without failure.
As far as I know there is nothing like it available for any price.....I could be wrong but I doubt it. I looked "pretty hard and long".
The price in a nice natural aluminum enclosure is $825 shipping included. Extra input adds 40 bucks...a third adds 20 more. Anodized black adds $40. It's taking 2-3 weeks right now, this may increase.
You can also go to The Horn Shoppe forum on their web site to read more about this preamp:
http://thehornshoppe.websitetoolbox.com/?forum=161088
Now, getting back to The Truth. First off, you’ll note that Corey Greenberg refers to his DIY build as a buffered passive preamp. However, I believe Ed Schilling has more accurately described a circuit that uses buffers as an “active” device. Buffers aren’t new to preamp designs and have been used by the likes of John Chapman, Nelson Pass, and I believe Guy Hammel among others. In essence the use of buffers in the circuit, if designed correctly, eliminates all the potential system matching issues normally associated with using a passive preamp in your system. As Ed Schilling mentions, cable length is no longer an issue. In addition, the output impedance remains fixed at each point in the volume control.
However, The Truth goes a few steps farther in keeping the circuit very simple and like the LSA design, eliminating the potentiometer from the signal path. In my opinion, one of the keys why these two preamps sound the way they do.
So by now you’ve probably figured out that I bought The Truth. I’ve had it in my system for a few weeks and have swapped it back and forth with the LSA. I’ve recently lent the LSA to a friend for evaluation and The Truth is now being used exclusively. I have hooked it up to both my VAC Auricle Musicblocs and Atma-Sphere S-30 driving Audiokinesis Jazz Module speakers. Sources are a CEC TL-51X/Lessloss DAC 2004 MkII digital front end and Galibier Design Serac/Colin Engineering Groove Master Phonostage analog front end. All running single-ended as unfortunately The Truth is not available in a balanced version.
Before getting around to describing my thoughts on the sound I would like to mention a couple things about The Truth. First off, using the volume control might be a little tricky for some folks. You will notice that even though you are rotating it, no music may be heard until you’re pretty far around the dial. In my case this was true regardless of the amps input sensitivity, which are quite different between the VAC (1V) and Atma-Sphere (2.83V). It wasn’t until about 1 o’clock that I started to faintly hear the music. However, once you reach that point, the sound level will rise pretty rapidly even with the smallest increments on the non-stepped volume control. Normal listening volume for me is around 3 or 4 o’clock depending on the amp. According to Ed Schilling, one of the benefits of using this much of the volume control is that The Truth operates quieter the further around the dial you go. Not that it’s a noisy preamp at lower levels, at least not to my ears anyway. I find like my LSA that The Truth is overall extremely quiet.
Secondly, The Truth does not use an on/off switch. Once plugged in it stays on all the time. No worries here as it does not run hot. However, even though it remains on constantly, Ed Schilling advised that it still takes about 10 – 15 minutes to sound optimal after music has been playing. Unfortunately I can’t recall Ed’s explanation as to why this is the case.
Now that that’s out of the way you might be curious as to the sound. Upon first impression the sound with The Truth in my system reminded me of the Wadia digital house sound. It was very fast, detailed, unforgiving, with a little edginess on the top. In fact in a conversation with another audiophile friend who purchased a unit right after me, and who also owns an LSA, we were discussing the possibility that the buffers were adding some coloration/artifact to the mix. Well as it turns out, my unit had a glitch that I stumbled on by accident and was indeed negatively affecting the sound. Upon inspection of a photo of the circuit I sent to Ed Schilling he immediate identified the issue and walked me through the simple procedure to remedy it. One thing I learned about Ed through this process is his customer service is impeccable. With the situation resolved the edginess was gone and The Truth began revealing itself.
Again, The Truth provides a very fast and detailed sound with plenty of dynamics. It is very transparent. Background is black and The Truth presents a nice 3-D sound stage (assuming it’s there in the recording to begin with). It will not hide flaws in recordings, or your other components for that matter. It gets out of the way and is quite enjoyable. I’ve found I can listen for extended periods with no fatigue. At its price point you can make the argument that it is a true bargain. For those of you into audio jewelry The Truth isn’t going to win any beauty pageants but it is well built in a nice aluminum chassis. The captive power cord may turn off some, but works for me as it does what it is intended to do. I have no desire to switch it out for an IEC.
For those wondering how it compares to the LSA I hate to disappoint but I won’t be making any comparisons. Both units are affordably priced and easy to obtain so try them for yourselves. The Truth is offered on a trial basis so in my opinion it’s a no-brainer and worth a listen. I will say three things. First, I do have an opinion on which one I like better. Second, both are staying with me. Third, The Truth provides all the benefits of a well designed passive without the need to worry about system matching issues associated with passive designs. Those who are hesitant to go down the passive road because of potential system matching issues, or their systems may not be passive friendly in general, can find a great no compromise solution with The Truth.
- ...
- 30 posts total
I read this thread and some of the referenced links with great enthusiasm. Extremely helpful since I had started a thread and basically asking the questions that are mostly addressed by the folks in this thread. I've been running my system without my (active) preamp for the past few days and like the outcome. Between my source components, my amp - with separate gain controls for each channel, and having the components right next to each other, I have plenty of volume and no obvious loss of sound quality. I say obvious with some reservation because it appears that the frequency range appears to be all there but I'm not sure about the soundstage. It is also difficult for me to do an A/B test to compare the sound with and without my preamp. So at the risk of sounding stupid, I'll go ahead my question: could a passive preamp, or active preamp for that matter, "add" soundstage to a piece of music? In other words, if an orchestral piece sounds little "flat" with no preamp, could adding a preamp enhance the presence of soundstage? Or, presence/absence of soundstage is completely dependent on the source content - its either there or its not. This is of course assuming that everything else in the music chain, including the music content is kept unchanged. Thanks. P.S. Is the First WattT B1 considered a passive preamp? If so, would it be a good option given what I have described relative to my system configuration, e.g., adequate gain/volume, very short distance between components, etc.? Much appreciated. |
"So at the risk of sounding stupid, I'll go ahead my question: could a passive preamp, or active preamp for that matter, "add" soundstage to a piece of music?" I would opine that the addition of a preamp or any other component or stage of gain or even a stage without gain will not make the soundstage better any more than it will make the sound more transparent or make the sound less distorted. |
I discovered by accident this thread and thought, it might be of interest to share *my* personal experience with the Truth line stage. It is *not* a positive one, but, despite the fact that I was quite angry about it or better said, about me purchasing it, I simply have to take my hat off to such an anecdotic “design” and business idea. So, what generated actually my analysis and observations ? I ordered the Truth after Arthur Salvatores review was out (www.high-endaudio.com, which I am a “follower”) , so I had to queue onto the burst of orders generated by his review. Around 2 weeks later I got my exemplar in its latest incarnation, although I am not sure if it was 100% the reviewed design, details to follow. The Truth line stage is more than anything else the paramount incarnation of a "garage product", but I didn't expect something different, as sound was (and is) my first priority. My intention was to replace my Coincident Statement line stage, a problematic component that I was not able to integrate free of hum in my system (well, this is another, but similarly annoying story). After unpacking the little Truth box, I observed that something was freely moving in its interior producing a vexing sound. So I had to open it. And indeed, I found a half inch solder wire. Probably a side effect of the formidable pressure put on the manufacturer due to an order tsunami . But now the box was open, and I was quite astonished. To put things into perspective I will try to give a kind of “360degree” view : 1. Sound. Basically, in what I am concerned, consistent with Arthur Salvatore observations (those are available on his site). There are caveats however, which I personally could *not* live with. 2. Communication and manufacturer support: Excellent and for me fully consistent with the image of a real business man. 3. Design. Well, not sure how to explain this, you should better sit down now. There isn't really a "design"; well, of course, there is one, but unfortunately I don't know the engineer at Analog Devices who designed the video buffer chip. For the rest we have one “Aunt Corey buffer” ( published in Stereophile here http://www.stereophile.com/solidpreamps/54/#p0AeZJuyLmPkY5bS.97) at input , a second, identical one at output and in between an “attenuator” in Arduino style of "how to control a photocell with a LED" (just google on this). Not even the Aunt Corey buffer is a "design" in the proper sense, as it is merely the buffer chip and ... well, …the buffer chip. Interestingly enough, the buffer and the photocell circuit can both make a cool exercise for any school experiment on electronics for beginners. No exaggeration here, it hardly gets simpler. Of course we grant the manufacturer the idea of combining all these together and offering them at a respectable price… speaking of price: 4. Price. A highly philosophical issue, I will leave this to you audiophile fellows as an exercise. Here is the raw data: costs of components (incl. case) evaluated at around 75-90 USD (retail) + labor (I would estimate max 2 hours including testing); for example the power supply in my exemplar was a MeanWell universal switching power supply (around 15 USD retail). The Truth costs around 1000 USD, but hey, we read it more than once with gear around 10K$: "it is not cheap but compared to inferior components costing twice, tenth or more, it is a *real bargain*". My personal position: it is (a little bit grossly) overpriced. 5. Build. Sufficient. 6. Myths. The manufacturer claims,” there are no resistors or capacitors in the signal path”. With respect to “capacitors” I agree, as it is dc coupled, for the ”resistors” a clear FALSE. It is not my intention to generate a discussion here about the foundation of this claim, and I mean it in the sense of electrical engineering, but you might want to revisit one of the following links: http://www.diyaudio.com/forums/everything-else/94506-shunt-attenuator-myth.html or https://www.southampton.ac.uk/~apm3/diyaudio/Signalpath.html ... just to find out in which "camp" you belong. I definitely belong in Steve Eddys camp. Any resistive attenuator is designed around a SERIES and a SHUNT element. For stereo you need 2 SERIES and 2 SHUNTS elements. It can't be achieved with only 2 photocells and there are only 2. If the photocells are building the SERIES path, there must be something else for the SHUNT, mustn’t it ? In this case it is a (very cheap) potentiometer wired with the central pin to ground for balance control and creating so the missing SHUNT element. And *it is* also in the signal path. The attenuated voltage is taken from this cheap potentiometer, not from the photocell. 7. Upgrade ideas for owners. An easy exercise. a. ANY state-of-the-art, diy or not, linear power supply to replace the general purpose switching one, in any flavor one wishes, single or dual configuration. From Sjöström Audio, diyaudioshop or Paul Hynes (should you want one of the best), all this stuff being available for very reasonable prices. b. Full LDR-attenuation path, series AND shunt. Examples abound. Lightspeed attenuator, Tortuga kit or the more advanced and at the same time reasonably priced btfsystems. Insert one of these between the two buffers. Now, I obviously don't buy that a cadmium photocell is in any respect different or superior against a Silonex optocoupler designed for audio purposes. 1. Caveats. The Truth volume control remains imo only a brainstorming. If you have doubts, you should take a look at the efforts done by people like Paul Hynes (LDR attenuator kit), Tortuga Audio or the formidable btfsystems LDR design with calibration . The Truth "solves" the calibration issue by inserting the balance potentiometer, clever, eh ? However, if you do the math, you will eventually find out, that, *if* you set the balance at *some* volume, so you are fixing a proportion of the two shunt elements , then this proportion is not valid anymore with another volume setting, as far as the 2 photocells have not been sorted for having a specific relation between their characteristic curves, which I doubt this was the case and I also doubt that it can be achieved in general. So there isn't an (electrical) balance reference point, balance is always "by ear". Also, the latency/response time of the volume control is simply too large making, a.o., a remote control unusable, an aspect pointed out also by Arthur Salvatore. Wrapping up: Can one live with the Truth linestage, are the volume control issues tolerable ? ...maybe yes. Personally I couldn't and sold it couple a days later taking a 400 USD loss and one more unfortunate experience. Einstein was quoted for having said: "Keep it simple, but not simpler" ... The Truth is imho "too simple" but not too cheap. Thanks for your time and sorry for my verbose contribution. PS. In his review, Arthur Salvatore raised the question of “Which of the both design artefacts, the buffer chip or the light-based-attenuation path, should be held responsible for the Truth stellar performance” ? I am personally quite inclined to attribute this to the electronic design and the achieved electrical characteristics of the video buffer chip. It would definitely be *my* Oscar nominee…. |
- 30 posts total