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
... 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….