AudioSceptic
Major Contributor
Yes, it does, and where are the labels?It looks like the left rotary button is placed lower than the other ?!?
Yes, it does, and where are the labels?It looks like the left rotary button is placed lower than the other ?!?
This is the discount version, labels will cost you another $250 per labelYes, it does, and where are the labels?
I am even ok for products that measures sub par and cost a fortune if they did the packaging and looks high end.... but this don't even do that! if that it can't even amplify the signal... why one would not opt for a passive preamp like Khozmo at a fraction of cost and provide perfect channel balance?....This is a review and detailed measurements of The Truth Pre Amp (its real name). It was kindly sent to me by a member and costs US $1,050. There are other options which increase the cost.
The version sent to me is an earlier one I am told with dual inputs (labels are wrong by the way):
View attachment 132684
There is a nice textured paint on the front panel which doesn't quite come out correctly on the image above. The two controls are for balance and volume. Strangely the max setting for the volume is where you see.
The back panel as Dave Jones would say is "how you doing:"
View attachment 132685
It is quite low budget for this pricing. Like the fact that AC mains is built-in. Don't like the fact that it has no regulatory certification (kind of the norm in this category of product).
The truth implies transparency. Let's measure it to see if it gets there.
The Truth Pre Amp Measurements
As usual we start with our 1 kHz dashboard using unity gain (2 volts in and 2 volts out). This required max setting on the volume, i.e. this preamp can only attenuate, it cannot amplify:
View attachment 132686
Well, this is not my definition of transparency. We have good bit of distortion which limits performance to about 14 bits in digital audio terms.
SNR is better though although one channel seems to be noisier than the other:
View attachment 132687
The right side is a new test where I adjust the volume to 1/4 output and measure again. This way we can see the effect of residual noise better and are simulating someone listening at less than max volume.
Frequency response is excellent with wide bandwidth:
View attachment 132688
I was surprised that crosstalk was not frequency sensitive and not that good:
View attachment 132689
Seems like there is some coupling on purpose between the channels??? Strange.
IMD test shows that prior to getting to max output performance starts to suffer:
View attachment 132690
This is due to low frequency distortion rising:
View attachment 132691
THD+N versus frequency shows performance that is well below (cheaper) competition:
View attachment 132693
Conclusions
Let's get the obvious out of the way: The Truth Amp does not speaker the truth! It adds its own noise and distortion. It is definitely not competitive with squeaky clean design we have access to today that have considerably less noise and distortion while costing less. That would normally lead to a "headless panther" rating but I felt generous and gave it one step higher because it is not broken like some other designs are. That, and the fact that the headless panther was helping with weeding in the garden today and wasn't in a mood to be in the picture. So I left him alone so he could search for his head....
Needless to say, I cannot recommend the The Truth Pre Amp.
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That is just idiotic.......
Currently available from Digikey, Element-14, RS, DigiKey UK.Richard Dunn was sure that they were illegal.
They do. It what I was handwaving about when I wrote "and unclear distortion effects in the resistor." It isn't clear that the distortion isn't also dependant on the amount of light. It is a mess.I understand CDS cells also have an unfortunate property that the resistance has a small dependency on the voltage across the cell,
Lordy, this is quite a mess.
A quick Google turns up a few internals pics here: https://www.superbestaudiofriends.o...ve-volume-control-for-dacs-sources.860/page-9
Forum comes compete with a snide remark about Amir.
Post above has the other pic I found.
The preamp looks like a total amateur build. There is so much wrong with it I would be utterly ashamed to put my name anywhere near something like this product, and as to charging $1k for it, it is just ridiculous.
The switch on the back is a chassis ground lift. Really. And the switch would never survive a realistic fault current. It might weld itself solid, it might vaporise before a breaker blew leaving you with a lethal live chassis. Some versions don't have the lift switch. It seems then they just don't bother to ground the chassis. The mains wiring inside is not to standard either.
The quality of the soldering is beyond poor. It is what I might expect of a 12 year old doing a circuit build for the first time with poor quality tools. The entire internal layout and construction is quite simply terrible and not of merchantable quality. There is clearly no understanding of ground loops and management of ground return, which will be a contributor to the mains pickup and poor noise figure. Not a cable tie in sight, which along with the terrible soldering will lead to poor reliability.
Now to the circuit. It is an op-amp buffer on the input and output coupled by a light dependant resistor lit by a LED controlled by the volume pot. That is it. There is no light shielding for the LDRs so the chassis had better be light tight to avoid interference from external light sources - especially modern LED lights flickering away. This is a funny idea that keeps raising its head from time to time. The volume control on the front doesn't touch the signal, but just runs the LED. But there are all manner of issues with the idea, poor noise being one of them, and unclear distortion effects in the resistor.
This is a product that needs calling out for what it is. No matter what else, its construction leaves it as an unsafe product that should not be sold.
There needs to be a panther past the headless one. This is deserving of it.
Spacemonkey links to a reviewer who has had one in his system since 2018 and seems unconcerned that the stereo balance shifts depending on temperature but then boldly types that it has "little electronic character of its own".
.....I have never heard of “emotional mobility” and “sense of appropriateness” being used to describe the sound of a component....
I’m feeling a little shameful here, I’m sure I should know this. What does the etc. represent? I can‘t think of what else the distribution of sound relates to.intonation, rhythm, dynamics, etc.
Not sure that panther is more forgiving. I am trying to figure out if all he does is send away failed pieces of garbage.Emotional mobility is perhaps the best explanation of how panther kept his head.