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The Truth Pre Amp Review

amirm

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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):

The Truth Pre Amp Review Preamplifier.jpg


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:"
The Truth Pre Amp Review back panel Preamplifier.jpg


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:

The Truth Pre Amp Measurements.png


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:

The Truth Pre Amp SNR Measurements.png


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:

The Truth Pre Amp Frequency Response Measurements.png


I was surprised that crosstalk was not frequency sensitive and not that good:

The Truth Pre Amp Crosstalk Measurements.png


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:
The Truth Pre Amp IMD Measurements.png


This is due to low frequency distortion rising:

The Truth Pre Amp IMD Spectrum Measurements.png


THD+N versus frequency shows performance that is well below (cheaper) competition:

The Truth Pre Amp THD+N vs Frequency Measurements.png


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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As always, questions, comments, recommendations, etc. are welcome.

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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amirm

amirm

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Some interesting bit from the product page: "
  • There are no capacitors or resistors (other than the photocell) in the signal path. There is no potentiometer in the signal path.
"
 

fredoamigo

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I am even more doubtful than the panther seems to be .
really very curious to know what the trigger is to buy this thing 1000 usd?

maybe the minimalist aspect plays that role?
 

Koeitje

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Even if the performance was good the build quality is a joke.
 

astr0b0y

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There’s a lovely subjective review here https://www.tnt-audio.com/ampli/the_truth_e.html that has topless shots. My favourite paragraph from the review:

My first few listening sessions were a bit disorienting. I was not quite able to put words to my impressions. It took me 2 or 3 days of heavy listening time really start to be able to answer the question “What am I hearing?” I have concluded, and I am still comfortable with this conclusion many months later, that the strangeness was due to the lack of noise and distortion. An impression of something missing. With The Truth Pre Amp not only must one ask “What am I hearing?” but equally as important “What am I not hearing?”.
 

B4ICU

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Just a say about it's look: I made nicer fronts to my DIY gear, when I was in high school in the mid 70;s. It looks bad also at the rear panel.
No ,marking' No symmetry, no logic in that design. Very poor.
 

Francis Vaughan

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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.
 
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