The Truth Pre Amp Review

[MakeMineVinyl]

I just dug up some of these from my stock of BUF03s, which I made probably 20 years ago or more.

They are some modules I made to fit two BUF03s into a dual opamp socket. Just for giggles, I'm going to plug it into the input buffer stage of my electronic crossover (pictures of this crossover are in the 'workbench' thread) and see what happens. I'm sure it will have more noise than what I have in that spot now, and surely will get a LOT hotter. Might be interesting just the same!

 

[MakeMineVinyl]

I just dug up some of these from my stock of BUF03s, which I made probably 20 years ago or more.

View attachment 136088

They are some modules I made to fit two BUF03s into a dual opamp socket. Just for giggles, I'm going to plug it into the input buffer stage of my electronic crossover (pictures of this crossover are in the 'workbench' thread) and see what happens. I'm sure it will have more noise than what I have in that spot now, and surely will get a LOT hotter. Might be interesting just the same!

I just installed this module into the only stage in my crossover which can accept an IC without a non-inverting input, the input buffer which is fed from the input transformer. Surprisingly I cannot hear any added hiss from the HF horns but the hiss I heard from my previous crossover might be because BUF03s were used in all the filters and the input buffer, so there were multiple stages of hiss generators.

One possible benefit from using the BUF03s now is that of output drive impedance into multiple parallel filter sections; this wasn't necessarily a problem before, but is less of a potential problem now. The BUF03s do get hotter, as do the rail voltage regulators, but not too severely and I can live with that.

Of course several veils have been lifted from the soundstage, and there is much better pace, rhythm and whatever other description an audio-neurotic could possibly come up with. I think the sun is shining a bit brighter too and my cat hasn't puked as many times on the bed. All is good.

 

[kannan]

I dont know how many have owned or heard this pre.
I was not aware of it till one landed on my bench for a minor service.

Apart from the measurements, this is one of the most transparent preamps I have heard.
Apart from some minor quirks this is worth every penny for the quality output one gets.

I don't care or bother about the brick bats that are bound to follow this post, but I have spoken the Truth about what I heard out of it.

 

[Laserjock]

I dont know how many have owned or heard this pre.
I was not aware of it till one landed on my bench for a minor service.

Apart from the measurements, this is one of the most transparent preamps I have heard.
Apart from some minor quirks this is worth every penny for the quality output one gets.

I don't care or bother about the brick bats that are bound to follow this post, but I have spoken the Truth about what I heard out of it.

What do you use for a preamp in your system?

 

[antennaguru]

I dont know how many have owned or heard this pre.
I was not aware of it till one landed on my bench for a minor service.

Apart from the measurements, this is one of the most transparent preamps I have heard.
Apart from some minor quirks this is worth every penny for the quality output one gets.

I don't care or bother about the brick bats that are bound to follow this post, but I have spoken the Truth about what I heard out of it.

I have heard this preamp at a friend's house, who was enamored that it used a light beam light to control the volume and had no noisy potentiometers or switches with noisy contacts in the signal path (advertising BS). Well, it did NOT sound good at all, and its remote volume control was super quirky. The volume increased/decreased too fast, and was near impossible to get right. This is simple to understand as Light Dependent Resistors coupled to an LED light control are not at all reasonable in their response (linear/log), and have a very narrow "sweet spot" in their adjustment where they are actually suitable. It's only slightly more adjustable than turning the lights on or off in your room as an analogy. LDR preamps are yet another attempt to entrap gullible folks with no technical background with a gimmick, in this case a light beam is used to control the volume, and also by suggesting that "passive preamps" are better than active because they lack active devices. Speaking of that his system lacked the system dynamics of an active preamp with gain, as I have found all passive preamps do with most sources. I guess the only exception would be a really powerful output digital source that has so much excess gain as to not need any preamp gain, like most other sources do. I heard demos on phono, tape, and digital, and all were shamefully reproduced compared to any cheap active preamp that a high school student could build around a pair of Op Amps, an Alps R27 volume control, and a rotary switch source selector. Eventually that friend decided to try a good solid state preamp, and never looked back at "The Truth".

 

[MakeMineVinyl]

This is simple to understand as Light Dependent Resistors coupled to an LED light control are not at all reasonable in their response (linear/log), and have a very narrow "sweet spot" in their adjustment where they are actually suitable. It's only slightly more adjustable than turning the lights on or off in your room as an analogy.

I have been doing pretty extensive work with LED/LDR devices, and I can certainly attest to the fact that they are very critical in their linear operating range (such as it is), and even more important, even very good ones have to be hand selected to get a pair which is close enough in their curves to be of any use. But more important than that is that the resistive element is noisier and more non-linear than any decent quality potentiometer.

 

[kannan]

What do you use for a preamp in your system?

I use a Teac DAC with inbuilt preamp.
When i used this HornShoppe pre in the setup, I disabled the pre in the Teac and ran a full output to it.
Yes the quirks are there like a slight channel imbalance when switching on again (but not all the times).

@antennaguru I was not enamoured by any of the technology it claims. When I first saw it from outside, I was wondering if it was even worth opening to check the issue at hand for which it came to me.
It was a minor wiring issue on one of the RCA outputs which took a minute to correct so I did not research much on what I saw inside.
I was expecting next to nothing when I just put it in my chain to check if the outputs worked. But my jaws simply dropped from what heard.
It was then I read upon it in detail.

Anyhow the next day it went back to its owner.

 

[antennaguru]

I use a Teac DAC with inbuilt preamp.
When i used this HornShoppe pre in the setup, I disabled the pre in the Teac and ran a full output to it.
Yes the quirks are there like a slight channel imbalance when switching on again (but not all the times).

@antennaguru I was not enamoured by any of the technology it claims. When I first saw it from outside, I was wondering if it was even worth opening to check the issue at hand for which it came to me.
It was a minor wiring issue on one of the RCA outputs which took a minute to correct so I did not research much on what I saw inside.
I was expecting next to nothing when I just put it in my chain to check if the outputs worked. But my jaws simply dropped from what heard.
It was then I read upon it in detail.

Anyhow the next day it went back to its owner.

More transparent than any other passive preamp using a potentiometer or step attenuator, used with your high line level output TEAC DAC? I think not.

On the bench the quirky exceedingly fast nature of the remote volume control would not be apparent either, but this is very important for a real world system where you're sitting back listening and using the remote volume control to set the listening level. On the bench you can just move the volume control manually and precisely to find the narrow sweet spot.

What I heard was dreadfully un-dynamic with sources other than a high level output DAC that admittedly has tons of excess gain and is about the only source that can have acceptable dynamics with a passive preamp. My audition included phono and tape as well as digital.

As far as the build quality goes I would be embarrased if one of my proto-boarded prototypes looked like "The Truth". The truth is that it's amateurish at best, in the worst sense of that word.

 

[kannan]

Teac outputs 2 volt gain which was enough to drive. I don't have any other analogue sources other than one CD player which I did not use with this pre.
This model I repaired does not feature remote control and neither does my Teac.
This hornshoppe had one input selector, a volume control and a balance adjuster in the front facia.

Yes the build quality is below average, but a big thumbs up to what I heard.

 

[MakeMineVinyl]

Yes the build quality is below average

Your 'average' must be an exceedingly low bar. If I produced something like this in my high school electronics class, I'd get (and deserve) a failing grade.

 

[antennaguru]

Teac outputs 2 volt gain which was enough to drive. I don't have any other analogue sources other than one CD player which I did not use with this pre.
This model I repaired does not feature remote control and neither does my Teac.
This hornshoppe had one input selector, a volume control and a balance adjuster in the front facia.

Yes the build quality is below average, but a big thumbs up to what I heard.

Wow, no remote control, and only one stereo input to one stereo output. If I felt like it, I could build such a passive preamp around a stereo Alps R27 potentiometer, or a stereo rotary switched SMT resistor loaded 21 step attenuator (perfect levels assured between both channels at each of the 21 volume level steps), 4 RCA connectors, and a Bud/Hammond Box for around $150 parts cost, and a half hour assembly time ~$50, and with 100% markup it would represent $400 (including my profit as the builder). Then the dealer can apply mark up as they see fit, or it could be sold direct as I believe "The Horn Shoppe" sells theirs (with no dealer markup). It would have lower cross-talk and no internal power supply or power input requirement at all. There you go, a passive preamp every bit if not more transparent as "The Truth" is within its narrow sweet spot, except that the sweet spot would now be widely across the whole range of the volume control. The only warning is that it's intended for DAC or CD player sources only, as it would be too undynamic with phono or tape sources. Now, there's "The Truth".

 

[manisandher]

LDR preamps are yet another attempt to entrap gullible folks with no technical background with a gimmick, in this case a light beam is used to control the volume, and also by suggesting that "passive preamps" are better than active because they lack active devices.

The Truth is not passive. It's active, but with zero gain.

Mani.

 

[manisandher]

Apart from the measurements, this is one of the most transparent preamps I have heard.

It's nowhere near transparent:
https://www.audiosciencereview.com/...ds/the-truth-pre-amp-review.23815/post-801561

Mani.

 

[AudioSceptic]

I use a Teac DAC with inbuilt preamp.
When i used this HornShoppe pre in the setup, I disabled the pre in the Teac and ran a full output to it.
Yes the quirks are there like a slight channel imbalance when switching on again (but not all the times).

@antennaguru I was not enamoured by any of the technology it claims. When I first saw it from outside, I was wondering if it was even worth opening to check the issue at hand for which it came to me.
It was a minor wiring issue on one of the RCA outputs which took a minute to correct so I did not research much on what I saw inside.
I was expecting next to nothing when I just put it in my chain to check if the outputs worked. But my jaws simply dropped from what heard.
It was then I read upon it in detail.

Anyhow the next day it went back to its owner.

So you will buy one yourself?

 

[antennaguru]

The Truth is not passive. It's active, but with zero gain.

Mani.

An LDR actually is just a resistor that changes its resistance based on how much light is shined on it. So from that standpoint it is actually passive as far as the signal path goes. The high distortion artifacts that were quite apparent in testing are from the non-linearity of the LDRs used, poor LDR implementation, poor power supply design/layout for the LED light part that shines light on the LDR(s) and whose intensity range is controlled by the volume control potentiometer, crude wiring paths/layout, etc. Nevertheless, it is a far less linear and smoothly controllable approach to a passive preamp than a simple potentiometer or step attenuator - without the whiz bang element of using light.

Also, just because it has a power supply doesn't mean it's not passive preamp. I could build a passive preamp around a remote control motorized Alps potentiometer and the signal path would only be going through the passive variable resistor (potentiometer). The power supply would only be powering the remote controlled motor that turns the potentiometer based on inputs received from the remote control and to power the digital readout to let you know what volume level it's set at, etc. That is a purely passive preamp approach that has a power supply, and adds the convenience of remote control, and volume level readout.

Nevertheless I have built numerous passive preamp prototypes, including an LDR version, and I still generally dislike ALL passive preamps for a couple of reasons. First, they have no gain to preserve the dynamics of analog sources which are not very high in output voltage like digital sources are. Second, the output impedance of a passive preamp varies depending upon the resistance setting of the variable resistor and at some volume control levels may be unsuitable for driving some power amplifiers, affecting the overall sound quality - which then demands the inclusion of an output buffer circuit which in turn introduces some negative effect on transparency, etc.

 

[MakeMineVinyl]

An LDR actually is just a resistor that changes its resistance based on how much light is shined on it. So from that standpoint it is actually passive as far as the signal path goes. The high distortion artifacts that were quite apparent in testing are from the non-linearity of the LDRs used, poor LDR implementation, poor power supply design/layout for the LED light part that shines light on the LDR(s) and whose intensity range is controlled by the volume control potentiometer, crude wiring paths/layout, etc. Nevertheless, it is a far less linear and smoothly controllable approach to a passive preamp than a simple potentiometer or step attenuator - without the whiz bang element of using light.

Also, just because it has a power supply doesn't mean it's not passive preamp. I could build a passive preamp around a remote control motorized Alps potentiometer and the signal path would only be going through the passive variable resistor (potentiometer). The power supply would only be powering the remote controlled motor that turns the potentiometer based on inputs received from the remote control and to power the digital readout to let you know what volume level it's set at, etc. That is a purely passive preamp approach that has a power supply, and adds the convenience of remote control, and volume level readout.

Nevertheless I have built numerous passive preamp prototypes, including an LDR version, and I still generally dislike ALL passive preamps for a couple of reasons. First, they have no gain to preserve the dynamics of analog sources which are not very high in output voltage like digital sources are. Second, the output impedance of a passive preamp varies depending upon the resistance setting of the variable resistor and at some volume control levels may be unsuitable for driving some power amplifiers, affecting the overall sound quality - which then demands the inclusion of an output buffer circuit which in turn introduces some negative effect on transparency, etc.

Unless I'm mistaken, the Truth preamp uses a BUF-03 video buffer IC on it's output. The BUF-03 has a very high input impedance which is probably required because of the LDR. The BUF-03 used to be the darling of the high end audio market. I use them for the input of my active crossover for no particular reason beyond I have lots of them and the fact that they have low output impedance and can drive 600 Ohms (I believe).

 

[antennaguru]

Unless I'm mistaken, the Truth preamp uses a BUF-03 video buffer IC on it's output. The BUF-03 has a very high input impedance which is probably required because of the LDR. The BUF-03 used to be the darling of the high end audio market. I use them for the input of my active crossover for no particular reason beyond I have lots of them and the fact that they have low output impedance and can drive 600 Ohms (I believe).

May well do so, but that unfortunately doesn't fix the LDR nonlinearities and noise issues. From the pictures on this thread there seem to be some different versions out there, customized per se. I know my friend's had the absolute worst remote volume control I ever used, and I don't see a motorized pot in any of the pictures here. All of this is just lipstick on a pig anyway...

 

[kannan]

Wow, no remote control, and only one stereo input to one stereo output.

You got me wrong or I should have explained better. The front facia includes one input selector I said, not one input. This pre that I serviced has 3 inputs.

 

[kannan]

So you will buy one yourself?

probably a used one if I can find in my country, the chances are however very very remote as I think not many are aware of it.
In fact, I find the website totally bland looking like the equipment with links to a few reviews and that's it.
Importing from US would make it twice expensive duty to local duties and taxes.
That said I am pretty satisfied with my Teac as I only use one digital source nowadays, either via digione signature or laptop through the DAC.
I am only stating that the Hornshoppe sounded very very good in my setup belying its appearance or build.

 

[Mart68]

Plenty of cheaper passive pre-amps around which - assuming compatibility with source and power amp - will sound just as good.