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The Truth Pre Amp Review

MakeMineVinyl

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I don't have any safety ground concerns; in my 1926 house, they didn't use separate ground wires back then, thus no problem. :D
 

Bob from Florida

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There are decades of standards built on the back of lives lost to stupid design decisions. There is a saying in engineering that the standards are written in the blood of those killed by poor designs. Safety design standards are not some sort of hand waving. It is a set in stone practice that a you need multiple faults to occur to have a lethal situation. Safety engineers will often use the "Swiss cheese" analogue when talking of accidents. Electrical devices need to provide multiple layers of defence against failure. And the manner in which they are implemented is carefully codified.

The Truth pre quite simply has been built with zero attention to any form of safety. The person constructing it simply has no clue. Phrases like "fault current" come to mind in the lexicon of terms that are just not understood. The build only needs a single failure in construction to become lethal. One. With the appalling construction quality such a failure it is going to be a matter of when not if. If there are hundred devices out there, there is a very good chance one of them will at some point in the next few years have such a failure. From any standpoint that it totally unacceptable. We might hope that there isn't a fatality. If there is you can be sure the victim's family will be lawyering up. In normal engineering practice adherence to accepted standards of safety are what protect you from such things.

I remember a short wave radio we had in the 1960's that was built in the 1930's. It had a two prong plug - un-keyed. Because it had a .1 uf capacitor from one of the power wires to chassis it made a shocking difference if plugged in the wrong way. If fact the manual stated if you felt a shock from the chassis to turn the plug around. Turns out the manuals direction was accurate! Certainly, safety has advanced significantly.
 

MakeMineVinyl

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solderdude

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I got zapped with 4kV, threw me around half the room/ Also accidentally put my fingers on a flyback transformer and am still alive.
Got a nasty zap from a not discharged capacitor (300V DC) from a non functioning SMPS etc.
There are people that died because of touching mains though.
A good leakage current circuit breaker can help a lot.

Still... workmanship is shoddy, performance is poor, no matter how you look at it. Not worth $ 1k. Period.
 

MakeMineVinyl

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I remember a short wave radio we had in the 1960's that was built in the 1930's. It had a two prong plug - un-keyed. Because it had a .1 uf capacitor from one of the power wires to chassis it made a shocking difference if plugged in the wrong way. If fact the manual stated if you felt a shock from the chassis to turn the plug around. Turns out the manuals direction was accurate! Certainly, safety has advanced significantly.

In my high school electronics class, we built AM radios which had no mains transformers or any other safety measures. The instructor warned us not to touch our radios at the same time as we touch each other since there was a 50% chance one of our AC plugs were inserted the "wrong" way. Great fun, that. :cool:
 

Colin James Wonfor

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I got zapped with 4kV, threw me around half the room/ Also accidentally put my fingers on a flyback transformer and am still alive.
Got a nasty zap from a not discharged capacitor (300V DC) from a non functioning SMPS etc.
There are people that died because of touching mains though.
A good leakage current circuit breaker can help a lot.

Still... workmanship is shoddy, performance is poor, no matter how you look at it. Not worth $ 1k. Period.
I did the same on a UHF 400W 400V transmitter and on the cathode of a EHT tube in a old Black and White TV both left burns, bloody hertz, that two of us still alive, suck an elf.
 

Colin James Wonfor

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The saddest shock I saw was a engineer getting killed with 150KV from a Xray Generator PSU at 150KW he caught fire, inside a gage nobody could get to him to help, poor man.
 

Speedskater

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I don't have any safety ground concerns; in my 1926 house, they didn't use separate ground wires back then, thus no problem. :D
And lots of people were killed with that old wiring system. Bathroom and kitchen electrocutions were way to common. Table radios were a death trap.
 

MakeMineVinyl

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And lots of people were killed with that old wiring system. Bathroom and kitchen electrocutions were way to common. Table radios were a death trap.
Well, yeah, doing things like using an electric hair dryer while taking a bath are not life affirming. Neither is playing on the freeway or on railroad tracks. People went out of their way to warn me about doing stupid stuff like that.

Getting back to the original topic, I don't really have much problem with the mains grounding so much as the totally clueless workmanship. Products like this are a race to the bottom if this level of quality is accepted as standard rather than being called out for the junk it is. Even in some extremely high end pricey gear (with elaborate CNC metalwork no less), I occasionally see workmanship which makes me cringe.
 
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JeffS7444

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I've had amiable online exchanges with Ed Schilling, and he's told flat out that his technical know-how is limited. I don't know when or how "The Truth" became a product: I vaguely recall it as a simple circuit diagram posted on his site for people to DIY. But goodness knows that some would-be customers can nag like they've never experienced a firm "No" in their life.
 

Speedskater

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Well, yeah, doing things like using an electric hair dryer while taking a bath are not life affirming. Neither is playing on the freeway or on railroad tracks. People went out of their way to warn me about doing stupid stuff like that.
Yet in 1926 and 1952 many more people were electrocuted at home than were killed on railroad tracks. Electricity was an invisible killer and many products and electrical systems were of unsafe designs.
 

Bob from Florida

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Yet in 1926 and 1952 many more people were electrocuted at home than were killed on railroad tracks. Electricity was an invisible killer and many products and electrical systems were of unsafe designs.
Your quote may be true, however, references would be in order.
 

Bob from Florida

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Fell free to post them. I don't think that anyone else is that interested.
I don't think you understand. You made a specific statement about deaths by electrocution. It is not my responsibility to prove your statements or disprove. You must have researched the subject before posting - right?
 
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I don't think you understand. You made a specific statement about deaths by electrocution. It is not my responsibility to prove your statements or disprove. You must have researched the subject before posting - right?
The ratios of electrocution to railroad track deaths in 1926 and 1952 are independent of the merits (or lack thereof) of the preamp in question.

I personally am offended by The Truth because I happen to know as a matter of fact that every time one of these gets sold, an angel loses its wings.
 

Francis Vaughan

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Because it had a .1 uf capacitor from one of the power wires to chassis it made a shocking difference if plugged in the wrong way.
Lordy, yes. Those capacitors have a name. They have become known as "death capacitors". Especially in tube guitar amp circles where vintage amplifiers are not consigned to the trash but are prized possessions. They are call this because they have a habit of failing. And when the fail they short out, with a 50/50 chance of bringing the chassis to live. Many of the stories you hear of guitarists being electrocuted on stage are, at their root, a failed death capacitor.
Capacitors used with mains potential are subject to a much harder life than just the mains voltage. Glitches on the mains can mean voltages many times higher than the nominal voltage, especially from things like motors and other inductive loads on nearby circuits. Modern capacitors used to bypass mains are specially rated (usually you will see "X" or "Y" ratings, depending upon how the capacitor is used) and are designed to self heal - where self healing means they will clear an internal short by vaporising it without otherwise suffering damage.
 

H-713

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As I mentioned, it's not a particularly safe design, but we should keep things in perspective. Unless it's been modified, a Dynaco ST-70 (and that is still a very popular amplifier) is far worse than this. There is no safety ground. If you don't have the top cage, there is exposed high voltage on the PCB. A Heathkit AA-121 is no better. Quite a few old tube amps operate with the shell of the filter caps at a high voltage potential, and the only thing protecting the user is a layer of 60-year-old cardboard. Don't even get me started on some of the old RF amps sold to hams.

This thing has questionable safety grounding, yes, but there is no exposed high voltage, it uses off-the-shelf Mean Well power supplies (which are certified and are a good brand), and although things aren't great inside, they aren't that scary.

Again, I'm not saying this is right, but it's important to keep things in perspective. There are commercial tube amplifiers available, some of which run plate voltages over 1000 volts (with plenty of current behind it). For those who are saying that the person who built / sold this preamp "should be jailed for safety violation", does that mean we should jail all people who sell vacuum tube amplifiers? The chances of a user coming in contact with a HV supply in a tube amp (broken tube, removing a tube from the socket, catastrophic failure) is probably a lot higher than the chances of the chassis on this becoming hot, and the HV supply in a tube amp is also, in most cases, a hell of a lot more dangerous.

Furthermore... I see knockoff equipment from overseas that is a lot scarier than this. I'm not saying this preamp is right (as I've outlined, there are a lot of things I don't like about it), but let's keep things in perspective.
 
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