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Schitt Audio Master Marketers

Sythrix

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#5

amirm

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#7
Thanks. Alas, there is a mistake on the schematic in the muting circuit:

1533146176481.png


There is no "23" volt supply anywhere. This would have been easily caught on the PCB design. If not, that pin is just hanging in there with the relay doing nothing.

It is also a lousy circuit with just a timer instead of checking for DC output on the headphone jack which can kill the headphone (and make you possibly go deaf) if the output stage dies. This is the same thing I think they have done on their own shipping product.

Anyway, it is good to see this effort from them. They could have just shipped the PCB of a random circuit.
 

amirm

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#8
It's actually a new PCB they designed just for coaster duty which strikes me as even more bizarre...
It is a great read on how they have superb handle on this "gorilla" social marketing. They set low expectation to appear humble ("we are not good at DIY"). Good bit of (nice) education on how designs work.

Good on them to not make any claims on why tube headphones amps are better:

1533146542719.png


In other words, it is tube because if it is a novelty.
 

DonH56

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#10
No feedback, no bias compensation, output driver uses an LED instead of diodes to match and track the output transistors and provide stable class AB operation, etc. Fortunately the mistake highlighted by Amir means the outputs will never be applied to the headphones. I see why it's a coaster.

BTW, the BoM says it is a 24-V relay, not sure where they mean to connect it, unless the driving transistor drops enough to hook to 30 V or the relay will pull in with 15 V.

But, they did not lie -- it is not what most would consider high-performance and they are up-front about that.
 

xxie

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#11
It is also a lousy circuit with just a timer instead of checking for DC output on the headphone jack which can kill the headphone (and make you possibly go deaf) if the output stage dies. This is the same thing I think they have done on their own shipping product.
In their defense, there is DC blocking cap on the output.

But I would like to have some protecting diodes on LM317 as in the data sheet suggested.
 
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#12
Some masterful trolling at work here, got to hand it to them. They'll lure the earnest and already converted, and incense the knowing few who might even take the trouble to examine this excuse for a coaster, never mind amp :D To whit, their marketing is measurably better than everyone else.
 

amirm

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In their defense, there is DC blocking cap on the output.
Good catch. I missed that as I was just focusing on what the protection circuit was doing. :)
 

DonH56

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#14
Even as a coaster it is lacking; no lip to keep moisture from rolling off, holes in the board allow moisture to the surface below anyway, a metallized and hard surface without insulation to protect the surface upon which it sits, etc. Or maybe they at least put little feet on the backside?
 

amirm

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#18
Probably? Did you measure it?
No, but there are published specs. FR by the way stands for fire resistance so that kind of testing is routine.
 

restorer-john

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#19
It is also a lousy circuit with just a timer instead of checking for DC output on the headphone jack which can kill the headphone (and make you possibly go deaf) if the output stage dies.
There's actually nothing wrong with the protection circuit as-is. It is an effective turn-on thump muting circuit.

DC is a non-issue as the buffer stage is capacitively coupled via C-102- DC cannot pass at all- even if the output stage fails. As long as the C12/R15/R6 time constant delay is sufficient, C-102 will charge via R-106 to half rail and there will be no noise when the relay contacts connect the headphones.

edit, saw someone else saw that too. :)
 

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