Amazon Valves. Trash or Treasure?

Neilb

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I've found myself absentmindedly browsing Amazon tonight (as we all do I'm sure). Sometimes you get that urge don't you for a bit of experimentation/tinkering/simply picking up a curiosity. I was specifically looking for Phono amps that could occupy less space between my turntable and amp. (One of those random problems to solve that pops into your mind for no reason).

Once i'd entered the words 'Valve Phono' into the search box I was right down the 'rabbit hole'. Some of these look really interesting...and yet everything tells me they should be avoided. Like a pot noodle. Am I wrong? Are some of these actually amazing? Has the law of volumes meant the price has been brought down without compromising quality and we all win??!! I would love to hear if anyone has been pleasantly surprised or even blown away by any of these components.

Are any of these cheap....and cheerful? ....or am I hopelessly mistaken...?
 

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rabski

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Things like that aren't completely terrible, but they aren't wonderful either. They almost all use valves as 'effects boxes' at best, or just for display at worst.

The obvious (to me) red flag with the pictures above is that you've got two valves, but the power supply says 12V DC. To run most double triodes in the 12AX family properly, you need to start off with around 250V HT. You're not going to get 250V from a 12V DC supply with anywhere near enough current no matter how clever you get with multipliers. I've seen similar circuits and they run the valve anodes at around 30-40V, which puts them well outside the proper operating point and makes them sound like what some people imagine valves sound like. Worse, I've seen some that just have glowing valves (usually with an LED under them) that actually don't do anything in the circuit at all. They are purely there for show.

You can't beat the laws of physics. Plus you can't beat the old rules: if it looks too good to be true.....
 

Neilb

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Things like that aren't completely terrible, but they aren't wonderful either. They almost all use valves as 'effects boxes' at best, or just for display at worst.

The obvious (to me) red flag with the pictures above is that you've got two valves, but the power supply says 12V DC. To run most double triodes in the 12AX family properly, you need to start off with around 250V HT. You're not going to get 250V from a 12V DC supply with anywhere near enough current no matter how clever you get with multipliers. I've seen similar circuits and they run the valve anodes at around 30-40V, which puts them well outside the proper operating point and makes them sound like what some people imagine valves sound like. Worse, I've seen some that just have glowing valves (usually with an LED under them) that actually don't do anything in the circuit at all. They are purely there for show.

You can't beat the laws of physics. Plus you can't beat the old rules: if it looks too good to be true.....
Wow...honestly...'show valves' with LED's? That's absolutely shocking isn't it. I'm almost feeling dirty for starting this thread now. Thank you Rabski this is a very enlightening answer...
 
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Neilb

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Things like that aren't completely terrible, but they aren't wonderful either. They almost all use valves as 'effects boxes' at best, or just for display at worst.

The obvious (to me) red flag with the pictures above is that you've got two valves, but the power supply says 12V DC. To run most double triodes in the 12AX family properly, you need to start off with around 250V HT. You're not going to get 250V from a 12V DC supply with anywhere near enough current no matter how clever you get with multipliers. I've seen similar circuits and they run the valve anodes at around 30-40V, which puts them well outside the proper operating point and makes them sound like what some people imagine valves sound like. Worse, I've seen some that just have glowing valves (usually with an LED under them) that actually don't do anything in the circuit at all. They are purely there for show.

You can't beat the laws of physics. Plus you can't beat the old rules: if it looks too good to be true.....
BTW when you say 'effects boxes' how would that work exactly? Do you mean it's essentially solid stage but there's a way to utilise valves to soften the output sound? 'Round off the egdes' somehow?
 

rabski

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BTW when you say 'effects boxes' how would that work exactly? Do you mean it's essentially solid stage but there's a way to utilise valves to soften the output sound? 'Round off the egdes' somehow?
Sort of. Almost any small double triode will work at very low plate voltage, but they will be way outside their ideal operating point. What you'll get is non-linearity and excessive harmonic distortion.

As it's a phono stage (and apparently MC capable at that) there has to be a solid-state gain stage in there. There is no way a double triode and 12 volts supply is going to get you enough gain for a phono stage.
 

Neilb

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Sort of. Almost any small double triode will work at very low plate voltage, but they will be way outside their ideal operating point. What you'll get is non-linearity and excessive harmonic distortion.

As it's a phono stage (and apparently MC capable at that) there has to be a solid-state gain stage in there. There is no way a double triode and 12 volts supply is going to get you enough gain for a phono stage.
very interesting....A kind of fake or deliberate colouration. 'Faux patina' as they say in the watch world.
 

rabski

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very interesting....A kind of fake or deliberate colouration. 'Faux patina' as they say in the watch world.
Plenty of designs do it to some extent or other. In fact, you could say that every design, whether valve or solid state, must do it or they'd all sound the same :)
 

toprepairman

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The box looks big enough to house a tiny HF inverter. You'd only need say 10mA at 250V, 2.5 Watts so taking maybe around 3 to 400 mA from the 12V supply. Add 300mA for the filaments and another 100mA for the rest of the electronics and the total draw would still be under 1 Amp.
 
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JANDL100

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A lot of gear has valves tagged on as a "featured afterthought", passing the signal through just for the hell of it.
I guess it's a kind of valve buffer?

This even includes well respected gear like Jolida (whoops, wrong - see next post) and Eastern Electric DACs and CD players, I think. I had a great sounding MHZS CD player like that as well.

I've got several Chifi headphone amps that do this as well. Sabaj, DOUK etc. These are generally well thought of in the Wam's headphone forum as decent entry level gear.
I really like them!

The valves don't get very hot at all, just a bit warm. I think that's a bit of a clue that they aren't actually doing much!

So I don't think there's anything necessarily fundamentally wrong with the idea. But it's not a "proper" valve circuit, that would cost a lot more, as far more knowledgably expressed by Rabski, just an add on to add a bit of flavour and fake audiophile cred.
 
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JANDL100

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Ah, OK, thanks John. I stand corrected.
Previous post edited accordingly.
Hmm, I wonder if the EE is also a proper valve amplification circuit?
I'm sure the MHZS wasn't.
 
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