The VALVE THREAD reboot!

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Friesiansam

Well-known member
All new vacuum tubes are produced in only a handful of factories world wide (they are located in Russia and China).
The largest factory in China (Shuguang) closed down in 2019. The vast majority of all new tubes today are now manufactured in the Expo-Pul factory in Russia, regardless of the brand printed on them - even the revived British 'Brimar' brand are made there.
Guitar amplification is the main driving force for the need for new vacuum tube manufacture and during covid there was a massive demand for musical equipment (including tube amplification) that created a world wide tube shortage (not helped by the closing of the Shuguang factory). Prices skyrocketed, but have since come down a bit.
Interestingly, Western Electric set up a factory in the USA to produce only 300B Hi-Fi power tubes and they sell for $1,500 for a matched pair.
McIntosh uses all Russian made tubes in all of it's amplifiers.

Brimar Thermionic Products Ltd say they are working towards UK valve manufacturing.
 

SallyB

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Jan 18, 2022
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Very nice...
What does 'Reverse' nmode do??
As far as I was concerned it swapped the left and the right channels, but according to WHF: “there’s also a two-step Bass Boost and a stereo reverse function that inverts the signal phase 180 degrees. In some systems, the inverted phase could give more focused results.”

Didn’t do much for me if I’m honest!😀
 
As far as I was concerned it swapped the left and the right channels, but according to WHF: “there’s also a two-step Bass Boost and a stereo reverse function that inverts the signal phase 180 degrees. In some systems, the inverted phase could give more focused results.”

Didn’t do much for me if I’m honest!😀
Interesting, just curious, it's not something you see everyday... :)
 

My2Cents

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It's more likely that this switch reverses the polarity of the left and right channels, it doesn't just swap left and right and it's got nothing to do with the focus of the sound. It's basically the same as you swapping the + and - connections around on the back of each speaker.
It was a common feature on early stereo amplifiers back in the early days of stereo vinyl because many master recordings got mastered out of phase.
This resulted in the sound-stage of the orchestra being switched - you would notice this on playback because the placement of the instruments would be reversed.
If you have such a recording and you switch it to 'mono' any sound common to both channels will actually cancel each other out and therefore be inaudible.
Many early Capitol stereo records in particular suffered from the problem of being mastered out of phase, but they were not alone. Early Decca and DG discs did also. By the late 70's most companies were complying with RIAA standards which helped to solve the problem.
 
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SallyB

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It's more likely that this switch reverses the polarity of the left and right channels, it doesn't just swap left and right and it's got nothing to do with the focus of the sound. It's basically the same as you swapping the + and - connections around on the back of each speaker.
It was a common feature on early stereo amplifiers back in the early days of stereo vinyl because many master recordings got mastered out of phase.
This resulted in the sound-stage of the orchestra being switched - you would notice this on playback because the placement of the instruments would be reversed.
If you have such a recording and you switch it to 'mono' any sound common to both channels will actually cancel each other out and therefore be inaudible.
Many early Capitol stereo records in particular suffered from the problem of being mastered out of phase, but they were not alone. Early Decca and DG discs did also. By the late 70's most companies were complying with RIAA standards which helped to solve the problem.
That’s absolutely fascinating, thanks for enlightening me
 

SallyB

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Jan 18, 2022
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It's more likely that this switch reverses the polarity of the left and right channels, it doesn't just swap left and right and it's got nothing to do with the focus of the sound. It's basically the same as you swapping the + and - connections around on the back of each speaker.
It was a common feature on early stereo amplifiers back in the early days of stereo vinyl because many master recordings got mastered out of phase.
This resulted in the sound-stage of the orchestra being switched - you would notice this on playback because the placement of the instruments would be reversed.
If you have such a recording and you switch it to 'mono' any sound common to both channels will actually cancel each other out and therefore be inaudible.
Many early Capitol stereo records in particular suffered from the problem of being mastered out of phase, but they were not alone. Early Decca and DG discs did also. By the late 70's most companies were complying with RIAA standards which helped to solve the problem.
Also surprising is that Leben included this feature when the amp first came out in, I believe, 1992!
 
But if it reversed the polarity of both channels, then the channels would still be in phase with each other.

I can only say that the 'reverse' switch on my Harman Kardon amp swapped the channels.
You may have encountered it as absolute phase. I remember a Meridian CD player I owned having a phase or invert switch. It reverses phase of both channels so they stay in phase with each other. It is based on the idea that a more realistic sound arises if when say a bass drum is hit, both speakers cones move outwards. If they both move inwards then absolute phase is inverted. Historically some studios tended to invert phase, and others didn't. Some amplifiers invert too; Hifi News reviews mention this.

(I think of it like blowing instead of sucking. Imagine trying to suck a pingpong ball across a table -v- blowing it!)
 
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SallyB

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You may gave encountered it as absolute phase. I remember a Meridian CD player I owned having a phase or invert switch. It reverses phase of both channels so they stay in phase with each other. It is based on the idea that a more realistic sound arises if when say a bass drum is hit, both speakers cones move outwards. If they both move inwards then absolute phase is inverted. Historically some studios tended to invert phase, and others didn't. Some amplifiers invert too; Hifi News reviews mention this.

(I think of it like blowing instead of sucking. Imagine trying to suck a pingpong ball across a table -v- blowing it!)
Just trying it now!😂😂
 

Gray

Well-known member
You may gave encountered it as absolute phase. I remember a Meridian CD player I owned having a phase or invert switch. It reverses phase of both channels so they stay in phase with each other. It is based on the idea that a more realistic sound arises if when say a bass drum is hit, both speakers cones move outwards. If they both move inwards then absolute phase is inverted. Historically some studios tended to invert phase, and others didn't. Some amplifiers invert too; Hifi News reviews mention this.

(I think of it like blowing instead of sucking. Imagine trying to suck a pingpong ball across a table -v- blowing it!)
Yes, some people say they can tell whether they're hearing a positive or negative reaction to the positive sound wave.

You'd certainly have the evidence on an oscilloscope - and it makes sense that it might be more audible than the difference between..............say.............cables 😏
 
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Friesiansam

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Yes, some people say they can tell whether they're hearing a positive or negative reaction to the positive sound wave.

You'd certainly have the evidence on an oscilloscope - and it makes sense that it might be more audible than the difference between..............say.............cables 😏
I'm sure there must be some people out there, that claim polishing the outer cover on all their cables, makes an audible difference...
 
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Yes and I can understand how the incorrect absolute phase could pass unnoticed.

What @My2Cents is describing in post #57 must be relative phase difference(s) - though I'd like to know just how any amp switch could cure them.
TBH I didn’t recognise that description. There is an extended explanation here:-


And since we’ve moved on from valves, I gather some amps invert phase between each channel to reduce load on the transformer. Further in the signal path it’s all corrected, so the output matches as you’d expect. Fascinating!
 
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