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Yamaha A-S1200 bass

On all A-Sxxxx (from 1100 and up, not sure about the 1000) the tone control circuit has an automatic bypass mode via a relay. There is no 'input direct' or 'tone defeat' push switch. The bypass is activated automatically and only when both the Treble and Bass knobs are in the middle position (straight up, there is little notch-feel).
The tiniest of amount you move one knob in any direction out of that notch, you will hear a little mechanical 'click' in the amp. That's the relay that switches the tone-board into or out of the signal path. There is a momentary, harmless, muting of the output: the time it takes the relay to physically switch (a mere fraction of a second, but audible). Only when you put both tone control knobs back in 'neutral' the tone control circuit gets bypassed again via the same relay, so same little click, same momentary muting. No other movement should interrupt output. There is a sort sort of exception. Example: say, you keep the Bass in neutral, and turn the treble from left to right, or vice-versa, crossing the middle position, the tone circuit will, for the brief period both knobs were in the upright position, switch the relay...
 
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Well, Yamaha support did respond to my 2nd message. They said... bla bla... they use the best parts, knobs... bla... all good...
 
I think, Yamaha wanted to create the interface as minimalistic as possible, to showcase how this amp is focused on sound quality.
I do like this intention. Yet the idea of removing the Pure Direct button is controversial to me. They did simplify the interface and achieved the goal on the surface, but I'm sure the schematic that listens to position of the knobs, and then trigger the relay, is more complicated than a simple on/off button. Thus defeating the purpose of the attempted simplification.

Also, one use case is removed by removing the button: It is no longer possible to swiftly switch between Pure mode and a pre-set tone correction without disturbing the position of bass/treble.
 
Hi,

Does anyone knows this: when I turn de bass an treble to the left or right on my Yamaha A-S1200, the music stops for a second?
Yes, my A-S2000 does that too, but it's really very short (milliseconds) and not a problem IME.
 
I think, Yamaha wanted to create the interface as minimalistic as possible, to showcase how this amp is focused on sound quality.
I do like this intention. Yet the idea of removing the Pure Direct button is controversial to me. They did simplify the interface and achieved the goal on the surface, but I'm sure the schematic that listens to position of the knobs, and then trigger the relay, is more complicated than a simple on/off button. Thus defeating the purpose of the attempted simplification.

Also, one use case is removed by removing the button: It is no longer possible to swiftly switch between Pure mode and a pre-set tone correction without disturbing the position of bass/treble.
You're not quite right.
On many amplifiers with a Pure Direct button, the tone controls are set to zero, but not all components are removed from the signal path. I've noticed this in the circuit diagrams of many amplifiers.
I like Yamaha's approach much better.
 
You're not quite right.
On many amplifiers with a Pure Direct button, the tone controls are set to zero, but not all components are removed from the signal path. I've noticed this in the circuit diagrams of many amplifiers.
I like Yamaha's approach much better.
Yamaha could simply achieve the exact same complete bypass via a switch that activates the exact same relay that in this, actually more complicated electronic design, is activated by the position of the tone-controls. It seems indeed to be about the minimalist look, just that one less switch. And, as Catch22 said earlier: you can't just switch between your tone-setting and tone-control off. You have to go all the way, every time. I'd 'suffer' a little dip-switch on the front panel for that.

I have long had the feeling that this is historically a somewhat typical approach for Japanese manufacture and engineering: "Look! We thought out this new, quirky solution to not-really-a-problem! Let's implement it! It'll be a little quirky, but it's our quirky!" :)
 
You're not quite right.
On many amplifiers with a Pure Direct button, the tone controls are set to zero, but not all components are removed from the signal path. I've noticed this in the circuit diagrams of many amplifiers.
I like Yamaha's approach much better.
The Yamaha A-S1000:

1726205857744.png
 
From the A-S1100:




1726241015958.png

When tone-control is set to defeat, effectively only the volume control, an analog ladder-type resistance (digitally controlled), is in the soundpath. And truly, fully discrete from then on...
The tone-control circuit, when in use, uses op-amps. I don't have an opinion on that.
This may be able to work like a fully discrete amp, but there is one big essential IC that controls the power-section, things like powering-up and down sequence, monitoring loads and imbalances, all sorts of protection. If that one ever gives out, for whatever reason in, say, 20 or 30 years, it's: goodbye amp. However discrete the whole signal path may be. I know this thread is not about that, but I know of several people owning ealy 90's Sony SE amps (truly among the best they ever made) that have defunct controller chips. Soundpath: should be perfect. Just won't power up and/or behave very unreliably. Virtually unrepairable, unless you can find an identical amp with a functioning chip to cannibalise. Stock of spares are long gone, never to be produced again. You will always find resistors, capacitors, all discrete components, but once they stop producing a model, they stop production of the chip that controls everything.
I was just thinking about this, thought I'd write it down. Ignore at your discretion :)
 
From the A-S1100:




View attachment 392091
When tone-control is set to defeat, effectively only the volume control, an analog ladder-type resistance (digitally controlled), is in the soundpath. And truly, fully discrete from then on...
The tone-control circuit, when in use, uses op-amps. I don't have an opinion on that.
This may be able to work like a fully discrete amp, but there is one big essential IC that controls the power-section, things like powering-up and down sequence, monitoring loads and imbalances, all sorts of protection. If that one ever gives out, for whatever reason in, say, 20 or 30 years, it's: goodbye amp. However discrete the whole signal path may be. I know this thread is not about that, but I know of several people owning ealy 90's Sony SE amps (truly among the best they ever made) that have defunct controller chips. Soundpath: should be perfect. Just won't power up and/or behave very unreliably. Virtually unrepairable, unless you can find an identical amp with a functioning chip to cannibalise. Stock of spares are long gone, never to be produced again. You will always find resistors, capacitors, all discrete components, but once they stop producing a model, they stop production of the chip that controls everything.
I was just thinking about this, thought I'd write it down. Ignore at your discretion :)
I know.
They use an IC from their AVR receivers in the A-Sxxxx.
I liked mine because of its weight and feel. But it's a bit of mixed bag in a pretty dress.
 
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