Tube Tone With Out Tubes

[printer2]

Originally Posted by donh

There is way more to it than this, but you did notice that the SS devices produce squared off peaks. Did you manage to notice that tube devices when overdriven produce rounded off peaks? Hmmmm?

Tube amps also produce square waves as do transistor amps. At times rather than getting flat peaks you might see a rise from the front of the wave to the back. This means that the lows are attenuated, most likely due to the transformer. If you have a rising slope the treble is attenuated compared to the bass. All depends on what frequency you are putting through.

[donh]

Originally Posted by printer2

Tube amps also produce square waves as do transistor amps. At times rather than getting flat peaks you might see a rise from the front of the wave to the back. This means that the lows are attenuated, most likely due to the transformer. If you have a rising slope the treble is attenuated compared to the bass. All depends on what frequency you are putting through.

If you have a rising slope the treble is accentuated compared to the bass. (yes, really. - do the math)

Tube amps, in general, tend to have rounded-off edges to the square waves - transistor ones not so much. Then there is all the other stuff - which is boiled down to: transistor amps clip with a harsh (pointy?) sound, and tube amps tend to clip with a rounder wider sound. Yes, this is subjective and yes there are LOTS of people with this subjective impression (count me unapologetically among them).

[moon]

The soft clipping is due to something called "island effect" which is usually described as electrons escaping round the sides of the control grid when the signal begins to push the tube into cut off. Eventually, when the voltage swings far enough, the current cuts off completely. It's a gradual rather than a sudden process - "soft" clipping.

This all happens on the negative swing. I don't know if anything happens to square off the wave on the positive side.

[H165]

"Wow... Pretty simplistic and narrow view of what tube tone is."

Tube tone is distortion. Pickering points this out early in his article:

"....subsequent designs have concentrated on duplicating the characteristics of tube distortion.

"The 'view' is certainly simple, even if the control of the distortion is complicated.

This article comes 30 years after I asked a friend of mine why I like the tube McIntosh sound better than the non-tube. His reply: "You probably like the warm distortion". An MIT PhD in audio electronic design, with 34 years experience in the field at the time, and also the man who nicknamed me "Golden Ears", I figured I'd take his word for it.

[donh]

Originally Posted by H165

"Wow... Pretty simplistic and narrow view of what tube tone is."

Tube tone is distortion. Pickering points this out early in his article:

"....subsequent designs have concentrated on duplicating the characteristics of tube distortion.

"The 'view' is certainly simple, even if the control of the distortion is complicated.

This article comes 30 years after I asked a friend of mine why I like the tube McIntosh sound better than the non-tube. His reply: "You probably like the warm distortion". An MIT PhD in audio electronic design, with 34 years experience in the field at the time, and also the man who nicknamed me "Golden Ears", I figured I'd take his word for it.

LOL

there ya go, then :-)

[clintj]

Originally Posted by moon

The soft clipping is due to something called "island effect" which is usually described as electrons escaping round the sides of the control grid when the signal begins to push the tube into cut off. Eventually, when the voltage swings far enough, the current cuts off completely. It's a gradual rather than a sudden process - "soft" clipping.

This all happens on the negative swing. I don't know if anything happens to square off the wave on the positive side.

On the positive side, you become grid current limited. Electrons flowing into the grid start countering the positive swing in signal, which tends to strongly compress the waveform. The 5F6-A Bassman's DC coupled cathode follower takes advantage of this, giving it that soft transition into distortion.

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[Bob Womack]

Geeze, I'd hate to see what would happen if someone threw in the additional factor of cathode bias to this discussion...

Bob

[Steve DeRosa]

Go ahead Bob - go for it...

[moon]

Originally Posted by Bob Womack

Geeze, I'd hate to see what would happen if someone threw in the additional factor of cathode bias to this discussion...

Does that create clipping or just compression?

[printer2]

Originally Posted by donh

If you have a rising slope the treble is accentuated compared to the bass. (yes, really. - do the math)

Tube amps, in general, tend to have rounded-off edges to the square waves - transistor ones not so much. Then there is all the other stuff - which is boiled down to: transistor amps clip with a harsh (pointy?) sound, and tube amps tend to clip with a rounder wider sound. Yes, this is subjective and yes there are LOTS of people with this subjective impression (count me unapologetically among them).

Turn it up some more and you will see the rounded tops flatten out. As far as transistor amps and harsh clipping, much of that is due to using a lot of global NFB. A transistor amp that relies on minimal local NFB has a rising distortion curve as it approaches clipping. It makes for a more musical guitar amp.

[Bob Womack]

Originally Posted by moon

Does that create clipping or just compression?

It creates compression and a sweeping change in the overtone reproduction based upon the volume envelope of the signal. I understand that the effect is dynamic even-overtone distortion.

Bob

[moon]

Sorry after I posted that I wished I hadn't because you probably didn't want to get dragged into this It's the geeky amateur amp-builder in me.

[printer2]

Champ styled amp at the onset of clipping and well into clipping.



Figured I would get both ends of the spectrum with this amp and a 1968 Bassman. No time to do the Bassman tonight, the Champ is part of my test bench so it was easier to do. Sorry for the traces but the camera was not cooperating.

[printer2]

Originally Posted by donh

If you have a rising slope the treble is accentuated compared to the bass. (yes, really. - do the math)

Been a while since I have done the math, hurt the first time so I think I will pass. I am more of a picture kind of guy.

[SantaCruzOMGuy]

I have 2 boutique tube amps... a suhr sl68 and a CAA PT100.

I can say with confidence that my Kemper profiling modeler sounds amazing. Its a game changer. The line 6 stuff sounded pretty bad.

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