Gear with adjustable slew rate?

[EngineEars]

Who knows of any gear that has a rise time feature like the Groove Tubes Vipre? If no other piece has it, how hard would it be to build a box with one knob and balanced I/O that adjust the slew rate? Thanks in advance

[tINY]

It's called a Low-pass-filter. I could build one for you, but you might already have some gear with one....


-tINY

[EngineEars]

Tiny...I'm not much of an electronics guru, but my limited understanding of a fast slew rate is measured by a piece of gear's ability to reproduce a square wave without much change in the shape of the envelope. If this is true it seems only natural that if you slow down the slew rate it's ability to produce transients gets limited, however that's more than just applying a low pass filter to the circuit, isn't it? In other words the sound's envelope (i.e. ADSR) changes not just the frequency range (i.e. VCF cutoff) when slew rate is delayed. (I'm a synthesis at heart, so pardon the synth ref.) A burst of noise through a lo pass filter sounds like a dull hit with a fast attck where the wave looks like a top hat. The same burst through a GT Vipre with the rise time slow sounds like a dampened but more full frequency hit with a slower attack, where the wave looks like a bike ramp. It's my understanding that this slower speed, plus other things of course, contributed to the vintage sounds of yesteryear as apposed the the fast and accurate equipment that is more standard today, which leads me back to my orginal post. Please correct me if I'm wrong here, thanks.

[StoneinaPond]

Slew rate: A term used to describe how quickly the output of an amplifier can track its input. Slew Rate is usually measured in V / usec. The higher the value (up to a point), the better the amp is at potentially reproducing the subtle nuances and dynamics associated with music reproduction.

As to the other part of your question (what other stuff is out there,) I'm afraid that I am of less help.

[tINY]

They are not exactly the same thing. But slew rate limits the highest frequency that your amp can pass at a given voltage level.

Practically speaking, the only difference you will hear is that there will be distortion on a Slew rate limited amplifier where a LPF will not have that distortion. You could simulate this but it would probably only sound good with tubes.


-tINY

[jbuntz]

There was another thread about this before. The Rise Time adjustment affects negative feedback. Negative Feedback limits slew rate in a soft manner. The Vipre affects transients kind of like analog tape. A limited slew rate is not always a low pass but a low pass always limits slew rate unless it's phase linear.