When doing my research on the Tone Master recently, I ran across a great review where the reviewer said that perhaps the attenuator on the Tone Master was really a master volume because, after all, it’s a digital/solid-state amp. Part of me agrees with this because let’s face it: Signal processing happens in the chips of the amp, and not tubes as there are no tubes in the amps.
But another part of me said that depending on where the Fender engineers placed the attenuator in the sequence it could very well be an attenuator. Just like tube amps, a solid-state amp has two basic stages (not including the power supply): The first is the input gain stage (in the tube world it’s commonly known as the preamp stage) that amplifies the incoming signal; then the output stage (power amp) takes the input stage signal, adds more power to it, then outputs it to the speakers.
This is an important concept because of how master volumes and attenuators work. A master volume is placed in between the input and output stages, essentially regulating the amount of signal that flows from the input stage to the output stage. An attenuator, on the other hand, is placed between the output stage and the speaker. And when cranked, the distorted sounds an amp produce are different -sometimes significantly – between a master volume and an attenuator.
Before continuing let’s make an assumption that we want to get an amp into overdrive at a reasonable volume level – let’s say bedroom-level.
To get bedroom-level volume with a master volume-equipped amp, you turn down the master volume way down and crank up the gain or volume knob. This will overload the preamp and cause the signal to distort. As the master volume is essentially a gate that regulates the amount of signal that gets to the power amp, because it’s turned down, the resulting volume is at a level that doesn’t blow your eardrums apart. In this scenario, the distortion is coming almost entirely from the preamp. At least to my ears, this type of distortion tends to have a sharper edge to it.
With an attenuator, on the other hand, as it regulates the amount of signal sent to the the speakers, both the gain and master volume knobs can be cranked up. This means that all the signal from the gain stage can pass into the power amp and saturate it and also drive it into overdrive. The combination of the two types of distortion produce a warmer and a little compressed output signal as compared to just preamp distortion. To be clear, I am in no way suggesting one type of distortion is better than the other. They’re just different.
Circling back to the Tone Master amps, to answer the title of this post, since they only have a single volume knob and no master volume, it seems to me that Fender’s attenuator is actually an attenuator, regulating the final signal that gets to the speakers, as opposed to a master volume.
All that said, I realize that all this is a big fat guess. And in the end, does it really matter? Probably not. I absolutely dig my new Deluxe Reverb. And frankly, whether the power scaling feature is an attenuator or not, the fact that I can crank the amp and not shatter my eardrums is all that matters.
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I’ll give you an example of a case where it might matter. I really wanted an alnico speaker to put in my tone master deluxe reverb. The problem is, it’s only 90 watts and the amp is 100 watts. If it’s truly an attenuator, I can just leave it at the 12 watts which would equate to about 55 actual solid state watts and I can crank the volume without blowing the speaker. Perhaps even a master volume would prevent this. But anyway, thought I’d throw that out there.
Zach, you have a point. But for me, it just boils down to whether or not I can get an overdrive sound at a reasonable volume. But I’m using the stock speaker, so it’s not something that is that concerning to me. But I can see where it would be in your case.
right. Even with the stock speaker and the attenuator at the lowest setting, and the volume at 10, it’s too loud for bedroom playing IMO. But you do get the rock and roll tube sounding overdrive at much lower volumes so it serves its purpose. Which is good because the speaker wire is not detachable from the power amp so you can’t easily add another attenuator.
I think 1 of 2 implementations are likely.
1. It’s a true reactive attenuator. That would explain the finite steps in the switch because you have a discreet resistance circuit for each step that handles the portion of the load not sent to the speaker (or all of it in the case of being muted)
2. they modeled a reactive attenuator in the software. I’ve read people talking about how attenuators are not necessary for the ICE class D power amps. So in that case, they just modeled what the real amp sounds like when attenuated at that level.
I think you might be onto something with your second point. When I go up in wattage, there is definitely more clean headroom, but it “feels” a little different from a true reactive attenuator so it could very well be that they’re modeling the attenuation. But it’s close enough for government work. 🙂