Marshall Vintage modern with master volume on max without attenuator on bedroom volume - are the power tubes working on full?

[stevemas]

I wonder if the the power tubes are pushed when the master volume is on full, but I’m lowering the volume with a compressor before the amp.

What I normally do is that I put the master level on full and introduce some volume via the ”body” and ”detail” which is set to clean. My pedals do the distortion etc. Just before the amp input I have a wampler ego comp which allows me to lower the volume. Now, in this setup, are the power valves being pushed the same way it would if the was to be played at loud volumes?

 

[67mike]

The body and detail act as master volumes as well.....so they limit volume as well.

 

[marshallmellowed]

I wonder if the the power tubes are pushed when the master volume is on full, but I’m lowering the volume with a compressor before the amp.

What I normally do is that I put the master level on full and introduce some volume via the ”body” and ”detail” which is set to clean. My pedals do the distortion etc. Just before the amp input I have a wampler ego comp which allows me to lower the volume. Now, in this setup, are the power valves being pushed the same way it would if the was to be played at loud volumes?

No, the only way a power section can be "pushed", meaning creating any power tube distortion, is if the power section has reached it's limit in terms of "clean headroom". Assuming the power tubes are operating at their "nominal" voltages, an amp has to be running at very high volume to achieve that. Otherwise, any distortion must be produced by pedal, preamp or phase inverter distortion (PPIMV circuits for the latter).

 

[JohnH]

I've spent quite a lot of time trying to figure out those kind of things on my VM combo. Across all the controls it's such a versatile amp that there are many ways to drive it and it's worth getting a sense of how they all steer the tone.

But I agree as above, there's no power tube distortion if the unattenuated amp is set for low volume, and that's true whichever way you set it to achieve this.

But, there's still amazing tonal effects available from the other controls. On a VM, the Master Volume is Post-Phase-Invertor. So you can get some output-stage drive from the phase inverter tube. But the power tubes aren't involved unless you get up to actual high output volume. But from about 4 up, it's sounding good. But loud!

But there's more... As you turn up the MV, the negative feedback in the power stage is kicking in. This activates the presence control and adds damping to the speaker to smooth-out the tone.

The result for low-volume use is the availability of massive clean tones at MV max, controlled by the presence, keeping the detail and body low (detail higher than body), and using the guitar volume.

Now hit the mid-boost button. It transforms into another awesome but totally different amp!

Used like that, it's a great pedal-platform where a good drive pedal sets the tone, shaped by the amp.

But, to really get the awesome drive tones from the big KT66's, you either need to be at properly high volume, or get/build an attenuator (see Workbench if you want to build one that was designed around these amps)

 

[Frodebro]

A little more technical explanation here, but the power section of an amplifier is always running at 100%. How hard it is actually working depends entirely on the strength of the signal hitting the front of the power amp-meaning what the controls in the preamp are doing.

Let’s use 1V as a typical “maxed out” signal coming from the preamp. If the master volume and channel volumes (if applicable) in the preamp are dimed, we can expect to see right around 1 volt coming from the preamp and hitting the power amp. If you turn down the master volume, you are actually reducing the signal coming from the preamp. So now the input of the power amp is only getting, say, 0.5 volts instead of the full one volt. As a result, the power going to the speaker(s) is reduced by half, and the power amp is working half as hard (and putting out half the voltage). These numbers actually vary a bit due to the physics involved, but I’m keeping it simple for the sake of the overall explanation.

Lowering the volume before hitting the preamp will equally reduce the voltage coming out of it, as will using a volume pedal or other form of volume control in the effects loop. Anything that reduces that preamp output is going to reduce the signal hitting the power amp.

The only way to push the power section hard while maintaining “bedroom” volume levels is to reduce (attenuate) the signal AFTER the power amp, meaning after the speaker output jack on the amp. This excludes power scaling, which is a whole different discussion.

 

[stevemas]

A little more technical explanation here, but the power section of an amplifier is always running at 100%. How hard it is actually working depends entirely on the strength of the signal hitting the front of the power amp-meaning what the controls in the preamp are doing.

Let’s use 1V as a typical “maxed out” signal coming from the preamp. If the master volume and channel volumes (if applicable) in the preamp are dimed, we can expect to see right around 1 volt coming from the preamp and hitting the power amp. If you turn down the master volume, you are actually reducing the signal coming from the preamp. So now the input of the power amp is only getting, say, 0.5 volts instead of the full one volt. As a result, the power going to the speaker(s) is reduced by half, and the power amp is working half as hard (and putting out half the voltage). These numbers actually vary a bit due to the physics involved, but I’m keeping it simple for the sake of the overall explanation.

Lowering the volume before hitting the preamp will equally reduce the voltage coming out of it, as will using a volume pedal or other form of volume control in the effects loop. Anything that reduces that preamp output is going to reduce the signal hitting the power amp.

The only way to push the power section hard while maintaining “bedroom” volume levels is to reduce (attenuate) the signal AFTER the power amp, meaning after the speaker output jack on the amp. This excludes power scaling, which is a whole different discussion.

So if I dime the preamp volumes (detail and body) and reduce the volume via the compressor, either before the amp’s input or via the loop, the signal is still not going to be high enough to push the power valves?

 

[stevemas]

A little more technical explanation here, but the power section of an amplifier is always running at 100%. How hard it is actually working depends entirely on the strength of the signal hitting the front of the power amp-meaning what the controls in the preamp are doing.

Let’s use 1V as a typical “maxed out” signal coming from the preamp. If the master volume and channel volumes (if applicable) in the preamp are dimed, we can expect to see right around 1 volt coming from the preamp and hitting the power amp. If you turn down the master volume, you are actually reducing the signal coming from the preamp. So now the input of the power amp is only getting, say, 0.5 volts instead of the full one volt. As a result, the power going to the speaker(s) is reduced by half, and the power amp is working half as hard (and putting out half the voltage). These numbers actually vary a bit due to the physics involved, but I’m keeping it simple for the sake of the overall explanation.

Lowering the volume before hitting the preamp will equally reduce the voltage coming out of it, as will using a volume pedal or other form of volume control in the effects loop. Anything that reduces that preamp output is going to reduce the signal hitting the power amp.

The only way to push the power section hard while maintaining “bedroom” volume levels is to reduce (attenuate) the signal AFTER the power amp, meaning after the speaker output jack on the amp. This excludes power scaling, which is a whole different discussion.

I have an attenuator but I wanted to try something new. I also heard before that attenuators wear the tubes, is that true?

 

[Frodebro]

So if I dime the preamp volumes (detail and body) and reduce the volume via the compressor, either before the amp’s input or via the loop, the signal is still not going to be high enough to push the power valves?

Correct. What controls the power section is the signal going into it, so anything that is in front of the amp or in the effects loop that reduces volume is doing the same thing as turning down the master volume- it is reducing the preamp output signal.

 

[Frodebro]

I have an attenuator but I wanted to try something new. I also heard before that attenuators wear the tubes, is that true?

Attenuators on their own do not change the wear on tubes at all, it’s when people run an attenuator then max out the amp and play it with everything cranked up that tube wear becomes more excessive-but that would be the same increased wear with the amp run at those settings without an attenuator. It just doesn’t seem like you’re driving it hard because the attenuator removes the deafening volume from the equation.

 

[JohnH]

From my playing around, if you dime the MV AND push it hard with the preamp, it sounds terrible! And with an attenuator as well, it sounds more quietly terrible. And that's the state where I reckon it's wearing the tubes hard. But if you bring it down a bit, either with the MV, or the preamp, or both, it reaches its sweet spot for awesome tone and you can tell that everything is much more relaxed. In that state I think tube wear would be moderate. Maybe a bit more than at a minimal level but not excessive.

 

[What?]

From my playing around, if you dime the MV AND push it hard with the preamp, it sounds terrible! And with an attenuator as well, it sounds more quietly terrible.

Same for my 1987 clone with a PPIMV. If the PPIMV is on full (effectively bypassed), for the amp to not sound too far gone I either need to not turn up the preamp volume too far or back off on the PPIMV to relax things.

 

[stevemas]

Thank you all for the replies!

 

[stevemas]

I've spent quite a lot of time trying to figure out those kind of things on my VM combo. Across all the controls it's such a versatile amp that there are many ways to drive it and it's worth getting a sense of how they all steer the tone.

But I agree as above, there's no power tube distortion if the unattenuated amp is set for low volume, and that's true whichever way you set it to achieve this.

But, there's still amazing tonal effects available from the other controls. On a VM, the Master Volume is Post-Phase-Invertor. So you can get some output-stage drive from the phase inverter tube. But the power tubes aren't involved unless you get up to actual high output volume. But from about 4 up, it's sounding good. But loud!

But there's more... As you turn up the MV, the negative feedback in the power stage is kicking in. This activates the presence control and adds damping to the speaker to smooth-out the tone.

The result for low-volume use is the availability of massive clean tones at MV max, controlled by the presence, keeping the detail and body low (detail higher than body), and using the guitar volume.

Now hit the mid-boost button. It transforms into another awesome but totally different amp!

Used like that, it's a great pedal-platform where a good drive pedal sets the tone, shaped by the amp.

But, to really get the awesome drive tones from the big KT66's, you either need to be at properly high volume, or get/build an attenuator (see Workbench if you want to build one that was designed around these amps)

I’ve experienced that too. The presence control gets more active.