Attenuation vs. Master Volume

[Axe Dragon]

Hi All,

Can you enlighten me on the tonal differences between attenuation and master volume?

Am I correct in understanding that they can both be used to allow a tube amp to break up at lower volumes (assuming the master volume amp also has channel volumes)?

What are the pros and cons of each?

Thanks,

Axe

 

[Cirrus]

A master volume goes after the amp preamp but before the power amp. At maximum it does nothing. As you turn it down it reduces the volume going into the power amp, so the power amp doesn't have to work as hard.

An attenuator goes between the power amp and the speakers. As you turn it down, the power amp is still working hard but the volume reaching the speakers goes down so they don't work as hard.

Personally, I find attenuators excellent ideas in theory but in practice I much prefer amps with good master volumes.

 

[imbuedblue]

Preamp tubes typically generate both odd- and even-order distortion when overdriven and sound similar to an overdrive pedal.

Power tubes typically generate even-order distortion when overdriven and sound more like compression. At the volume levels where power tube distortion comes into play, you are also hearing preamp distortion.

Master volume controls reduce the signal going from the preamp section to the power amp section, allowing you to run the preamp tubes into distortion at lower volumes.

An attenuator reduces the output power level going from the power amp section to the speaker, allowing you to run both the preamp and power amp into distortion at lower volumes.

Speakers can also distort. My main amp is an AC30H2 with two Celestion Blue speakers. A big part of the sound of that amp for me is the speaker distortion, so attenuators never worked for me with that particular setup.

 

[Silent Sound]

You're question is kinda vague. Here's the deal, there's more than one type of master volume, and there's more than one type of attenuator.

With master volumes, you could have a pre phase inverter master volume, in which case you control the amount of gain going into the phase inverter. This has been the most common type of master volume over the years and generally won't impart any phase inverter distortion until near the top of its range. Sometimes these have bright caps attached which will make the amp brighter at lower levels, and darken up as you increase the volume. This is to compensate for the fact that most amps naturally sound darker at lower levels and bright up as you increase the volume. Next you have the PPIMV, or post phase inverter master volume. These do allow for phase inverter distortion at lower overall levels. However, there are multiple ways to do this as well, and some effect the bias of the power tubes (Lar Mar), while others do not. Most will effect the feedback loops like your presence and resonance controls, making them less effective at lower levels. Then there's power scaling, which is kinda like a master volume of sorts, but it effects the available power to the power tubes, versus the signal going into the power tubes. If you limit the power available to the power tubes, you limit the amount of power going out of them and cause them to distort more at lower levels. However, as with all tubes, the way they distort changes as you vary the supply voltages.

Among the attenuators you have resistor based attenuators and speaker motor based attenuators. Basically, you're installing a very expensive power soak in between your speaker and amp to turn some of that electricity into heat instead of sound. The good thing about these is they allow you to overdrive the power amp section of the amp and overload the output transformer, while still keeping the volume down. The down side is not every amp sounds good when you distort the power tubes and OT, and attenuators are known to kill a lot of the treble off a guitar. Many attenuators add some treble back in to compensate for this, but it won't sound the same.

Which is better for you will depend on which amp you play and how you play it. There's no point in putting an attenuator on a Mesa Dual Rec. That amp gets it's distortion from the preamp and won't really breakup much in the power amp side. And even if it does, it won't sound good. But if you play a Tweed Deluxe and use your guitars volume control to effect the amp's distortion, then an attenuator can be a great idea, as it would give you all the control you'd expect from the amp at loud volumes, but at a more manageable level. Keep in mind, however, that any method you use to cut back on the volume will effect the tone, one way or another. As they say, there's no such thing as a free lunch.

 

[Figaro]

Preamp tubes typically generate both odd- and even-order distortion when overdriven and sound similar to an overdrive pedal.

Power tubes typically generate even-order distortion when overdriven and sound more like compression. At the volume levels where power tube distortion comes into play, you are also hearing preamp distortion.

Master volume controls reduce the signal going from the preamp section to the power amp section, allowing you to run the preamp tubes into distortion at lower volumes.

An attenuator reduces the output power level going from the power amp section to the speaker, allowing you to run both the preamp and power amp into distortion at lower volumes.

Speakers can also distort. My main amp is an AC30H2 with two Celestion Blue speakers. A big part of the sound of that amp for me is the speaker distortion, so attenuators never worked for me with that particular setup.

But turning down a master volume also reduces speaker distortion...

 

[imbuedblue]

But turning down a master volume also reduces speaker distortion...

I never said it didn't. I don't use master volume or attentuation. If I need less volume, I use a smaller amp.

 

[Figaro]

I never said it didn't. I don't use master volume or attentuation. If I need less volume, I use a smaller amp.

This discussion is about master volumes vs attenuators so I thought since you said you like speaker distortion and attenuators never worked for you, that you like master volumes. Sorry.

 

[Blues Lyne]

I never said it didn't. I don't use master volume or attentuation. If I need less volume, I use a smaller amp.

I'm assuming you are using a less efficient speakers with with the smaller amp, otherwise it wouldn't be any different as far as speaker break up is concerned. You could also use less efficient speakers with a master volume, attenuator or power scaling.

To be clear, I'm not arguing with what works for you at all. Just pointing out that into the same speakers, the method of lowering the volume shouldn't affect how the speakers will react. The method of lowering the volume can have make a big difference in overall tone though.

 

[Blues Lyne]

You're question is kinda vague. Here's the deal, there's more than one type of master volume, and there's more than one type of attenuator.

With master volumes, you could have a pre phase inverter master volume, in which case you control the amount of gain going into the phase inverter. This has been the most common type of master volume over the years and generally won't impart any phase inverter distortion until near the top of its range. Sometimes these have bright caps attached which will make the amp brighter at lower levels, and darken up as you increase the volume. This is to compensate for the fact that most amps naturally sound darker at lower levels and bright up as you increase the volume. Next you have the PPIMV, or post phase inverter master volume. These do allow for phase inverter distortion at lower overall levels. However, there are multiple ways to do this as well, and some effect the bias of the power tubes (Lar Mar), while others do not. Most will effect the feedback loops like your presence and resonance controls, making them less effective at lower levels. Then there's power scaling, which is kinda like a master volume of sorts, but it effects the available power to the power tubes, versus the signal going into the power tubes. If you limit the power available to the power tubes, you limit the amount of power going out of them and cause them to distort more at lower levels. However, as with all tubes, the way they distort changes as you vary the supply voltages.

Among the attenuators you have resistor based attenuators and speaker motor based attenuators. Basically, you're installing a very expensive power soak in between your speaker and amp to turn some of that electricity into heat instead of sound. The good thing about these is they allow you to overdrive the power amp section of the amp and overload the output transformer, while still keeping the volume down. The down side is not every amp sounds good when you distort the power tubes and OT, and attenuators are known to kill a lot of the treble off a guitar. Many attenuators add some treble back in to compensate for this, but it won't sound the same.

Which is better for you will depend on which amp you play and how you play it. There's no point in putting an attenuator on a Mesa Dual Rec. That amp gets it's distortion from the preamp and won't really breakup much in the power amp side. And even if it does, it won't sound good. But if you play a Tweed Deluxe and use your guitars volume control to effect the amp's distortion, then an attenuator can be a great idea, as it would give you all the control you'd expect from the amp at loud volumes, but at a more manageable level. Keep in mind, however, that any method you use to cut back on the volume will effect the tone, one way or another. As they say, there's no such thing as a free lunch.

I think I'd be more likely to lump power scaling with attenuators, since they both let the power tubes break break up while lowering the volume. When power scaling is implemented as you mentioned (just scaling the power tubes) they do break up more as you lower the voltage. However, if you scale the entire amp, in my experience with a Skipzcircuits Vari-Watt, it keeps the same tone/breakup as it is turned down, at least until the very lowest levels. I use an EV SRO-12L so speaker break up isn't part of the equation. If you use a speaker that breaks up, it will clean up however you lower the volume.

 

[SonicBoom]

Great explanation, Silent Sound. I'd only add that there is one additional type of attenuator since some of the popular new ones use this method, and those are reamplifiers. Units such as the UA and Badcat attenuate the signal coming from the guitar amp before running it through an internal solid state linear amplifier. This preserves tube saturation characteristics while allowing the user to control the vol. level via the SS amp.

 

[Axe Dragon]

You're question is kinda vague. Here's the deal, there's more than one type of master volume, and there's more than one type of attenuator.

With master volumes, you could have a pre phase inverter master volume, in which case you control the amount of gain going into the phase inverter. This has been the most common type of master volume over the years and generally won't impart any phase inverter distortion until near the top of its range. Sometimes these have bright caps attached which will make the amp brighter at lower levels, and darken up as you increase the volume. This is to compensate for the fact that most amps naturally sound darker at lower levels and bright up as you increase the volume. Next you have the PPIMV, or post phase inverter master volume. These do allow for phase inverter distortion at lower overall levels. However, there are multiple ways to do this as well, and some effect the bias of the power tubes (Lar Mar), while others do not. Most will effect the feedback loops like your presence and resonance controls, making them less effective at lower levels. Then there's power scaling, which is kinda like a master volume of sorts, but it effects the available power to the power tubes, versus the signal going into the power tubes. If you limit the power available to the power tubes, you limit the amount of power going out of them and cause them to distort more at lower levels. However, as with all tubes, the way they distort changes as you vary the supply voltages.

Among the attenuators you have resistor based attenuators and speaker motor based attenuators. Basically, you're installing a very expensive power soak in between your speaker and amp to turn some of that electricity into heat instead of sound. The good thing about these is they allow you to overdrive the power amp section of the amp and overload the output transformer, while still keeping the volume down. The down side is not every amp sounds good when you distort the power tubes and OT, and attenuators are known to kill a lot of the treble off a guitar. Many attenuators add some treble back in to compensate for this, but it won't sound the same.

Which is better for you will depend on which amp you play and how you play it. There's no point in putting an attenuator on a Mesa Dual Rec. That amp gets it's distortion from the preamp and won't really breakup much in the power amp side. And even if it does, it won't sound good. But if you play a Tweed Deluxe and use your guitars volume control to effect the amp's distortion, then an attenuator can be a great idea, as it would give you all the control you'd expect from the amp at loud volumes, but at a more manageable level. Keep in mind, however, that any method you use to cut back on the volume will effect the tone, one way or another. As they say, there's no such thing as a free lunch.

Thanks for this! To clarify, I'm looking for a bedroom volume jtm45. I want the driven tone both at full and low volume.

The marshall 1962HW will definitely be too loud for me. My favourite clone is the Germino Classic 45 which offers a master volume option, but I haven't heard or played it. The toneking royalist offers a reasonable clone tone with an attenuator but I also haven't heard or played that.

I'm trying to target my search which requires the most authentic driven JTM45 tone at lower volumes.

Any more advice?

 

[SteveO]

The "cranked big amp at bedroom volume" thing is something people have been chasing for years. Part of the sound of a big, loud amp is the amount of air being moved and the Fletcher-Munsen effect.

I gigged for years with a (solid state) TubeWorks MosValve power amp in my rack. No tubes to worry about a 'sweet spot' or 'power amp dirt', yet that amp sounded completely different at high volume than it did when using it at home.

 

[Axe Dragon]

I'm sure that's true, but I still seek advice for my search

 

[kingink]

Axe Dragon, if you're wondering which would be the more useful/toneful technology--attenuator or master volume--given the two amps you mentioned, I would kind of say both can work really well. To me it seems a good attenuator or MV is a matter of execution and I generally think Tone King does a great job with the former and I imagine Germino does a great job with the latter.

The times I've tried the Royalist, I thought it sounded great, even at low volumes. Awesome, juicy tone and feel. And I thought the attenuator was excellent (same with the Sky King, Falcon, and Metropolitan--Mark Bartel seems to know his way around attenuators).

I've never tried a Germino, but recently demo'd a Friedman Dirty Shirley and thought the master volume was terrific and equally as good as the attenuator on the Royalist.

The point being, both methods of volume control can work well and impart good tone and feel even at pretty low volumes.

Of course, maybe you weren't wondering about any of this in which case never mind...

 

[bgh]

I don't know how much help this is going to be, but here goes.

I use both. At home, I mainly use the master volume on both my Nomad and my Mark IV. Both have preamp sounds that I really like and use. The MV keeps them both at a decent level (and the Weber has controls to compensate somewhat for that loss of treble).

I have a Weber attenuator that I use at home for when I want to crank either amp just to see what a particular setting sounds like "at volume". True, some tone is lost by the attenuation process, but it does give me an idea.

Even though Mesas get most of their characteristic sound through their preamp circuits. They are typically biased cold and have a good bit of headroom. Even so, like most amps, they do have a different sound "at volume" than they do at "bedroom" levels.

You may want to consider having both tools in your toolbox.

Hope this helped.
Thanks for reading.

 

[Stig Ø]

To me, master volume sounds better that attenuation, based on my experience with the THD Flexi w/HotPlate. The Suhr Badger 30 uses power scaling and sounds - to my ears - as close to transparent as possible. I did some testing with attenuation vs master volume vs wide open with my Flexi some weeks ago. You can hear the clips of each one here: http://www.secondfloortones.no/thd-flexi-50-amplifier-part2/

To my ears (and fingers) it sounds and feels stiff, for lack of a better word. The Hot Plate is 10 years old or so, so I imagine there's been some development and improvements to the stuff that is new now.

 

[JB6464]

Imho re-amping blows away straight up attenuating.
You get the main amp hitting the sweet spot (loud) on a load and then bring the desired second amps volume up to your needs without blowing your face off .
Sounds much better than squishing the amp down in db's through an attenuator and robbing the top end with an over compressed amp tone.

 

[Figaro]

I agree that power scaling sounds the most natural. The VAC circuit in my Samamp sounds great.

 

[Blix]

To me, master volume sounds better that attenuation, based on my experience with the THD Flexi w/HotPlate. The Suhr Badger 30 uses power scaling and sounds - to my ears - as close to transparent as possible. I did some testing with attenuation vs master volume vs wide open with my Flexi some weeks ago. You can hear the clips of each one here: http://www.secondfloortones.no/thd-flexi-50-amplifier-part2/

To my ears (and fingers) it sounds and feels stiff, for lack of a better word. The Hot Plate is 10 years old or so, so I imagine there's been some development and improvements to the stuff that is new now.

Hot Plates are 20 years old now, and they prety much suck compared to the latest generation of attenuators. No contest.

I have a Torpedo Reload which is load+reamping and it's pretty damn sweet, also it's got a contour EQ knob to compensate for the FM-effect at low volumes.

 

[Blues Lyne]

Imho re-amping blows away straight up attenuating.
You get the main amp hitting the sweet spot (loud) on a load and then bring the desired second amps volume up to your needs without blowing your face off .
Sounds much better than squishing the amp down in db's through an attenuator and robbing the top end with an over compressed amp tone.

Reamping can sound really good, but you are still attenuating the main amp down in dB's through an attenuator and then reamping it.