What's Up with the Mesa Walkabout Mid Knob?

[KJung]

Page 10 of the Walkabout manual has factory sample settings.
#2 is labeled: "Scooped" R & B - this definately means scooped mids.
It has the passive mid control knob fully counter clockwise (to Left), as well as some cut in the 350 Hz region
on the mid band of the parametric EQ.

This, IMO, pretty obviously implies that scooped (diminished) mids is when the mid control is fully CCW - therefore flat is fully CW.

On page 3 of the manual, under helpful hints - it says the mid works like a normal passive control, and BOOSTS a broad band of frequencies as it is increased. This wording is what is confusing some of you - but it is simply a description of how your ears will perceive this control - it SOUNDS as if the mids are being boosted - but they are merely being re-introduced to the spectrum from the fully cut mids when the control is fully CCW.

Again - think of the tone control on a passive Fender bass tone control - as you increase the control CW, it SOUNDS as if the treble is being boosted, but in reality, we all know that this is not true - fully CW is flat, and fully CCW is actually CUTTING this range.

Have you ever heard a Mesa with the mid control turned fully clockwise The reality is that, with this circuit, flat (meaning a relatively even balance of mids to bass and treble, when those active controls are in the noon position, is probably somewhere in the 9 o'clock region.

It's all kind of a moot point since it's pretty obvious that setting that control past noon will 'mid your ears out' with most basses and cabs!

 

[scottiwkt]

Thanks to cmhgreg for looking at this at a low level to figure out exactly what is happening. I have to do the same thing at my job with network sniffers to see what is happening on the wire. The saying in my field is 'The sniffer never lies...'.

Same thing here, the frequency graph can't lie.

Thanks, I will now sleep much better knowing how it really works.

-s

 

[theshadow2001]

Again - think of the tone control on a passive Fender bass - as you increase the control CW, it SOUNDS as if the treble is being boosted, but in reality, we all know that this is not true - fully CW is flat, and fully CCW is actually CUTTING this range.

Doesn't this all make some sense ? It is not all that confusing.

If you have a fender passive bass and run it into a pre amp that simply amplifies and doesn't eq ie flat then into a power amp would you say you have a passive or active tone control on your fender? You'd still say it's passive.

This is exaclty what happens in the mesa. Passive tone control that's amplified after. I'm sure if we looked at the circuit for a passive tone control with an amplifier set afterward and an active tone control capable of both cutting and boosting they would be quite different.

As bill fitz said in the other thread I linked to. It's a question of what defines an active tone control. An active tone control can both cut and boost. The passive mid control is boots only due to it being run through an amplifier afterwards. This is most likely the definition mesa are using.

 

[KJung]

Thanks to cmhgreg for looking at this at a low level to figure out exactly what is happening. I have to do the same thing at my job with network sniffers to see what is happening on the wire. The saying in my field is 'The sniffer never lies...'.

Same thing here, the frequency graph can't lie.

Thanks, I will now sleep much better knowing how it really works.

-s

I'm still a little confused, and don't know how to read that graph.

So, here are the questions I would need answered to really know:

1) Is it basically flat turned either all the way or mostly CCW?

It seems that answer is yes, but the graph doesn't make sense to me (my problem...not the graph or poster)

2) Is it 'passive'?, which would mean that the Mesa hybrids are MASSIVELY mid voiced, and the 'passive' mid control is like a 'reversed classic passive tone control'. Or... is it really a 'boost only' that is mislabeled (i.e., still relatively flat CCW, but boost when turned up versus 'reduced attenuation' of the passive mode.

 

[theshadow2001]

I'm still a little confused, and don't know how to read that graph.

So, here are the questions I would need answered to really know:

1) Is it basically flat turned either all the way or mostly CCW?

It seems that answer is yes, but the graph doesn't make sense to me (my problem...not the graph or poster)

2) Is it 'passive'?, which would mean that the Mesa hybrids are MASSIVELY mid voiced, and the 'passive' mid control is like a 'reversed classic passive tone control'. Or... is it really a 'boost only' that is mislabeled (i.e., still relatively flat CCW, but boost when turned up versus 'reduced attenuation' of the passive mode.

If you look at the graph you can see three wave forms plus the blue bar graph thing that I don't know what is. But there are two that are essentially the same. The ones that are the same are when you flick between pre and post eq switch on the DI one wave form is pre eq the other is post. The post eq is taken with the mid fully CCW with the bass and and treble at 12 ie the amp is set flat. We can say it's flat because when the tones are set to this postion it's exactly the same as the wave form that bypasses the tone controls completely (when the DI is set to pre)

The third wave form is with the mid fully boosted. You can see it is raised up above the other two flat wave forms in the middle of the graph from the low mids up towards the high mids. It's raised up like this because it has been boosted by the tone control

It is passive. But it's boosted afterwards by an amplifier. (Don't think of an amplifier as just a big lump of a power amp or a head its just a micro chip i.e a MOSFET)

So we turn the mid fully CCW. This removes a big chunk of mid frequencies. But after this those attenuated frequencies are boosted by an amplfier so they are put back in and everything is flat again. So now we have a mid passive mid control fully attenuating mids. However the repsonse is flat because those mids have been boosted back up by an amp.

As you turn the control clockwise you reduce the amount of attenuation of those mid frequencies. But because when they are fully attenuated the tones are boosted back by a small amplifier up to make everything flat the more you turn on the control it goes from flat to boosted

I dunno if I did a good job explaining that or not.

 

[KJung]

If you look at the graph you can see three wave forms plus the blue bar graph thing that I don't know what is. But there are two that are essentially the same. The ones that are the same are when you flick between pre and post eq switch on the DI one wave form is pre eq the other is post. The post eq is taken with the mid fully CCW with the bass and and treble at 12 ie the amp is set flat. We can say it's flat because when the tones are set to this postion it's exactly the same as the wave form that bypasses the tone controls completely (when the DI is set to pre)

The third wave form is with the mid fully boosted. You can see it is raised up above the other two flat wave forms in the middle of the graph from the low mids up towards the high mids. It's raised up like this because it has been boosted by the tone control

It is passive. But it's boosted afterwards by an amplifier. (Don't think of an amplifier as just a big lump of a power amp or a head its just a micro chip i.e a MOSFET)

So we turn the mid fully CCW. This removes a big chunk of mid frequencies. But after this those attenuated frequencies are boosted by an amplfier so they are put back in and everything is flat again. So now we have a mid passive mid control fully attenuating mids. However the repsonse is flat because those mids have been boosted back up by an amp.

As you turn the control clockwise you reduce the amount of attenuation of those mid frequencies. But because when they are fully attenuated the tones are boosted back by a small amplifier up to make everything flat the more you turn on the control it goes from flat to boosted

I dunno if I did a good job explaining that or not.

You did. PERFECT! Thanks.. that makes total sense, and matches what my ears tell me with the MPulse tone controls.

Thanks!

K

 

[theshadow2001]

It's good that I impart knowledge.

I just hope its right

 

[KJung]

It's good that I impart knowledge.

I just hope its right

I know the feeling! I think you are pretty much right on with this one. That matches what I remember in a previous thread, and also matches pretty much what Bill F. posted in the thread link above.

I'm actually pounding on my MPulse600 right now... that mid control is really cool... from relatively modern and clean to growly, punchy grit all with one knob... and that doesn't even take into account the strong interaction with the gain level. Really something !

 

[cmhgreg]

In response to some of the comments regarding what the graph says as opposed to what one hears and perceives, I should add that when I listened to the recorded tracks, there was no perceptible difference between the "pre" track (preamp bypassed) and the "post" track with the MID knob fully CCW. At that point I immediately suspected that the flat setting for the MID knob was fully CCW. But being the cynic that I am, I wanted to verify what I was hearing with something more objective than simply my own personal observations. Thus, my use of the Frequency Analyzer.

I think the key to my test was having some type of base line (pardon the pun) measurement and, thanks to the DI switch having a pre/post setting, that bass line in this test was the track recorded with the DI switch on "pre".

 

[KJung]

In response to some of the comments regarding what the graph says as opposed to what one hears and perceives, I should add that when I listened to the recorded tracks, there was no perceptible difference between the "pre" track (preamp bypassed) and the "post" track with the MID knob fully CCW. At that point I immediately suspected that the flat setting for the MID knob was fully CCW. But being the cynic that I am, I wanted to verify what I was hearing with something more objective than simply my own personal observations. Thus, my use of the Frequency Analyzer.

I think the key to my test was having some type of base line (pardon the pun) measurement and, thanks to the DI switch having a pre/post setting, that bass line in this test was the track recorded with the DI switch on "pre".

Very cool!

 

[theshadow2001]

Thanks for doing the test greg. It's finally put the whole mesa mid thing to rest. Plus you gotta love a pudding with a whole lot of proof in it.

 

[Rhythm5]

I just picked up a Walkabaout and I agree with Ken. The mid control around 9:00 or 10:00 sounds really nice, but at full CW it's mid overdose.

 

[cmhgreg]

Thanks for doing the test greg. It's finally put the whole mesa mid thing to rest. Plus you gotta love a pudding with a whole lot of proof in it.

You are most welcome. Maybe I'm just a geek at heart, but the test was somewhat fun and helped me rationalize all the money I have spent on recording gear lately.

And it is nice to finally understand how that MID knob works. In the process of doing my test I discovered what they were talking about in the manual in terms of the subtle coloring you can accomplish with the MID control. I never understood it before, but now I think it is a nice feature. I like to set up the tone controls for a certain tone (usually flat) and then dial in a different sound on the parametric for when I use a pick (or a different bass), using the foot switch to activate the parametric when needed. This alleviates the need to mess with the dials during a gig. Knowing how the MID knob works should help me dial in my sounds even better.

And I have to say I agree with Rickenboogie: it does indeed sound great (no matter how I set it up!)

 

[jweiss]

Thanks! I'm a relatively new mpulse 600 owner and my impression has been that the amp was heavily mid-voiced (in addition to thunderous lows). Well I've been putting the mid selector at 12 oclock thinking that was flat

 

[62bass]

I was setting my mids at 12:00 thinking that was flat. Now I see I was actually boosting them. And I still had a big bass sound. That says something about the Scout cabinet and explains why with other cabinets I've had to cut mids some to get enough perceived bass. Very interesting.

 

[KJung]

One more comment! Just like the mid control being somewhat unusual versus other amps, the treble control is voiced uniquely also. I believe the shelving start point is around 2K (EDIT: I had this wrong... it's even lower.. under 1K!!!!)... very, very low. This results in the treble control really acting more like an upper mid control. This makes sense, since the MPulse line seems targeted more toward rockers than funk/pop guys.

I find that cutting the treble control just a touch (11 o'clock), and then using the upper band of the semi-parametrice mids set at around 4K (the more typical treble center or start point) results in the amp really 'cleaning' up in the upper mids and sparkling a bit in the treble region.

Just like there is a lot of sound in that mid control, the treble control also can really 'revoice' the amp quite a bit with subtle changes.

This EQ power is a blessing and a curse with these amps. They are definitely not 'plug and play', but there is a very wide range of clean to moderately grindy tube tone in them when the mid and treble controls are varied IMO.

 

[pickles]

Thats the best 3-band EQ ever. I have the 600, which is the same circuit according to the manual. There are a huge number of great tones in there. Do not be afraid to turn up or down the bass and treble controls to get a balanced tone at the mid setting you want. Gain and mid have a HUGE impact on tone, so experimentation is typically rewarded. All knobs on 2 o'clock sounds huge, and has a similar balance to all flat, but a very different tone.

That said, I love the flat setting of the 600. All knobs strait up, maybe a little compression, parametric off. Really versatile since its clean and clear, lets your playing come through and lets you bass' natural tone shine ... but its also got guts and oomph to lock in with the kit and get the booties shakin.

Really great heads.

Passive mid EQ with a mid boost in the stage after sounds right. I love the passive mid/active hi and lo setup.

 

[pickles]

the treble control is voiced uniquely also. I believe the shelving start point is around 2K... very, very low.

Yes ... that control is amazing! It actually makes the bass sound brighter and more present instead of just dialing in click!

The bass control is also uniquely voiced to add fatness, not just bottom end boom. Similar principle, they both have a nice wide bandwidth.

So musical.

 

[Chef]

Neat thread.
My walkabout Scout is really my #1 rig anymore, for both DB and slab.
One hand carry, plenty of juice and tone.

 

[cmhgreg]

I find that cutting the treble control just a touch (11 o'clock), and then using the upper band of the semi-parametrice mids set at around 4K (the more typical treble center or start point) results in the amp really 'cleaning' up in the upper mids and sparkling a bit in the treble region.

That's almost exactly how I have mine set up most of the time!