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[Jonathan Johnson]

When I was designing studio efx (back in the 70s-80s) the bench test equipment was less helpful. The variability of human audition was a factor I had to work around. Effects could sound different after a coffee break (it happened to me).

So what you need is a listening environment with unchanging electronics and minimally-changing acoustics (what you wear and where/how you sit will change the acoustics!), where you play a single reference track. Then you sit in silence for a while before moving directly to your listening test.

The purpose of this exercise is to "recalibrate" your mind and ears.

[John Roberts {JR}]

So what you need is a listening environment with unchanging electronics and minimally-changing acoustics (what you wear and where/how you sit will change the acoustics!), where you play a single reference track. Then you sit in silence for a while before moving directly to your listening test.

The purpose of this exercise is to "recalibrate" your mind and ears.

I was at a friends recording studio tweaking an effect (studio flanger). The group decided they needed a smoke break... no wacky tobacky but they fired up outside, while I drank a cup of warm sweet coffee whatever beverage from the vending machine in the break area.

I have no clear thesis for what happened, but things sounded night and day different when we returned. As I recall I unhappily called it a day shortly after that. Perhaps fatigue was another factor, listening hard can be hard. 

FWIW I was listening over good studio monitors in the sweet spot of the control room. I attempted to control as many variables as I could.  Things as subtle as tilting/rotating your head can change intra-aural delays and affect audition (or maybe it was blood sugar and/or caffeine from the crappy coffee).   

JR

[Stephen Kirby]

Yeah, this introduces still another variable which is the interaction between physical input [i.e. playing guitar] and aural output.  A whole 'nuther beast entirely....    Which is why guitar 'tone' is perhaps the MOST subjective thing of all.

And yeah, it certainly helps if you're a good enough player to deliver a reasonably consistent input in order to quantitatively measure changes in your design...

Actually, with an electric guitar the amplifier is part of the instrument.  So the way it responds to variablities in input is part of what makes a better amp.  And why top session players would seek out someone like Howard Dumble to tailor the timbral and dynamic response to their desires.

[brian maddox]

Actually, with an electric guitar the amplifier is part of the instrument.  So the way it responds to variablities in input is part of what makes a better amp.  And why top session players would seek out someone like Howard Dumble to tailor the timbral and dynamic response to their desires.

+1

I was trying to say what you just said. I just kinda missed. 

[John Roberts {JR}]

Actually, with an electric guitar the amplifier is part of the instrument.  So the way it responds to variablities in input is part of what makes a better amp.  And why top session players would seek out someone like Howard Dumble to tailor the timbral and dynamic response to their desires.

I would call it an "extension" of the instrument, with some "instrument like" sound characteristics, but yes especially for lead guitar they work together interactively.

While several of my design engineer friends have moved on, the one I had in mind was the guitar amp designer responsible for the Peavey 5150. He basically collaborated with Eddie Van Halen, translating Eddies requests into hardware. Eddie tweaked the wood used for the amp cabinet, because even that can make a sound difference. Players can hear things we mortals do not.

JR

PS: That amp designer friend now owns a successful guitar pedal efx company http://www.amptweaker.com/page/Amptweaker-Pedals-4.aspx

PPS: I disavow any knowledge about the JR pedals. 

[Tim McCulloch]

Funny, JR, because I can easily hear the differences between technique, strings, bows, rosins and probably the wood in acoustic instruments but the minute it becomes a guitar rig, guitarists start hearing stuff that to me is the equal of the Emperor's New Clothes.

The slightest touch to a knob (no visible movement) will send them into vocal wailing about how their "tone" was changed.  Nothing fucking happened.  Nothing.  Nobody else hears a change, either.  I don't doubt they can hear changes of many types, but a unmoved control?  That's up there with "touch the knob and smile" monitor mixing.

[John Roberts {JR}]

Funny, JR, because I can easily hear the differences between technique, strings, bows, rosins and probably the wood in acoustic instruments but the minute it becomes a guitar rig, guitarists start hearing stuff that to me is the equal of the Emperor's New Clothes.

I try not to argue with people about what they say they hear...

The slightest touch to a knob (no visible movement) will send them into vocal wailing about how their "tone" was changed.  Nothing fucking happened.  Nothing.  Nobody else hears a change, either.  I don't doubt they can hear changes of many types, but a unmoved control?  That's up there with "touch the knob and smile" monitor mixing.

Of course if "nothing" was changed he was just a crazy guitar player.

If he was a crazy guitar playing, paying customer maybe he was right by default. 

But what tone is he talking about? Can he hear the room from up on stage? Is his guitar running through the PA? Nah, I don't really want to know... 

=======

I chewed the fat for several hours with the good guitar amp designer to try to understand where the mojo comes from and while it is mostly subjective there is some there there, IMO.... While not exactly black magic there are also subtle tricks involved in guitar cabinet design, that cost nothing or almost nothing but made a huge difference in the sound.

JR 

[Stephen Kirby]

Tim, if it was an old Mk series Mesa Boogie I'd believe it.  I had two of them.  A MkIIc+ (which is supposed to be the holy grail of the series) and a MkIII.  Both got sold as they were way too finicky on stage.  Especially the MkII.  You could literally tap the knobs without them changing position and the sound and response would change.  If you moved a knob an entire position from one number to another it could go from that famous singing tone to choked off garbage that was murder to play though.  These amps were all happy accidents as a result of empirical playing around with the circuits that if you got them tweaked just so could sound and feel glorious.  But there was very little engineering behind them.  I had a friend who worked there for awhile and was a degree'd EE.  His task was to try and make them stable and production repeatable without upsetting the tone gurus who fell into the magic prototype.  So as a result, you could actually touch a knob without noticeably moving it and a guitarist could instantly tell.  Imagine a frequency selective compressor that changed from 2:1 to 20:1 with a hair's breadth movement of a control.
I know folks who will put up with them for those magic moments.  Too distracting for me to spend the whole first set bumping the knobs around.

[John Roberts {JR}]

Tim, if it was an old Mk series Mesa Boogie I'd believe it.  I had two of them.  A MkIIc+ (which is supposed to be the holy grail of the series) and a MkIII.  Both got sold as they were way too finicky on stage.  Especially the MkII.  You could literally tap the knobs without them changing position and the sound and response would change.  If you moved a knob an entire position from one number to another it could go from that famous singing tone to choked off garbage that was murder to play though.  These amps were all happy accidents as a result of empirical playing around with the circuits that if you got them tweaked just so could sound and feel glorious.  But there was very little engineering behind them.  I had a friend who worked there for awhile and was a degree'd EE.  His task was to try and make them stable and production repeatable without upsetting the tone gurus who fell into the magic prototype.  So as a result, you could actually touch a knob without noticeably moving it and a guitarist could instantly tell.  Imagine a frequency selective compressor that changed from 2:1 to 20:1 with a hair's breadth movement of a control.
I know folks who will put up with them for those magic moments.  Too distracting for me to spend the whole first set bumping the knobs around.

Yup, without getting too inside baseball, vacuum tube guitar amps often combine extremely high impedance circuitry with extremely high gain, so crosstalk and pickup between gain stages can lead to unintended audio paths feed-forward or feed back. Many tube are dual gain stages within one bottle, so PCB layout must be careful to keep the two stages from talking into each other, or letting them do so in a useful way. If there is point to point wiring involved inside, results could get pretty random if lead dress is not well managed.

It is possible to make two guitar amps with literally the exact same schematic and exact same components, that sound night and day different because of layout and lead dress,,, that doesn't mean they can't be repeatable, if the chaos is under control from the design stage. If the designer doesn't understand how he got the sound, he will have a hard time replicating it.

My friend was an EE so had to wear both hats, making them sound good, and again...and again...

JR

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