Can an amp’s tone change if...

York Audio

Fractal Fanatic
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Can an amp’s tone change if it’s in a head box or a combo?

This is gonna sound like an Eric Johnson claim, but I recently bought a Mesa DC-5 Dual Caliber amp. The guy had two of them, one in a head box and one in a combo. They’re different revisions so they sound sound like two different amps and he said I could keep whichever one I wanted and put it in the combo housing.

Yesterday I did some deep critical listening comparing the two amps
and landed on the one that suited my playing style better. In every test, it came out the winner. It was less compressed, had more note definition, and a more usable gain sweep compared to the other amp. It was in the head box and so I swapped out the amps. Today I listened again just to make sure I picked the right one and now the other amp sounds better now that it’s in the head box.

So my question is, can the housing change the tone? The only variable I can think of is the speaker in the combo and wondering if somehow the magnetic field is interacting with the tubes or some other component and changing the response. Sounds crazy, but I can’t figure out why the amp I chose sounds so different in the combo housing.

@FractalAudio have you ever experienced this or have any idea what might be causing the change?
 
I'm looking forward to this discussion! Just for clarification, do these differences show up in recordings or only when listening to them live?
 
I'm looking forward to this discussion! Just for clarification, do these differences show up in recordings or only when listening to them live?
Recorded. I had the cab in an iso room mic’ed up and I’d record them with same settings, replicated settings to match one to the other, different levels of gain, master volume, etc.

Going back to my recordings, I still chose the same amp, and today’s recordings sounded completely different after changing their housing. So bizarre.
 
I'm thinking it is component level differences between the two specimens.
Can you easily switch the guts and see what happens?
That’s the thing I’m talking about. My favorite one was in the head box and so I swapped “guts” and put it in the 1x12 combo housing and now it sounds different. Weird, huh?
 
Can you easily remove the speaker and see if the tone changes while in the combo box? A friend of mine had a Friedman head (I think?) and bought their combo box conversion. He said the tone changed but I think it was more due to the different speaker. Hard to say!

now we need axe amp models in combo and head formats ;)
 
That's what came to my mind.
@York Audio, Does the amp sound different if you take the speaker out of the combo enclosure?
I need to try that. I’m letting the amps cool off and then I’ll try again without the speaker in the 1x12 and see if there’s any validity to my insanity. :)


Can you easily remove the speaker and see if the tone changes while in the combo box? A friend of mine had a Friedman head (I think?) and bought their combo box conversion. He said the tone changed but I think it was more due to the different speaker. Hard to say!

now we need axe amp models in combo and head formats ;)
I thought about getting a head box made for it, but Mesa wants to charge me $400 plus shipping, which seems a little high. If I ever get a head box, I’d happily send it to Cliff. It’s a very different Mesa flavor and it’s absolutely fantastic!
 
Recorded. I had the cab in an iso room mic’ed up and I’d record them with same settings, replicated settings to match one to the other, different levels of gain, master volume, etc.

Going back to my recordings, I still chose the same amp, and today’s recordings sounded completely different after changing their housing. So bizarre.

You do realize that your amps potentiometers can have anything between 10 to 20% tolerance in values? So imagine two nominally the same 500K pots, one can be 400K in practice and the other 625K. Ever wondered why when you apply the exact same amp settings of your guitar hero to the exact same amp model in your Axe and it doesn't quite sound the same? That may be the answer. And that's excluding the fact that ALL your analog electronic components have similar tolerance levels. Buying quality components helps, but its never going to sound quite the same.
 
You do realize that your amps potentiometers can have anything between 10 to 20% tolerance in values? So imagine two nominally the same 500K pots, one can be 400K in practice and the other 625K. Ever wondered why when you apply the exact same amp settings of your guitar hero to the exact same amp model in your Axe and it doesn't quite sound the same? That may be the answer. And that's excluding the fact that ALL your analog electronic components have similar tolerance levels. Buying quality components helps, but its never going to sound quite the same.
why did the same amp sound different when the only change was where it was mounted? variance in pots doesn't explain the same amp sounding different. not sure this is relevant to this convo? i think he realizes pot variance ;)

@York Audio is my guitar hero btw :D
 
I've had this experience and thought I was crazy. I have a rackmounted Mesa Lonestar. Throughout the years when I was touring, I've put it in a combos, racks, and now a combo shell that's built to hold rack mounted amps. Each time something about the amp changed. It's been using the same Black Shadow C90 that came in the amp new. Same tubes, never replaced a grid resistor, or a fuse ever.

I always chalked it up to how the cabinet resonates with the amp on top of the cabinet, as opposed to mounted inside etc or the hole that is open when the cabinet is open. In other words, something about the cabinet changed and that changed the tone. Most of the time I just adjusted the knobs to compensate and basically chalked it up to the cabinet.
 
i wonder if it sounds different completely unmounted... i know amp designers build and test it without any mount; i've seen the Mark V or something unmounted with JP testing it at mesa lab.

all these years it was designed without a box and then the customer gets a different sounding thing :O

i wonder if mr. york can just call up mr. smith and ask his opinion...
 
I doubt the magnetic field would have any real impact. The field from the speaker magnet would be fixed. I would think you'd need a varying field like from a coil or transformer to really interact with anything. Who knows though. Stranger things have happened.

Microphonics could possibly play a role if the chassis is mounted differently. Vibration could interact with the chassis and components differently then. However, York Audio's scenario had the cab separated in an iso room, so the chassis probably wasn't being vibrated at all.
 
I remember reading something back in the day about the way the tubes would vibrate a little in combo amps- as in, components in the tubes were vibrating relative to each other, etc. It seems like it would lead to pretty serious tube failures if they were really being shaken that hard, but who the heck knows.
Really interesting observations @York Audio ! Looking forward to seeing this thread continue!
 
But how decoupled is vibration with an amp head sitting on a half or full stack? WADR I don’t think the tube vibration thing passes the smell test.
 
not sure about changing the tone but I have a combo amp that suffers from tube rattle - they make some spring loaded pads that put pressure on the tubes, that supposedly fixes it (don't use it enough to pay $30+ for the spring kit).
 
Well this thing has been one heck of a wild ride. After swapping guts three times, I finally made a decision on which one I'm keeping regardless of the head/1x12 combo housing. I ended up taking them both out of their shells and comparing the circuit boards and it was interesting to see the differences between them. One has handwritten text and the other has printed. There are some different components throughout the amp with different values as well as some components found in one amp and not in the other. I'm wondering if the one I like is actually a prototype. Mesa's serial numbers say the first DC-5 is DC-1024, and the one I like is DC-0923.

As far as the tone being different depending on which box the guts are in, I noticed that I always liked the head which is positioned on top of the combo and think it may have something to do with the amp's physical proximity to my power unit. That's the only thing I can think of. Thankfully, I put the one I like in the 1x12 housing with no speaker and it's sounding pretty fantastic! Well, the Lead channel is fantastic... the clean channel on this one sounds like a 2-channel Dual Rec's clean. I'm gonna see if putting a 12at7 in one of the preamp slots makes it any better. The clean channel on the other head is gorgeous, but the Lead channel has so much gain it's almost unusable past 3.
 
But how decoupled is vibration with an amp head sitting on a half or full stack? WADR I don’t think the tube vibration thing passes the smell test.
That was my impression as well when I came across that. Hot tubes are pretty fragile too.
 
Makes total sense to me. I had a Carment Ghia 1X12 and made a head shell and separate speaker cabinet. The head and cab did sound "better" than the combo. Don't get me wrong, the combo sounded great. The head and cab just felt different in a good way.
 
Contact Bob at sourmash guitar cabs. I had him build multiple head shells for me when I converted amps from combo to head. He did a fantastic job. All you have to do is send him the measurements.Great pricing and quick turnaround. Just checked my old emails. Less than 200 for the build.
Marshall 4010 combo changed into head



Rivera M60
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