Amp Rotation

[László]

I get what I need by the simple expedient of substituting different PI tubes until I go "that's the one!"

Exactly what I do. And what many amp designers do, too.

The best, I've found, work by ear. A lot of stuff can be measured, but certain things just don't lend themselves to measurements, and the ear is the ultimate arbiter.

I wondered, because in my limited experimentation with PI tubes, I formed the opinion that it takes an amp you can push the power stage at least "pretty hard" for the PI tube to make a significant difference.

A lot depends on the circuit design, the tubes, etc. But mostly on your personal taste.

After 20 years of experimenting with PI tubes, I'd say you have to try them in the PI position to know what will work for you. And what will work for you might not work for someone else.

As an aside, I found that the Siemens 12AX7 works well in several of my amps in the PI position. But when I say, 'works well', I'm saying it works well for me.

Everything, and I mean 100% of everything when it comes to tube choice, is personal taste and nothing more. There's no 'best' and never will be, and this is why people buy different amplifiers.

"What about modelers, Les?"

"Modelers? They're not real amplifiers. Next question."

 

[Deleted member 5962]

Sort of, kind of agree with most of what you've said, with a single proviso: to get particular singing tones, in my experience, you have to slightly unbalance the PI in a particular way. It also continues to work - to a degree, at least - at slightly lower volumes than you'd expect; though it's as much in your touch as it is in the amp when you're at lower volumes, so the jury is still out there.

This has also generally proven to be both circuit-specific and amp-specific; so what has worked in one amp often hasn't in another (very similar) example. I had two Coli MkIIBs, and sold the one that I couldn't get to where I'd wrestled the other amp. The one I let go still sounded phenomenal, as they tend to, but just not as close to my "ideal".... and I'd got to the point in life where I finally realised that I just didn't need to keep a spare: the big IIB is darn nearly unbreakable.

It's not something you can measure, as far as I've been able to determine yet, and despite the best part of two decades spent futzing about with this notion. This has been mainly in my Two Rocks, Boogies, and Groove Tubes amps*.

You have to do it by ear, unless maybe you're HAD himself, or someone who's at that level of understanding.

I get what I need by the simple expedient of substituting different PI tubes until I go "that's the one!" There's usually a particular one that stands out as more effective in a particular circuit, and to this day, I haven't found a reliable way to shortcut good old trial and error.

Hence the bucket of decent 12A*7s. After the best part of twenty years, I'm somewhat down from the hundred or so I started with in there.......



[* not Hiwatts - they're just going to be Hiwatts, whatever you do: get the PI close to balanced, and off you go. Hiwatt is going to be Hiwatt.....]

I hope I’m not saying something you already know… but it does explain your journey, as well as what I was mentioning.

Many amp designers design a little bit of asymmetry into the PI stage of their amps. I can’t claim to know what percentage of amps do this, but it’s common. So THAT is why they recommend balanced PI tubes! Because, the only way for you to get it exactly as they designed it, is if you used a balanced tube. Then, whatever percentage of asymmetrical clipping they design in, is exactly what you’ll get… IF you push that stage into clipping.

Thing is, you can’t then argue with someone that “you need to use a balanced PI tube” because how do you know what that person will like or prefer. Let’s say I design amp, carefully test and then build it with say 5% higher voltage on one side than the other and of course, tell you to use a balanced tube so you can hear the magic I designed…. How do I know you won’t like an unbalanced tube, that makes it be 10% different, better? Or the real wild card… since you’d have to know a thing or two about circuits to now which way you are pushing the already built in asymmetrical clipping, depending no which side of your preamp tube is hotter…. your unbalanced tube may be pushing it further into asymmetrical clipping or… it might be pushing back to, or even the other side of symmetrical clipping.

Every unbalanced PI tube that you use, depend on how far off balanced it is, is either making the designed in level of asymmetrical clipping more than it was designed to be… or less. If it’s off by the right amount in one directly, it might even be making it symmetrical.

So, while they way they clip is very important, the tubes balance, imbalance, and which way and how much it’s imbalanced will all come into play IF you push the PI stage hard. So, in some ways, and again ONLY if you push that stage hard, it may be the most important tube of all to experiment with.

 

[Wyzard]

Yes, a lot of what you write about is stuff I've factored in. It seems we've considered this matter in a similar way over the years

Naturally, you're covering the designers' intention, and doing so about as well as I'm capable of putting it myself.

However, it all falls foul of one inevitability - that of distribution about and around the desired value of un-balance, arising from the complexity inherent in both the componentry and the physical manufacturing process. There isn't a single one of us "tone navigators" that hasn't, at some point or another, discovered that supposedly identical amps (even with consecutive serial numbers) don't respond the same way*. What we've all done subsequently with this knowledge is probably a function of our individual impatience with the physical world as we find it.....

Then there's the passing of time, and the aging of the amp - which is to say, the entirety of its component parts, and the ever-increasing complexity of their interactions. Non-linearity isn't something that magically decreases over time.

It's also worth mentioning in passing, that what some designers intended (yes, I'm looking at you, Red Rhodes and buddies...) isn't always what you actually get when the rubber meets the road.


Hence the need to tailor to specific touch.



[*not even when you swap their tubes over.... been there, tried that, been p*ssed that I wasted my time.

"Some piglets have it, some donkeys don't!!" as Eeyore would doubtless put it]

 

[Deleted member 5962]

Yes, I know some guys who have it down to "whenever it's time to replace the PI tube in THIS amp, I look for one that has 3mv higher rating on the 2nd triode, than the 1st." Because that gives the amp in question the best level of asymmetrical clipping "for them."

I don't have a massive stash of NOS tubes, like some of you. But if you push the back end of an amp, it's definitely worth rolling some tubes through the PI slot to see what you prefer.

 

[Wyzard]

Yes, I know some guys who have it down to "whenever it's time to replace the PI tube in THIS amp, I look for one that has 3mv higher rating on the 2nd triode, than the 1st." Because that gives the amp in question the best level of asymmetrical clipping "for them."

I'm just idly curious - what sort of amps are these guys running them in? I'm guessing they're not D-styles of any sort.

 

[Deleted member 5962]

I'm just idly curious - what sort of amps are these guys running them in? I'm guessing they're not D-styles of any sort.

I'm just talking about general comments people have made when discussing this topic at TGP. Don't remember the specific amp that person was talking about but several people mentioned having specific mis-matches they looked for.

I do definitely remember that one of the guys in the discussion had a few older Marshall amps though, JCM 800 and Plexi types.

 

[Wyzard]

If you're trying to use Marshalls for anything remotely like what Eric Johnson does, this strategy is pretty much required; and doubly so if you're running them through EVM12Ls.

I used to use big Fenders (black panel Showman amps, which I still have examples of) before I got into Boogies (so: forever ago ) and I vaguely remember paying a reputed tech to test, install and dial in PI tubes. To this day, futzing with this stuff is ingrained.

And since I do a lot of it myself, much cheaper.

 

[jak3af3r]

I'm just idly curious - what sort of amps are these guys running them in? I'm guessing they're not D-styles of any sort.

I doubt it. Most D-styles have a dedicated trimmer for that. Which, in theory, should be a simple addition to an existing circuit that should eliminate the search for a specific tube.

 

[Deleted member 5962]

Which, in theory, should be a simple addition to an existing circuit that should eliminate the search for a specific tube.

Actually... it would be a simple addition. hmmm

 

[Jo-]

My main amps that I like to use are my Fender 65' Deluxe Reverb or a modded Bassman which has been 'trainwrecked' in a 15" cab (that used to belong to Tyrone Shuz, I jumped at the opportunity when he offered to sell).

But this week I've been playing with my Hughes & Kettner Tubemeister 18 and also my old PRS SE50 head, running them through the old PRS 4x12 cab from the old HG70 solid state series. The 594 Hollowbody sounded fab through the Tubemeister, the single coils were so much more singlecoily sounding. Sounded great through the SE50 too, although totally different.

 

[Bogner]

Had some fun banging around on the Sound City Master Lead 50 today. Right before my ears started bleeding I began running it along side my PRS Archon 100 and they worked nicely together. I look forward to more playing with them together and seeing what I can come up with sonically.

 

[Jo-]

I haven't played my Bogner Shiva for nearly 12 years now. I was thinking of selling it all those years ago and moved it downstairs into the dining room along with it's 2x12 closed back cab. Well it's been there ever since as I couldn't be bothered with the hassle of shipping it or people getting buyers remorse. Maybe I should just take it to my local Guitar Center and let them have it for pennies. What does the collective say?

On the flipside of that though, I've been setting up my stereo rig, which is bascially a 72 Bassman which was Trainwreck modded combo with a 15" speaker and my vintage '65 Deluxe Reverb. They make a nice stereo pair for my effects.

It's not very pretty, but they do sound wonderful. Been playing my Singlecut Hollowbody Standard.

These are the other vintage amps I have fun with....

I still wonder if I should drag the Shiva back up stairs... but it's sooo heavy.

 

[bodia]

I haven't played my Bogner Shiva for nearly 12 years now. I was thinking of selling it all those years ago and moved it downstairs into the dining room along with it's 2x12 closed back cab. Well it's been there ever since as I couldn't be bothered with the hassle of shipping it or people getting buyers remorse. Maybe I should just take it to my local Guitar Center and let them have it for pennies. What does the collective say?

On the flipside of that though, I've been setting up my stereo rig, which is bascially a 72 Bassman which was Trainwreck modded combo with a 15" speaker and my vintage '65 Deluxe Reverb. They make a nice stereo pair for my effects.

It's not very pretty, but they do sound wonderful. Been playing my Singlecut Hollowbody Standard.

These are the other vintage amps I have fun with....

I still wonder if I should drag the Shiva back up stairs... but it's sooo heavy.

Maybe take that Bonner to Brian’s? A trade, or sell on consignment? Better than getting gouged at GC

 

[Jo-]

Maybe take that Bonner to Brian’s? A trade, or sell on consignment? Better than getting gouged at GC

Oh Brian's guitars here in CT? I've never visited in person yet, maybe i should.

 

[Bogner]

Don't sell your Shiva.

 

[sergiodeblanc]

I haven't played my Bogner Shiva for nearly 12 years now. I was thinking of selling it all those years ago and moved it downstairs into the dining room along with it's 2x12 closed back cab. Well it's been there ever since as I couldn't be bothered with the hassle of shipping it or people getting buyers remorse. Maybe I should just take it to my local Guitar Center and let them have it for pennies. What does the collective say?

On the flipside of that though, I've been setting up my stereo rig, which is bascially a 72 Bassman which was Trainwreck modded combo with a 15" speaker and my vintage '65 Deluxe Reverb. They make a nice stereo pair for my effects.

It's not very pretty, but they do sound wonderful. Been playing my Singlecut Hollowbody Standard.

These are the other vintage amps I have fun with....

I still wonder if I should drag the Shiva back up stairs... but it's sooo heavy.

Whoa! I’ve never seen a snow leopard lookin bengal kitteh before!

 

[jxe]

I haven't played my Bogner Shiva for nearly 12 years now. I was thinking of selling it all those years ago and moved it downstairs into the dining room along with it's 2x12 closed back cab. Well it's been there ever since as I couldn't be bothered with the hassle of shipping it or people getting buyers remorse. Maybe I should just take it to my local Guitar Center and let them have it for pennies. What does the collective say?

On the flipside of that though, I've been setting up my stereo rig, which is bascially a 72 Bassman which was Trainwreck modded combo with a 15" speaker and my vintage '65 Deluxe Reverb. They make a nice stereo pair for my effects.

It's not very pretty, but they do sound wonderful. Been playing my Singlecut Hollowbody Standard.

These are the other vintage amps I have fun with....

I still wonder if I should drag the Shiva back up stairs... but it's sooo heavy.

cat game, i am dying.

 

[Wyzard]

No cats, just KOTs here KOT, FTT Ambi-Space, Hiwatt DR103 and Fane Crescendo make for a great combination.

On the subject of Shivas: a friend of mine used to run one, and it sounded really good. Since he's one of the most musical guitarists I know, it's no small recommendation that he chose to play one for most of the stuff he was doing.

 

[11top]

So I was switching around some amps and cab combinations and pulling out some amps I haven't played in a little while just to change things up and felt like I got some new amps. I always loved the amps but not playing them for a bit and then playing them almost felt like I got more new amps..lol. I guess the moral to my story is instead of buying new gear, just pull out the stuff you haven't played in a bit and it will probably feel like you got some new gear! See how much money I saved everybody!

I just twist a couple of knobs.

 

[Alnus Rubra]

I haven't played my Bogner Shiva for nearly 12 years now. I was thinking of selling it all those years ago and moved it downstairs into the dining room along with it's 2x12 closed back cab. Well it's been there ever since as I couldn't be bothered with the hassle of shipping it or people getting buyers remorse. Maybe I should just take it to my local Guitar Center and let them have it for pennies. What does the collective say?

On the flipside of that though, I've been setting up my stereo rig, which is bascially a 72 Bassman which was Trainwreck modded combo with a 15" speaker and my vintage '65 Deluxe Reverb. They make a nice stereo pair for my effects.

It's not very pretty, but they do sound wonderful. Been playing my Singlecut Hollowbody Standard.

These are the other vintage amps I have fun with....

I still wonder if I should drag the Shiva back up stairs... but it's sooo heavy.

Love the little leopards