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Why do pre amps have associated cabinets ?


NucleusX
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No idea if this has been asked before, but what's the story here ? We all know this isn't how things work in the real world.

As strange as it is, I actually like this feature. Pre's help to save DSP and the cabinets help to mitigate the thinness.

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I think you answered your own question...

 

Pre's are really for DT Amp integration where the HD Pre Amp is then linked to the DT power amp and Cab.

 

Or if you are using a real amp and cab and just want to replace the pre-amp (into FX Loop Return).

 

But conveniently if you choose to use a Pre with Cab into an FRFR you get a slightly less accurate amp model, but more DSP to play with for other effects or a second amp.

 

Having Pre and Full models and the ability to switch cabs (including No Cab) it would be strange not to offer all the possible combinations wouldn't it?

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There is no analogue in the real world where a cab is directly front ended by a pre amp. As for the DT, it has its own

cabinet, so a cab sim before a real cab would be an inaccurate representation too wouldn't it ? Pre amps would be

useful for any amp with an fx loop really. Least we can bypass cabs with pre amp sims to keep things logical if needed.

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In the HD500 the Pre Amp and Full Amp only differ in the modelling of the Power Amp contribution to the sound.

 

A valve power-amp is an imperfect design that introduces distortions and which doesn't always respond well to fast changes. The HD500 models this in some detail including introducing the crossover distortion that you get when each side of the sine wave in a Class B amplifier circuit is amplified separately and the two halves are not perfect half sine waves (it exists on solid state designs too).

 

Without the Power Amp model the HD simulates instead a perfect power amplifier at a nominal volume level (being perfect it's contribution doesn't change with volume), so you get the Pre Amp, a perfect power amp and the speaker if you have included one.

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In single path tones the HD does not model the classic approach of putting effects like flanger/phaser or chorus in the amp effects loop (or using builtin guitar amp reverb or vibrato effects). Single path HD tones are more like the use case where the guitar amp is mic-ed and then effects are added in an effects loop of a (sub-)mixing console getting the mic-ed amp signal.

 

If you really wanted to model the classic approach you probably need an external power amp (feed it with an HD preamp and typical effects loop models from path A) and then bring the miced external amp signal back into the HD to run any console effects (e.g. delay, echo, or reverb) in path B and send it to your main console. You can use an L6 DT amp to do that (and get a bunch of power amp options) and use the DT XLR out to save the mic-ing.

 

The HD just does not offer pure power amp models. At least there is no mentioning in the L6 documentation how to 'neutralize' the preamp in a full amp model. Thus I guess the intent is not to support building tones that insert effects between an individually selected pre and power amp model within a single HD.

 

That said (I have never tried), you may be able to fake a pure power amp model with a neutral tone stack setting and 0% Drive (on L6's DT amps almost all tone stack settings including drive do not change the power amp tone (Presence above 50% does for Type I and III)). You'd need to control the 'power amp effect' with CHA Volume and the 'AMP Parameters' alone (at least if you want to stick to following the classical effects placement approach).

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  • 1 month later...

Was never an issue for me configuration wise, was just a curiosity that suddenly came to mind, so I thought maybe Line6 had a specific

intention or reason for making it possible that wasn't obvious to me. Even if there isn't, I'm glad the option is actually there at my disposal.

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The PODHD is not a bunch of miniaturized amp pieces stuffed into a box.  It's code stuffed into a box.  They did the best they could, which I'm very happy with.  But there's a few idiosyncrasies' such as PreAmp and Cab.  My guess is they couldn't separate their code modules in a way that would easily allow a PreAmp without cab.  Or they just plain forgot to make it an option.  Or it sounded like crap...

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