Fender Champ Amp 5f1 as stompbox ?

[Krinor]

Thanks for the tip. But I am one of those hard nail analogue freaks. I have a Vamp2 by Behringer. It has a Tweed Champ emulation. It' s okay, but it doesn't give me that dynamic feel.

The thing is: Not only do I want a champ emulation for low volume pratice, I also want to build it myself. A digital circuit, allthough some of them are pretty okay, is not what I am after.

[Ben N]

Hey, go for it. I have a V-Amp2 as well, so I know what you are talking about, but I will tell you that I doubt you will do any better THROUGH HEADPHONES with a SS "emulation" of your amp--digital really excels at that. But the exercise will be fun nonetheless, you will learn stuff, and you may end up with a great dirtbox, no matter what you call it or how you use it. There was a lengthy discussion here a while back as to whether all those ROG ad similar FET-based amp circuit adaptations deserved to be called "emulations," but call them what you like, they do sound good, even if they don't exactly emulate the amps.

[Gilles C]

Just to give you an example of what Fender and Boss think this kind of pedal it should be.

http://www.youtube.com/watch?v=VRbw1e4uomA

[Mark Hammer]

I'm surprised nobody's mentioned this already but, the problem with emulations like the Prof. Tweed is that they're not modelling the power amp section, which in something like a Champ is the most important factor in getting 'the tone.'

Bingo.  As the proud owner of a real honest to goodness 5F2-A, I can truthfully say that with the volume control below 6 (out of 12), there is VERY little to distinguish it from any other amp.  It's not until you start to push that little sucker that the speaker, the output transformer, and the input stage, start to deliver the goods.  Simply mimicking the tube structure in SS form does nothing to replicate that.

Does that mean the other FET emulations are no good?  Not in the least.  Several of them have an interesting gain structure and distinctive tone-shaping controls that will yield up interesting and useful tones, even though there is no deliberate attempt to model/emulate the behaviour of the transformer and speakers....when pushed.  Some of the attempts to model any of the cascaded gain-stage amps also provide the opportunity to have "self-contained" overdrive.  In contrast, the various 3-tube (preamp, power, rectifier) tweed Fenders have very sparse and generally uninteresting input/preamp stages and certainly nothing particularly innovative or powerful about their tone controls (when they even have one).  Their particular magic comes when you stick some else in front of them and turn them up.

So, while I do not wish to deter anyone from trying to work with FETs, using classic amps as basis for design, understand that sometimes they will deliver nothing special on their own, and will need lots of help before anything interesting starts to happen.

I know the topic has come up before, but it seems like none of us have ever ventured that extra step to try adding small interstage transformers onto the output of SS emulations such that some additional transformer-derived grind might be pursued.  It may well turn out to deliver much less than expected, but you won't know until you try.

[B Tremblay]

I'm surprised nobody's mentioned this already but, the problem with emulations like the Prof. Tweed is that they're not modelling the power amp section, which in something like a Champ is the most important factor in getting 'the tone.'

Please note that runoffgroove.com does not refer to our amp-inspired FET distortion circuits as emulations because they are not emulations, nor are they intended to be viewed as such.   Instead, look at them simply as a distortion circuit that can have a moderately similar sound when compared to the "parent" amp.  During development, we certainly tried to get close to the sound of the amp, but are fully aware that they cannot capture all the nuances of tubes (both preamp and power) and transformers.  We believe that they sound good for what they are, despite their inherent limitations, and hope that others will also see them that way.

Some people will make up their minds once they've seen the schematic, others will dismiss them after hearing the sound clips, and some builders will actually try them out and then decide.

[Mark Hammer]

Please note that runoffgroove.com does not refer to our amp-inspired FET distortion circuits as emulations because they are not emulations, nor are they intended to be viewed as such.   Instead, look at them simply as a distortion circuit that can have a moderately similar sound when compared to the "parent" amp.  During development, we certainly tried to get close to the sound of the amp, but are fully aware that they cannot capture all the nuances of tubes (both preamp and power) and transformers.  We believe that they sound good for what they are, despite their inherent limitations, and hope that others will also see them that way.

Some people will make up their minds once they've seen the schematic, others will dismiss them after hearing the sound clips, and some builders will actually try them out and then decide.

Entirely fair.  I think it is appropriate to view them all as "what if" experiments that are valid on their own merits.  That is, "what would you get if you had a series of FET-based stages that followed the gain structure of what is found in amp X?".  So far, people have been pleasantly surprised, and I think the approach is far from exhausted.

I think it is also worth noting that some commercial digital models of amps tend to focus their efforts on the overload/distortion properties.  My cheesy Zoom GM-200, shown here, supposedly "faithfully emulates the sound of 11 legendary guitar amplifiers".  (Yeah right.  And I "faithfully emulate" Arnold Schwarzenegger when I fake an Austrian accent and talk like Rainer Wolfcastle.)

At low drive settings, there is nothing to distinguish them that EQ-ing could not do, and perhaps that is really more of an attempt to capture the qualities of the speakers than of the amplifier itself.  The differences are all about what they are supposed to sound like when cranked.  Of course, to be fair, that's a big part of the charm of amp models, isn't it; being able to nail how amp X sounds cranked.  The thinly veiled Twin model does sound markedly different from the thinly veiled Marshall model and AC30 model.  of course, whether they capture the "true" sound is another thing.

EDIT: Just stumbled onto this: http://www.aes.org/e-lib/browse.cfm?elib=11310  That could be an interesting read.

Finally, without wishing to beat this to death with a stick, you will note that part of generates the characteristic tone of older tweed amps is that they werre often matched with 8" speakers that could simply not handle the bass with aplomb.  The low-end breakup is part of the allure.

EDIT #2:  Okay, okay.  last edit.  I promise.  A wee bit of googling located the above-cited paper and a bunch of other related papers from the same lab here: http://www.music.mcgill.ca/~wlm/papers/  Av Hollinger, who used to be on the forum back in the days when he came up with the "Interlarder" distortion, is now doing his Masters in gestural controllers at McGill, where this author is.  I'll have to ask him if their still doing much in perception of distortion.

[Krinor]

Thank you all for your elaborate discussion on this topic. It was very informative. I think most of us will agree that replacing tubes with fets is indeed an exciting experiment and of course a fet cannot replace a tube and emulate the sound. It is a totally different thing. As in all other experiments where you try to get "that tone" of say for instance Jimmy Page - the magic is not entirely in the pedals, but in the whole package; The player, the instrument, the pedal, the amp, the settings on that same amp. Damn, even the temperature, the humidity, the time of day (or night), the amount of beer involved etc. etc.

I like that "what if" notion. For me nailing that 5F1 tone is not THAT imperative. I'm more on that ROG "what if" stage and I'd like to see what happened. Then after I realize that the result is not even close to the real thing I would probably put the thing in a cabinet and start to experiment with woods and the speakers to try to obtain that bass cutoff etc.