I’ve recently been interested to see if the recent band of analog solid state guitar amps are starting to catch up on tube ones. I understand that digital is getting close in terms of tone, but I’m thinking more about feel, and I still think you need analog for perfect feel. Still even if you like modelling, you still need an analog power amp to hear it, and it does seem that a consensus is emerging that power amp and its interaction with the speaker that effects the feel the most, but more on that later.
Update:
It seems that most of the more recent Quilter amps are class D, but according to this patent and forum post, may still have some form of current feedback applied:
http://www.google.co.uk/patents/WO2013082166A1
http://www.ssguitar.com/index.php?topic=3098.0
http://www.google.co.uk/patents/US7924091
First the list.
It starts of with some boutique amps, the Award Session Blues Baby and Ethos Overdrive Amp. Most of the others on this list are all analog solid state amps with current feedback (Fender/Quilter/Tech 21), a few are hybrid tube preamp/ss power amp (Koch/Micro Terror) and some are Class D with no current feedback possible (PowerBlock/Magnum 44).
Current Feedback
The thing that seems to have improved solid state guitar amps since the ones I’ve tried that were made in the 80s/90s, seems to be current feedback, sometimes called current drive or constant current source (CCS). This places the speaker partly in the negative feedback loop of the amplifier causing it to sound/feel more like a tube amp. The following links, particularly the first one, are good for learning about what it means:
http://education.lenardaudio.com/en/13_guitar_amps_3.html
http://www.current-drive.info/9
http://sound.westhost.com/articles/guitar-amps.htm
http://www.award-session.com/bluesbaby2.html
The idea seems to have been around for a while. This thread seems to list some quite using it:
http://www.ssguitar.com/index.php?topic=2346.5
But it only seems to have become more mainstream as Fender started putting it in their solid state amps around 2003 like the “Dynatouch”, Frontman and Champion series, I believe in the early 2000s. You can see the resistor between the speaker and ground on schematics like the Fender Frontman 25R:
http://support.fender.com/schematics/guitar_amplifiers/Frontman_25R_schematic.pdf
A few companies like Award session mentioned above and Albion even use it in how the market their amps:
http://www.albionampsus.com/albion-ag-series/
The season of mainstream all analog current feedback amps maybe short lived though. Fender soon started adding DSP and modelling as they moved on from Frontman to Champion series and class D amplifiers seem to be becoming more popular for their size and efficiency, and I think even with the smaller manufacturers sticking with it, and even it is technically possible, it will be hard to get near a tube amp simply because there have been so many manufactures constantly working on trying to make great sounding tube amps, and there are far fewer solid state ones. It’s hard to imagine guitarists perceptions on tube vs. solid state changing too. The major manufacturers (Fender/Marshall) just want something cheap, and don’t try to produce anything that sounds close to their valve amps and I did notice it was quite hard to find that many demos on youtube of solid state amps, and often the ones there were by beginners with bad technique therefore tone. Still it was interesting on catching up on everything that has happened in the time after I’d decided tube amps were just “better” and now.
Update:
One final thought though. I’ve tried a lot more solid state amps since writing this. There still seems to be something wrong with feel and tone. Session say that we use solid state pedals for overdrive, so why not like a solid state amp, but there still seems to be something about a tube amp, and how pedals were designed to go into one. Tube amps are a whole system that produces what we expect as guitarists. There doesn’t seem to have been as much effort into replicating that entire system using solid state components.
