Impedance Switching Possible?

[Rick Turner]

Are you holding the Line 6 guitars as a paragon of great sound?

I wouldn't...

[peskywinnets]

No....which bit did you read that into?

Be carefeul, it's all too easy to slip into a pair of elitist flairs....and start shaking your ass round the "It's all about me" dance floor.

We were talking about piezos & headroom required, so - forgive me if I got the jist wrong - I mentioned Line6 because they shift literally thousands of units using a preamp powered at just 5V .... I make no judgement on their sonic fideility, but I can tell you that they'd be in commercial tatters if the screwed that one decision up & their piezos clipped. (their piezos don't clip @5V, single supply)

[Rick Turner]

My point earlier, which you seem to have overlooked, is that I have found piezo pickups to sound better when mated with higher than "normal" voltage power supplies. I don't care how many units Line 6 has moved...in those guitars the pickup sound is hardly relevant. It's a controller, not something that you listen to. Folks here are usually trying to push forward with regard to sonic excellence, not simply talk about any old thing that squawks. You can run piezos passive; you can use a 1.5 volt preamp.

You may simply not care about audio quality, but only whether any signal at all comes down the line. For driving a synth or DSP modeling, that may be all that's required.

I'm interested in high quality audio. I've not heard that with Line 6 guitars.

Also, I'm very familiar with Lloyd's hex pickup bridges, and I put them on some of my own guitars because making two or three hex bridges a month was becoming a real bottleneck in my own guitar making. I use an 18 volt supply for the preamp, and they sound pretty good. I liked my own hex pickups better, but for entirely practical reasons, I'm not making them at this time.

[Steve Conner]

You can "boutique" all you like, but a good op-amp has a dynamic range of about 120dB. The difference between 5V and 18V is 11dB, so if you run it off 5V you lose 11dB of headroom. The dynamic range is still 109dB, which is enough for any conceivable audio purpose.

If the kit downstream can accept a 15V p-p signal, then it loses 11dB of dynamic range too because the op-amp can't fully drive it, which may be an issue. But in the Variax it's going straight into an ADC that also runs off a single 5V supply, so the extra headroom would be wasted.

Op-amps with low idle current tend to suffer from crossover distortion, and that can be an issue in preamps that have to run off a battery. That's the reason why I agree with Rick's advice, not headroom as such.

The real issue is that Line6 make mainstream stuff down to a price and have zero boutique cred. Except for that time Martin Taylor showed up at a gig with his Line6 Spider set on "Insane".

[David Schwab]

I was playing in a band with a guy that had a Variax. I've also tried them out in music stores. Oddly enough I found the acoustic models more convincing than the electrics! I'd dial up a Les Paul or Tele patch, play a little and think "OK... if they say so!" I didn't find them to sound anything like the guitar they are supposed to be. But the acoustic patches sound compressed like you are listening to a recording of an acoustic guitar.

The overall impression was always that the guitar was far away sounding. It was always lost in the mix, even though the guy had a loud JBL powered PA cab as an amp. He was also using a Mac laptop running Guitar Rig. I'm guessing it was the lack of transient response that caused that.

It's a cool idea though. I remember talking to my old sound man back in the 70's about these ideas. He was an engineering student and now works for designing o-scopes. I figured if you can digitize the signal, you can manipulate it and then convert it back to analog. Of course back then the hardware didn't exist that would do that in real time. It's kind of like when I got the idea for these electronic book readers you see these days after seeing 2001: a Space Odyssey...

[Steve Conner]

Well, guess what, I still prefer paper books, and I still prefer an old-fashioned electric guitar plugged into an analog amp with spring reverb.

DSP is a big part of my day job, and it's always interesting to think about how it could be applied to music. I still have mixed feelings about putting it inside the finger-ear-brain feedback loop, though.