Okay, rebuilt the entire thing from the ground up. But I killed the 68nF cap in Figure 3. Replaced it with a spare 47nF I had laying around (closest thing I had) and the circuit didn't work at all. Finally figured out that Figure 3 was giving me the trouble. Replaced the cap with a 30uF cap...

My trimmer is behaving poorly.

Thanks for all the help guys. I'll go back and triple check everything and look at the grounding. Keep the ideas coming!

Hey all. This isn't my first build, but I'm currently attempting the "Infinity Universal Preamp" for my bass guitar. And it ain't going too well. My building has always been a mess, but it works. So far, I've gotten audio to output, but it's incredibly distorted and there's a ton of hum. The hum...

Nope. Either they are from different eras (and thus different production designs), or they aren't the same tube.

Unplug the device before you do this.

Quote: Originally Posted by Uncle Erik Eh, who cares? There are better ways to learn about headphones. Though maybe one of the organizers for CanJam 2010 should drop an invite to Apple execs. Their products are deeply entwined with headphones - it would be good for them to come to a...

But you can usually tell when one is on its way out. Distortion and channel imbalance are two good indicators that a tube is dying.

Quote: Originally Posted by rds I thought the RA-1 uses Solens... I think it did. Maybe he just wanted different caps. Solens don't seem to get the best rap in capacitor reviews.

Last time I checked out the project's thread, it sounded like the beta builds were blowing transistors or something.

Thanks for the link. It looks like that's exactly what I need.

Oh. Oops. When you say crude, does that imply a bad design, or a non-optimal, yet still on par, way of doing it? But what's the opamp doing, then? And why can't I just bypass this all with a +18V regulated power supply? Isn't that what this is doing?

My next project is going to be the Infinity Universal Guitar Preamp for use with my bass. The designs call for a dual rail PSU that supplies +9 and -9 volts. See the 5th page of this: http://www.techniguitare.com/projets...ms-V1.1-En.pdf How come I can't just use a PSU that supplies +18...

Expect them to last a while, but plan on having a spare. That's what I do. Just like transistors, tubes can and do have failures. Fortunately, it is much easier to replace a bad tube than a bad transistor.

Yep, there shouldn't be a difference unless you use a wire that is too thin for the current going through it. But for headphone purposes, you'll be fine with whatever kind of wire you choose.