Bluexurious, new custom tube amp

[jordileft]

Hi, as my end-of-career project, I and another student from my university made a custom amp. We designed the schematic, chassis and cabinet. It's a 15W push-pull class AB with three 12AX7 in the preamp and two EL84 in the output, it has a Celestion G12-65 and a Ruby Tubes reverb. We design it to be similar to Fender amps in order to play from jazz, blues and other soft styles to rock. We name it Bluexurious and it really sounds great. Its similar to a Blues Junior or a Princeton but with some more controls, a warmer tone and with less noise and a additional channel for having a little more boost for solos, which can be controlled by te switch on the front or by footswitch. We really enjoyed doing this project so we wanted to share with people around the web. Here it is a photobucket with some pics and youtube video with some demos, it's not high quality 'cause I recorded with the video option of my photo camera but it gives you and idea. I hope you like it.

http://s767.photobucket.com/albums/xx312/jordileft/
http://www.youtube.com/watch?v=_rX-Og3EuXs

[Phil_S]

Well...I think all builders know that feeling of satisfaction of building the first amp. This will hardly be your "end of career" as amp building is addictive. You've come a long way. So, congratulations and welcome to the league of amp builders! You deserve lots of credit for getting this far.

I'm going to level a bit of criticism at the build. I don't mean this to be unfriendly, or to diminish what you've accomplished. I think you could do better, much better.

I think I hear lots of hiss in the youtubbe demo. I'd find that unacceptable. Typical causes of hiss are bad capacitors (even when new out of the box), loose connections (tighten all bolts), intermittent connections (cold solder joints, loose wires, loose tube sockets?), faulty input jacks. Tubes can be inherently noise and you might benefit from swapping tubes. High gain amps (yours isn't one) will be subject to hiss just because they introduce lots of amplification and any hiss picked up in the first stage will get amplified as it makes its way through the signal chain.

Tone is subjective and I'm going to refrain from commenting, as I'm already going to get in enough trouble with what I'm saying here

BTW, your guitar chops are very good, so keep it up!

Your layout and lead dress may work just fine, but all those crossed and flying wires are problems looking to happen. To be brutally honest, you've broken all the traditional rules for lead dress. While there is nothing inherently wrong in breaking with tradition, experienced builders tend to stick with the traditional approach because it's effective at avoiding problems. If you check around, you'll uncover picture galleries of some very tidy builds. It takes practice and patience to make your build organized and neat. IMO, neatness does count.

Conventional wisdom suggests signal wires on the chassis, filament (a/c) wires in the air, separate high voltage (B+) from signal wires, and cross wires at right angles where crossing can't be avoided.

I'm not fond of the solder bridges on the bottom side of the board. This is a spot where I'd say you have a better than 50/50 chance of making a cold solder. Solder is not wire and it looks as if you used it as a wire substitute. Solder is for solidifying the connecting point between/among wires. You might find that replacing the solder bridges will help with hiss and this is the first thing I'd go for.

Since you've just finished college (did I get that right?), you probably don't need to be told to make changes one at a time. Otherwise, you'll never know what works and what doesn't.

Enjoy your amp. Tweak it. Good luck.

Phil

[M Fowler]

jordileft

Congrats on building your amp and the fine playing. The main thing is you built the amp, I think the cabinet too, and you seemed to be enjoying making the video. I was checking out the knob positions from style to style to see where they were ending at.

You owe it to yourself to find some cash and build another amp this time dump the pcb construction and lets see what you come up with.

[dave g]

That's not PCB, it's perfboard

[Zippy]

That's not PCB, it's perfboard

As the accompanying text cites, the perfboard EXAMPLE is of a TrainWreck - the OP is using circuitboard (with some pretty sloppy technique).

[tonestack]

That's not PCB, it's perfboard

As the accompanying text cites, the perfboard EXAMPLE is of a TrainWreck - the OP is using circuitboard (with some pretty sloppy technique).

Dave is correct. It's either XXX or XX perfboard.

[M Fowler]

Yeah your right, I had PCB on my brain all the time knowing it was perfboard constructed, sorry guys, I miss spoke.

Mark

[Phil_S]

I wouldn't know the difference between xx or xxx, but it sure looks like some sort of breadboard with holes in it and perfectly good material, IMHO. Just not something I'd choose to work with. It's the way it was used that surprised me. It appears what Jordileft (OP) did was to cut the board so it is almost as wide as the chassis. He then attached front and back faceplate-like panels that I imagine fit snugly inside the chassis. Then he flipped it over so the bottom of the board is facing out, the reverse of what conventional builders do. In a sense, he reinvented the wheel and not in the best way. It's still a successful build.

Jordileft: again, I feel it's important to note that we are not "piling on" here. Anyone who can build an amp deserves lots of credit as it just might be considered by some as a dying art. And, like others have observed, you seem to be enjoying it. Hitting the high points, there is every reason for you to feel really, really good about what you accomplished. I guess, though, what you did looks quite a bit different from what we usually see and that invites the sort of commentary you see. By orienting the board "upside down", you sacrificed ease of service and the width of the board forced a number of compromises in lead dress. It's still a successful build!

Keep it up. We'll look for your next project.

[jordileft]

I wouldn't know the difference between xx or xxx, but it sure looks like some sort of breadboard with holes in it and perfectly good material, IMHO. Just not something I'd choose to work with. It's the way it was used that surprised me. It appears what Jordileft (OP) did was to cut the board so it is almost as wide as the chassis. He then attached front and back faceplate-like panels that I imagine fit snugly inside the chassis. Then he flipped it over so the bottom of the board is facing out, the reverse of what conventional builders do. In a sense, he reinvented the wheel and not in the best way. It's still a successful build.

Jordileft: again, I feel it's important to note that we are not "piling on" here. Anyone who can build an amp deserves lots of credit as it just might be considered by some as a dying art. And, like others have observed, you seem to be enjoying it. Hitting the high points, there is every reason for you to feel really, really good about what you accomplished. I guess, though, what you did looks quite a bit different from what we usually see and that invites the sort of commentary you see. By orienting the board "upside down", you sacrificed ease of service and the width of the board forced a number of compromises in lead dress. It's still a successful build!

Keep it up. We'll look for your next project.

Don't worry, you are completely right, I really thing that a constructive criticism is one of the best ways to make someone improve. I'm very keen on my amp, but it's obvious that there's a lot of things to improve. I tied the wires in this way trying to make it as short as possible, and this type of board is a bakelite board. About solder bridges you may be right, in other electronics projects (not amp projects) it's normal to use solder bridges, 'cause essentially they are like PCB paths but bigger, but I didn't know it wasn't good for a amp, there are so much things I didn't know, 'cause here, in Spain, there's so much less information, it's a little bit more difficult to find some amp parts and people who can give me some advices, there's no so much amp builders here and another factor that was working against me was time, 'cause my project tutor told me a date to give in the project, and I had to spend less time than I would like with some construction issues, and in the meantime I had to write all the written document, with everything justified, so I had less time than I expected for the first amp. About the chassis, as I decided to design my own chassis, I make some decisions about its form and the way all the pieces fits that follows closer my common-sense than any professional experience about building amps, so obviously, there are some construction ideas that wasn't right.
By the other hand I hope this is not going to be my first and last amp project and I'm sure that if I build another amp in the future, as I won't be hurry, I will spend more time to think better all the things and will ask for advice in order to follow more strictly all the traditional rules.
Sorry for my poor english... Thanks!

[tonestack]

I wouldn't know the difference between xx or xxx, but it sure looks like some sort of breadboard with holes in it and perfectly good material, IMHO.

XX and XXX are NEMA grades for paper-based phenolic sheet. XXX is the highest grade of paper-based laminate. Paper-based phenolic sheet is also known as Bakelite sheet (after the inventor of the resin, Dr. Leo Baekeland). Most people are used to seeing what is known as NEMA grade G-10/FR-4. G-10 is a type of glass epoxy laminate sheet. FR-4 is basically G-10 that has been treated to be flame retardant (FR-4 is the most common PCB material). A lot of material that is labeled as being G-10 is actually FR-4. Other NEMA grades that find their way into amps are LE (linen fabric-based phenolic sheet), CE (cotton fabric-based penolic sheet), and GPO-3 (glass and polyester laminate).

[tonestack]

About solder bridges you may be right, in other electronics projects (not amp projects) it's normal to use solder bridges, 'cause essentially they are like PCB paths but bigger

There's nothing wrong with using solder bridges. I am a licensed amateur radio operator, and you ought to see the type of construction that hams use to prototype radio circuits (many of which run 500+ watts of power). What you did is clean compared to "ugly" or "Manhattan" circuit construction. The major drawback to the type of construction that you used is maintenance.

[Merlinb]

Hey Jordileft, what's that quick run of 5 notes you play exactly 35 second in? I like it...

[Phil_S]

... 'cause here, in Spain...

This is real irony. Your English is good enough, I wouldn't have known. I did, however, point you to a Spanish language Plexi website. Spend some time there. It is a good website. When I found it, I asked my daughter to translate for me.

Given your explanation, I applaud your creativity. You figured out enough to make it work, and it works well.

Good luck.

[jordileft]

Hey Jordileft, what's that quick run of 5 notes you play exactly 35 second in? I like it...

It's just major pentatonic adding 3rd minor as a bluenote, or adding 3rd major and 6th to pentatonic minor. I don't know if it has a specific name.

[mane]

Hola Jordi.

Congratulations.

Where are you in Spain?