Back to the Grind

I drilled the chassis with the benevolent guidance of a great friend at Ardent Studios in Memphis. Thanks Chris! Got to run a drill press for the first time. It was a great learning experience, only botched one of the output holes. Chris was able to fix it though. Phew! Here are a few pics of the process.

Drill plan taped to chassis

Running the press

All done!

Next step is to paint the chassis. That will probably happen tomorrow afternoon. Hopefully I can get it built by Tuesday to start testing out.

-Mark

Ax84 Kit Arrival and Resources on Arduino-Controlled Filter

A couple of updates on the project!

The Amp:
When I initially decided on the AX84, I wanted to save little cash by collecting all of the parts separately. After about a week of reading, searching, and phone calls with a couple of professionals, I decided to buy the kit for convenience. Much thanks to Robert Hull of TubeDepot.com for spending half an hour on the phone with me discussing this project. He advised I buy the kit for my first build considering I may not know all of the factors to buy the exact parts the design demands.

The kit arrived today and I couldn't be more excited! Have a look:

I am working on preparing the drill plan for the chassis today. Hopefully, I can get the holes drilled within the next couple of days. I need to get the amp operational by the end of the week. Muse's song "Our Time is Running Out" keeps coming to mind...

The Mod:
Well I've been scratching my head over this one all summer. I'm no electronics designer so getting this Arduino-controlled filter idea off the ground is coming slow. About a week ago I posted a thread on AllAboutCircuits.com to get some advice on implementing this idea. The users their offered some great advice and helped me eliminate a few ideas I had. Here's the link to that thread. http://forum.allaboutcircuits.com/showthread.php?t=87333

My professor emailed me this website as a starting point for this design: http://graffiti.virgin.net/ljmayes.mal/comp/vcr.htm

An FET can operate in one of two regions. Either the Ohmic region (pentode) or the saturation region (triode). While I understand the difference between the regions, I'm not sure why or how pentode/triode correlate with them. At the time of writing I came across another great resource:
http://users.ece.gatech.edu/~lanterma/sdiy/datasheets/transistors/vishay_fet_cvr_an.pdf
I might discus the contents of this publication in future post.

Well, I need to get those drill plans together. More than likely the frequency of posts will increase now that I have the kit.

Cheers!
-Mark

Amp Design Selected, Time to Assemble the Parts!

Well, after a solid month of reading, googling, and talking to people smarter than me, I have selected an amp design.

http://www.ax84.com/home.html

The ax84 is a common beginner's tube amp project and one I am excited to start on. I knew a few weeks ago I wanted a smaller wattage, single-ended, class A amp. These are the most simple designs and I NEED simple. Haha.

I'm tempted to buy the kit, but have decided to at least research the cost of assembling the parts separately. My professor has told me I could get some sheet metal from the machine shop on campus to build a chassis. The tubes and transformers can be bought from local electronics providers. I already own plenty of resistors and capacitors. I plan to put together a parts list tomorrow and determine what all I have.

I plan to build the amp as designed to ensure I can build an operational piece of equipment. But I need to integrate an arduino somehow. Tone control seems the simplest and most rewarding mod.

Here are a few thoughts I have going forward with this idea:

I need filters that are voltage controlled as the arduino outputs voltages. The current filters are controlled with variable resistors, I'll probably need to pull that entire stage out and replace with my arduino circuit. This may be very challenging as impedance matching and a host of other commonsense circuit design necessities become apparent. I imagine PSPICE simulation of this circuit will be helpful. SPICE and I have a rocky past, so this very well may be the most frustrating part of this project.

Well, here is the circuit I'll be soldering together within a couple of weeks!

Notice similarity this schematic has with my black box sketch from last week. Glad I learned something this summer!

I'm out for today,
-Mark