6DG6GT Tube Amp Design Update 6-12-2014

6DG6GT_Tone_StackI couldn’t stand it. I really didn’t like the tone stack that I included in the 6DG6GT amp. After reading the GMOON Instructable the other day, I found out that he used the Big Muff Pi tone circuit as shown in Duncan’s Tone Stack Calculator. I decided that I liked the simplicity of the Vox style tone stack. I’ve added this to the 1.5 version schematic. Check out the page dedicated to all of my tube amps here: Tube Amp Builds…all in one place. The image shows the new tone stack built on my existing turret board. Since this is a prototype, I suppose I can live with a few parts that appear to float in mid-air.

One thing to note is that I wired the bass pot backwards. This is because I really want all of my knobs to be at full clockwise for the twangy, overdriven sound. That’s pretty much where I’ll keep it especially since I usually¬†play my guitar on the neck pickup which tends to lend to a darker sound.

6DG6GT Tube Amp Design Update 6-9-2014

6DG6GT Images and Descriptions

The amp appears to be complete. In case you missed it, here is the final schematic: 6DG6GT_Tube_Amp_SchematicV1_51 – June 19, 2014

Modifying VHT Special 6 Footswitch

Adding an LED Indicator

VHT Special 6 FootswitchI enjoy my VHT Special 6, and I can’t find many things that I would change about it. The one most annoying thing isn’t exactly related to the amp except that the footswitch that was sent with it is just a switch in a metal cone. Occasionally, I get caught trying to play a guitar solo without the boost enabled. I found that the switch of the original footswitch pedal is already modifiable to make it work with just a battery, an LED, a current limiting resistor, and a 1/4″ stereo audio jack.

VHT_Special_6_switchOriginally, I assumed that when the switch was closed the boost was enabled. I built a whole circuit and enclosed it in the enclosure. The 1/4″ stereo jack was used to connect the switch to the amp, and it also turned on the power supply which powered a transistor to invert the LED. Once assembled I found that I didn’t even need the transistor inverter. I already had the hole drilled for the jack so I kept it in. Here me out on this one…You could simply connect the switch to the original cable and opt not to install the jack, but if the button is pushed in this manner, the LED will illuminate. The stereo jack serves two purposes: it connects the switch to the amp, and it completes the negative path from the battery to ground to enable to LED to illuminate.

VHT_Special_6_original_switchThe original switch is a single pole dual throw (SPDT) switch with the ground soldered to the outside tab of the switch. The common is from the amp’s circuitry that, when grounded, disables the boost. In order for an LED indicator to work, the common connection has to be the ground. The image in the second paragraph shows this connection. I just desoldered the switch and removed it from the original footswitch housing because I chose to install it in a small box from Radio Shack. The enclosure is a 3″ x 2″ x 1″ plastic box. You might want to consider a larger box. It’s possible to fit it all in there, but it’s a tight squeeze, and the final layout is asymmetrical.

VHT_Special_6_modified_footpedal_schematicThe image to the left shows the schematic of how the new switch will work. When a mono guitar plug is inserted into the stereo jack, it completes the ground path for the battery. When the footswitch is pressed, it toggles between the amp circuit being grounded (boost off, LED off) and the LED being grounded (boost on, LED on). When the boost is off, the LED is not connected; It is left floating, which like like having an infinite sized resistor that completely block current flow through the resistor.

Bill of Materials (Radio Shack)

modified VHT Special 6 footswitchYou’ll want to do a dry layout before drilling holes in your box. I placed my 9v battery between the two screw posts on one end of the box. Then I laid out the jack, switch, and LED holder to make sure nothing touched. By following the wiring diagram, you’ll make each connection as shown. I used a bottom made of metal (not the original supplied one), so I hot glued the switch contacts. I also hot glued the battery wires down to ensure that they don’t get pulled out on accident. I drilled pilot holes using a 1/8″ drill bit, then I used a stepper bit and a whirly gig to take each hole to its final size. I decided to solder all the parts together after I installed them into the box.

This was an easy and cool project. It took about an hour to make the whole thing once I decided on the design. Once completed, you’ll never have to guess or audibly check to see if your boost is on. The LED will tell you!

VHT_Special_6_footpedal_wiringVHT Special 6 footswitch wiring diagram

I’m back in action, but slower than ever

I have a lot to talk about in a small space. I probably won’t get to it all. I’d like to start by embedding some explosions:

Do Your Research

Not all colleges are the same!

The next thing that I’d like to do is put out a small piece of advice: watch out where you choose to go to college. I’ve learned a hard lesson by attending a private online college to get my Engineering Degree; avoid those for-profit colleges if you must! Check to make sure that your major is ABET accredited. I knew that DeVry’s online Electronics Engineering course was not ABET accredited, but I was also lead to believe that it was about to be. Fool me once, shame on you. I won’t let that happen again, but it’s too late! The damage i$ already done. I couldn’t get a job in the engineering field (and glad I didn’t), and I can’t pursue a Master’s degree at the college of my choice (and I’m really unhappy that I can’t).

What I’ve been up to

Some may have noticed that Tech-Tut.com went completely silent for a long time. I wasn’t in college… I’ve just been busy. I recently closed my electronics and computer repair business because it was taking up too much time, and the money was not worth it.

I also celebrated one year at Beans and Strings as an Assistant Manager and music instructor. I’ve devoted most of my time to my job and my family, and I just haven’t had as many hobbies going on that I could blog about. I think I did more hobby stuff when I was in college. I also had a streak of bad luck with my projects, too. It really bums me out to blog about my failures. Perhaps I should do that, too.

There’s more to come. I have projects that I’ve been working on. I’m also a real person so life happens, and my blog is not always the forefront. Going forward I want to do a better job with organizing and arranging projects. In the past, what you see is what you get. Hopefully the future will be easier to find and easier to understand.

Peace and blessings to you in the maker community. Drop me a line.