Backing up a bit.

I ran into an issue with Amp #2 when I went to plug the tubes into those nice gold bottom mount sockets. It was extremely hard to get the tubes into the sockets and harder yet to get them back out. I'm going back to the regular ones and have those on order. They allow easy tube changes without any risk of bending pins. Since I'm removing those sockets I also decided to do some house cleaning and will shorten each wire to its minimum length. Doing so will reduce noise in the circuitry. I will then know what that length each wire should be so I'll be able to use this recipe in the future amps. This will make it a lot easier to wire up. I also found another builder's amp and his heater wires where a work of art. So I took his lead and created a new set of heater wires that are much prettier than the previous ones.

New heater wire harness

My friend requested a Send and Return effects loop, so I needed to re-arrange some items on the back panel. I also had to add another hole. In the end I think it was for the best because now things will be laid out in a nice orderly fashion. But there isn't any more room for holes, so that's about it on the bells and whistles for this amp.


Here's Mizzen doing quality inspection. The ole sniff test.

I brought the two pieces I have done back home so I can start practicing the art of laying out, cutting and securing the Tolex to the cabinet. This is my first attempt so I plan on using some other materials to figure out how to do the corners and such correctly. I have some vinyl laying around so I might practice with that first to get the hang of it. The last thing you want to do is have the contact cement curing away while you figure all of this out.

Amp # 2 Works!

I was able to get Amp #2 working tonight. At first there was no sound, I only had the guitar leaning against the table. I then noticed the guitar's volume knob was at zero, DUH!
Amp #2 works. I'll still need to add some more stuff to it. The preamp circuit, the attenuation circuits and clean up the wiring a bit, but it's coming along nicely.

On the faceplate front I have the face plates mocked up in PowerPoint. I'll be submitting them in a few days.

No Mas! No Mas!

I've explored countless avenues and I'm giving up on making my own faceplates. I'm going to contract Amplates (www.amplates.com) to make them. Last night and tonight I'm been carefully measuring the chassis and drawing up the specs for them to start their process.

Tonight after I finished measuring the chassis for a 2nd. time to make sure I had valid measurements I started hooking up the Big Iron. No not a Harley Davidson, but rather the Heyboer Transformers made to Graydon's (www.gdsamps.com) Vintage 18 Watt Specifications and manufactured by Heyboer in Flint Michigan.

Pictured here is the Power Transformer. I'm hooking of the rear components because I need to test things out and validate that my resistor choices for the attenuation levels are going to work out. Later when the back face plate comes I'll only have to desolder the fuse, and the power cord receptacle to install the rear plate.


Here's the output transformer. That might go in tomorrow night, but I need to pick up some rubber grommets to protect the wires passing trough the chassis holes.

Turn it down please!

Tonight I started working on the Attenuation for Amp #2. My friend will want to practice at home and most likely play in some smaller venues. I'm building into the amp the ability to reduce the volume at the speaker, but hopefully not affect the quality of the sound too much. This will allow the amp to be cranked up to get the desired distortion, all the while enjoying a volume level at the speaker that is neighbor friendly. There is also the possible situation of playing in a smaller venue where a full 18 watts is way too much power. Besides having the ability to go to eleven this amp will also be able to go to a polite eleven.

I found this schematic along with an excel sheet that calculates the values for the various levels of attenuation given a speaker impedance value.
(Link to the site with the excel sheet http://www.wohlgemuth.de/board/bridged_att_calculation.xls)


Luckily I had some turret board material and some turrets on hand. This set allows for two levels of attenuation. These these values will produce 9db or about 2.3 watts of output. The other level is for at home use with 20db or about 0.2 watts of output. I'll be able to tweak these values just by changing the resistor values out.
There will be an Attenuation Switch on the back of the amp that will function like this:

• Up - 2.3 watts
• Middle - Off (Removes it from the circuit)
• Down - 0.2 watts

Mouser (www.mouser.com) didn't stock a 15watt 30 Ohm resistor, so I went to the next higher wattage rating to obtain the needed Ohm value. I'll most likely fashion a metal screen to protect and hide these resitors but still allow them to radiate the 18+ watts of heat at full tilt. Mind you that since we are talking waves, that roughly only .7 of the 18 watts is required.

Speaker Cabinet #1 for Amp #2

Yesterday I made two new baffles for the second attempt at cutting out the speaker holes. Here is a picture with my template nailed to the backside of the baffle. I'm using a flush trim bit in my router, the bearing will ride against my template making for a nice round cutout.


This time I cut a smaller circle using my jig saw to allow for any slop in the cutout. I also didn't have to try to make a perfect circle. Which made it a lot quicker and easier to cut. You can see that I have a good 1/4" of wood that I'll need to remove with the router bit.

Here's the hole after removing all of the extra wood.

Finally, two baffles I can be proud of.

Here I'm lining up the speaker with the hole to make sure it is centered. From the backside I then used a center punch to mark the holes. Carefully drilled almost all the way through the baffle and installed 4 Wood screw/machine screw studs into the back of the baffle.

This is the backside of the baffle. I used my speaker for a guide.

Here is the bottom plate for Speaker Cabinet #1. I had to route the baffle Dado (Left to right, at the bottom of the pic). And a rear Dado for some gussets and nailers for the rear panels, that are removable. I'm using Tightbond III waterproof glue for these cabinets.

I had to work quick to get the sides and the baffle in place. I didn't have time to take pics on each placement. The top went on next (to the right in the background)

Here's the cabinet all glued up. I used some 18ga. brads, using my air nailer to clamp everything in place and to provide some more strength. Through the cutout you can see the rear gussets. I'm also going to add strips in the dado to act as a base for the rear panels to screw into and to strengthen the rear part of the box a little more. These should make a good seat, with a chair height of 20 inches they should be about perfect to sit on.

It was getting late, but I was able to make the front trim. This will add some width to the front of the cabinet and make it look thicker from the front.

Another pic of the nearly completed Cabinet #1. Cabinet #2 will go together in a few minutes. I figure I only have about 2-3 more hours of work get these and the head ready for covering.

This is the backside of #1.

Messed up the baffles, Arrghh.

Today I went to my shop to work on the Speaker Cabinets for Amp #2. I started by using a compass to draw a circle for the speaker hole in the baffle. I then drilled a pilot hole to allow the jig saw blade to fit into. Cutting a perfect circle was not easy and, even though I went slow but the cut was not vertical. As a result the hole was less than perfect.

I then devised a better way of making the speaker hole. I grabbed some thin plywood and drew the speaker cutout size on it. I then drilled a pilot hole to the inside edge of the circle. Mounted that thin plywood on top of another piece of plywood that I clamped to my router table. Installed a 1/4" cut out bit into the router. I then put a nail in the center of the thin plywood circle and nailed it to the bottom piece of plywood. This allows the thin plywood to revolve while the 1/4 bit made the cut in the thin plywood. the result was a template with a perfectly round circle cut out of it.

Here's my template. My next step is to make new baffles (using the vacuum bag method). They are curing in the garage right now with the vacuum pump running away keeping a good clamping vacuum on the new set of baffles. Tomorrow I'll cut out the speaker holes using the jig saw again but this time much smaller than the targeted diameter. Then I'll affix my template onto the top of the baffle and use a flush cutting router bit to remove the rest of the wood and create a perfectly round speaker hole in each baffle.

Here is my template, the flush trim bit bearing (not shown) will ride against the inside wall of the circle.

Wired the Tube sockets tonight.

Face Plate update.
Thursday Night, the 11x17 transparencies arrived. I was able to print the faceplate onto them. the 3m photo mount spray adhesive didn't work well at all. It might have been the temperature. It was a little cold an the adhesive was to hard to deal with. I then tried a test using epoxy. This was promising. My only problem was that I didn't have a J-Roller to squeeze out enough epoxy, the result was a little wavy, instead of totally flat. I might pickup a J-Roller tomorrow and try the epoxy route again. A J-roller is a rubber roller about 2-3 inches wide with a handle about a foot long so you can apply a lot of pressure. It's mainly used for attaching Formica using contact cement.
I spent a good part of the evening building the ink jet face-plate printing machine. The rest of the time was spent working on hooking up the tube sockets on Amp #2.




The heater wires were a little easier this time around, but they are still a pain to hook up. Those are the black twisted ones. They are twisted to help reduce noise in the amp.

A possible way forward.

Last week I had ordered some 11x17 Laser Transparency Film. Today it arrived. My plan is to print out the face plate text and dials onto the film and laminate it onto the backside of the Lexan Face Plates. Then paint the back of the film with gold metallic paint. I'll try that out tomorrow after I head to Kinko's to print out the face plates on the film.

Tonight I was able to get most of the front panel components wired to the turret board.
Here's the front panel controls.
Left to Right
Trem Tone, Trem Volume, Trem Inputs, Tone, Volume, Inputs


Here is the other part of the front panel with the Trem Speed, Trem Intensity, Trem Tone and Trem Volume controls. I was also able to finish mounting all of the components to the turret board. The Sprauge Atom Cap came in, and I yanked the two 8.2k resistors and put the far better Riken Ohm (http://angela.com/rikenohmresistors.aspx) ones in their place. They are the two blue ones with the gold leads. just to the right of that big Blue Capacitor.

Amp #2 Populating the Chassis.

Amp #2
Over the last few days I've been able to get the rest of the holes cut and enlarged in the chassis.
Tonight I was able to get most of the front and back panel components in place. For the Rectifier and the Power Tubes I found these Gold plated bottom mount sockets. I like them better than top mounts. For the preamp tubes I went with top mounts because they need the housings and a bottom mount doesn't make sense for those sockets.



Here is the Back panel with the Components Listed Left to Right.
1/4" Jack Preamp-Cabinet Emulating (post output transformer)
Preamp Volume Control
1/4" Jack Preamp - Clean
Preamp Switch Cab-Off-Clean
Speaker Attenuation Switch On-Off
Speaker 1
Speaker 2
Tremolo Foot Switch
Speaker Impedance
Voltage Selector
AC IN
Fuse


Front Panel Components Left to Right
Pilot Lamp
Power Switch On-Off
Standby Switch On-Off
Tremolo Speed
Tremolo Intensity
1/4" Input Jack Hi Tremolo Channel
1/4" Input Jack Low Tremolo Channel
Tone
Volume
1/4" Input Jack Hi
1/4" Input Jack Low

Started working on the cabinets.

Amp number 1 is still on hold pending a breakthrough on the faceplate labeling front. I found that 3M Photo Mount spray adhesive is most likely the way forward. I did a test and sprayed in on a full color 4x6 postcard card that we got in the mail. I glued it to the Lexan and tried to get all the air out and it worked great. The adhesive caused no optical fuzziness that I could tell. There were a few air bubbles so I'll be doing the lamination in a vacuum bag to suck out all of the air.

Amp #2 is moving along. I received the color choices from my friend. I've been playing around with the design and have it about 95% figured out. This past Saturday I took a road trip to NC Hard Wood Store http://www.hardwoodstore.com/. The last time I visited them was a couple years ago. They have since moved into an even larger space. This is great because they have even more selections that previously. OK I admit I spent about 30 minutes just walking around looking at all of the wood species. For Amp #1 I picked up so nice Paduak. It was 3/4" thick so they cut it to the length of 4', jointed one side and planned it down to 5/8" for the whopping sum of $1.10 labor. The wood ended up being $18. For amp #2 I picked up some 1/2" Baltic Birch.

Since I'm using plywood for the construction, Dovetails are not an option. Amps made of a hardwood or Pine can be dovetailed but Plywood would weaken and de-laminate over time. The classic joinery technique is to use rabbits and I'm going the extra steps by installing gussets on all of the corners. The cabinets will be pretty much bullet proof in their strength.
Here's the head cabinet fresh off the router table. Stacked like a house of cards with just gravity holding it together.


I wanted to get a feel for the dimensions so here is all of the pieces taped together with some scrap wood to hold them somewhat in place. This is looking at the backside. The middle speaker cabinet will have a slant half way up (Marshall Stack style)

Amp #2 from the back/side angle.

Though I wanted to just start putting the cabinets together I needed to construct the most important part first. The baffle. In this case for added PUNCH I'm using 2 sheets of 1/2 Baltic birch glued together with epoxy and vacuum bagged to eliminate any air voids in the lamination.
Here I've added the epoxy and have previously drilled two locating holes where the speaker is to be cut out. the locating holes will keep things in perfect alignment while its being vacuum bagged.

This is with the top sheet added along with two wood dowels hammered into place.
Ready for bagging prep.

The first time I tried to vacuum bag some wood, my bag popped. The sharp corners of the wood poked right through the bag. I've learned since then. I now add some cloth or in this case some paper towels to eliminate any sharp points that would cause a leak.

Here's the vacuum bag (I picked these giant Zip Locks up at Lowes).

Here's a video of the vacuum process. I had picked up a nice vacuum pump on eBay for doing some other lamination(s). Since this Speaker Baffle is about 18" x 19" and there is 14.7 PSI of air pressure at sea level. Using a vacuum bag in this application causes 5027 Pounds of total force to be applied to the plywood. This is the Best Clamp Ever invented, as it has an even clamping force throughout the work piece. And is much easier than trying to drive an SUV onto such a small area.

Day 2 Amp 2

I was able to get about 90% of the board completed. I'm waiting on some parts to arrive prior to completing the rest of the board. I can't wait to hear the Sozo caps (http://www.sozoamplification.com) along with two Riken Ohm (http://angela.com/rikenohmresistors.aspx) 1/2 watt carbon comp gold plated resistors also arriving soon. Those Riken's will be put in the most critical section (resistor wise) of the amp. Here's the back side of the board. The wire is tinned silver stranded Teflon coated.

Here's a closeup showing the Sozo Mustard caps.

The top of the board, I'm still waiting on three capacitors to arrive. The 5w power resistor on the right hand side (white rectangle) is a 150 ohm. Amp #1 had a 130 ohm. I went with a 150 ohm on this one because it is easier on the power tubes, so they will last longer.

Serial # 002 is born

The last few days have not gone well. I've been trying to come up with a solution for creating a face plate. Up to now I've tried the following things:

• Spy paper( leaves fine paper fibers that will mess up the background color paint)
• Water slide decals. They are not very transparent, it looks blurry.
• Window Cling film (Blurry)
• Transparency, air bubbles

Sunday showed promise, I bought a el-cheapo ($32.99 at Wal-mart) ink jet printer and tore it apart. I'm going to build a ink jet printing machine to print directly onto the Lexan faceplate. The paint should seal and protect the ink, since I'm printing on the back of the Lexan faceplate.

While Amp #1 is still waiting on the face plates and the Ink jet machine, I've started work on Amp #002. This one is for a friend of mine.

Onward to Amp #2

I've tweaked the layout a little to add more room for the larger components and also to keep the components further away from the board standoffs. Here I've made a template (Mirrored) using spy paper and have just ironed it onto the Turret board.

Here's a video of the spy paper dissolving in water. I could have just held it under that water and it would have instantly dissolved, but this way you can see that as soon as this paper gets wet all the binder is gone. All that is left is just a bunch of pulp fibers.

The finished freshly labeled turret board.

Here's a video showing how the turrets are riveted onto the turret board. The cone shaped anvil in the drill chuck spreads the tubular turret outward, thus securing it in place.

The Finished Turret (The underside, since it is tubular a wire can be attached here, as well as on the topside of the board)

Amp #002 is born. I have to pickup some silver solder at Radio Shack tomorrow. Then I'll start soldering some components in place.