Allen Amps V-18 Build Project
|I ordered the Allen Amps (www.allenamps.com) V-18 Project amp, which is a kit version of the Sweet Spot. Mine is the 12" speaker option with an
Eminence Red Fang speaker. I'll also be running 6V6s power tubes, although 6L6s are also an option.
I've also included some "assembly tips" at the end of this page for those starting a similar build.
|Here are the nicely packaged parts for this kit as received from David Allen:
|Here are the electronic parts for the chassis assembly. Lots of parts!!
|After the first afternoon of work, I was able to get the front and rear faceplates mounted, the input jacks and pots
mounted and wired, the filter cap bank built, wired, and mounted, and the transformers/choke mounted on the chassis. None of the
transformers are wired yet. I also got all of the tube sockets mounted.
Here is a view of the front of the chassis with what I have done so far:
|Here's a back view of this afternoon's work:
Here's a closeup of the mounted capacitor board assembly:
Notice the rubber grommets go between the circuit boards, which then mounts directly to the chassis. The nuts for the plastic mounting screws go inside the chassis - be careful tightening them, they don't require much torque.
|I wired in the power transformer, rerverb transformer, and output transformers. Also installed the bias jacks and
related parts. Also put in the AC cord, power switch, and standby switch. The tube sockets have the heaters wired, and any other wiring
that doesn't go to the circuit board.
There are still many "loose" wires that will be attached to the main circuit board once it's installed.
I also got the circuit board populated:
|I soldered the circuit board and installed all the leads that go to the various other chassis componants. Try not to bend the
leads back and forth too much. Being single core wire, it will break after a few bends back and forth. If this happens, just cut another piece
of wire and reinsert it into the solder joint, making sure to make a good solder after the wire is in to avoid any cold solder joints.
|Here is a pic of the circuit board mounted in the chassis. Now I'm ready to start soldering all the leads and remaining wires.
|I finished soldering all the leads from the circuit board to the various places (i.e. controls, tube sockets, etc.). It's ready to plug in and try it out!
|Another angle of the completed chassis.
|I installed the chassis into the cabinet and plugged in the power cord. I set up my voltmeter to bias the tubes using the handy-dandy bias jacks on the back panel (what a great idea!).
I flipped the power switch and waited one minute as per David's instructions,
then flipped on the Standby switch. I was reading 170 mV at the bias jacks, which gets set to 20-25 mV for 6V6s ... WAY too high!! Then the fuse blew.
Here's the culprit!
I pulled the chassis back out of the cabinet, and discharged the filter caps so I wouldn't electrocute myself. As I was reviewing the wiring diagrams and my circuit board, I noticed there wasn't a connection from the bias potentiometer to the circuit board. DOH!!! I soldered the lead on, reinstalled the chassis into the cab, and put in a new fuse. I don't know how I missed that lead, but I did! So triple check your work before throwing the switch!
After applying power this time, the bias was reading 9mV, which I adjusted to the recommended range (20-25mV). I checked the other tube and it was within .1 mV. Sweet!
But how does it sound you ask??? Great! I played it for about an hour through three different guitars. The amp is very quiet, and has that Fender sparkle and "punch" too. The amp is very responsive to pick attack. I have to say I really love the sound of a Princeton Reverb, and David has nailed that with this amp (which is based on the Princeton Reverb circuit). The reverb is lush but not overbearing, and the tremelo sounds great too. The 12" Red Fang sounds makes this amp sound huge too.
Of course, I'm still on the "honeymoon" with this amp, so I'll post back in a couple of weeks with my continuing impressions with the amp. But, I think it's a keeper!!
My compliments to David Allen for his kit offerings (and his amps!). The V-18 amp kit was complete and not missing any parts. The components are top notch, and the finish work is great too - to include the cabinet fit and finish. This is the third amp I've built, and is the second Allen Amps kit one I've assembled (Class Act was the first one). This is also the most complex amp I've assembled. I spent three days doing the assembly, and those weren't full days. I tried to spread it out to avoid making mistakes from being too tired.
|The front view of the finished project:
|A rear view:
I just picked up a Tuki amp cover from David. These are really nice, and they fit like a glove! These are more than just a "dust cover!" They are padded, so should offer some good protection during transport.
|I had a great time assembling this amp! I'm almost sad it's over, but I think I'll enjoy playing my new #1 amp just as much as building it!|
First, always measure each component to make sure you are installing the correct value. Double check your values ... i.e. Is it 47, 47K, or 47M ... it matters! ;-)
Second, always triple check your work! You will make mistakes, from connecting things to the wrong place to putting in the wrong valued component. The trick is finding and correcting them before applying power and frying something!
Do as much wiring of the chassis as you can before installing the circuit board (star ground, bright switch/capacitor, input jacks, reverb transformer/jacks, PT and OT, power tube socket resistors, etc). Keep the 68K resistor leads short and angle them up steeply (on the input jacks) so they clear the circuit board.
The main "star" ground:
Crimp the leads all together in the large lug and then solder. It works best to make that star ground connection before you install the circuit board and then attach the green wires to the circuit board later. I found it to be quite challenging to get all seven ground leads into the lug for crimping, and one escaped on my first try. So, I used one of the wire ties to hold the leads together after stripping off about an inch of insulation. Then trim the excess off the group of wires after crimping them in the lug to avoid blocking the screw hole. Remember to also solder the wires to the lug after crimping.
The drawing doesn't show wires going to the heaters, but the pins on the sockets are labelled. For the preamp tube sockets, think of "H1" being pins 4 and 5 jumpered together and "H2" being pin 9 for each preamp tube.
After you wire the tube heaters, then install and wire the bias resistors and bias jacks, then the power and standby switches, then the speaker jacks.
Don't install the bias jacks and resistors until after the heaters are wired as it is crowded in that area. When you do install the bias resistors, crimp the two into a small lug and solder for added reliability. Bolt that lug to the back between the bias jacks with #8 screw with lock washer under the head inserted from inside the chassis and a #8 Keps lock nut on the outside. The #8 screw is your ground for measuring the bias, and having the threads on the outside give you something to clip your voltmeter leads to.
The Sprague 47uf 100v for the bias pot can be a tricky one to install. This capacitor shorts out the vibrato function when the depth pot is turned all the way down to prevent bleed through vibrato when you don't want it. It basically goes from the center terminal of the bias pot to ground. The best way to do it is crimp a lug on the very end of the + lead and fasten it under the PT mounting stud with the other lugs. Twist the left lug of the DEPTH pot 90 degrees. Insert the negative lead of the capacitor through the left lug of the depth pot and then on down to the center lug of the bias pot. It will reach but the capacitor body will be pretty close to the lug of the depth pot. You can put a small length of heat shrink tubing over the bare lead between the two pots for looks but it would be difficult for it to touch ground.
Or you can attach it "conventionally" (i.e. not bending any of the pot lugs) but put heat shrink tubing on the leads for protection (I put it on both leads, but the negative lead is the most important one to make sure it doesn't short to ground).
NOTE: because the bias supply is a negative DC voltage supply, that 47uf cap gets connected with its + end to ground. This is opposite from normal where usually the negative lead gets grounded (like the main filter caps).
Here is how I did mine:
Install all of the components on the circuit board, double check the components, then you can start soldering. It's also easier to catch errors by doing it this way insteading of "soldering as you go."
There are three "dashed lines" connections indicating the jumper runs under the board using the bare lead of the capacitors to make the jumper connection. Use the excess leads of one of the components to jump over to the neighboring eyelet to keep the eyelets from getting crowded with separate jumper wires.
Setting the power tube bias on first power up:
Turn the pot all the way up (from out side of chassis, fully clockwise like "diming" a volume control). This lets the tubes draw the least amount of current. Then you can bring up the current to the correct level.
Before sliding your chassis into your cab or applying power for the first time, make sure you clean out all the bits of wire and other stuff that seems to accumulate in there while your assembling the amp. This will ensure that no bits of wire or solder fall onto the circuit board or other parts and short something out.
Well, that's it! I hope you have as much fun building your amp as I did, and I'm really enjoying playing my V-18. There are a lot of tonal possibilities and I'm still exploring it.
Remember on the V-18 that the mid control is also the RAW control! Setting the mid control over 3 makes it start acting as the RAW function and starts lifting out the tone stack. So a "normal" mid setting to fully utilize the tone stack would be 3 or less.
I hope you find these tips helpful in assemblying your V-18 amp! Thanks to David Allen for providing most of these tips, and offering such great amps!