Buildin' Me a Tube Amp!

[kysrsoze]

After tons of reading/studying, cutting and pasting tips out of forums, etc., I finally got it together and ordered all the wiring, fasteners and and my ax84 Hi Octane kit from Doberman amps. Everything was included and overall, the build guide, schematics and layout sheets were pretty helpful. ax84 is a great site with a lot of knowledge in their membership.

I got the chassis painted (and only screwed up a small portion of it), then proceed to attach all the hardware, pots, etc. Today, I started wiring it up. Got my eyelet board all wired up and I've installed my PT primaries, and I'm getting a nice 7 volts on the heater wires, with a nice, blue power light operating. Over the next couple nights, I'll marry the eyelet board to the chassis and get all the final connections done. I figure I've got about 6 to 8 hours or so left, plus some troubleshooting.

I'm leaving the whole thing stock, with the exception of two small changes. First, I'm adding a lead/rhythm switch, which is really simple and shuts down one of the gain circuits and converts it from an HO back to a P1. I'm also adding the optional octal power tube socket so I have a lot of flexibility in power tubes. I chose to stay with cathode bias, b/c I want to keep this first build simple and I don't know how much of an urge I really have to start messing with tube voltages. I'd rather just play the thing.

It's a lot of tedious work, but a little more simple than you think before jumping into it, not to mention a very interesting project. Here's my handiwork so far...

[nicolasrivera]

Congratulations, looks like lots of fun.

[Phildog]

Man! That looks fun. Was it expensive? Was the chassis prepunched?

[rocknhorse1]

Those are some great sounding amps. Have you seen this website? EHN's AX84 Page
Lot's of demo's and info on the AX84 amps on that page.

Looking good so far.

[Case24]

Looks like a really good kit! Nice work so far.

[eddy999]

Good stuff. Enjoy the build - i'm sure you'll miss even the 'tedious' bits when you're finished!

[Lurko]

Looking good, but you need more solder in those eyelets, man. You're asking for a cold joint or loose connection the way the components are barely tacked on the edges, there.

[Lyle Caldwell]

+1 on the solder.

You'll also want to use some hot glue to hold those big caps to the board - they will vibrate enough to eventually break the solder joints or even the cap leads if you don't.

[Lyle Caldwell]

Edit - looks like you might already have the glue. Didn't see it clearly at first.

So, well, nevermind...

[Lurko]

Originally Posted by kysrsoze

I'm leaving the whole thing stock.

That's what you think!

[Case24]

Originally Posted by Lurko

Looking good, but you need more solder in those eyelets, man. You're asking for a cold joint or loose connection the way the components are barely tacked on the edges, there.

Don't you think he's leaving room for the flying leads?

[kysrsoze]

Yups, pre-punched. I know my limits. It's a nice kit. The kit ran about 400 bucks, including the pre-punch, octal add-on and all tubes. Not too bad, IMO. Of course, the wire, paint/clearcoat, loc-tite, silicon and all that stuff is extra, but I'll be able to re-use it. I've got a Firefly board I'll probably do next.

BTW - I did anchor the big caps with silicon, and I've got a lot of soldering left to do on the eyelet board. I've only soldered those connections that won't have another connection when it goes in the chassis, so most of the soldering still needs to be done. Everything else is just positioned in place for final construction, and I'll clip the ends more once I'm done soldering.

The ones which are already soldered look OK though, right? I have had to use a massive amounts on the eyelets I've already done so far.

[Lurko]

Yeah, they look fine. This is why I prefer PTP or turret boards over eyelets. You can burn up a half a roll on one board!

[kysrsoze]

OK, I've made a little more progress. The eyelet board is in, and all primaries, secondaries and speaker jacks are wired up. Next up is wiring all the controls and the tube sockets to the board. Latest photo...

[Lurko]

Very tidy. You may want to hold off, though, on gluing those wires down. If you have any squeals or oscillation you'll need to chopstick those a bit to find the optimal placement.

Also, cardinal rule: No wire nuts or electrical tape in the amp! Use shrink tubing, which won't slowly transform into a sticky mess over the years and won't rattle against the chassis like a wire nut can. My 2 cents.

[kysrsoze]

Originally Posted by Lurko

Very tidy. You may want to hold off, though, on gluing those wires down. If you have any squeals or oscillation you'll need to chopstick those a bit to find the optimal placement.

Also, cardinal rule: No wire nuts or electrical tape in the amp! Use shrink tubing, which won't slowly transform into a sticky mess over the years and won't rattle against the chassis like a wire nut can. My 2 cents.

Very good point, Lurko. I like that comparison.

Thanks.

[kysrsoze]

Well, I'm 98% done with my HO build! I finished the first-time power-up routine (was nervous as hell), but it all worked and I fired the thing up. It stays cool, with no squeal and no hum - dead quiet with the volume and both gains cranked. Lastly, it sounds fantastic through my 2x12 cabinet - very responsive to picking and the guitar's volume knob. The cleans are good, but multiple gain circuits in this thing give it some awesome distortion, from light to very heavy. It's only a 5-watter, but it's plenty of volume for any home, and it sounds good at low volumes too. I can't wait to throw some pedals in front of it.

I've kept it stock (yes... for now), with the exception of the lead/rhythm switch, which was ridiculously easy and works well. I made a couple minor mistakes. I have my bass and treble controls backward (too used to old stereo equipment), but I noticed while I was doing it so I rewired to work with the labels on the chassis. I also should have put the lead/rhythm switch near the input jack, but it works just fine. Now I just need to wire in the octal tube option so I can use 6V6s and similar tubes, and build a cabinet for this thing.

I attribute first build success here to a great design, a nice kit from Chris Hurley (Doberman Amps), my ability to follow well-written directions and excellent advice. I've shamelessly stolen tips from most of the members at ax84.com - they have oodles of knowledge.

Here are a few pics of my halfway decent job...

[chriseskew24]

Great job. I have to try one of these kits someday.