New Build started. Guitar and amp (Now with sound clips!)

[strelok]

My dad is retiring this summer so I thought it would be nice to build him an amp to get him back into playing guitar and this seemed like the perfect opportunity. I wanted something low watt as I don't think he will ever be playing anywhere but at home, but I also wanted it to be a push pull amp. At some point I came across the 6k6GT and it seems like an excellent choice as a pair of them will produce about 10 watts. Still quite loud but I also plan on adding a VVR.

Now the question is what pre-amp? That was quickly answered when I came across this video:

https://www.youtube.com/watch?v=JASfKMCL6Ag

Tweed Deluxe with 6k6gt's in the output. Perfect. He loves classic rock and this nails it. From what I gather this is the stock 5E3 circuit but with .022uf coupling caps instead of .1's. Also had a SS rectifier. I was on the fence about whether or not to go tube or SS, but I eventually settled on SS as it's one less thing to worry about. I also just really like the way this amp sounds.

Aside from that and the VVR, I decided to do the input slightly different. One input jack, with a pair of 33k grid resistors feeding the grids of the first 12a*7. So its similar to having the channels jumpered on a conventional deluxe. I also decided that I will use a split cathode configuration. Normal channel will have a 1.5k resistor bypassed by a 10uf cap. (Due to splitting the cathodes doubling the cathode resistor is necessary to achieve the same bias point as before and halving the bypass cap (approximately) to give the same LF roll off.) For the bright channel then I will steal a page from Marshall and give 2.7k and .68uf a try for the cathode resistor. May have to do some experimenting to get it right. Also might try a .0022uf for the coupling cap on the bright channel.

So tonight I got the first bit of work done. I couldn't find a chassis that was the size I needed so I thought I'd try my hand at bending my own chassis for a change. I ordered some aluminum cut to size from a local supplier along with some 90 degree 2x1x1/8th angle for the end blocks and mounting to the cabinet. I don't have access to a sheet metal brake, so I ordered an excess of the angle to clamp to the bench to make my bend.

It took some experimenting to get it right, I ordered two 15"x11" aluminum sheets as I knew I'd probably fuck up the first one. It didn't turn out too terrible and with some work it will be usable for a later project but the second one turned out fairly nice. It still needs a bit of evening out with the hammer but I'm fairly pleased with how it came out. I then cut some 7" sections of the aluminum angle and I plan on brazing them to the chassis. I've never done this before but it doesn't seem too hard. If it doesn't work out I know someone who has a TIG welder that could take care of it for me. I also should add that .06" aluminum is a lot more ridged than I anticipated I could have probably gone with .05" and it would have been fine, but hey now it's at least extra solid haha.

Here's a few pics of what I got done tonight and a schematic and layout. Sorry for the smudges. I drew them a couple months ago and they've been lying around on my desk getting various beverages spilled on them.

http://imgur.com/a/jHc8f

I plan on building the amp into a mini head and cabinet configuration like I did with the single ended express. 1 12" speaker. Probably a Weber 1225 or the like. Though I'd like to make it a bit nicer this time. Round over corners etc. Probably will stain it something tweed-ish colored and make up a nice face plate for it.

Now where would a new amp be without a nice new guitar? My Dad has always wanted a strat, but I could never talk him into buying one. Well I've had this mighty mite body laying around for about a decade that I picked up at a guitar shop for a song. I'm planning on building that up as well. Probably a maple neck/fret board, white pick guard. SSH configuration with a mini PAF style pickup in the bridge. Here's a few pics of the body:

http://imgur.com/a/I3fZQ

[gktamps]

Sounds like a really cool project! I really like 6K6 tubes, having used them in a THD BiValve, but as I understand it they need an OT with about 13k impedance, correct? Do you know what transformer you will use?

[xtian]

I hope I caught you early. Build for 6V6, which allow for a little clean headroom in the 5E3. The VVR is a great idea, and makes the 5E3 incredibly flexible. I ended up putting Russian 63PS (6L6) tubes in mine, for 15 watts with about 320 plates (after subtracting cathode). Super sweet. You saw my Trinity build log? Plenty of photos and a layout for you to check out.

The 0.02 PI caps are a good idea, and the SS recto. Bridged input. That's exactly what I did. Easy, one input, one volume.

Did you already get an OT? A Fender Vibrolux 35 watt OT give you a lot of flexiblility (runs great with 6V6 or 6L6) and only costs $40.

Good luck, and don't cry when you discover 6K6s don't have enough clean output!

[strelok]

Sounds like a really cool project! I really like 6K6 tubes, having used them in a THD BiValve, but as I understand it they need an OT with about 13k impedance, correct? Do you know what transformer you will use?

Thanks! Yeah around ~12k is about right for these. I have the rest of the parts I need sitting in the shop at work so I didn't get any pics of those yet. Just went with Hammond iron like in the video but beefed up a bit. 125E for the output and 269GX for the power. The nice thing about the Hammond output is it has a wide variety of impedances to choose from. Should be about 315v for the B+.

Good luck, and don't cry when you discover 6K6s don't have enough clean output!

Haha I'm not worried about it. This is just meant to be a low powered bedroom amp, a few watts of clean would be more than enough. However with the transformers I bought it could be made to run 6v6's without much trouble too.

I did see your trinity build. It looks very nice. Was quite helpful for the VVR since I was unsure what MOSFET to pick now that the NTE is long gone. I'm also thinking about giving that tru-oil finish a try. It looks really good. Might mix it up with some yellow linseed oil based die to give it a bit of that 'tweed' color. I'll probably keep the volume control's separate since with the split cathode configuration it will be nice to be able to dial in different proportions of each channel.

[xtian]

Good plan. Looking forward.

[strelok]

Alright time for an update. Got the brazing done today. Learned some lessons in the process. Namely, heat causes metal to expand and warp. The pieces of aluminum angle that I cut that fit perfectly and held themselves in place didn't stay in place so well once the metal started getting hot. Unfortunately I don't have a clamp long enough to hold them in place, so it took some finagling. I realized last night after doing a trial on some of the scrap angle I had left over that the torch was going to take absolutely forever just to heat up the metal for one joint. So I decided to place the chassis over a gas burner to provide some more heat. This worked really well except for the fact that it discolored the top of the chassis and caused it to warp some. I had to redo a couple joints to get it more level and even. Its still FAR from how I would have liked but, it is what it is and its usable. Think I might name the amp wonky, given the outcome of the chassis The upside is the joints came out strong and now the chassis feels stiffer than an eight Viagra erection.

The next time I do this, I'm buying one of those $40 sheet metal brakes from harbor freight and I'm going to do it all in one piece. Add an extra 6 inches to the width so I can just bend a 1 inch lip and a 2 inch side so that all that needs to be done is braze or weld the corners. I really did underestimate the strength of the .06 aluminum, thought it would be much more flimsy. Now that I know that the angles are totally unnecessary.

When it was all done and over with the chassis was quite yellow and discolored with a fair bit of run off from my shitty brazing work. I decided to grind some of it down to hide my shame with a dremel tool. I liked what the grinder did to the aluminum so I decided rather than spend an hour sanding I would do that to the whole exterior of the chassis. I think it looks pretty cool. Maybe not so great in the pics, but in person its nice, and eh its something different haha.

Got all the holes drilled and the major components installed without too much trouble. Tomorrow the only mechanical stuff left will be to install the terminal strips then I can get on to the fun stuff. Who knows might even have it up and running tomorrow night if there aren't anymore major fuck ups.


http://imgur.com/a/b2dBa

[xtian]

Felling your pain,bro.

[strelok]

Good news though! I ran into the owner of the company I work for today at the shop. He talked me into sending it along with some of our other metal work to get powder coated. So I can quit the mental firestorm as to whether or not I like the grinder finish lol. He recommended I have all the holes drilled before it goes off so I got that done today.

As for the wonkyness of the chassis, I was able to fix a large portion of it. Part of the problem was the chassis was not sitting flush with the end pieces, so I put a c-clamp on the end, reheated the joint with the torch and burner, as the joint melted I tightened the clamp down to make it square and flowed a bit more of the brazing rod in to make sure I didn't get a cold/shitty joint (or whatever the brazing equivalent is). The only downside was a lot of the molten brazing material ran down the side onto the front, luckily I caught it while it was still pretty hot, melted it some with the torch and was able to flick most of it off with the rod. Then I ground it flat with the dremel. Did a bit more work with hammer and flattened the top out a bit too.

It looks a lot better now. I'm not ashamed of it anymore Its definitely not perfect but it will do. The powder coating will cover up my shitty brazing work and overall I think it will look pretty nice. I'm definitely feeling a lot better about how the project is going now. Even if I have to wait a week or two for the powder coating.

[tubeswell]

These seem like a bargain

I have something similar on my workbench. Perfect for chassis folding

[img:225:225]http://thumbs3.ebaystatic.com/d/l225/pi ... 9828_1.jpg[/img]

[strelok]

Yeah definitely getting one of those if go this route again.
Chassis went off to the powder coating yesterday. Meant to take pics before it was dropped off but my battery died in my camera. Should be back in couple weeks. Might have to pull out my SE express and see if I can get rid of that stupid oscillation to keep me occupied in the meantime.

[Structo]

I meant to say you should put masking tape where you want your grounds to be to prevent the problem of grinding that powder coat away.
Or the tube socket mounting holes as well.

That stuff is tough!

[strelok]

Yeah it would have made it a little easier. However I'm used to having to do it though as all the amps I build for work need it done for the grounds as well. The dremel takes care of it pretty quick. This particular powder coat isn't the worst I've ever come across when it comes to that, thankfully. The rest of the holes *should* have enough clearance to allow the sockets/pots ect to fit without any scraping or grinding, though we'll find out when I get it back.

[strelok]

Chassis came back from the powder coat today. Looks pretty nice. I think it turned out alright for my first time bending a chassis. Now on to the building. Oh wait we're out of terminal strips. Fuck! Time to start scrounging

[img2976]http://i.imgur.com/OjXMXU4.jpg[/img]

And a few more pics:
http://imgur.com/a/jmJYt

[M Fowler]

The chassis bending and powder coat turned out very nice.

You probably know this already but doesn't hurt to remind people of simple details. Make sure if the inside of chassis is powder coated too that you will need to sand grounding points so plan that out.

Mark

[strelok]

Thanks! Yeah its coated on the inside, should be no problem to take off with the dremel tool. Also learned from the last build I did that if you're not soldering grounds to the back of the pots its important to grind off the area around the holes so the body gets grounded as well. Otherwise terrible squealing results. Maybe not so much in an amp like this but in the SE express it had me chasing my tail for a bit.