Slow "Scope Creep" Amp Build

[PeteG45]

This may be the slowest amp build in the world. It's been in the planning stages for months and even up to last week is still changing. I actually started the build process on 09/10/09 and I haven't gotten far but it is moving forward.

I don't have much time to work on it and I don't expect to have it done until Christmas of maybe after. Definitely by New Years. Or maybe Valentines Day. Well you get the idea.

I started with the Weber 5F2A layout and started making changes. Here is the list to date:

second 6V6 in parallel
separate cathode bias so I can use one tube or two
switchable cathode bias resistor to support single 6L6
upgraded OT to WSE15
added presence control
added resonance control
added impedance selector switch
added NFB switch
added voicing switch a la the Two Stroke amp

I think that's most of it. Here is the layout:

[PeteG45]

OK so here's what I've actually done. I started with this on 09/10/09



Which turned into this

[PeteG45]

A little while later I got a little more done



and then



Once the holes were drilled I test fitted the sockets front controls and jacks. I couldn't resist putting in some junk tubes and taking a picture. It's the first time that it ever looked like an amp. Woo hoo!

[gayler]

Very cool! How thick is that chassis? Did you bend it yourself?

[PeteG45]

The aluminum was about .06 inches thick. It is 3220 aluminum I think. Yes I bent it myself using a simple jig and a 25 year old Black and Decker Workmate (greatest tool in the world). The jig was a flat board with a stop 2.5 inches from the end. The aluminum and the jig got clamped in the workmate so that the top edge of the jig was just about the surface of the workmate. Then I sandwiched the the rest of the aluminum between two clamped boards so that it could only bend where I wanted to to. Then I applied my "Tele belly" and away it went.

Not perfect but it came out pretty well and only $13 and change. I disassembled the jig and used it for the end pieces.

[Groovey Records]

Well to me you've done a whole lot of work.

SO do I understand you are going to build a single ended parallel 6V6 Two Stroke Amp that can also be run on one 6V6 ?

How will the NFB switch effect the Presence Control

How will the Voicing switch affect the resonance control ?

I always wanted to build Dave Hunters original 2 stroke and never bought into the "it was to hard for most with little advantage over the new design" reason for not continuing with it.

[PeteG45]

Yup. Like I said it started out as a 5F2A and evolved into this. I'm not sure what impact the NFB switch will have on the presence control which will be part of the fun. The same goes for the voicing switch and resonance control. It's funny how close this ended up to being like the Two Stroke. That was not my intention and the only thing that I took directly from the two stroke was the voicing switch.

[PeteG45]

This past weekend I got around to testing my caps for their inner and outer foils and assembling my front controls. I used the front side of the chassis as an installation jig to hold all of the parts while I soldered them in place. Not all of the connections are soldered yet as I'm still waiting on some wire and parts from Weber but at least one end of each component is soldered.

Because the voicing switch was a late addition that I didn't account for I had to route a channel into the oak end cap to more comfortably fit the the switch and it's wiring. The 1M Ohm resistors should keep the caps charged and reduce popping when changing voices.

I did the bus the way that Gabi from "SoundGarageTales" demonstrated on youtube. If you're thinking about building an amp and you haven't watched his videos I highly recommend them. Because I use Switchcraft jacks I bent the ground bus out and over the jacks for plenty of clearance. I left enough of one of the 1M resistor's legs to be able to wire that directly to the bus when I assemble.

Here are some more photos:

[PeteG45]

Just for clarification, from the input jacks the controls are Volume, Tone, Presence and Resonance and the voicing switch is on the other side of the input jacks. In the first photo the switch is actually mounted as it will be when the amp is done as I was testing the index hole for the switch.

I just checked FedEx and my next batch of parts are "out for delivery"!

This is the notch in the end cap. The notch comes pretty close to the screw hole but it's oak so it should be fine. I'll sand the edges down so that it can't hurt the wires of my knuckles.

[Cap'n Kier]

Looking great!

I've been planning my build for months now and haven't got nearly as far as you!
I've got some odd parts but no money = very slow progress!

I especially like the ground bus - will have to check out those videos ;)

Will you be making your own cabinet?

[PeteG45]

I already have a 1X12 extension cabinet (a project from a few months back) that I'm using with another amp. I have a bunch of oak 1X10 shelving that I'll use to build a head cabinet when I'm done. It'll be as heavy as lead but it should look nice and my wife will appreciate that.

I understand the money thing, that's part of my slow progress too. That and very little time. My wife and I are in the final stages of the expensive process to adopt a second daughter from China. Between the adoption costs and hopefully traveling to China in November this project doesn't get the attention that it might otherwise. That's OK with me, I'm getting more out of it because of this ridiculously slow pace.

"Scope Creep" is doubly apt because the scope keeps creeping and the build is barely creeping along.

[G-log]

Great so far!Nice idea for bending up the chassis.I built a 5f2-a/ Two stroke from an old stereo and am really pleased with it-I never stop the tweaking!I think I might try the parallel tube setup like yours next. What Power transformer are you using? I am considering an upgrade for mine and I am not sure which one.

[PeteG45]

The PT is the Weber W022772 and I'm using the Weber WSE15 for my OT.

Bending the chassis ended up being easier to to then I thought. The tough part was the initial push because I didn't know what to expect. Kind of a leap of faith. The second bend was easier.

[Jelle]

Great work and very interesting! Thanks for documenting it.

[Groovey Records]

delete duplicate

[Groovey Records]

I hope you find a way to make a cab with both 8" & 10" speakers

have you seen this?

[Cap'n Kier]

I'm planning on building a "stretched" 5E3 cab for my Two-Stroke to use an 8" + 10", but with a little more space to try out 2 x 10" if I wanted in the future...

Damn I wish I could start it already!! :D so much to learn still!

[PeteG45]

I have an extra piece of baffle that hasn't been cut yet. If i remove the side baffle mounting cleats from the cabinet (leaving just the top and bottom cleats) I might be able to squeeze an 8" and 10" speaker in there.

I got my board, wire and some parts last night. I like the way Weber measures wire. The extra few inches of each color eliminates my concerns about not having ordered enough wire. The orange and red wire is almost exactly the same color. I had planned to use the orange to make the presence control wiring stand out but, unless I'm partially color blind, it won't make much difference visually.

The board is a Weber TB-3 which is a generic eyelet board. I spent some time placing the components on the board and adjusting the spacing to line up with tube sockets, switches and the chassis. I'm going to have to cut an inch or two off of the end of the board but I knew going in that this would be the case. I'm in the process now of redrawing my layout to the actual hole and component placement. I can finally see clearly how things are going to connect for shortest wire runs and now I can add the wire colors that I'll actually use.

I'll post again when I have my redrawn layout complete.

Thanks for all of your comments.

[PeteG45]

Here is the updated layout drawn more to scale. Based on how the tube sockets line up with the board this is very close to what it should look like. The P.T., rectifier and other power components will be placed further to the left then shown in the image so I will have a little more room on the left end of the chassis.

I also had to add some wire because the space across the three rows of eyelets was wider than some of my components. Something to keep in mind if you plan to use one of these boards. Even the Weber "extended lead" resistors are not long enough the reach across all three rows of this Weber board.

I'm planning to use a piece of shielded cable from the volume pot to pin 7 of my preamp tube. I'll ground it at the pot. Is this a good idea or should I just use a piece of 22 ga. solid core wire?

[PeteG45]

OK next revision. After mounting the input jacks correctly (how they will actually be mounted, not for soldering ease) I realized that I needed to allow a little more room for the input jacks so I'm going to remove the upper right corner of the board. Turns out that the flexibility of this board is pretty convenient.

[PeteG45]

Here is a shot of the board after I notched it for the input jacks and another one partially populated and some joints soldered. I'm amazed at how much I've learned already from this build. Like don't bend the chassis until you understand the dimensions of the board. Oh well, so far no fatal blunders.



and

[fernando]

nice!

[Docron10]

nice job

[PeteG45]

Thanks guys. I found a local shop that should have filter caps so I might get the board finished up this weekend. I just need to find time to get over there. I should have gone today at lunchtime. Oh well, maybe thursday.

[PeteG45]

I went down to the shop and his prices were a bit high. Basically double of what Antique Electronic Supply charges. I'd like to support him since he's a new shop but he looks pretty busy with a lot of repair orders. I think that I'm going to have to save the money and buy online.

[PeteG45]

This is probably not the update that your expecting. My wife, my daughter and I are going to China to adopt our second daughter! Probably in the next few weeks!!!

This does mean that the amp build is on hold for now. We're going to be pretty busy for the next five weeks or so and then it's going to be Christmas WITH TWO DAUGHTERS!

This has been in the works for four years and now it's finally coming together.

[big-daddy-59]

Congrats on the new adoption, Pete.You warned us that it might take you till Valentine's to finish this amp. Let's just hope you don't come up with any more ideas for it. Else you will never get done.

[PeteG45]

Thanks Big Daddy. Maybe Santa will bring me a set of trannies for Christmas.

With God as my witness I will finish this amp by Valentines Day!

[Scott S]

Originally Posted by PeteG45

Thanks Big Daddy. Maybe Santa will bring me a set of trannies for Christmas.

With God as my witness I will finish this amp by Valentines Day!

[Ben Harmless]

I, Benjamin M. Harmless, do give you my permission to adopt a child and delay your amp project further.

I'll keep reading this thread though!

[PeteG45]

Originally Posted by Ben Harmless

I, Benjamin M. Harmless, do give you my permission to adopt a child and delay your amp project further.

I'll keep reading this thread though!

Whew, that's a relief. We were afraid that you wouldn't let us go :o).

We got our travel dates and we will be gone on Thanksgiving Day. It means we'll have to catch the Cowboys and the Aggies games in LA. I wonder it the Texas/Texas A&M game will even be a nationally televised game?

I think that I'm going to box up the chassis and parts that I have to protect them from damage. :o(