Given enough peeps and the fact that we don't have to source each and every components plus take advantage of volume shopping, if any, it should be possible to add in some float for a "free kit" or at least a set of nice irons to motivate Craig for his next build!!!
Whoa, hold up guys! I don't want to be a buzz kill but...
I'm more than happy to share my schematic, case and top layout drawings, and the BOM with you guys. But I'm not interested in putting together a kit, organizing a group buy, or creating a set of assembly instructions. I've got way too many other projects I want to get started on and technical writing is definitely not my strong suit. I also really don't enjoy dealing with vendors, ordering, receiving, shipping, or that sort of thing. Sorry
To give you an idea of what this 12 wpc single ended tube amp costs, here is a partial BOM of just the big ticket items.
Output transformers (2) - Edcor CXSE25-5K - $91 each
Obviously you can substitute some cheaper components and save a little. But the above adds up to $518 and that doesn't include the case, tube sockets, switches, power jack/cord, fuse and holder, speaker binding posts, RCA jacks, resistors, wire, nuts and bolts, etc....
I think the "group buy" aspect is more for roman machining. If you are willing to share a BOM, schematic, and drawings I believe that is more than generous and what "we" (speaking for myself) would be thankful for.
Roman, do you have any tips for AL CNC? (on a regular wood router CNC)?
Holding the work-piece down is very important. I just screw brass or AL to spoil-board. You can run the first pass at 0.0001 and use additional screws where needed. Alloy may be suitable or not for machining. Jig Plate machines like butter. 360 brass machines well too. 260 brass is horrible to cut. Mike was in my shop then I was cutting it. It's a nasty and loud noise! Feed and speed are also very important. Mill fabricators will provide free online calculators. That also depends on how powerful (or torque capable) your spindle is. Metal CNCs have high torque, low speed spindles. I don't think standard spindles go much over 7000rpms. Wood CNC spindle will have lower torque and high speed capability.
I think the "group buy" aspect is more for roman machining. If you are willing to share a BOM, schematic, and drawings I believe that is more than generous and what "we" (speaking for myself) would be thankful for.
Well, it was just an idea. I can certainly make good looking casework and drilling and machining a piece of AL is not that big of a deal. But soldering the amp together and testing it, is not something I want to do at all. Let's play with it a bit more and see if there are couple of guys here who love electronic work but cant glue 2 pieces of wood together, let alone, drill accurate hole on non ferrous metal.
I personally love working with the aluminum. For these tube amps the aluminum plate is generally 0.062 - 0.090" thick. So I just use my drill press, a couple hole saws, a knockout punch, and hand files. The hand filing takes quite a bit of elbow grease, but it's gratifying when it turns out just the way you want.
A spring-loaded center punch really helps locating accurate holes. Drilling a small pilot hole is mandatory. Harbor Freight sells a decent center punch for <$5.
But my favorite part is designing the layout and wiring it to maximize performance and give that tidy and intentional look. I enjoy bending component leads and slinging solder
I know, I know... a picture is worth a 1000 words... and I will take some and post them asap. But just an update. I had work off today and was able to finish the power supply section. Things are falling into place better than I designed. I am getting really excited about this amp project. I have made several significant improvements over the first build and even some over the beta prototype. This power supply is an order of magnitude better than the first (which sounded quite good). For S&G's I weighed the amp thus far. Holy crap... 41.5 pounds!!!
It might not look like the prettiest/cleanest layout, but there are very specific reasons why I placed things where they are and how every wire is routed. From experience I have learned how to make a hum free tube amp.
The power supply design is a full wave tube rectifier topology followed by a CLCLC filter for the output stage, followed by another LC filter for the gain stage. AC ripple at the output will be in the micro-volt range.
I just finished building everything except the shielded line-level wiring from the RCA input jacks to the Alps volume pot.
I powered up the beast for the first time tonight... Incredibly great results!!! The B+ voltage was designed to be 400 Vdc. Measures B+ is 408 Vdc. Everything else is well within 5%. AC ripple is less than 50 uV. Power transformer core is barely warm to the touch after 30 min.
Can't wait to hook up a pair of DIY speakers and have a good listen.
Very nice indeed. What are the options for swapping tubes after build...(for grins)? Im guessing there will be some biasing involved if " rolling" is an option?
Ani, I hope to finish the input wiring when I get home tonight, then take a few pictures.
Nick, two different power tubes can be rolled, and two different driver tubes. For a driver tube the Russian 6N1P sounds great and they are cheap (like $6, only one needed). That's what I used in my prototype. A step up would be a 6DJ8 which I'll be testing. Those can range from $13.99 for a modern production JJ, all the way up to $200 for a rare NOS tube. For power tubes my design is optimized for KT88 tubes, but will also work well with EL34 tubes. I ran some EL34's in my prototype and they sound fantastic. You give up a couple of watts of output and a tiny bit of bass response, but they have really great mids and highs and they can be purchased at tubedepot.com for as little as $13.99 each.
Forgot to say the tubes mentioned above can be rolled with no bias changes required at all.
I was able to finish the input wiring and take a few pictures... time for supper now, then time with the family. I'll post pics after that if I don't pass out (rough day at work).
I still need to secure the line in wiring, fabricate and install a bottom cover, turn and install some cool feet, and turn and install a cool volume pot knob.
Comments
Whoa, hold up guys! I don't want to be a buzz kill but...
I'm more than happy to share my schematic, case and top layout drawings, and the BOM with you guys. But I'm not interested in putting together a kit, organizing a group buy, or creating a set of assembly instructions. I've got way too many other projects I want to get started on and technical writing is definitely not my strong suit. I also really don't enjoy dealing with vendors, ordering, receiving, shipping, or that sort of thing. Sorry
To give you an idea of what this 12 wpc single ended tube amp costs, here is a partial BOM of just the big ticket items.
Output transformers (2) - Edcor CXSE25-5K - $91 each
Power transformer - Allied 6K7VG - $53
DC chokes (2) - Triad C-14X - $19 each
Output tubes (2) - Genalex Gold Lion KT88 - $60
Rectifier tube - Sovtek 5AR4 - $20
Driver tube - 6DJ8 - $30
DC filter caps (2) - ASC 60uF - $18 each
Interstage coupling caps (2) - Mundorf Supreme .33uF - $13 each
Volume pot - ALPS - $13
Obviously you can substitute some cheaper components and save a little. But the above adds up to $518 and that doesn't include the case, tube sockets, switches, power jack/cord, fuse and holder, speaker binding posts, RCA jacks, resistors, wire, nuts and bolts, etc....
You are being volen-told!
I think the "group buy" aspect is more for roman machining. If you are willing to share a BOM, schematic, and drawings I believe that is more than generous and what "we" (speaking for myself) would be thankful for.
Alloy may be suitable or not for machining. Jig Plate machines like butter. 360 brass machines well too. 260 brass is horrible to cut. Mike was in my shop then I was cutting it. It's a nasty and loud noise!
Feed and speed are also very important. Mill fabricators will provide free online calculators.
That also depends on how powerful (or torque capable) your spindle is. Metal CNCs have high torque, low speed spindles. I don't think standard spindles go much over 7000rpms. Wood CNC spindle will have lower torque and high speed capability.
Let's play with it a bit more and see if there are couple of guys here who love electronic work but cant glue 2 pieces of wood together, let alone, drill accurate hole on non ferrous metal.
A spring-loaded center punch really helps locating accurate holes. Drilling a small pilot hole is mandatory. Harbor Freight sells a decent center punch for <$5.
But my favorite part is designing the layout and wiring it to maximize performance and give that tidy and intentional look. I enjoy bending component leads and slinging solder
The power supply design is a full wave tube rectifier topology followed by a CLCLC filter for the output stage, followed by another LC filter for the gain stage. AC ripple at the output will be in the micro-volt range.
I powered up the beast for the first time tonight... Incredibly great results!!! The B+ voltage was designed to be 400 Vdc. Measures B+ is 408 Vdc. Everything else is well within 5%. AC ripple is less than 50 uV. Power transformer core is barely warm to the touch after 30 min.
Can't wait to hook up a pair of DIY speakers and have a good listen.
Nick, two different power tubes can be rolled, and two different driver tubes. For a driver tube the Russian 6N1P sounds great and they are cheap (like $6, only one needed). That's what I used in my prototype. A step up would be a 6DJ8 which I'll be testing. Those can range from $13.99 for a modern production JJ, all the way up to $200 for a rare NOS tube. For power tubes my design is optimized for KT88 tubes, but will also work well with EL34 tubes. I ran some EL34's in my prototype and they sound fantastic. You give up a couple of watts of output and a tiny bit of bass response, but they have really great mids and highs and they can be purchased at tubedepot.com for as little as $13.99 each.
I was able to finish the input wiring and take a few pictures... time for supper now, then time with the family. I'll post pics after that if I don't pass out (rough day at work).
I still need to secure the line in wiring, fabricate and install a bottom cover, turn and install some cool feet, and turn and install a cool volume pot knob.