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Old 18th November 2005, 07:24 PM   #1
santiu is offline santiu  United States
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Default Enclosure suggestion/questions

Hey guys, so my K-12M kit arrived in the mail the other day, and I can't wait to get started.

I had a few questions about an enclosure though. I was planning on using a copper plate on the top to mount everything too. Is ~1/16" thick a good thickness, or would you go thicker/thinner.

Also, any ideas on making the transformers look nicer? They are pretty ugly with their yellow plastic insulation on the windings. In fact if it wasn't for all the plastic, I wouldn't mind how they look. Can I paint them? Alternatively I was thinking of making covers to just go over the whole thing. Are there any heat issues with transformers I need to be aware of?

Can you guys recommend a good source of knobs? I'm looking for a retro-y plastic/resin knob for the volume control.

thanks a bunch I can't wait to get started building this thing!
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Old 18th November 2005, 07:56 PM   #2
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Default AES

Quote:
Can you guys recommend a good source of knobs? I'm looking for a retro-y plastic/resin knob for the volume control.
Antique Electronic Supply
www.tubesandmore.com
And not just knobs but lots of other retro goodies as well.

You could make some covers for your xfrmrs like the ones suggested for the Mullard 5-20. Drill some evenly spaced ventilation holes near the top & bottom edges (etc.) and paint them as you like.
1/16" copper plate should be thick enough but as you know copper will oxidize over time, so you will have to apply something to prevent this.
I'm not familar with the K-12M kit you speak of. Do you have a link(s) to it or a description?

Good luck & Cheers
Wayne
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Old 18th November 2005, 08:58 PM   #3
santiu is offline santiu  United States
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wow, great source of stuff... thanks!

As for the kit:
http://www.s5electronics.com/gpage1.html
http://ca.geocities.com/gmilitano/Tubes/K-12M/K-12M.htm : this is a page from a fellow diyAudio member who built the kit

As for the copper. Yeah, I'm aware that it will tarnish over time. I'm sort of ignoring that because I don't know what to do about it. I was thinking of trying this product Everbrite. Do you know of other solutions? How about an automotive polymer based wax?

thanks again for the help!
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Old 19th November 2005, 01:10 AM   #4
Sherman is offline Sherman  United States
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Quote:
Originally posted by santiu
wow, great source of stuff... thanks!

...As for the copper. Yeah, I'm aware that it will tarnish over time. I'm sort of ignoring that because I don't know what to do about it. I was thinking of trying this product Everbrite. Do you know of other solutions? How about an automotive polymer based wax?

...

I second the vote for Antique Electronic Supply. Great stuff there.

As for the copper plate, I would drill all the holes and whatever other openings you need first. Then clean and polish it and spray it with a clear laquer. That should seal it and keep it from tarnishing.

I built one of those kits as my first tube project and I still use it. I built a wooden base for mine and mounted the PCB and transformers on wooden cross-pieces inside the box. I then cut a piece of aluminum to fit in the box, drilled the holes for the tubes and cut holes for the transformers to poke through. Nothing is actually mounted to the aluminum, it serves as a cover.

Keep in mind that when you build the kit, if you want to do a "tube out" chassis that you will have to mount the components, except for the tube sockets on the "wrong" side of the PCB in order to mount the PCB close enough to the top plate of your chassis.

If I were doing this kit again I would mount the PCB to the top plate with 1/2" standoffs and mount the transformers either under the top plate (you are right, they are ugly!) or on the top plate with some type of cover. The power transformer does get quite hot so some ventilation would be required in any cover you might make.
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Old 19th November 2005, 04:18 AM   #5
santiu is offline santiu  United States
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If I put the transformers inside the case, do I need to worry about where I route the speaker wires?

I was going to put the transformers behind the tubes, but I was also planning on having the speaker terminals on the back of the enclosure. I just want to make sure I don't introduce any noise into the signal.

thanks!
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Old 19th November 2005, 12:46 PM   #6
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Talking I'm getting old

Quoting myself:
Quote:
Originally posted by: cogsncogs
I'm not familiar with the K-12M kit you speak of.
How could I not know?! I even have the article in AudioExpress!
Yes that's a very good kit for the money, using the 11MS8 triode-pentode!
I have a suggestion; If you mount the xfrmrs at the rear of the amp you could make one cover/enclosure mounted all the way across the rear of the amp to cover all of the transformers. Put the ventilation holes on the back-side of the cover so they won't be visible from the front. Also a cage would look great!

Quote:
Originally posted by: santiu
If I put the transformers inside the case, do I need to worry about where I route the speaker wires?
If you mount the input and output connections on the rear of the amp, keep them as far away from each other as practical and use shielded/screened coax for the input wiring and insulate the input RCA jacks from the chassis, and only ground (circuit ground) the coaxial cable on one end, usually at the volume control. Hope that makes sense! That should work fine.
Also at the input jacks place one or two 4700pf to .047uF caps (ceramic caps or polyester/Mylar, would be OK in this position, no need to get 'fancy'!) from the grounds of the jacks to the chassis depending on what type of shielded cable you use i.e. two separate cables or dual signal conductor with one shield (braided shielding is best IMO) i.e. balanced microphone cable, as close to the input jacks as possible.
If my description is unclear I could draw up a little diagram and post it here for you. Keep us posted!

Cheers
Wayne
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Old 22nd December 2005, 05:49 PM   #7
santiu is offline santiu  United States
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Okay, I finally have some time to put in some more work on my K-12M kit (been so busy lately). I've got the PCB all soldered up (with the components on the "back" side). I've got a couple basic questions that I was hoping you guys can help me out with:

1) Should I replace the 2-wire power cord with a 3-wire one? If so, should I also ground (i guess this would be earth ground) the metal plate that everything is being mounted too (which shares the PCB ground)?

2) I picked up this switch last night @ RatShack. Is it big enough:
http://www.radioshack.com/product/in...ductId=2062518

3) Does anybody have a wiring diagram I can see for how I should wire up the power?

4) Is there really a big difference with gold versus regular jacks/speaker terminals? I got this for the input terminal last night:
http://www.radioshack.com/product/in...ductId=2103425
I know it has 2 extra terminals on it, but I'm mounting the terminals to wood, so this makes it nice and easy that they are already mounted their own board.


Quote:
Originally posted by cogsncogs
If you mount the input and output connections on the rear of the amp, keep them as far away from each other as practical and use shielded/screened coax for the input wiring and insulate the input RCA jacks from the chassis, and only ground (circuit ground) the coaxial cable on one end, usually at the volume control. Hope that makes sense! That should work fine.
Also at the input jacks place one or two 4700pf to .047uF caps (ceramic caps or polyester/Mylar, would be OK in this position, no need to get 'fancy'!) from the grounds of the jacks to the chassis depending on what type of shielded cable you use i.e. two separate cables or dual signal conductor with one shield (braided shielding is best IMO) i.e. balanced microphone cable, as close to the input jacks as possible.
If my description is unclear I could draw up a little diagram and post it here for you. Keep us posted!
Could you explain this a bit more? I'm a bit confused. I understand what you mean about insulating the inputs from the chassis, but I don't quite understand the capacitors. Also, could you point out to me what type of wire I should use to run the inputs to the board (link would be good).

Looks like I need to make another small order with Parts-Express for some binding terminals (ones that I can just screw onto the wooden back, or are long enough to make it through the wood), so if you guys think of anything else I might want, please advise!

thanks a bunch for all your help!
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Old 22nd December 2005, 06:07 PM   #8
Sherman is offline Sherman  United States
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I would replace the 2 wire AC cord that comes with the kit and definitely not use that clumsy inline on-off switch. The switch you have chosen will work fine.

To use a 3 wire, grounded AC power cord just connect the green (earth ground) wire to the chassis (or your copper plate). Drill a hole through the plate and drop in a 4/40 or 6/32 screw. If you have a crimp connector tool crimp a spade connector on the end of the green wire and attach it to the screw with the nut.

Wire the other two wires just like you would if you used the 2 wire AC power cord.

I haven't heard any difference between gold-plated jacks and connectors and nickel-plated or rhodium plated. I've used them all. But I have never claimed to have 'golden ears'. The advantage of gold plating is that it doesn't rust or tarnish, and rust or tarnish on your connectors will affect the sound.

To mount your input jacks and speaker binding posts to the back of your wooden case you might consider mounting them to an aluminum or copper plate then cutting a hole in the wood back and mounting the plate from the inside of the case. Attach it with six or so small stainless steel wood screws. You can run a ground wire from that plate to the earth grounding screw on your main copper plate. You will want to insulate your jacks from the plate however.
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Old 29th December 2005, 04:37 AM   #9
santiu is offline santiu  United States
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Default Very Very Slowly making progress...

Well, I test fit some stuff today. I'm slowing making progress... hopefully I'll make the frame (from those oak boards it's sitting on) this weekend.

The input jacks are in the mail. They will be mounted in between the volume knob and the output transformer behind it.
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Old 29th December 2005, 04:40 AM   #10
santiu is offline santiu  United States
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Default one more with the flash

mmm... shinny, and it's still unpolished and tarnished
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