Hi everyone,
I figured instead of leaving more casual droppings in the original thread here, I would start my own in hope of sharing what I've learned as I go. After following the original thread
started in Sept. of 2009, I had to re-read the whole thing about 4 times and continuously go back to it. 1890 posts by really cool people with a ton of insight. What started all of this off for me was my first ever attempt at putting together a Chinese 6P6P tube preamplifier kit. I figured if I could do that, I could do anything. Wrong! The preamp was a success in part thanks to some kind folks around here who helped get me through it. I went in search of DIY amp sites and came across Pete Millett's site and his DCPP 'Engineer's amp' here . Further reading and searching put me onto the huge thread mentioned above. Many people have been through there and with the help and exploits of George of Tubelab, the Big Red Board was taught to do new tricks that far exceed the initial specs. This is where I bit off more than I could reasonably 'chew'. I'm a child of the 60's and a teen of the 70's and an ex Punk of the 80's. Loud was and is the way I like it when I can still get away with it 🙂. I latched onto the idea of almost 100 watts per channel and haven't looked back. I decided to go with the method described in the original thread using 6HD5 and 6GU5 tubes, 2 Antek AS-2T230 toroidals (1 to power the board and 1 to power the plates of the Edcor 100 watt output transformers). A small additional toroid will provide bias power.
I started this off making 2 mistakes. Mistake #1 was guesstimating the size of the chassis I would need before having everything else in hand. I figured if I had to wait 6 weeks for Edcor output transformers and a couple for the Antek toroidal transformers, I'd have something to do by drilling holes and populating the Big Red Board. I ordered my chassis and it was here in a week from Eastern Canada. I figured hey...a couple of extra inches over the size recommended by Pete Millett and I'd be ok. Yeah right! The chassis looked great, was plain aluminum and had no holes punched. It would have been great as a chassis for a guitar amp but in no way would it properly support 30 lbs of transformers.
The second mistake I made was not taking my time making the holes with 'close enuf' electrician's knock out punches. I figured I could always enlarge what was too small and live with what was too big. 'Close enough' only counts for horseshoes, hand grenades and crap fights'! To be honest it could have worked but if one is going to put an investment of time and money such as is required here, do it right and don't be too frugal. It bit me in the butt for sure. Here is a pic of the first chassis as I abandoned it.
Finally, after a shorter than anticipated wait, the Edcor output transformers arrived. Still smelling of fresh Edcor blue paint, these things were beautiful!
The Anteks are definitely ugly ducklings next to these babies. See..you can tell I'm getting hooked by referring to transformers as sexy and beautiful. Here is a pic
of the heavy stuff
This is where it starts.... I needed a chassis that would support the weight and give ample room for addons should they be needed. The Edcors are just under 4" wide x 5" deep.
The Anteks are roughly 5 inches across and 2 and change high. I wanted to place a toroid on top and one 'below' deck. The can to cover the toroid uses up about 6" x 6". Spaced nicely I figured on 16 inches. Height I went with 5 inches and a depth of 16 inches. This puppy will be big! I went chassis hunting and eventually came across a man on the Chinese mega site TaoBao. Think of Amazon with a zillion vendors and everything in the wrong language. After a bit of a struggle I managed to sign up for an account and bought a chassis.
He agreed to cut the holes with CNC on the face and the top. I didn't get the transformer holes cut as I wasn't sure of placement yet. The 4 holes in the faceplate are for 45mm panel meters. The first ones I bought ended up kicking me in the butt again as they weren't the best quality. I did find some nice ones with real glass and everything 🙂. To get the holes done I had to provide the gent with drawings that he could load up and have the machine follow. Pete supplies a .dxf cad drawing of the amplifier's top panel with all of the components. This file can be loaded up in any CAD software and the component layers turned off. I created a top panel the size of the new chassis and cut and pasted the board
tube socket cutouts and standoff screw holes. The front panel was a simple scaled rectangle with 4 spaced 46mm holes drawn. After that it was a simple matter of txt chat with the shop owner and he confirmed the file was good. If you want the store link or cad file feel free to bug me 🙂
Here's the new chassis as received. It arrived broken down and really well packed for the trip. He included enough anodized Phillips
screws to build 5 chassis! Workmanship and quality is flawless. One couldn't get a better fit. The front panel is 8mm thick!
Next we have to work on laying out everything and making more holes. Pete supplies a pdf file of the top panel that needs to be scaled up in size.
Scale it to 150% and you'll have it scaled perfectly. I cut and pasted the board in 2 parts to be able to print on letter size, cut it out and taped the 2 pieces together.
It wasn't really needed but I like to see where the board will sit. Next was to print and cut out transformers. Edcor provides dimensional drawings and I roughly guesstimated the
toroidal can size. Nope, I ain't drilling those holes until I have the darn thing in my hands!
Here's the proposed layout. Should leave lots of room for extras like bridges etc. inside
As always, if this is too long winded, tell me to clam up! Most of it seems really basic but for us
beginners, it might prove useful 🙂
I figured instead of leaving more casual droppings in the original thread here, I would start my own in hope of sharing what I've learned as I go. After following the original thread
started in Sept. of 2009, I had to re-read the whole thing about 4 times and continuously go back to it. 1890 posts by really cool people with a ton of insight. What started all of this off for me was my first ever attempt at putting together a Chinese 6P6P tube preamplifier kit. I figured if I could do that, I could do anything. Wrong! The preamp was a success in part thanks to some kind folks around here who helped get me through it. I went in search of DIY amp sites and came across Pete Millett's site and his DCPP 'Engineer's amp' here . Further reading and searching put me onto the huge thread mentioned above. Many people have been through there and with the help and exploits of George of Tubelab, the Big Red Board was taught to do new tricks that far exceed the initial specs. This is where I bit off more than I could reasonably 'chew'. I'm a child of the 60's and a teen of the 70's and an ex Punk of the 80's. Loud was and is the way I like it when I can still get away with it 🙂. I latched onto the idea of almost 100 watts per channel and haven't looked back. I decided to go with the method described in the original thread using 6HD5 and 6GU5 tubes, 2 Antek AS-2T230 toroidals (1 to power the board and 1 to power the plates of the Edcor 100 watt output transformers). A small additional toroid will provide bias power.
I started this off making 2 mistakes. Mistake #1 was guesstimating the size of the chassis I would need before having everything else in hand. I figured if I had to wait 6 weeks for Edcor output transformers and a couple for the Antek toroidal transformers, I'd have something to do by drilling holes and populating the Big Red Board. I ordered my chassis and it was here in a week from Eastern Canada. I figured hey...a couple of extra inches over the size recommended by Pete Millett and I'd be ok. Yeah right! The chassis looked great, was plain aluminum and had no holes punched. It would have been great as a chassis for a guitar amp but in no way would it properly support 30 lbs of transformers.
The second mistake I made was not taking my time making the holes with 'close enuf' electrician's knock out punches. I figured I could always enlarge what was too small and live with what was too big. 'Close enough' only counts for horseshoes, hand grenades and crap fights'! To be honest it could have worked but if one is going to put an investment of time and money such as is required here, do it right and don't be too frugal. It bit me in the butt for sure. Here is a pic of the first chassis as I abandoned it.
Finally, after a shorter than anticipated wait, the Edcor output transformers arrived. Still smelling of fresh Edcor blue paint, these things were beautiful!
The Anteks are definitely ugly ducklings next to these babies. See..you can tell I'm getting hooked by referring to transformers as sexy and beautiful. Here is a pic
of the heavy stuff
This is where it starts.... I needed a chassis that would support the weight and give ample room for addons should they be needed. The Edcors are just under 4" wide x 5" deep.
The Anteks are roughly 5 inches across and 2 and change high. I wanted to place a toroid on top and one 'below' deck. The can to cover the toroid uses up about 6" x 6". Spaced nicely I figured on 16 inches. Height I went with 5 inches and a depth of 16 inches. This puppy will be big! I went chassis hunting and eventually came across a man on the Chinese mega site TaoBao. Think of Amazon with a zillion vendors and everything in the wrong language. After a bit of a struggle I managed to sign up for an account and bought a chassis.
He agreed to cut the holes with CNC on the face and the top. I didn't get the transformer holes cut as I wasn't sure of placement yet. The 4 holes in the faceplate are for 45mm panel meters. The first ones I bought ended up kicking me in the butt again as they weren't the best quality. I did find some nice ones with real glass and everything 🙂. To get the holes done I had to provide the gent with drawings that he could load up and have the machine follow. Pete supplies a .dxf cad drawing of the amplifier's top panel with all of the components. This file can be loaded up in any CAD software and the component layers turned off. I created a top panel the size of the new chassis and cut and pasted the board
tube socket cutouts and standoff screw holes. The front panel was a simple scaled rectangle with 4 spaced 46mm holes drawn. After that it was a simple matter of txt chat with the shop owner and he confirmed the file was good. If you want the store link or cad file feel free to bug me 🙂
Here's the new chassis as received. It arrived broken down and really well packed for the trip. He included enough anodized Phillips
screws to build 5 chassis! Workmanship and quality is flawless. One couldn't get a better fit. The front panel is 8mm thick!
Next we have to work on laying out everything and making more holes. Pete supplies a pdf file of the top panel that needs to be scaled up in size.
Scale it to 150% and you'll have it scaled perfectly. I cut and pasted the board in 2 parts to be able to print on letter size, cut it out and taped the 2 pieces together.
It wasn't really needed but I like to see where the board will sit. Next was to print and cut out transformers. Edcor provides dimensional drawings and I roughly guesstimated the
toroidal can size. Nope, I ain't drilling those holes until I have the darn thing in my hands!
Here's the proposed layout. Should leave lots of room for extras like bridges etc. inside
As always, if this is too long winded, tell me to clam up! Most of it seems really basic but for us
beginners, it might prove useful 🙂
Everything looks good so far. As impressed as I am with the chassis, I'm even more impressed you could navigate taobao. I've tried to create an account and use the website a few times and I just can't make it work for me.
Maybe time to put something together to help folks register there. I had found a tutorial somewhere a few years ago and just took a chance. TaoBao is a deep, dark place 🙂 I'm ashamed to say how much I landed that chassis for!
Today was a slow and lazy day (a good Sunday). The new panel meters arrived and I have to say I'm happy I grabbed them. These guys are made by Yutai Instrument and are available on AliExpress here. They are literally 1/2 the price landed from their store on TaoBao.. Nicely finished and they use real glass unlike my previous frugal experiments.
Installing them was pretty straight forward as the main holes were already cut. I asked my wife which way she'd like them and she chose to have only the faces visible vs. the entire front housing. Good thing! Mounting this way fit whereas front loading them would need hole enlarging. Weird because the drawings state it's the same size either way. If you are like me and haven't done this before, take your time. I needed to remove the panel and lay it down flat in order to mark holes for drilling and tapping. A small square will ensure these guys are straight up and down in relation to the front panel. If I had a suitable drill press this would have been a cakewalk but as it is, my precision little guy didn't have the reach. Trusty Makita to the rescue. Mark off the max depth you want to drill with a piece of tape on the bit and have at it. Just be careful to stay straight up and down and take your time. I am using m3 screws so 2.5mm is the hole needed for tapping. What I really hate doing is manual tapping. The small tap is tapered at the start and hardly starts threading before reaching the end. More research needed! Any machinists around?
Installing them was pretty straight forward as the main holes were already cut. I asked my wife which way she'd like them and she chose to have only the faces visible vs. the entire front housing. Good thing! Mounting this way fit whereas front loading them would need hole enlarging. Weird because the drawings state it's the same size either way. If you are like me and haven't done this before, take your time. I needed to remove the panel and lay it down flat in order to mark holes for drilling and tapping. A small square will ensure these guys are straight up and down in relation to the front panel. If I had a suitable drill press this would have been a cakewalk but as it is, my precision little guy didn't have the reach. Trusty Makita to the rescue. Mark off the max depth you want to drill with a piece of tape on the bit and have at it. Just be careful to stay straight up and down and take your time. I am using m3 screws so 2.5mm is the hole needed for tapping. What I really hate doing is manual tapping. The small tap is tapered at the start and hardly starts threading before reaching the end. More research needed! Any machinists around?
You're a brave man, I'm glad to see it turned out well!
Machinist here, not an expert by all means but I think you should look for a tap like the one to the left:
Thank you!! I'm off to find some. I'm trying to find a way to sneak a small drill press into the house too ;}
hello Ron:
I have faked bottom cutting bits by starting the hole with a normal tapered bit. Once it bottoms out you should have enough threads to use a bottom cutting bit. To make one I took a second tapered bit and ground the pointy bit off the end. You have to be careful to not overheat the bit or it will be too soft to cut. But with aluminium you should be okay. A bit of a MacGiever trick but it worked for me.
Of course with a bit of cutting oil you steel screw will also work for aluminium. Just blow out the chips so the hole is not filled up.
I hope this helps
I have faked bottom cutting bits by starting the hole with a normal tapered bit. Once it bottoms out you should have enough threads to use a bottom cutting bit. To make one I took a second tapered bit and ground the pointy bit off the end. You have to be careful to not overheat the bit or it will be too soft to cut. But with aluminium you should be okay. A bit of a MacGiever trick but it worked for me.
Of course with a bit of cutting oil you steel screw will also work for aluminium. Just blow out the chips so the hole is not filled up.
I hope this helps
Toroidal mounting question..I had an idea to avoid using the bolt that came with the Antek transformers. I did a quick search and didn't see the likes so either I'm onto something or I'm out to lunch 🙂 The idea I had was to use a 1/2 inch nylon threaded rod and nut. I've been reading too many horror stories about the dreaded shorted turn and didn't want to take a chance. The length of the rod is to be about 3.5 inches in length so it should be pretty strong. I will of course use the included large steel retaining washer and the rubber discs along with some extra rubber to raise the transformer a bit. Am I brain addled?
Nylon is a bad idea to mount a power transformer. Use the included bolt. A shorted turn is extremely easy to avoid, only let the bolt pass through one side of the chassis, finished! Seriously, don’t use nylon to mount a power transformer, that is wrong for many different reasons, the most of which are safety related.
Advice heard loud and clear! Thank you. I guess the worry is breaking/shearing off should bad things happen. I'll use the bolt. It will only be going through the top.
Yes, nylon experiences what is known as “creep”, it doesn’t stay in one place. It’s also not strong enough to reliably mount a transformer of that mass. The normal supplied steel bolt is perfectly fine, and since you are only mounting it through one side of the chassis, there is no way you can have a shorted turn. Congratulations on your project though, up until now everything looks amazing! I don’t think you’ve been off more than you can chew at all, seems like you’re gonna be just fine😎
If you have any more questions, we’re all happy to help👍🏻
If you have any more questions, we’re all happy to help👍🏻
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I'm happy people pass on advice and knowledge. You probably saved me grief down the road or even from serious pain! I was a commercial electrician before the 'c' word hit and some of my greatest joys from that trade were being able to pass on the 'right' way to apprentices.
Today I finished making holes in the top panel to accommodate the output transformers and one of the Antek toroids. Thanks to McTavish I didn't bugger up and use the nylon threaded rod. In order to give the toroid's leads a bit more room to wrap in closer, I raised it about 6mm by using temperature resistant, high density rubber discs. These are pretty much the same stuff Antek provides but far thicker. The nut and bolt provided was the perfect length and the toroid was snugged down using the provided steel retaining disk/washer and rubber pad. 5/8 inch holes were bored through the chassis top plate and rubber grommets added for wiring to pass through. The ugly bed pan on top leaves something to be desired. If it had a spike I could almost see the resemblance to an old 'pickelhaube' 🙂 Might be a plan for the future! The same size holes were bored for the Edcor output transformers and the holes in the rubber isolation pads enlarged to make room for the rubber grommets. I had to pop everything in to see what it was about and to feel like something was accomplished. Grabbing the new chassis was a good move as there is no way that weight would sit well in the original. Next time, I'm going to have the guy with the CNC make all the holes 🙂 I'll be picking aluminum out of my feet for days! Wife's gonna kill me. The joys of apartment living. Up next, back panel and holes for Neutrik-clone RCA jacks, binding posts and AC