Arke
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Post by Arke on May 26, 2022 9:01:10 GMT
[EDIT: Please note this is being written retrospectively as the BB3 is finished now. It's an 'after the build' diary!] Hello all, This is my first build thread, so please be gentle! I discovered Oli and Bigbottle Audio by chance on a forum. I contacted Oli and he was very helpful and friendly, so I decided to give a BB3 a go. Oli agreed to supply a fully built PCB and I would do the rest (with lots of guidance from Oli!). I spent a while researching a decent chassis, but struggled to find anything that looked very well made for a decent price. Most looked quite flimsy and rattly, so I decided to try and design and make one myself. Perhaps a little foolish, however, I love a challenge and really enjoy the design and construction aspect. I used Sketchup to design the case - this would give me good 3D visualisations and allow me to spot any potential construction/assembly issues. The exact 3D design would provide accurate build dimensions - after all, I ideally wanted the case to look reasonably professional! I decided to design he case to be very solid and to have no visible fixings on the front, sides, back or top. The sides, back and front are mitred like a picture frame and the base slots into shallow channels. The top plate drops into a shallow rebate and is framed by the sides, front and back with a small shadow gap.    The chassis is 'full width' at 430mm and around 310mm deep and 90mm high. The PCB is mounted on the right and can be viewed through a small rectangular window. The transformer will be mounted on the left as far from the PCB as possible.  The sides, front and back will be constructed from 10mm aluminium plate and the top and base plates from 4mm aluminium. The finish will be 'brushed'. More to follow... |
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Post by firebottle on May 26, 2022 9:50:03 GMT
10mm and 4mm, that's going to be heavy! Fair play on your plans.
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Post by electronumpty on May 26, 2022 9:55:20 GMT
I made one with a bottom and back aluminium plate of 4 mil, the front sides and top are veneered ply, just 4 mill aluminium on 2 sides is heavy enough!
Love the look though.
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Arke
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Post by Arke on May 26, 2022 10:05:18 GMT
I made one with a bottom and back aluminium plate of 4 mil, the front sides and top are veneered ply, just 4 mill aluminium on 2 sides is heavy enough! Love the look though. Agreed, it is a bit over engineered! It is bolted together internally so I needed a reasonable depth to drill and tap blind holes. |
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Post by macca on May 26, 2022 11:01:43 GMT
1 centimetre thick panels?
I've always said that there's a gap in the market for phono stages that are immune to small-arms fire.
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Arke
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Post by Arke on May 26, 2022 11:13:33 GMT
1 centimetre thick panels? I've always said that there's a gap in the market for phono stages that are immune to small-arms fire. Yep 1cm thick - small arms fire should be OK! I'm not a person that likes to under-engineer! You'll see this when I add the speaker and sub build threads. The top plate sits in a top rebate so I wanted the sides/back/front to look substantial from above. Also, needed adequate thickness to tap holes from the inside. (this will all become more obvious soon). |
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Post by brucew268 on May 26, 2022 11:32:42 GMT
So you're going to use 1cm aluminium plate and then router or CNC the rebate into them? That's some proper machinery and tooling to do that well! In house or job out?
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Arke
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Post by Arke on May 26, 2022 11:38:24 GMT
So you're going to use 1cm aluminium plate and then router or CNC the rebate into them? That's some proper machinery and tooling to do that well! In house or job out? All at home in my workshop. Next posts will show the cutting, rebates and 'valve window'. I've got a table saw, pillar drill and hand held router. |
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Arke
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Post by Arke on May 26, 2022 12:21:37 GMT
SOURCING AND CUTTING ALUMINIUM: After some research I sourced the aluminium from Metals4u. I used a flat bar for the front, back and sides. It was cheaper for imperial sizes so I opted for 4" x 3/8" cross section - this gave a 9.5mm thickness and I would cut the 102mm down to my desired chassis height. Top and bottom are 4mm plate. I felt that 2 or 3mm would flex too much. My background is more in woodworking, so using aluminium was reasonably new to me and I wasn't sure how easy it would be to cut and rout. After some research I bought this blade for my (Dewalt 745) table saw:  and this router bit for aluminium: trenddirectuk.com/trend-50-05x1-4hsse-aluminium-cutter-5mm-diameter.htmlI don't have a cross-cut sled for the table saw so made a simple plywood jig to keep the flat bar at exactly 90degrees to the table saw fence:  After A LOT of noise I successfully cut the mitred 'picture frame' sides, back and front:   I was very impressed with the blade. The ally was very easy to cut and accuracy was perfect - nowhere to hide with this design! |
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Post by electronumpty on May 26, 2022 12:53:18 GMT
Dunno about small arms, looks like an NLAW will be needed.....🙂
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Post by antonio on May 26, 2022 14:03:23 GMT
That's a fine start, I'm sure this chassis will look great when finished and have a few on quite amazed.
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Arke
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Post by Arke on May 26, 2022 14:50:41 GMT
CHANNELS AND REBATES: I used the table saw to cut the lower channel for the base and the top rebate for the top plate. The blade height was set accurately with a digital depth gauge and a few test cuts were made to check accuracy. This is the lower channel for the base:   This is the top rebate:  Top plate in rebate:   This is all quite rough at the moment, as loads of finishing to do later. |
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Arke
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Post by Arke on May 26, 2022 17:35:59 GMT
ROUTING THE VALVE WINDOW: This is the part I was most anxious about... I wasn't sure how the aluminium would rout and the 'valve window' had to be perfect as it is a key feature. I set about making a plywood template to give the outer shape. I used a 10mm guide collar on my 1/4" palm router and the router bit is 5mm diameter. Therefore, the ply template had to be 2.5mm larger all round to give the finished window size.  Next the outer template required an inner rectangular. This is designed to give a 10mm channel for the guide collar to follow. It serves 2 main purposes: firstly to stop the router base from tilting; secondly it is screwed down through the 4mm workpiece and into a piece of scrap - this holds the central rectangle of aluminium and stops it suddenly moving once the window is fully cut. The 4mm depth was cut in 4 x 1mm depth passes. It was surpringly straightforward and the 5mm router bit cut perfectly.   |
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Post by brucew268 on May 26, 2022 18:58:29 GMT
Well done! I wouldn't have thought a palm router had the muscle for that, though 1mm passes makes sense. For drilling I know the quality & alloy of aluminium and the speed of the cutter can affect the quality of the outcome... so well done.
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Arke
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Post by Arke on May 26, 2022 19:05:44 GMT
Well done! I wouldn't have thought a palm router had the muscle for that, though 1mm passes makes sense. For drilling I know the quality & allow of aluminium and the speed of the cutter can affect the quality of the outcome... so well done. Thanks. I do have a 1/2" plunge router too, but thought I'd try the palm router first as it's easy to handle. The router bit was only 5mm diameter, so not too much material removal with each pass. |
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Arke
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Post by Arke on May 27, 2022 8:17:14 GMT
IEC AND RCA RECESSES: I planned to use the CMC gold plated copper RCAs, which specify a max chassis thickness of 5mm. The rear panel is 9.5mm, so I decided to create a recess around the RCA inputs and outputs. The IEC doesn't require a recess, but I thought it would be nice for symmetry. Therefore, two matching recesses were required at a depth of 5mm. The RCA recess is 90mm wide to match the valve window on the top, and the IEC recess is symmetrical on the other side. I adapted the valve window template to create the recesses. The recesses were routed by hand with the palm router and 5mm aluminium router bit. Passes were at a 1-1.5mm depth and a Trend cutting wax was applied to the bit which each pass. One recess took about 45mins.    An additional template was used for the IEC (with fuse holder) cut out:  M4 holes were drilled and tapped for IEC fixing:   11mm holes drilled for input and output RCAs:  I have not fitted the load plug RCAs, but can easily add these at a later date. Load resistors have been soldered direct to the PCB. I have an MC cart, so have currently omitted the MC/MM selector - again, this could easily be retro fitted. A ground point will be added soon. |
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Post by pete on May 27, 2022 8:22:56 GMT
This is looking fantastic, amazing work
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Post by brian2957 on May 27, 2022 8:32:50 GMT
That's fantastic work, especially since you're using hand tools. Great work  |
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Arke
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Post by Arke on May 27, 2022 8:35:12 GMT
This is looking fantastic, amazing work Thanks Pete. I've worked with wood for many years, but metal working is pretty new to me - in some ways it's pretty similar. The aluminum does have the advantage that it doesn't have grain like wood, so doesn't splinter and seems to finish well. |
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Arke
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Post by Arke on May 27, 2022 8:38:04 GMT
That's fantastic work, especially since you're using hand tools. Great work  Cheers! A milling machine and metal lathe would be lovely, but a bit overkill (and way out of my budget!) for occasional projects. It's surprisingly fun and challenging trying to work out how to achieve good results with hand tools. |
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Arke
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Post by Arke on May 27, 2022 13:37:24 GMT
CORNER BRACKETS: Thanks to all those still following! I hope you're finding it interesting - not too long until it's finished!This was fiddly and took quite some time! Every corner bracket had to fit perfectly otherwise the mitred corners wouldn't line up and that would look rubbish! First I cut 4 corner brackets - these were made from 15.5mm x 15.5mm (1.5mm thick) aluminium angle. These were cut to length and each piece drilled with 4 (4.5mm) holes - 2 holes for each side of the mitred corners. I then marked up the fixing positions in the ends of the sides/back and front. These would require a blind hole (not all the way through) and then a blind tapped thread. I used a pillar drill with a digital depth gauge (very useful) to drill each blind hole to 7.5mm depth - this would leave 2mm material in a 9.5mm thick workpiece.  I had to buy an M4 bottom tap which would allow me to tap within 2mm of the base of the 7.5mm hole. This would give about 5mm of thread and reasonable thread engagement - not perfect, but enough to hold a case together. This job was OK once I'd got going, but was rather repetitive and boring! Finally, 16 M4 threads tapped!    The 4.5mm holes in the angle brackets gave me some leeway to line up the mitres perfectly. |
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Arke
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Post by Arke on May 27, 2022 14:01:02 GMT
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Post by antonio on May 27, 2022 14:32:14 GMT
As others have said already said, amazing work, well done. A bomb proof shelter will be a piece of cake now  |
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Post by brian2957 on May 27, 2022 14:33:49 GMT
Need a high degree of accuracy with this job. Looking good. What blade are you using in the table saw BTW ?
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Arke
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Post by Arke on May 27, 2022 15:10:06 GMT
Need a high degree of accuracy with this job. Looking good. What blade are you using in the table saw BTW ? Cheers. Picture of blade at start of thread. It's a Trend multi material TCT blade. Works well on ally and plastic |
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Post by pete on May 27, 2022 16:59:56 GMT
This is real precision engineering! Great stuff
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Post by brian2957 on May 27, 2022 17:15:27 GMT
Need a high degree of accuracy with this job. Looking good. What blade are you using in the table saw BTW ? Cheers. Picture of blade at start of thread. It's a Trend multi material TCT blade. Works well on ally and plastic Thanks, that's handy to know if I ever stop cutting wood and start cutting other things How did you find that blade. I'll be looking at replacing mine soon. I think I've cut through too many nails as I repurpose old wood for new projects quite a lot of the time |
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Arke
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Post by Arke on May 27, 2022 17:24:32 GMT
NOT FEELING SO BLUE: I had designed the BB3 with a blue light - mainly as it's the same as many previous builds and it looks great on other BB3s. However, since the valves are on show and will glow orange the power switch LED changed to orange.  The switch required a 16mm hole, so quite a beefy drill bit. I drilled 3mm first, then 6mm, then 11mm to build up gradually - I wasn't sure if my drill would handle 16mm straight through ally.   Many of you will probably have noticed that the outer finish has improved... I spent a few hours with the belt sander (clamped upside down) and sanded a 'brushed' finish with 120 grit paper. Final sanding was done by hand with 120 grit. Nearly ready for final assembly...  |
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Arke
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Post by Arke on May 27, 2022 17:31:12 GMT
VENTILATION: I planned to have the 'valve window' seamless with no slots or holes, so needed to ensure adequate ventilation. After some chats with Oli, we decided it would be best to ventilate in the base in front of the PCB and in the rear panel above the RCAs and behind/above the PCB. This would draw cool air over the PCB and and out of the rear. 8 x 6mm holes in base in front of PCB:  8 x 6mm holes on rear above RCAs:  Front and rear panels nearly ready!!!  |
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Post by brian2957 on May 27, 2022 17:36:18 GMT
Very neat work again. This is gonna look rather nice |
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