Well, here it is...my first DIY audio project. It's a gainclone. I'll put more info up later and more pics. For the mean time, I think it sounds great. I had an Onkyo TX8211 and this sounds MUCH better than it. It fits in perfectly with my college dorm room. Very compact...about 13x10x3. More info coming soon.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The casis is all aluminum. My friend and I desinged the case in SolidWorks and then ordered sheet aluminum from www.onlinemetals.com. We drilled/tapped everything by hand but had the front and top pannels brushed using a TimeSaver machine. All the aluminum was then clear anodized. As soon as I can get my hands on a digital camera again, I'll post more pics. The schematic I used is attached.
I made a PCB using a cad program and press n' peel blue. I can upload artwork if anyone is interested. On the psu, I used a pretty standard setup except that I used 6000 uF per DC rail. I'll post a parts list and everything as soon as I can.
An externally hosted image should be here but it was not working when we last tested it.
I made a PCB using a cad program and press n' peel blue. I can upload artwork if anyone is interested. On the psu, I used a pretty standard setup except that I used 6000 uF per DC rail. I'll post a parts list and everything as soon as I can.
How was your experience with onlinemetals.com? I've been looking at them as a possible source for my own projects.Doovieman said:
Also, how'd you do the junction between the top and the sides? Is that two separate pieces, or did you run a single piece through a bending brake, or..?
onlinemetals.com was pretty good for what I wanted. I knew I was going to use TimeSaver 220 on the front and top panels so any blemishes would be removed. That being said, there were certainly a few blemishes/scratches/burrs to begin with. My goal was to create everything my self on the chassis including the feet and knobs. The feet were made by ordering round rod from them and brushing them by hand. They turned out very nicely but it took quite a bit of time to smooth them out and make them all the same height. The tolerance of onlinmentals.com is not to great. "+1/8 inch -0" is what they say but I had a few pieces of rod that were more like +.2 inch. I don't recall having anything cut to small. If you're expecting CNC milled and cut aluminum, this is not the place to go. They deliver good quality, stock, sheet aluminum cut with a sheering machine. I don't recommend the idea of using their round rod for anything too cosmetic because the rod was really the stuff in the worst condition...several burrs and scratches. Now, when I asked for my cassis to be clear anodized, I also asked for a heavy etch which made a very nice finish and took care of several of the scratches. As a result, there are NO scratches/blemishes on the outside of the case, but on the inside there are a few minor ones...that doesn't bother me so much so for me, onlinemetals.com is great. All in all the cassis you see in the pics (and I promise more) cost $30 plus a lot of time! It's tough to explain how the whole thing sticks together so I'll wait to do so until the guy next door lets me borrow his camera.
That is simply beutiful! And, thats exactly the way I want mine to look when I build it. PLease post internal pics soon! Also, where did you get the heatsink?
Thanks a lot for the kind post JCoffey! I got the heatsink from Accel Thermal. You can find them at http://www.accelthermal.com/. I got a 3 inch piece of the 96-2 model...for free...hehe. I'm a college student so they were kind enough to send me sample stock. I think the regular price is something like $50 for it, but they didn't really seem to have any set prices. Other places I looked for heatsinks included thermalflo.com and avvid. The guys at Accel were by far the most helpful. I'm pretty sure that this heatsink can dissipate more than 100 watts no problem. I'm using two LM3875TF chips on it and I don't EVER feel the sink get warm. I've left my amp on for a few days now and I've checked every time I come in my room and it's always at constant room temp. As promised...the pics.
This is the back side (obviously) with that massive heatsink. I've got 4 inputs and two outputs (again, obviously)
This is the back side (obviously) with that massive heatsink. I've got 4 inputs and two outputs (again, obviously)
An externally hosted image should be here but it was not working when we last tested it.
Here's a top view:
and another:
An externally hosted image should be here but it was not working when we last tested it.
and another:
An externally hosted image should be here but it was not working when we last tested it.
Upclose and personal with my PCB and powersupply circuits.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I thought this was kind of cool when I designed my box. I'm sure it's not an original thought but I still like it! I used these "standoffs" to elevate my circuit boards from the bottom panel. I'm not sure what they're actually called so if anyone knows, please let me know:
An externally hosted image should be here but it was not working when we last tested it.
So now for some of the info about what I used etc etc. Somebody asked how I attached the top panel to the actual box. I used .25 inch X .375 inch aluminum rods. They were drilled and tapped at either end so as to attach the front and back panels together. On the front panel, I used some cosmetic stainless steel hex screws and on the back I used a flat head stainless screw and countersunk them. There are four such rods as I think you can tell from the pics. The bottom rods have two holes in the sides in addition to the two holes in the front and back. Those holes were tapped and two flat head stainless screws (on either side of the cassis) go through the top/side panel and into the rod. I countersunk the holes for those screws so that they'd look nice. My friends had some doubts as to the structural stability of using the rods from one side of the cassis to the other...I put my entire weight (165 lbs) on them and they did not bend.
As for the electronics:
I'm using a 100k audio taper pot from mouser and a 2-12 input selector switch from mouser. I thought about using attenuators and alps pots etc etc but I came to the conclusion that a pot is a pot (for the most part). My PCB uses all metal film 1% resistors (found at mouser). You can see the schematic on an earlier post. I started out using the MUR80 (or whatever they are) diodes from on semi but I went to Mike Quinn's electronics in San Leandro, California (for any of you Bay Area DIYers this is the BEST electronics distributor ever) and saw bridges at 8v 400amp and decided those would work well too. For $5 I got two of those bridges, 16 50V 1500 uF caps and 10 16V 47uF caps. All caps and bridges are in perfect condition...this guy is awesome. The PSU uses 3A fast blow fuses (also mouser) and teflon coated wire (nice and thick) for the +- dc rails. For the ground I used really fatty pure copper wire (also found at Mike Quinns) that he gave me fore free. All my RCA/binding posts are gold platted (I’m not sure it actually makes that much of a difference…yes yes, in theory it does blah blah blah) but they’re there anyway. I’m using a plitron transformer which I am NOT impressed with. When I checked the AC with NO load off the transformer on a scope, the signal was hardly characteristic of a sinusoid. It was clipped at certain points which I attribute to the hysterias of the material inside the transformer. Oh well. You may have also noticed that there is a white toroid over the secondary wires from the transformer. It acts as a low pass filter so that it gets rid of really high frequency garbage. It’s probably overkill but my dad gave it to me so I’ll use it! I think that's about it so let me know if you have any suggestions for next time!
As for the electronics:
I'm using a 100k audio taper pot from mouser and a 2-12 input selector switch from mouser. I thought about using attenuators and alps pots etc etc but I came to the conclusion that a pot is a pot (for the most part). My PCB uses all metal film 1% resistors (found at mouser). You can see the schematic on an earlier post. I started out using the MUR80 (or whatever they are) diodes from on semi but I went to Mike Quinn's electronics in San Leandro, California (for any of you Bay Area DIYers this is the BEST electronics distributor ever) and saw bridges at 8v 400amp and decided those would work well too. For $5 I got two of those bridges, 16 50V 1500 uF caps and 10 16V 47uF caps. All caps and bridges are in perfect condition...this guy is awesome. The PSU uses 3A fast blow fuses (also mouser) and teflon coated wire (nice and thick) for the +- dc rails. For the ground I used really fatty pure copper wire (also found at Mike Quinns) that he gave me fore free. All my RCA/binding posts are gold platted (I’m not sure it actually makes that much of a difference…yes yes, in theory it does blah blah blah) but they’re there anyway. I’m using a plitron transformer which I am NOT impressed with. When I checked the AC with NO load off the transformer on a scope, the signal was hardly characteristic of a sinusoid. It was clipped at certain points which I attribute to the hysterias of the material inside the transformer. Oh well. You may have also noticed that there is a white toroid over the secondary wires from the transformer. It acts as a low pass filter so that it gets rid of really high frequency garbage. It’s probably overkill but my dad gave it to me so I’ll use it! I think that's about it so let me know if you have any suggestions for next time!
No suggestions, other than keep up the good work. This is one of the cleanest integrated GC's I've seen. Good motivation for me to try that route for a friend's system.
Thanks for the posts!
Sandy.
Thanks for the posts!
Sandy.
Thanks Sandy H!
Joe Dirt-
Not sure what you mean "how is your gain justified"...use node equations/laplace and figure it out... As for the 47uF, I built a prototype using a 22uF but it lacked bass in my opinion. Using a 47uF will extend the low end frequency response.
Joe Dirt-
Not sure what you mean "how is your gain justified"...use node equations/laplace and figure it out... As for the 47uF, I built a prototype using a 22uF but it lacked bass in my opinion. Using a 47uF will extend the low end frequency response.
*drooools*
Very nice indeed...
Question: How hard is the press and peel stuff to work with for PCB? I have heard of some iron on stuff as well... It would make life a whole lot easier as well if i can do that.... Either that or i am going to stick to the P2P version...
Armers
Very nice indeed...
Question: How hard is the press and peel stuff to work with for PCB? I have heard of some iron on stuff as well... It would make life a whole lot easier as well if i can do that.... Either that or i am going to stick to the P2P version...
Armers
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