markiemrboo Posted January 28, 2007 Posted January 28, 2007 (edited) I expect the Pre will be just fine without any ventilation. If you remember the pics I posted of my Preamp in your other thread, the case has no vents at all. That thing happily sits on for weeks (if not months) at a time, I only ever turn the power amp on and off. It would be different if there were valves involved, but obviously there aren't. Good to know. I expect the case for that is metal though, so conducts small amounts of heat? I'm not sure that ABS plastic is a good thermal conductor (I actually don't know....but it's plastic!). I think it will probably be OK. Hopefully. I don't *really* want to make 'speed holes' Edited January 28, 2007 by markiemrboo Share this post Link to post Share on other sites More sharing options...
jammin Posted January 28, 2007 Posted January 28, 2007 Metal, yes. I suppose there is a bit of convection cooling going on there. If you add speed holes, you have to add go faster stripes as well. Don't amps like being nice and toasty anyway.. or is that just something I've vaguely remembered/made up on the spot? (Again, that's probably valves anyway... a valve power amp is like a space heater ) Share this post Link to post Share on other sites More sharing options...
markiemrboo Posted January 28, 2007 Posted January 28, 2007 Metal, yes. I suppose there is a bit of convection cooling going on there. If you add speed holes, you have to add go faster stripes as well. Haha! Of course Don't amps like being nice and toasty anyway.. or is that just something I've vaguely remembered/made up on the spot?(Again, that's probably valves anyway... a valve power amp is like a space heater ) I've heard all sorts of strange things. But no, I don't think you made that up Some people seem to reckon that even IC's and stuff sound better when they're warm... but I dunno what to think about that really. Share this post Link to post Share on other sites More sharing options...
markiemrboo Posted January 31, 2007 Posted January 31, 2007 (edited) The new pot and power amp cases arrived today. The new pot is so much better, the volume works good on both channels now. It's quite loose to turn too, which is nice. Feels alot nicer to turn than my Cambridge Audio even! I've trimmed down the shafts on them so that the knobs are very close to the case now, and the volume control has a slightly larger knob on it. I was thinking about some kinda power indicator light, either drilling some small holes around the volume control and glueing an LED or two near them, hopefully giving a glow visible from outside and around the knob, or the same thing but a couple at the bottom front of the case, so it would give a glow from the bottom front. I marked it out with masking tape for the bottom front idea, but... when I opened it up to do the whole LED thing.... it just seemed like so much effort. Mainly because of the resistors. I'm rubbish at 'point to point' soldering (i.e solder resistor directly to LED leg) and just don't feel comfortable doing it that way The power amp cases are.... worse than I imagined, quite frankly. I don't like them much at all.... and it turns out it's just gonna be too much effort to remove all the rubbish inside to make everything fit..... then I would have to paint it black to look nice. I'm looking at two plain square wooden boxes on ebay for Edited January 31, 2007 by markiemrboo Share this post Link to post Share on other sites More sharing options...
hardnrg Posted January 31, 2007 Posted January 31, 2007 (edited) I'm rubbish at 'point to point' soldering (i.e solder resistor directly to LED leg) and just don't feel comfortable doing it that way might i suggest The Third Hand (aka Helping Hands) ? you can see mine in action (yes, action shots, wooo!) in my 7800gt voltmod guide handy for in-line soldering and even wires to the copper side of the pcb (which i hate doing with only two hands!) i'd probably drill a small 1.5mm hole, and mount/glue the led behind it... probably mount and glue it... drill a hole in something to make a "polo mint" type thing, glue the led in the middle, and maybe file the top down flat, flush, and glue the polo-mint-led to the chassis hehe Edited January 31, 2007 by hardnrg Share this post Link to post Share on other sites More sharing options...
markiemrboo Posted February 1, 2007 Posted February 1, 2007 might i suggest The Third Hand (aka Helping Hands) ? I do keep telling myself I will get one of these one day i'd probably drill a small 1.5mm hole, and mount/glue the led behind it... probably mount and glue it... drill a hole in something to make a "polo mint" type thing, glue the led in the middle, and maybe file the top down flat, flush, and glue the polo-mint-led to the chassis hehe Possibly something like this. To be honest I am happy with the preamp as it is. The power amps are annoying me now, so I am concentrating on getting them sorted. I ordered a couple of those boxes and two smaller transformers (one per channel, so I can properly have one regulated supply per channel). Lets hope this will work Share this post Link to post Share on other sites More sharing options...
markiemrboo Posted February 11, 2007 Posted February 11, 2007 Finally time for an update! The wooden boxes arrived, but they were reaaaally quite tall, so I ended up deciding against using those too! I've put the rebuilt power amp in to the old 2U case for now, but with two transformers. I am wanting to build a simple wooden case at some point, or even just replace the front plate and top / bottom panels of this 2U case with wood. I don't know why, but I want to use wood for at least parts of the case Things got exciting during the power amp rebuild: - I powered it on and turned it off quickly to check for explosions (ha), no explosions! - Measured the power supply output voltages and all was good. - Great stuff, connected power supply to amp's.... no explosions - Got out the scope and checked for anything suspicious and didn't see anything. - Played some simple test tones / music without a load. All looked OK. - Plugged in the ancient test speaker, it was playing music! The bass sounded quite terrible, but I blamed this on it being, well, a crap speaker and the fact it wasn't in an enclosure. - Kept it playing for a while. Hooked up the scope to see if it was actually the amp making the bass sound crap. Started turning up the volume and saw the top of the wave's going flat and with a little notch, looked like the chips protection circuitry was kicking in VERY prematurely. Seconds later, the speaker made some pretty awful noises and everything went quiet. The amp had somehow managed to get itself in to some massive high frequency (MHz) oscillation, which obliterated the speaker! - Tried many things throughout the day to find out why it suddenly broke in to oscillation, with a dummy load (3.3R 2W resistor). Poor resistor got abused, the oscillation was so bad that being on for any more than about 3 seconds would cause the resistor to get VERY hot and start making cooking noises / smoking! The cause of the oscillations ended up being the fact that the input feedback return was connected to the output zobel return (which 'catchs' high frequency rubbish AFAIK). A bit of a silly idea looking at it now, but I didn't want to be running loads of wires all over the place. Very easily solved by cutting the ground trace connecting the feedback return to the zobel return and running the feedback return back to the star ground point via a wire. I'm happy with this, it's what most DIYers do it seems. I've just now sorted both PCB's and done a lot of testing. All seems great now With no input, there is absolutely no noise AT ALL from the speakers! No hiss, no hum, no buzz, no turn on / turn off thumps or other funny noises... nothing! Very pleased with that! Hooked up straight to the sound card gives me a little very faint hiss, so it looks like I might be looking in to a new sound card sometime soon Mobile phone interference also seems to be far less than the original power amp boards, which is nice. You can't hear any inteference when music is playing, and only a tiny bit if the phone is right next to the speaker cables otherwise, apparently. The preamp, this obviously will amplify the hiss coming from the source, but compared to the Cambridge Audio, there is definately less noise. Close listening reveals the Cambridge, along with the hiss, actually has a quiet buzzing / humming / clicking sort of noise coming from the woofer and tweeter. Am I happy now? Yes I finally feel like I am making some progress! Slightly better picture of the power amp, now I have my camera back! The power amp insides. Still quite messy, but there's alot of room at the front. I may stick the preamp in there when I manage to figure out the whole wooden case thing and finish debugging the preamp Just a quick picture of the preamp with wires coming out of it Share this post Link to post Share on other sites More sharing options...
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