DIY digital PWM amp project

I guess LesW at Avondale might also be worth an approach.

Paul

 

I've already spoken to him, but that was before I realised just how large a case I was going to need (and when I hoped to get one from iagaudio.com) but I might see if he can help me out with the dimensions I need.

Michael.

 

What about an acrylic/perspex case? Might be easier to DIY and "smoked" (ie opaque) perspex would look quite cool IMO...

Michael.

 

Forget it, I've found the case I'm going to get:

http://www.par-metal.com/20series.htm

The 20-16164x case which is 16x16x4 inches is perfect and I can get it finished in black or clear anodized.

I think I'll order one tomorrow . Pity it has to be from the US though (customs costs).

Michael.

 

Can you not get a shorter transformer and use the iagaudio.com case ?

 

Not really, 800VA toroidals don't come much smaller than the one I have and in any case, it's already cost me £50! The par-metal.com case is big enough and it's also considerably cheaper than the iagaudio.com case (and not as nice looking, I know). Also, since iagaudio.com didn't respond to my e-mail request about custom sizes they don't get my business

Michael.

 

The amp that is based on 2 x ZAPpulse 2.2 SE modules on their front page looks quite short :-

http://www.lcaudio.dk/

 

Oh that's a 500VA not an 800VA

 

Yes, their new "Predator" amp uses two ZAP Pulse 2.2SE modules (like mine) and two transformers (one for each channel) but the PSU it uses is much smaller.

They sell the 500VA transformers which they recommend allthough I'm not quite sure how much smaller than mine they are.

In any case, I've just got off the phone from ordering a case from Par-Metal in the US. $55 + shipping, estimated to be about $40. Having it shipped to Portugal so I can expect to pay roughly 100% on top of that in customs charges (ie total of nearly $200) :inferno: but it's less hassle than shipping it to the UK and carrying it with me on the plane

I'm actually hoping to get the full breakdown of the exorbitant customs charges on this one and then I'm going to send a copy with covering letter to the US Department of Trade (or whatever it's called), suggesting that Portugal is engaging in restrictive trade practices by charging illegal extra tarriffs on US goods.... :MILD: Someone needs to light a fire under the arses of the Portuguese customs authorities :JPS:

Michael.

 

Turns out things aren't so bad after all with customs. The case cost me $55 + $40 postage ( ) from the US but I only had to pay €21 in customs charges and the case is fabulous. The bare aluminium has a sort of gold colour which is some process that Par-Metal use similar to anodizing but it isn't the same (but it has the same effect of preventing oxidization). The whole case is painted grey (as I requested) allthought the front panel is a nice thick piece of anodized alu. that really looks the business.

So, I've just finished probably the most tedious part of the project which is making the various holes in the rear of the casing to fit various sockets. Here's the rear of the case with the holes all made:



The rectangle for the IEC inlet was a bit of a bugger. Had to drill holes and then use a hacksaw. Fortunately alu. is a soft metal and easy to work with. The large holes for the XLR inputs I made using a Ruko 16-30mm cone drill bit. Those cone drills are really something else. Made a perfect hole with no burring and was a doddle to use.

Here's the panel with all the bits in place:



And finally, here's the rest of the case with the bits more or less laid out as they will be. One huge transformer, huge power supply and a couple of tiny PWM amplifier modules. Looks a bit absurd but I know it will sound great



This weekend will hopefully get the xformer, PSU and amp modules screwed down to the base of the case and have pretty much everything wired up. Watch this space...

Michael.

 

Hurry up mike, we are all getting very impatient to find out what you think of it

 

This is turning into a fascinating diary Mike, come on more updates needed.

A quick question, what level of prior knowledge of kit building, soldering, etc do you have. Or more simply, how many levels above novice is your current project aimed at?

Thanks.

 

The case looks a nice, hope it sounds great with the Bent pre Mike

GAZZ

 

I would have got a lot further today if I hadn't had to:

- replace the tap in the kitchen sink and clean out the sink downpipe ( the stuff that accumulates there is sooo gross :chunder: )
- try and get my wife's new LaCie external FireWire CD-RW drive working :inferno:

I've never built a hifi kit of my own before but I have a fair bit of soldering experience and electronincs experience. When I was a student I spent a summer working for Philips building police/taxi radio base stations

Philip, I guess it all depends. In many ways I am a novice at this thing. What's most important is a bit of common sense and problem solving skills. The hardest part of the project by far was making the holes in the rear panel and fitting all the sockets etc. I don't expect to have any issues with the soldering.

Today all I've managed to do is fit the obligatory blue LED to the front panel, which is a seperate (and thicker) piece of anodized aluminium. I'm also just in the middle of finalizing where everything will go before I drill the holes in the base of the case.

Michael.

 

There you go, it will sound superb. Just put a damp piece of string inside, and you won't know any different, such is the power of the blue LED. :JPS:

 

pour bicarbonate soda,salt,and finally vinagar down the sink

learnt any new swear words yet

 

Yes -

Michael.

 

OK, next update: I've finished drilling all the holes in the bottom of the case to attach the various bits and pieces and they all line up properly!

Yesterday finished soldering the rear panel and screwed down the transformer and PSU and hooked it all up. A bit nervous when I first switched it on but I heard the click from the slow start relay and nothing caught fire . Measured the output voltages at the PSU and they were rather high...+/- 75v . It's supposed to be about +/-62v. Measured the output voltages of the transformer secondary windings and was getting much higher than the 45V a/c spec. Then, I checked the AC voltage at the mains socket...300v . Something tells me my digital multimeter is telling porkies and over-reading voltage. I might see if I can get a new one today as mine is really a POS that's extremely old.

Here's the status so far:



Only remains to connect up the actual amp modules now. However, it's 25C today and I'm off to the beach

Might finish it off this evening though....

Michael.

 

I've decided not to try and rush it and finish it off this weekend. Even if I did I would have to wait 2 weeks before being able to listen to it so there's no hurry.

Today I had a great day at the beach and I'm going to the movies. Tomorrow is the 30th anniversary of the 25th April revolution in Portugal that overthrew the dictatorship so we're having a load of friends round for a bit of a party. Also looks like it's going to be another gorgeous day. Not to mention the small matter of the Imola Grand Prix which I'll be recording to DVD to watch in the evening so just no time you see......

I will definitely finish it the weekend 8th/9th May though

Michael.

 

:grrr: