Wednesday, 28 November 2012

Building another O2+ODAC combo

The past few days I've been building another Objective amplifier+DAC combo for a guy at

He ordered the stuff and got it sent to me, I picked it up on monday afternoon and started building directly. The first evening I finished most of the O2 board, except one of the battery terminals and the power connector.
On day two I sanded the legs of the power connector to make it fit through the holes and I used a glove to mount the last battery terminal (it gets very very hot!). For that job I borrowed a dremel copy from my neighbour. It was the first time ever I was using a dremel but it was simple and straight forward. Really liked it!

I then measured all the voltages and everything was fine, well under the limits. Tested it briefly with my phone as a source and a pair of old crappy headphones connected to it. Everything sounded as it should.

It was then time to mount the ODAC to the O2. Again using the dremel to cut the bolt from ~40mm to ~10-15mm. Very handy but it made a nasty noise. Found a broken CAT5-cable in a drawer and cut off ~10cm and took two of the pairs and stripped the insulation. Only strip a couple of millimeters here, not a centimeter as with speaker cables. Solder them to the board the right way this time, not as I did with my own amp.

Time to test run everything. Hook it up to the computer and test play it. No sound. No matter how hard I try there's no sound from it. I start double-checking all the wires and solder joints, nothing wrong. I try moving the ground cables to another spot on the board, no success. Then it hits me, maybe I didn't cut the traces on the O2 board well enough. The PCB was black so it was very hard to see. I look a sharp object and started scraping some more on the PCB and apparently they weren't entirely cut off. Cut them off properly and then it worked as it should.

Listened to it the whole evening and it sounded very very good, as it should. The product is now packed back into its box and I will ship it to the buyer tomorrow.

All in all it has taken me about 5-6 hours in total to build it. Much faster than the first time, because I knew where all the parts should be, I knew how to measure the voltages and I knew how to connect the ODAC to the O2. If you're a beginner and has very little or no knowledge of soldering and electronics, it might take 10-20 hours.

If you're interested in letting me build one for you, just send me an e-mail or write a comment or something.

And here's some pictures.

It's very nice to have a dedicated table for this!

All resistors marked and ready

Sanding the legs of the power connector with a dremel tool

My amplifier (the black) and the new silver one.

Up and running. The LED isn't yellow, it's red, it just looks yellow in the picture. 

Tuesday, 27 November 2012

Stop the loudness wars and release High Definition Music Downloads

I've found an interesting petition at

I found it via a thread at

"Music gives many people enjoyment, but the dynamically compressed albums available today are short changing people of this enjoyment.
As music lovers we are fed up with the high level of dynamic compression used on albums available today and would like to see the immediate introduction of “HD / Unlimited” music, where the recording has not been dynamically compressed and has been optimised for sound quality.
We believe that this is the way forward to reintroduce people to music the way it’s meant to sound. The technology is there, I’m sure the demand is there, Record Labels make it happen!"

Sign it and join the movement. There's also a Facebook group, make sure to join it as well (if you have Facebook).

Extreme lack of time but still finding enough to work a little every now and then

So, I've been very very busy the last few weeks. National exams at school, hosting a Learning School student from Shetland and some other stuff going on as well. But I have managed to work some on the speakers.
This weekend I managed, with some help from dad, to glue the remaining side panels. Whenever I find time I will start making holes for drivers and terminals, and making sure that the drivers fits nice to the brace. No pictures unfortunately, since my memory card decided to die on me on saturday (new one coming though, thanks Amazon!).

Tuesday, 13 November 2012

Making a new set of cables

Since the cables to the woofers weren't long enough to enable pulling out the drivers when the cabinet is finished I have decided to make a new set of cables. If I use the cables originally intended for the top woofer for the bottom woofer instead I will be able to pull out the driver when the cabinet is finished. Then I'll make a new cable to the top woofer so I can pull out that driver too if I'd need to. The tweeter cables is still too short for that but I don't think that's a problem since I can reach the terminals on the tweeter by removing the top woofer (the terminals are on the upper side of the tweeter). So if I, for some reason, would have to remove the tweeter I will have to remove the upper woofer as well.

I was about to start making that new pair of cables today but I quickly ran into problems. I had no big enough cable shoes. The biggest ones I had were 2.5mm and I need something like 6.35mm like I have for the other cables. Might be the local car workshop has some I could buy, but that workshop is really far away from where I live so I'll wait until dad comes home so we can take the car instead of me having to bike there.

Sunday, 11 November 2012

Rain, cables and bloodshed

Last day of the weekend, pissy weather outside. It has been raining non-stop the whole day. Better spend some time working on the speakers then.

My goal for today was to prepare all cables to the drivers and maybe solder then to the filter. I'm happy to say I achieved most of that, except soldering the cables.

I started off with searching for the cable shoe tool. I know exactly what the box looks like and where it should be but for some reason it wasn't there. Eventually I found it, after searching for almost 20 minutes in the workshop, the garage and in the car.

Time to start stripping insulation of cables and mounting them cable shoes.
All tools ready!
The result. As you can see I've started to remove a bit more of the insulation to make the cables easier to handle.

First cable finished! I'm leaving the insulation in the other ends for now. I'll strip it off when I'm soldeirng the cables to filter.
I must say the cable feels very high quality!
All cables done!

Another close up of the cables. I used to masking tape on the tweeter cables to prevent them from untwisting themselves.
Cable shoe for the tweeter cables. Pressed this one a bit too hard so it broke. But I think it still has connectivity.

Now you might wonder why I put "bloodshed" in the title. I'll explain...
After having done two woofer cables I was going to strip some more insulation off a cable. I put the knife to the cable and pressed with the side of my thumb on the knife. The problem was, I had the knife the wrong way, edge pointing upwards, so I cut myself in the thumb. About one centimeter long and a couple of millimeters deep. It was bleeding quite a bit but thankfully it didn't hurt much at all. This led to an hour's break while I was stopping the bleeding and making sure I could keep working without the wound opening again. I solved it with some cotton pads and a bit of masking tape to hold in in place.

As I have mentioned before I need to glue the coils to the filter board. The coils are quite heavy (probably 300-400g) and wont stay in place by themselves. I found some glue in a drawer and decided to try it out.

Glueing in process, holding the coil in place with a clamp.

One thing struck me just before writing this post. I may have made the cables too short. Well, they are long enough to go from the filter to the drivers, that's no problem, but I probably wont be able to pull out the drivers when the box is finished. If I'm lucky I'll be able to pull the drivers out far enough to get a grip of the cable shoes and pull them off the driver terminals. If not, well, it will be quite difficult to do any modifications to the filter or inside in general.

I do have around three meters of cable left though, so it would be possible to make new cables for the upper woofers and take the old upper woofer cable and use them for the lower woofer. But for that I'd need new cable shoes. I do have cable shoes in my blue litte metal box but I'm not sure if they are the right size. I will take a look at that tomorrow and ask Ingvar if it's a good idea to do so or if I wont have to.

Saturday, 10 November 2012

Reply from Ingvar regarding the problems

Earlier today I wrote that I had a couple of questions to Ingvar, and I emailed him.

I got his reply now and this is what I learned:

  • The woofers are to be wired parallell.
  • I need to drill the holes in the tweeter a bit bigger to make the bolts go through.
  • The cable shoes are to be squeezed around the cable, not soldered.
  • The thick cable is also meant to be used between filter and binding posts.

I haven't got enough time to work any more today, but I guess I'll continue tomorrow getting the cables right.

Masking tape, drivers, cables and filters

This saturday is a very boring saturday. Useless weather outside so I'm not planning for any outdoor activities today. But there's lots of time for indoor activities, like starting to fix cables for the Oy speakers.

To know the exact lengths I will need to assemble a cabinet, put drivers and filter. Then I can cut the cables to proper lengths and put cable shoes on them and make them ready to be soldered to the filter. Of course I started with assembling the cabinets. Starting with a side panel flat on the floor, then add bottom and back panel and tape this together. Then add a baffle and tape it together with the rest. Add the top panel and you have a cabinet with an open side, perfect for this kind of work. Flip the cabinet over so it stands on the back panel and add drivers and screw them in place place with a couple of bolts so they don't fall out and get damaged. Add some more tape to make sure the cabinet doesn't fall apart.

Ingvar had told me to put the filter behind the lower woofer, so it is easily accessible for modifications and changes. But when I started with the cables I realised I had no idea if the woofers were to be wired in series or parallell. So before I can start cutting cables I need to know how I shall wire them.

I then decided to go on with the tweeter cables, because they can only be done in one way. But when I tried to bolt the tweeter to the baffle I realised that the bolts didn't fit through the holes in the tweeter. That's a problem, a big problem. Now you might think "just use smaller screws then" but since the holes in the baffles are for bolts and now screws a smaller screw wont work either because the holes in the baffle are too big. I've sent an email to Ingvar and I'm waiting for him to reply.

So I can't really do much at the moment. I could mount cable shoes to the cable ends but I'm not sure how to use the cable shoes Ingvar sent. It doesn't look like I'm suppose to squeeze them like ordinary cable shoes, might be I'm supposed to solder them. But I'll wait for a reply from Ingvar before I'm doing anything permanent. Since I'm home alone for a week now I could leave the cabinet in the middle of the hallway without my parents complaining.

Thursday, 8 November 2012

Glueing sidepanels and having lack of time

Blogging is a bit slow at the moment, lots of things going on in real life so I am having problems finding time to post anything to the blog. But yesterday I finally had some time with dad so we glued some side panels for the dMar-Kel70T.

I also found a funny mistake when I dry fitted the side panels. I had put damping material all the way everywhere, not thinking that the damping material takes some space. That meant I had to cut off some of the damping material at the ends of the side panels to fit the damping material stuck to the bottom and top panels. Will have to do that for the baffles too.

Glueing in process. Weight plated being used to put pressure from above and some more weight plates to keep it from falling over.

A  big mess!

Due to the extreme lack of time I haven't even had time to clean up in my room. This is how it looks like at the moment and it's like walking in a maze.

Thursday, 1 November 2012

Done with the green felt material

Just a quick post, mentioning that I'm done with the green felt material for the dMar-Kel70T. I was in the city yesterday so I bought some more hot glue for the gun so I could glue the remaining piece for one of the top panels.

Pretty good fit for cutting it free hand, right?

T-nuts and filters

This will be a rather long post, since I've forgotten to write what I did with the filters last saturday and I haven't really had time until now to do it. It will also contain what I have done today, which is quite a bit as well.

Let's start with what I did last saturday.
Here I have hammered nails into the board, wired some copper cable between them and soldered it. Also dry-fitted the components.

This is how it looks like. Still no components soldered to the board.

I didn't do much more on the filter that day. I wasn't sure how everything was to be soldered so I had to ask Ingvar before proceeding. I sent him some pictures and he said I needed dual nails for the capacitors too.

So that's what I decided to do today. Add two nails and some more copper wire to each board. Then solder it to place. Add components and solder them to place as well.
Capacitors soldered to the copper wire.
Both boards finished, all components soldered to place.
The filters aren't fully finished yet though. The coil is pretty heavy (it's all copper) so it has to be glued in place. I asked Ingvar if he though that it was enough to use a hot glue gun but he said I should get something stronger and I don't have that at the moment. Will need to find something that's strong enough.

Since I couldn't do any more on the filters I moved on to the baffles. I decided to fit all the t-nuts and mount a driver and see what it looks like. But first I had to email Ingvar and ask him how I was supposed to fit the t-nuts. I have never worked with such before so I didn't know if I was supposed to somehow screw them in place, hammer them in place or press with something. He told me that hammering them was good.

First six t-nuts in place, only a lot to go.
Driver mounted to the baffle. For the finall install I'll make sure to have the binding posts pointing down instead since that's where the filter will be.
A front view of the driver mounted to the baffle.
Enough playing, time to remove the driver and start with the remaining t-nuts.

All t-nuts in place. I had to use a lot of force for the upper tweeter t-nut because it overlapped the one for the  woofer.

That's enough for today. Hopefully I'll get to start building these soon, I can barely wait! But first I'll have to finish the dMar-Kel70T, otherwise they'll never be done ;)