Thursday, 22 October 2015

Experimenting with a quieter power source for the MiniDSP

As exams are approaching I find myself spending more and more time by my desk with faint background music on as I study. As I lean forward over my books my head comes within 40-50cm from the speaker drivers so any noise will be very audible.

I have been running the MiniDSP hooked up to my system even though I am not using any subwoofers at the moment. This is because the mid bass becomes a bit overpowering in my room as soon as I turn up the volume a bit. I have been using a small wall wart as a power supply for my MiniDSP 2x4 for years now but the noise haven't bothered me at all since I haven't been listening near-field. If I sit a couple of meters away from the speakers I can't hear any noise at all.

I did some googling on the problem and found a thread where some guy suggested powering it with a 9v battery to see if it was the wall wart that was introducing the noise, because apparently batteries are supposed to be a quiet (but not very convenient) power source.

By chance, I happen to have some 9v batteries lying around from my previous O2+ODAC builds.

The sacrifical cable to the left, a 2.5mm male to 2x2.5mm female cable.
I also had a spare cable which I ordered just a couple of weeks ago. The plan was to use it as a replacement cable for my Koss Porta Pro headphones, but I realised I should get something sturdier (which I have, just waiting for my heat shrink to arrive from China).

I started by cutting off the useless 2.5mm female connectors. I mean, have you ever used one of those? Well, I haven't.
Shielding/ground and signal wire.
Apparently the cable had a shielding/ground wire and a signal wire, which makes sense after all. I decided to use the outer ground wire since it was thicker and I didn't have to peel an extra piece of insulation.

The next problem was how to connect the wire to the battery, without holding it in place with my hands. One of the connectors on the battery allows for winding the cable around it but the other one does not. But as it happens to be, batteries are not the only things I get left after building an O2+ODAC combo. I get spare battery connectors as well. Might as well sacrifice two of them for this experiment.
Wire soldered to a battery connector.
This way I can attatch the cables to the battery without holding them in place. However, another problem appeared. These connectors are meant to be soldered in place on a circuit board, fixing them in place so they can't rotate and touch eachother which creates a short circuit. My solution to this was electrical insulation tape.
Tape-wrapped and insulated battery connectors.
I used my trusty soldering iron to melt the tape in a few places to fuse it together so it wouldn't fall apart as easily.
Finished "product".
After finishing the battery connectors I simply connected the other ends of the cables to the MiniDSP. No fire, no smoke, no weird sounds. All good. Next step - connecting it to the amplifier. No fire, no smoke, no weird sounds. All good so far. Turn on the amplifier and wait for the "click" that turns on the sound. Dead silent, no background noise. Wow, did this really work? I turn on some music but the speakers are still dead silent. I unplug the battery and plug in the USB cable. Background noise appears again along with the music.

My first thought was regarding the age of the battery. I think the battery I tried was from my own O2+ODAC build several years ago. I take it these batteries are not high-end and maybe they lose charge by time? I fetched my DMM to check the voltage.
3.91 volts, the MiniDSP 2x4 requires at least 4.5 VDC.
Turns out I was right, the battery had lost too much charge. But as it happens to be, I had seen some other batteries in my box full of newer O2+ODAC supplies while I was getting all my tools which where in the same box. I fetch the newer batteries and measure them. The first one measured around 7.5 VDC and the other measured 8.83 VDC as you can see in the picture below.
8.83 VDC, the MiniDSP 2x4 can handle up to 24 VDC.
I connect the new battery to the MiniDSP, I connect the DSP to the amplifier again and as I turn on the amplifier and hear the "click" I can instantly hear the background noise again. I put on some music to see if it actually works with a battery and it did work, however not any better than the wall wart.

I am a bit disappointed with the results, I was really hoping to get rid of the noise with a quieter power supply. I guess it must be the MiniDSP itself making the noise and I will have to delve deeper to try to find a solution to this, because otherwise I wont be able to use the MiniDSP in my current setup.

Friday, 17 April 2015

The components for ten O2+ODAC combos have arrived

Earlier this week I went to pick up the package containing everything I need for the ten O2+ODAC headphone amplifier combos that I am going to build. It was heavier than I thought it would be but then I remember that the power adapters and the cases do have a bit of weight to them after all.

I have been incredibly busy this whole so I haven't had time to do anything else but open the package making sure everything was there, which it of course was.

Cases, panels and knobs in the bottom right. Power adapters in the bottom left. Component bags in the top. PCBs in the middle and USB-cables to the left and ODAC boards to the right.
Today I had a bit of spare time so I decided to start marking the resistors. Previously I have only been building the amplifiers one by one and so I have had to measure the resistors every single time which of course takes a lot of time. I estimate that it takes maybe 15 minutes to properly mark all the resistors in one bag of components. I have ten now. So I figured that if I mark one bag properly I can use it for reference when doing the other nine bags and so I should be able to save a lot of time. This way each bag took about four minutes so I guess I saved over one and a half hours of work.

Since there were no bits of paper on the two single resistors I had to make custom "flags" for them. A bit of tape and a small piece of paper worked just fine for labelling them. 

I am not sure when I will start building these because so far I haven't had time to do any advertising and I haven't gotten any requests yet either. This was thought to be a summer job but the earlier I can start advertising and selling the better it is. Selling ten of these in Sweden is likely going to take a while.

If you are interested in buying, send me a message at

Monday, 23 March 2015

Will be ready to sell O2+ODAC combos in Sweden within a week or two

I have good news for my Swedish readers. I just placed an order on ten O2+ODAC kits and I'm hoping I will get them by the beginning of next week and I'm hoping to build at least one or two before going on holiday over easter. If you want to buy just an O2 and not the ODAC, let me know and I'll make special arrangements for that.

My plan is to sell a finished O2+ODAC for ~2000SEK+shipping. I will offer custom gain settings for no extra cost. Unfortunately I will not offer any other extras such as 6.3mm output, back panel power or other colors than black (which seems to be the most popular).

Finished black O2+ODAC
So, what do you get when ordering an O2+ODAC combo from me? You get a fully assembled, fully functional amplifier and DAC. You get a 90cm gold plated (looks fancy) USB-cable. Underneath the case there will be small rubber feet to prevent scratches and stop the case from sliding around on your desk. The volume knob will be black brushed aluminium for a nice quality feel. The power adapter is a very compact one with a cord that is long enough for most people. I estimate it is around 1.5m. On request I will add gain resistors which can be useful if you want to switch gain settings in the future. I will make it so that no soldering will be required to change gain resistors, just pluck them out of the socket with a tweezers and put in the new ones. Standard gain will be 2.5x/6.5x. I haven't actually had any headphones that have needed more than 1x but for an example the Sennheiser HD600 needs a high gain. My Denon AH-D2000 and my Koss Porta Pro are just fine with 1x. 

If you are interested in buying one from me, contact me at

If you are not in Sweden but you still think that this looks like a kickass amplifier combo, then check out this site and buy your own DIY-kit.

Thursday, 19 March 2015

Planning to start selling O2+ODAC headphone amplifier + dac combos again

Hello dear readers,

A while ago I had a service where I would build O2+ODAC combos for people for a small fee. I quit that partially because I felt I wasn't paid enough and because I didn't feel like I had the time. However I will be getting more free time now so I could start doing it again but then there is the problem of monetary reward for me. Previously I would end up with a really crappy hourly wage if I would just take single orders for people and build them on request. I am now planning to invest in buying maybe 8-10 sets to build and sell to people. For me this would mean that I make more money per unit sold and you as a potential customer wouldn't have to wait ~1-2 weeks, I could ship as soon as you have paid me and the combo would be in your hands in one or two days.

As I mentioned this will be an investement, a rather big one considering I'm on a student's budget. So before I spend a lot of money ordering the components I would like to know if there is any interest in buying pre-assembled ready-to-run O2+ODAC combos. Remember, this is only for people in Sweden. If you are interested, let me know! Send me an email at or post a comment below.

My plan is to order within a week or two if there is a big enough interest.

Also, I have recently become an affiliate of so if you want to buy any of his products, be it a ready-made amplifier, ODAC or maybe even a DIY-kit, please feel free to use these links below if you want to support me since I get a small percentage of the money you spend on his website if you use the links below.

Full O2 amplifier DIY-kit
O2 amplifier DIY parts-kit
ODAC DIY board only
O2+ODAC headphone amplifier+dac combo
O2 headphone amplifier
ODAC RCA version

Remember, let me know if you are interested! Also, if you are interested in buying anything else from his site and you are intimidated by buying from overseas, let me know and I can add it to my coming order and you can buy it from me instead.

One last thing, if you are not in Sweden but you are still interested in building your own amplifier, use the links above and for instructions check my construction guide and my notes here

If and when I start building again I will create a new, much more detailed step for step guide including everything a total beginner will need to know to build a complete O2+ODAC combo. I may even do a full video guide if there is enough interest.

Saturday, 16 August 2014

One year later...

As it turns out it is one year since I last wrote something on this blog. On year may not seem so long for some of you out there and I can totally understand that. Even when I was in school, one year would just fly by with only a few major happenings throughout the year. This past year though, has been something absolutely incredible.In this post I will do my best to sum up the year that has passed but I will also tell you a bit about my future. So, let's begin where we left it last time...

My last post was about the AKG K490NC headphones. I didn't buy them just because I wanted a new pair of headphones but because I had been accepted to the Global Active Programme, previously known as Learning School. I will not go to much in depth about what the actual programme was or what kind of work I did since it isn't really relevant for an audio blog. GAP meant that I would be travelling around the world for a year, and I couldn't bring my Denon headphones and my Koss Porta Pro aren't really suited for use in airplanes, buses and so on. So therefore I invested in a pair of noise-cancelling headphones.

My travels started in Scotland, where I visited Glasgow, Edinburgh, and Aberdeen along with two of the people I would be travelling for the year. We then continued up to the Shetland Islands where we were based at a high school doing various kinds of voluntary work. Then during autumn break we headed off to Italy for a short holiday. We visited Rome, Florence and Venice. After that we flew to Germany where we visited a high school in a small town, not much bigger than where I grew up. In the middle of our stay in Germany I got invited to go on a trip to Japan and of course I could not resist that so I spent almost two weeks over in Asia. I came back for one last week in Germany before heading home to my old school for a month before Christmas break.

I did a few audio-related things during this part of the trip, beginning with visiting the Mareel arts & cinema center in Shetland Islands. It's a modern top-quality music venue that also has cinemas, recording studios, and so on. We were given a guided tour by one of the employees and he showed us around the studio, the radio-room, the projector-rooms in the cinemas, and so on. It was a really fascinating place and a really valuable resource for the people living on the islands. During my stay in Shetland I was also lucky to see The Revellers live (a local folk rock band, they're good!).  In Italy it was much less informal. There I saw lots of street musicians and one night in Rome I ended up with some strangers rehearsing for a ukulele gig. A Swedish girl and an Italian guy playing ukulele and the singer was a Russian girl. Amazing people and amazing music led to a really good night. Germany, Japan and Sweden didn't include anything specific that I can think of.

The next part of the trip, the longer part, started on the 20th of January when I flew to America. Here we met up with a new member of the group. We had ten days of holidays before school started so we visited Philadelphia, Washington DC, and New York. It was very cold but nevertheless we had a good time. The school we visited in the US was about 45 minutes drive outside of New York and it was really interesting seeing bits of the American high school life with my own eyes. When our stay there was over we continued on towards New Zealand, with a one-day stopover in Los Angeles and two days in Fiji. In New Zealand we were in Christchurch most of the time working at an all boys high school and we also did a couple of trips to various places around the south island, including Fox Glacier. Our next stop was Canberra, the capitol of Australia. It wasn't quite what I had imagined Australia to be like but I still enjoyed it very much and the school we were at was really interesting. The last two weeks in Australia we had easter holidays so some of us spent part of the first week hiking in the Snowy Mountains and then for the remainder of the holidays we went to the south coast and then Sydney. Sydney was incredible, probably my favourite city on earth. There were great street musicians, we were even lucky enough to see Winterbourne, check them out!

As you probably know, the great Opera House is in Sydney. I had a brief look at the concerts that would be on during our stay in Sydney. There was one with Jeff Beck and another with Iron & Wine. I had no idea who either of them were, although I guess I should know who Jeff Beck is since he is kind of famous. Me and my friend went to the ticket office to see if there were any tickets left to either of the shows. There were only a few tickets left for Jeff Beck and it was the row in the very back of the chamber and it was quite pricey so we rejected it. However there were quite good tickets left for Iron & Wine so we decided to go with that. I think each ticket was about 80AUD, which isn't too bad for a concert in the Sydney Opera House. The concert was absolutely amazing, great music, great musicians and the sound and acoustics was mindblowing. I couldn't take any photos with my camera in there but I did film the last song of the concert with my phone, I could upload that to YouTube later on.
Sydney Opera House
The rest of the trip didn't include any audio-related events but after Sydney we flew to Cape Town, South Africa, and stayed there for five weeks. After that we had a one day stop over in Dubai, a week of free time in Prague, three weeks of work and conference in south-eastern Czech Republic and then before going back home again on the second of July I spent three days in Prague to wind down a bit.

Since I came home I have mostly been at home. A day or two every now and then working at the summer house and a couple of days visiting friends. Two weeks after I came home I got the results for my university applications. I don't know if I have mentioned it here on the blog before but my plan was to get a master of science degree in media technology at Luleå University in northern Sweden. Last year the programme got cancelled because of too few applicants. I decided I wanted to try to apply again but this year they had cancelled it before the applications started. I hadn't really thought of any other options. Of course there was the option of studying in Stockholm, but accommodation would be way too expensive there. I searched around a bit and found two other universities offering the same programme, one in Norrköping and one in Karlskrona. I decided to apply to Norrköping and at the very moment I'm sitting in my new room in Norrköping. I am sharing a three room apartment with two other guys and I just moved in today. I couldn't bring my big speakers or the subwoofers so right now I only have the Mar-Kel70 and my Denon headphones. There are not many options for speaker placement in my thirteen square meter room so I'll have to be happy with the only possible way, one meter apart and on top of a bookshelf. The bass is quite boomy but I'm planning on experimenting with the MiniDSP some day the EQ the worst peaks. The school starts on Tuesday with a two week long introduction course in mathematics. The first year will mostly be mathematics, physics and other "engineering" courses. First in my second and third year will I start with the more media-specific courses.