So, here we go again – today is the 11th anniversary of this blog (!). The last year has been quiet, mostly due to the usual reasons of life, work and the other small things that compete with DIY audio for my attention 🙂
I’m still here though, and I have no plans except to continue at this new pace. I still have loads of projects I want to get to – old and new, speakers and electronics, some nearly completed and some still waiting to be explored.
The focus at the moment seems to have gone back to headamps for reasons I have described in the last few posts, but there are lots of other things in the pipeline as well. My main system has gone from being fully dedicated to experimentation to a more “daily life” mode, but with that comes opportunities as well.
I have a new “centerpiece” of my system, an Eversolo DMP-A8 streamer/preamp, but I still have some flexibility in terms of adding active/passive speakers, replacing power amps etc. so there is still plenty of room for experiementation – but with the convencience of being able to get music at the touch of a single button as well.
I hope you can settle into the slower pace as I have, but continue following and I am sure there will be more interesting content going forward 🙂
I’ve started building a fair few new headphone amps for my dynamic headphones (old and new) lately, but I also took the opportunity to dig out my Stax SR-007a electrostatics from storage. I only had a basic amp for these which really worked (a small Stax SRM-252), plus of course a number of half-finished DIY-projects. However, my local Stax-vendor popped up with a great offer on an older ex-dem SRM727 mk. 2 amp, and I decided to buy that.
Reading online reviews of the Stax amps it seems like there is a world of difference in sound and many improvements to be had from moving to one of Gilmore-amps – and to be honest, there may well be. I’m just at a stage now (it happens from time to time) where I prioritise having equipment that simply works.
I’m still going to keep building amps (and finishing the projects I started). However, just being able to put the amp on the table, turn it on and then sit back to enjoy some music clearly has a charm of its own 🙂
Part of my (ongoing) cleanup of old projects is this – a power amp I’ve been meaning to finish even though I don’t really need it. It’s not a new idea and based on a pair of leftover ICEpower 200AC amplifier modules (and a leftover transformer) coupled with my original A-series linear PSU board.
These modules are not exactly “state of the art” in class D terms given that they were launched nearly 20 years ago based on a class D implementation even older than that. Similarly the “hybrid” design with a class D amplifier and a linear PSU is also getting rarer these days (in favor of fully-switching designs with an SMPS either onboard or on the side). Looking at what I have added to the transformer and PSU to make it work (fuseboard and softstart) I can definitely understand why.
Not only are the 200AC modules technologically a bit long in the tooth, I also have to admit that sound-wise they aren’t really state-of-the-art anymore either. That said, considering how much space the actual amplifiers take up the sound they produce is still pretty impressive.
The transformer I’ve used is slightly undersized, but with separate PSUs per channel and the somewhat more forgiving behavior of a mains transformer compared to a switching supply and it should be OK – I don’t expect I’ll ever need to run this at full power anyway.
Alright, one project down – dozens more to go 🙂
So, the Easter break has come (and almost gone again). Although I didn’t get quite as much DIY-time as I hoped for – between the last few panicky things that had to be closed at work and some unavoidable projects around the house – I still managed to “reset” from a long period where my focus has been almost 100% on my job. Hopefully my workload will be back to around normal levels after the break.
I managed to keep the ratio of “new projects started” vs. “old projects finished” at a reasonable level (= around 1:1 …) and once again I note with some embarrassment how little resistance it seems to take to get me to abandon or at least pause a project. Fortunately, that means picking them up again later is even easier, so looking forward to hopefully showing a few more completed builds in the not-too-distant future.
A selection of other things I managed to complete includes a balanced-output Bluetooth-received based on an Aliexpress PCB. This has a PCM1794 DAC and a QCC5125 Bluetooth receiver and it’s mainly intended as a simple test source. It’s a bit rudimentary but it works and sounds OK for the purpose. I might redo the front panel at some point to feature a power switch and the SE output that I could not fit on the back panel, but certainly not a priority for now.
I also completed one of my “own” designs, which is a small discrete output delay circuit for preamps and headamps. It’s not my own design, but made by diyaudio-member Andy/iamwhoiam who sadly does not seem to be active anymore. Andy’s original design was minaturised to the extreme in order to be able to retrofit it into existing equipment. My version is slightly larger, but still quite compact. It’s an important part of one of my coming builds so yet another impediment to progress removed then. Project files coming shortly as well in case someone else finds it useful 🙂
I’m still super busy at work, but somehow I have managed to squeeze in a bit of audio DIY to help me think of something else when I do have a free evening or a day off. A somewhat unexpected side-effect of the workload is that because I spend the whole day in noisy offices and meetings I feel the need to sit down and relax on my own when I am off. That has meant I have started listening to headphones at home again, something I haven’t otherwise done for a good long while.
The first thing I did was to create a “listening station” on a corner of my coffee table (more permanent solution probably coming at some point…). I put up an amp and a DAC and started with my AKG K812s which is more or less the only headphones that I have otherwise used for the last many years. I like the AKG sound signature and the K812s are very comfortable. I also looked through what else I had in terms of headphones of yesteryear, starting with the AKG K501 (a trusty friend, even though they sound a bit bright), the AKG K701 (nice, but I dislike the original pads so I have ordered some replacements which are hopefully better) and – lo and behold – my original pair of Grado SR325s.
I bought these second-hand from a head-fi’er in the US in around 2003 but never really used them much. Both the original earpads and the (at the time very coveted) “TTVJ flat pads” completely disintegrated the moment I touched them. However, at the bottom of the box were a pair of unopened yellow pads for the Sennheiser HD414. These were a popular Grado upgrade at the time I bought the headphones and even after 20 years in storage they were still in perfect condition. Time to try them out then! I have to say the Grados are still a good pair of headphones, but they are lacking in comfort and to say that they are outclassed by the K812s in terms of sound is a bit of an understatement. Still, a wonderful throwback to when I first started in this hobby.
The amp I started out with was also an “old favourite” – the EL2k. This sounds great – and it is also pretty much “state of the art” for 2004 so that is quite fitting. I don’t think I ever published pictures of my finished amp using the original 75mm version, so here’s one. I have rotated in other amps and I have to say I still think this one sounds great. I also remembered that these were the first EL2k boards I built and they actually use the EL2008 buffer rather than the “full-fat” EL2009 buffers which I used later on. That seems like a shame, so since I have more of the EL2009s left I went back to the design and redid a new version which I can hopefully show off shortly.
I hope to “resurface” a bit more in a month or so, but for now I can at least offer the encouragement that something is going on despite the busyness 🙂
Time flies when you are having fun – or when you are just very busy with a big project at work!. Here are the project files for the subwoofer preamp I showed in the previous post.
As I have mentioned previously separate “bass modules” is logical approach to speaker design given my constraints in terms of speaker size, speaker placement and desire to experiment. This implies a “2+1” construction with a small(ish) two-way top section and a larger bass module which typically also doubles as a speaker stand. The filtering between the top section and the bass module is usually active because the crossover frequencies are low and because an active filter is way more flexible for this application.
An obvious add-on to the active filter is then DSP-based bass EQ. However, DSP is a powerful tool for audio experimentation and it has many use-cases but sometimes you don’t need all these powerful features and just having a couple of knobs to turn is enough. I have been thinking about basic analog active filters before and even bought a couple of cheap kits from Aliexpress. They sort of work, but one of the things that is a bit annoying is that there is no documentation so I didn’t understand exactly how they worked (and I always seemed to had an excuse not to read up on the theory of active filters).
Some weeks ago I found an old article on a blog on Sensibleaudio.dk written by diyaudio.com user “Baldin” who is quite knowledgeable about electronics (as an E.E.) and also a fellow Dane. The schematic seemed pretty much spot-on what I needed with just adjustable volume and frequency. A couple of follow-up questions around the filter design were answered quickly, so I understood the circuit design before doing a new PCB layout and I was able to simulate a few parts changes myself.
I made a few small changes to the original schematic, mainly getting rid of the original discrete regulator and replacing it with a pair of 78xx/79xx ICs. Partly because this is a bit simpler and partly because my immediate use-case is to recycle a couple of old ICEpower250ASP amps into some basic plate amps. The ICEpower modules have an onboard +/-12V supply, so it could even been used without the regulators, but to provide a bit more versatility I decided to keep them on the board.
This is a simple circuit, but still I am reminded how surprisingly satisfactory it is to not only finish a project but also to learn something new in the process, even after having this hobby for so long 🙂
…and it’s that time again, saying “goodbye” to 2023 and “hello” to 2024.
2023 was a pretty quiet year around here to be honest and 2024 looks to be the same. Don’t worry I’ll still be around, but as mentioned in the last post at a continued low pace for at least the first few months of the year. Otherwise there’s loads to look forward to in terms of projects – I’m just not sure exactly when I’ll get round to doing them… 🙂
As usual I have to say a big “thank you“ to everyone who is reading, commenting and messaging me. I’ve said this many times, but this is one of the key reasons that no matter how busy I am it is always at the back of my mind that I want to keep posting here as much as time permits.
Christmas is (almost) here, and with it a welcome long break from work. I’ve been super-busy the last couple of months, which is also why I’ve only posted sporadic updates to the blog. To be honest I expect that to continue until at least around Easter, so even with nearly two weeks off now I am getting that “now or never”-vibe and I hope to spend a few days catching up on some projects. I don’t have any concrete priorities as such, but as usual I find myself looking at stacks of half-finished DIY-projects and piles of partially-processed MDF so I should be able to get something meaningful done 🙂
Since it is Christmas, a few weeks I thought I had managed to secure a proper present for myself. After months of monitoring classifieds more or less throughout Europe I managed to find a Stax SRD7 transformer box which I wanted to recase and use with my Electrostatic headphone bias-circuit: Sadly I was just informed that the package has been lost/damaged and isn’t going to show after all. The financial loss is manageable, but this is my first lost package in years and so I can’t help swearing at the fact that they had to lose the one package which cannot be replaced and not one of the (literally) hundreds of others that I order every year! Anyway, the search goes on and I will be lucky at some point!
Will post more once I hopefully have something more interesting to show, but until then I wish you and those around you a very happy Christmas! 🙂
So after my dismal failure with a cheap TPA3255 board some time ago I thought it was about time to try again. I therefore bought a new TPA-board from Aliexpress – slightly different type than last time but same basic idea – and the price was only around 25 USD.
I’ve just briefly tested the amp for now, but it seems well-behaved with no turn-on and turn-off thumps. This may seem like a minor concern, but I know from past experience that if an amp has major issues here I will never really be happy using it on a daily basis and so it ends up being a big problem.
I’ve also (only) done a quick sound testing with some test speakers. The TPA3255 has a reputation for good sound and this board does not seem to be an exception. Of course a serious audiophile will want to experiment and may be able to find something better, but to be honest for any “normal” person (i.e. non-audiophile) this is could well be “all the amplifier you really need”. Not entirely unexpected, but still pretty impressive for something that is so cheap.
I have plans to case this board at some point and/or buy a second one for 4-channel use, but it may take some time (I am super busy at work right now). One modification I will have to attempt is to remove the tantalum input capacitors (argh!) and replace them with something better – hopefully I can do this with a better result than last time, but wish me luck 🙂
theslowdiyer 