A new flavour…

I finally managed to get an opportunity for a taste of a type of class D that I haven’t tried before – a Pascal Audio S-Pro2 module. I unfortunately missed buying a small lot of these a couple of months ago at a price which were at least the deal of the year if not the decade, but here was a single module at a reasonable price on a local classifieds side and so I could not resist buying that instead.

Pascal Audio is a(nother) Danish amplifier module company. It was actually founded by a group of ex-ICEpower people and although there are some clear similarities in product portfolio and product thinking, most of the Pascal products are focused on professional, PA- and musical instrument applications. This does show in things like power levels, channel configurations and module features. However, Pascal have also managed to creep into several hifi brands including Gato Audio, Jeff Rowland Design and many others – even edging out ICEpower from some of them. Irrespective of that, the quality reviews I’ve seen range from app. “massively better than ICEpower and Hypex” to “horrible sound and very poorly engineered”. As usual, the truth is probably somewhere in the middle but I guess we’ll see about that.

The S-Pro2 is a two-channel amp with onboard PSU that will do around 500W/channel in stereo and 1000W in BTL. This means it’s providing roughly twice the power of an ICEpower250ASX2 in almost the same form factor, making it (supposedly) the smallest 1000W amp on the market. As you can see from the pictures this version is an OEM-version without the usual aluminium base plate, which actually doesn’t bother me since it should make mounting the module to a “proper” heatsink much easier (and yes, even at 90% total efficiency a 1000W amplifier & PSU combo is still going to need pretty serious heat sinking if you want to get close to full power!).

While I do (sort of) have a specific project idea in mind for this module it’s going to take a while. First step is to (attempt to) develop a proper adapter PCB for the 26-pin signal connector to break the various module connections out to something that is easier to work with. Once that is done I’ll move on from there to some real testing, but that will definitely take some time 🙂

Project files: Electronic Load files (untested)

My post on Kerry Wong’s electronic load continues to be one of the posts that consistently drives referrals and traffic to the site, even four years on from publishing it. I guess this is more of a testatement to Kerry Wongs’s original idea and design than to my efforts, but it also means that regularly someone will email me and ask what happened to the project. For the last few years I’ve only really be able to answer “not much more than what you can see” and “no, I am not expecting to do anymore about it in the foreseeable future”.

However, I have been thinking that I should get a grip on myself and at least package up my design files so that someone else might be able to carry the project forward forward. Last week another email from a reader managed to prod me just enough that I finally relented and started doing just that, so here I am publishing something that I generally do not like – a completely untested design. However, i do hope that someone can continue with the design and get it tested and running because I’m sure it is worth it (and if at some point I need a load myself, I will be grateful that someone else has done the work 😉 )

More MeanWell IRM PSUs…

As regular readers will know I have been using the Mean Well IRM-series AC/DC PSU modules quite a lot. There are many positives to these modules (size, cost, standby consumption etc.) and only a few downsides, mostly the limited output voltage options and the rather noisy output. The noise doesn’t matter so much when used for auxiliary supplies, but for things like preamps, headphone amps etc. I’m sure it’s possible to do better.

However, because the IRMs are a switching design with a relatively high switching frequency (app. 100kHz), cleaning up the output on the IRMs should be relatively easy with just a passive “Pi”-filter (CRC or CLC). Because of the high ripple/noise frequency even a low series resistance/inductance and a little bit of extra capacitance should have a dramatic effect. Some time ago I started making a single-rail PSU based on an IRM-module for a clean and compact 5V supply for my “Music Box” project, but I realised that actually these would be applicable in many projects so I ended up with several different versions (single/dual, different power levels, integrated/separate filtering etc.)

As I’ve just received what I think is the last variant, an integrated dual version with space for two 15/20W IRMs, now seems to be a good time to collect everything and release the project files so they will be up as soon as I am back from my summer holiday in a week or so. Until then, I hope you enjoy the summer 🙂

Experimenting with ESPs… (part 2)

One of the few projects that has moved a little lately is my ESP-based IoT-experiments (which started here). As mentioned then, I had just managed to crack how to do the mains-powered PCB layout I originally wanted to make so that’s what I have been spending time on building and refining since. Having a mains-powered board makes more sense when you need mains power for a relay anyway, otherwise a plug-in USB supply is just as good (or actually better/safer). The board is shown here in full prototyping mode, it is going into a case – of some sort – very soon.

Apart from adding mains power to the board I also removed the original DHT22 sensor and replaced it with an off-board BME280 instead. That was super smooth and it works even better than the DHT, not to mention that it also measures barometric pressure. I’ve been looking at other sensors as well (UV, air quality, light intensity etc.) but they don’t really make a lot of sense for my immediate application (which is remote monitoring of temperature and humidity in my basement).

Since I finished my original version I’ve made a few enhancements to the software and so now I’ve got the code for both LCD and web-UI mostly finished and especially the web part was a great learning experience. As mentioned in the previous post, it’s also a learning experience I am not sure I would have been able to complete without the help of the excellent ESP- and Arduino tutorials by Rui and Sara at Randomnerdtutorials.com, so obviously very grateful for those.

Now I can still do more improvements to the software but instead of picking at it for another six months I think I’ll try and package it up shortly and then publish it here so that someone else can hopefully have a go at it as well. Stay tuned! (but as usual, don’t hold your breath while you wait…)

Back to the future – of DACs?

For pretty much as long as I can remember, there has been a DAC “arms race” going on where manufacturers competed to give the biggest numbers – 16, 18, 20, 24, 32 bit resolution and 48, 96, 192, 384, 768 kHz sampling rates. Irrespective of whether you had the source material to make use of these massive numbers – or even whether the laws of physics made them obviously pointless in the real world, the “bigger number is better” philosophy was still adhered to.

For a few years though, some people have been going “back to basics” with DAC chips such as the TDA154x and others, as wells as discrete “R2R” dac designs such as the Soekris boards and the Schiit Multibit converters. These designs often don’t offer the full resolution of high-res material, but if you don’t care about that – or if you are still listening primarily to 16/44.1 material – then they offer something else, namely a different (many would say “better”) sound. I’ve previously written that I find the ESS ES90xx dacs to often be very impressive at first, but after a while I get a bit of listening fatigue. It could be me or my imagination, but it’s happened enough times that I start to see a pattern (at least when system matching doesn’t mask it) and so I have been trying to stay clear of ESS-dacs and see what else is on the market.

Now, as usual for this I don’t really need another DAC, but I am still curious 🙂 Not quite curious enough to splash out on a Soekris board to play with to be honest, but still curious enough to clicking the “buy it now” button on ebay for this board. It’s based on the AD1865 IC in dual-mono configuration and once again what pushed me over the edge was that I could get a half-finished board with SMD components soldered, so I had some influence over the design of the board.

Assembly was quite easy because I only had to pick and mount the through-hole parts, but even that was enough to make me remember how much I hate black PCBs. Not only because the seller showed that the board was green in the picture, but also because this is a matte black finish that I haven’t seen before and which makes it 99% impossible to see any traces on the board. Fortunately everything worked the first time, but if it hadn’t I am not sure I would have bothered with that much troubleshooting before giving up. Manufacturers: I know green PCBs are considered “boring”, but they WORK! or if you desperately want something else then blue or red still allows you to see the traces, so please stick to those colours. (OK, rant over 🙂 )

The board has one coax input. I opted for a BNC here because that was the socket I had on hand and that might end up being a mistake, but it works now (with an adapter). There’s also an I2S input meaning it’s possible to connect a second source such as a USB card or similar. As usual, I’ve only done basic listening testing with “baseline” I/V opamps (the OPA2134 and the LME49710) but it’s definitely not making a bad first impression 😀

Not quite sure what to do with this one yet, but possibly a “Music box” version 2? Anyway, more listening impressions to be added later I guess.

Project files: Hypex UcD400OEM adapters

Well, since I shared these on diyaudio already I supposed they should be here as well 🙂

Idling…

Another long break since the last post, but to be honest nothing much has happened over the last few weeks. I have been waiting for some PCBs to turn up and have been busy with non-audio related DIY as well. I’ve also added a few new empty boards from eBay to the project pile but that’s about it.

The PCBs I have been waiting for from manufacturing were a simple dual-PSU based on IRM-modules and another Borbely design – hopefully I’ll have those populated in a few weeks so I can showcase them.

I’ve also previously promised myself to resist the urge to take up more loudspeaker projects, but a few weeks ago a MiniDSP PWR-ICE125 amplifier popped op on my local classifieds page at a reasonable price so now that promise has been broken as well.. No concrete plans yet, but one of the things I’ve investigated before is how to do a “soundbar/soundbase”-style active TV-speaker and some DSP-capabilities would come in handy there. I’ll start by looking at the drivers I have in stock and see if there is anything that be used for that purpose 🙂

Oh, and a final moan about parts availability. I was browsing through Mouser the other day trying to find an 7905 regulator in an isolated package. It looks like JRC are discontinuing some of these negative variants, which is a bit alarming. I genuinely never thought I’d see the day where I’d be concerned about availability of things like three-terminal regulators and BC54x-transistors, but here we are. On the plus side, I’ve noticed that some of the newer audio-grade opamps from TI (OPA16xx) are surprisingly cheap (but of course SMD only) so it’s not all bad but in general parts availability for “normal” diy’ers is declining so rapidly that you can either worry, stockpile or both! 🙂

Bryston BP26 preamp clone…

Even though my pile of finished (and half-finished, and not-even-started-yet…) projects seem to be steadily growing, I can’t help but keep an eye on eBay for new and interesting designs to add to it. I’m not sure I can describe fully what makes a design “interesting” to me, but something about how it looks, how well thought-out it seems to be in terms of features, whether it seems to be well-engineered and also whether it’s fully-assembled or PCB/kit so I can influence component choices etc. myself – and of course whether it looks like good value.

The latest thing I stumbled upon was a blank PCB of a (supposed) clone of a Bryston BP26 preamp. To be honest Bryston is one of those brands that I know about but have never really had any particular opinion about. I get the impression that their stuff is solid and well-engineered, but their representation in Europe is sketchy and the design of their products has never really managed to catch my eye. However, regardless of the supposed provenance of this kit – you never really know how close to the original these “clones” actually are – a fully discrete preamp design with both balanced and SE inputs is definitely interesting. The board looked good on the pictures and as I had most of the expensive components (connectors, relays etc. ) and quite a bit of the other stuff on hand already, I decided to take a chance on it.

Normally the quality of these ebay-offerings is a bit hit-and-miss to say the least, but this one I’d place firmly in the “hit” category. The board is good quality and it is supplied with documentation that is well above average for what you can expect. Full, readable pdf-schematic, full BoM (with just a few untranslated comments in Chinese that you have to work out), a basic adjustment procedure (only one trimpot per channel) and – something completely unheard of – a mechanical drawing of the rear panel cutouts for the connectors!.

The board came together quite easily, and although it took a while for me to operate the input selector correctly during testing to actually get sound (…) there were no real issues getting it to work. The board seems stable and well-behaved in initial testing, meaning no nasty turn-on/turn-off thumps, no noise and no unexpected spikes in DC-offset or bias at any point.

Normally I’d try and finish the full pre as quickly as possible, but this time I’ve chosen a slightly different strategy. I’m going to listen to the board in my own system before i decide if I want to commit the extra money for the final enclosure (mostly because a customised back panel is probably going to cost about the same as all the other components combined). While I am waiting for a PSU board that should be here in a couple of weeks, I’ve repurposed an old bottom plate into a makeshift test bottom. Let’s see and hear what this thing can really do then 🙂

Anniversary…

Yes, it’s that time of the year again – the time where this blog celebrates its anniversary!

This time it’s number six and it is of course even more surprising than last time that I’ve gotten this far. The pace has slowed a bit I think, but I’m still going and in all honesty the backlog of potential projects and content is still huge.
So, if you readers promise to stick around I promise to do the same 😀

Until next year, thanks for reading and thanks for your questions/comments and feedback because that is truly what really makes it worthwhile for me to continue posting! 🙂

Project files: The BBA3FE

Haven’t really had time to fully complete my BBA3FE project yet, but as I am otherwise happy with the design I might as well release it in case anyone wants to have a play with it 🙂