An ICEpower 50ASX amp – the easy way…

Some weeks ago a reader on the blog asked me some questions about various pre-made options for putting together a simple amplifier based on the ICEpower 50ASX2 module.

One of the options mentioned was to buy a case-kit for the module from Ghent Audio in China. I’ve seen pictures of these cases before and not only do they look quite good, they also come pre-drilled and silkscreened which for most DIY’ers is the hardest part of building stuff. I answered the questions as best I could without any hands-on experience to offer, but as I had an older black 50ASX-module left over I decided afterwards to get a case for myself and try them out.

After the usual waiting on shipping (which wasn’t actually that bad – app. 2.5 weeks), the case kit arrived. Everything is included, a power switch assembly, AC inlet, terminals etc and it seems to be decent quality all round. I didn’t buy the full cable kit, which would have made it even easier to assemble, but still it’s not too bad.

Putting together the basic kit with the module, feet, switch etc. ready for cabling only took around half an hour or so. If you look at the pictures I’ve made a few “adjustments” to the kit by using stainless screws and feet (the kit comes with black screws and matte silver feet), but otherwise it is as delivered and of course using the original parts would also have been just fine. The terminals are decent quality, but not the best I’ve seen. Also, the terminal holes are drilled too large (presumably to accommodate changing suppliers) which is slightly annoying but by no means a deal-breaker.

A bit more digging in the parts drawers revealed some suitable pre-made cables for signal and speakers – and a problem: my stock of JST connectors for the power connections has run out (or run away :-))

So yes, in conclusion this is definitely an easy way to build an amplifier (just as long as you ensure you get all the parts before you start 😉


Hypex UcD in progress…

It’s been quite some time since I have posted about a project that I have actually completed – and so I’m a little ashamed to say that this post won’t break that trend 🙂

It’s a class D power amplifier based on Hypex UcD400HG modules. As with many of my other projects, it started with a few leftover parts and some thoughts about what to make from them. In this case, it was the chassis and the “centrepiece” of the design, namely a gigantic 1000VA transformer. Trying to decide what to do with that lot soon led to some obvious choices:

  • It had to be class D because there was very little space for the actual amplifier and heat sinks once the transformer was installed 🙂
  • The “upstairs/downstairs” layout that I have mentioned before became a necessity to make use of the internal height of the chassis.
  • I wanted to reuse my PSU-boards because I already had spare PCBs, but they wouldn’t fit and so I had so make a smaller version.

I know Hypex has shifted to their newer N-Core technology and started building integrated modules with onboard SMPS, but the old UcD-modules still have a reputation as excellent amplifiers. The plan is to upgrade them with the Hypex HxR-regulators once I confirm that everything is working properly.

The “final problem” is how to provide heat sinking. I have my eyes on some pre-made heat sinks that should do the job, but they are from a supplier where I don’t normally order so costs are a bit higher than I would like. I might eventually break down just to get it over with, but in the mean time I have a couple of other options in mind as well 🙂

Class D experiments…

There are many class D technologies on the market at the moment, but one of the ones I haven’t tried (until now at least) is the International Rectifier “IRAUD7”-amps (IRF has been acquired by Infinion).

Consisting of the IRS2092 driver IC and various purpose-built FETs (many of them two FETs in a single package suitable for half-bridge designs), this is by most accounts a good-sounding and scalable class D technology. It’s also one of the few technologies where you can actually have a go at your own PCB layout if you want to. The schematics are available in IRFs published reference designs (here and here) and although making good PCB layouts for high-power switching electronics isn’t easy, it is actually possible to do.

Of course, when something is so easily available it tends to get exploited. It wasn’t long after IR introduced the designs before the market was flooded with several cheap clones, some using their own PCB layouts and some using IRs own Gerber files which are also published on the website. I had my eyes on some small (credit-card sized) boards to try for a while as they were really cheap (do an ebay-search for “IRS2092” and you’ll see 🙂 ), but eventually spotted this “luxury” version (at least based on appearance and observed parts quality) and fell in.

This build is the “low power” version with the IRFI4019 FET, but there’s also higher-power version with the IRFI4020 FET. Since the seller I bought from made a mix-up in ordering I actually ended up having a pair of each version, but I wanted to start with the low-power version. Then I might go dual-mono on the high-power boards later on if the sound quality proves it worthwhile 😀

The PSU consists of a 200VA transformer and a cheap supply PCB with 45mF capacitance per rail – mostly because that was what I had in my parts drawers. I’ve tried to keep the mechanics as simple as possible since I consider this build an experiment, but having the amp and PSU on a mounting plate simply makes everything much easier so I decided to “splurge” a little anyway :). The front panel is blank until I decide how the amp is going to be used.

Even though the pictures show the amplifiers uncabled (which they still are), I did manage some sneak listening on the modules and I am looking forward getting these into my main system for a proper test 🙂


50ASX BTL conversion (part 2)…

So, I’ve done some more testing on my BTL-converted 50ASX-modules…

As you can see, I’ve used a slightly less improvised test setup compared to last time (it looks worse than it is…). While I wouldn’t call what I have done “extensive testing” by any means, my gut feeling is that this works 🙂 It also ties in well with how the other ASX-modules work and some “insider knowledge” from years ago that I can still recall 🙂

Note and disclaimer: I would very much appreciate if someone else tried this to verify and maybe do more testing, however I will accept no responsibility for damage to property, people or pets (or anything else for that matter) if you find a problem – this is DIY after all 😀

You can of course hack this conversion anyway you like, but I opted for removing the old jumper altogether and soldering in a new one. If you do that, be advised that the ASX-board is four layers and soldered with lead-free solder, so it will take a bit more heat to reflow the joints than I am at least used to. If you use a soldering iron that is too small, you’ll just heat up the board and possibly damage it.

My suggested approach would be to cut the jumper on the top side of the board. Heat the solder joint from the bottom and pull out the jumper wire with small pliers. Then clean the remaining solder off the board with desoldering braid or (better yet) a vacuum desoldering station if you have access to one. Then solder in the new jumper in the BTL position. There isn’t much space to work on and you should be careful not to damage any of the (sometimes annoyingly) small SMD-components on either side of the board. Once the new jumper is in place, follow the wiring diagram for the BTL-version in the 50ASX data sheet/designer’s manual and you should be good to go.

Bear in mind that what you end up with isn’t a “real” balanced (= differential) amplifier, but two SE amps referenced to ground and driven with opposite phase input signals to produced a bridged output. As such, the input ground is still required in order for the amp to produce a correct signal on the output. I’ve found a good sketch here for LM3886 modules that should show the correct input wiring. Output on the ASX is taken from the P104 connector, so ignore what the sketch shows here (and of course the DC wiring is irrelevant as well).

If you do try this, let me know how you get on 😀

PS: Yeah and the picture is still crap – but don’t worry, the light should be better from around April onwards 😉


ICEpower 50ASX – SE to BTL conversion

I’ve recieved a few questions (and participated in a diyaudio discussion thread) about converting ICEpower 50ASX2 SE modules (which are fairly easy to get), into 50ASX BTL modules (which aren’t). I was pretty sure this could be done without component substitutions by simply desoldering the W401 jumper and resoldering it into the W400 position (marked BTL on the bottom of the board) but as I had no modules left, I couldn’t try it. Now I’ve managed to get my hands on some more modules and I’ve actually tried converting one of them and the good news are – I think it works!

I haven’t actually measured anything (not sure what to measure to be honest) but I get clean audio out on the BTL speaker connector (P104) and a very loud buzzing noise on the other output, so at least it isn’t running stereo anymore. No guarantees on anything yet though, but it’s definitely promising.

Oh, and don’t laugh at my improvised test setup, it is necessary because I don’t have a proper balanced source in the house at the moment and I couldn’t be bothered to crimp new cables just for testing 🙂 Incidentally, don’t laugh at the poor picture either – winter in Scandinavia means the days are so short that I can only take pictures in daylight during the weekend…

Next up is to convert a second module, build some better cables and try it “for real” in a stereo setup – hopefully this weekend 🙂


Tripath TK2050 monos…

Well, it’s been a while since I posted a project that was actually finished…. and this one isn’t either 😀

It’s a pair of monoblock amplifiers based on Arjen Helder’s Tripath TK2050-boards. Arjen Helder is/was a Dutch guy living in China who around 5 years ago sold some great DIY boards based on the Tripath class D ICs. He’s probably mostly known in the DIY-community for the low-power TA2020-based amps, but he did make a few designs based on the more powerful TK2050 chipset as well. I bought a couple of the TA2020 boards when they were available because they were cheap and sounded great, but I managed to stay away from the TK2050 boards back then because I did not have anything to use them for (come to think of it, I don’t now either… 🙂 ).

Unfortunately I am nearly powerless to resist the temptation of an ebay-bargain so I snapped up this pair that I stumbled upon a couple of months ago without much hesitation. Originally, the plan was to mod the boards a bit replacing the stock capacitors, in/out connections etc. However, some of the traces seem to be very thin and as it isn’t possible to get a replacement board if I damage something I limited myself to just replacing the input caps.

The power supplies are a couple of Mean Well EPP-150s which were “left over” from my JLH-Evo build. They should be more or less spot-on for this when used in dual-mono mode and the small 4” x 2” size is an advantage as well.

The mechanics consist of pair of Chinese-made enclosures (selected because they were the right size for the job…) with custom rear-panels. I was going to use the stock rear panels, but a couple of stupid measurement-errors that I did not notice until after drilling made that a lost cause 😉

What’s missing is only really a few cables, but that isn’t my favourite part of a build and so I might save it for a long dark winter’s night instead 😉

Simplifying ICEpower integrated amps…

Another old idea that I have resurrected and polished up a little 🙂

Many people (and many of my readers) want to build small integrated amplifiers with ready-made amplifier modules, e.g. the ICEpower ASX-series. It’s not that difficult as-is, but what if there was a single board that could help to convert an ICEpower ASX-module into a proper integrated amp? Well, there is now 😉

This module is basically made up of three parts bolted on to the same PCB.

– four single-ended inputs, switchable with relays
– a selector circuit that enables input switching with a single pushbutton (or with a rotary switch if you prefer)
– a power supply to utilise the on-board (but unregulated) AUX power supply on the ASX-modules as a power source

The only thing missing here is a pre-amp of some sort which must be a separate PCB, but can be powered from this board. The “Minipre” circuit was specifically made for this job but other circuits would certainly work as well – as long as they can run off +/-12VDC.

I made the first iteration of this board several years ago but managed to mess up the power supply arrangement so the original version didn’t really work (grr!). That I decided to get this circuit out of the drawer quite recently is no coincidence – I happened to find a single 50ASX module which I thought I had used already and so you can probably guess where this will eventually be going 😉

PS: While I prepare the project files for publication, let’s take the most obvious Q&As straight away 🙂

Q: Can it be used with other ICEpower modules, e.g. ASP/ASC-models?
A: Yes, but you’ll have to bypass the onboard power supply regulators etc. on the selector board as the ASP and ASC-modules have a regulated AUX-supply. Also, this board is intended for SE inputs and not balanced inputs (see below).

Q: Can the board be used as a standalone circuit or with other types of power amp modules?
A: Yes, but you’ll probably need a small unregulated dual power supply (15-18V) to power it. The current requirements will depend on which preamp-circuit you are using, but around 100-200 mA should be enough.

Q: Do I need to be able to program microcontrollers to build this?
A: No, the input switching is based on a 4017 counter IC so there is no code in this project at all.

Q: Can I use a rotary switch to select inputs?
A: Yes. Just connect the switch to the I/O header and omit the 4017 IC and its supporting components (a dedicated PCB for this is coming very soon).

Q: Can I stack two boards for balanced inputs?
A: Probably, although I haven’t tried it. Build a full “master” board and then a separate “slave” board without the PSU and selector components. Connect the I/O headers between master and slave for power/control and it should work (again, note the “should”-part…).

Surrounded – again!

This is an old project that I have resurrected now as I would like to get my surround-sound setup back into working order (not that I expect I’ll be using it that much, but still…)

It’s a 2+3 channel ICEpower ASX-based setup with 125ASXs in BTL-mode at the front and 50ASXBTLs for center and rear. The 2-channel amplifier very nearly identical to my previous 125ASX-based amplifier but it does have three USPs compared to that build:

  • Transformer-coupled (balanced) inputs using Lundahl LL1527 transformers.
  • Two switchable inputs so it can be connected to both a stereo source and a surround-processor simultaneously.
  • ”Audiophile” form factor (i.e. around 44 cm. wide and much larger than is really necessary 😀 )

The 3-channel amplifier also has Lundahls at the input but no input switching (for obvious reasons).

Many upmarket manufacturers use transformers on the inputs of ICEpower-based amps and Lundahl in Sweden make some of the best ones around. The LL1527 isn’t usually employed as an input transformer, but if I’m reading the specs correctly it’s actually fairly well-suited to the lowish input impedance of the ICEpower modules so it should work well. The alternative (which would also fit on my boards) is the LL1540 which is a purpose-built high impedance input transformer. And well, if all else fails the way that these are mounted would mean that I could probably develop an active circuit instead 🙂 (differential opamp-board anyone?)

Just like my as-yet-not-completed “Ring” amp project the front channel amp has switchable inputs so that it can be used in a combined stereo/surround setup. Switching after the respective volume controls make more sense to me, but of course I haven’t actually lived with it yet so let’s see if theory meets practice in this case 😀 This switching is relay-based and uses the balanced selector modules I posted about earlier – yes, sometimes those piles of leftover prototype PCBs come in very handy :D.

There isn’t actually a lot missing – mostly cabling – before this is done, but I hate cabling so it might take a while to do it anyway 😉

New Chinese miniamps…

A few weeks ago I stumbled across a post on diyaudio mentioning the latest in (the long line of) ultra-mini class D chipamps offered on eBay/Aliexpress. The boards looked interesting and so I “splurged” for a pair which turned up this past weekend. Although in all honesty “splurged” probably isn’t the right term here as I paid a grand total of 12.50 EUR for the pair – including shipping (!!).

Like many of the other small amp boards, this one uses the TPA3118d2 class D IC from TI. The TPA3118 chip has a fairly good reputation on diyaudio and it will give a reasonably high power level when used as a mono amplifier (called PBTL-mode). The chip has a thermal pad on the underside and so uses the PCB copper as the heatsink surface. Unlike many other similar boards though, these boards are pure poweramps (no onboard volume pot) which is fine for me. They are also tiny at 35 by 46 mm – which means even two channels side-by-side are still visibly smaller than a credit card (!!)

So, very small, very cheap, quite powerful, and decent sound quality – what’s not to like? Not a lot actually. It would have been nice if the chip had been the TPA3116 which has the thermal pad facing upwards. Even through there isn’t a lot of space, it would still have been possible to fit a small heatsink on top of the chip and thereby (probably) improve the thermal performance and get a bit more output power.

Another slight negative is that the input capacitor is an X7R ceramic type which really isn’t the best choice for audio. Because it’s a 0603 SMD it’s also tiny and very difficult to replace/exchange with something better. The boards seem to be set to the highest gain (36 dB) which is good if the source is a smartphone or similar, but on the high side if it’s a typical hifi source like a DAC. Again, adjustment of the gain would require replacing 0603 resistors which is not that fun a pain in the … but overall it’s a minor downside.

The boards in stock form don’t have any connectors for inputs and outputs, but I’ve added some to my pair to make testing a bit easier. I need to do a bit more listening with these “prototypes”, but if the sound quality is any good I do have a specific project in mind for them for later 🙂

Project files: Amplifier PSUs

Digging in the back catalogue a bit again here.…and found some of my power supply boards that I haven’t published yet 🙂

What is it?
Power supplies for amplifiers, d’oh! 😀 Two basic variants, namely a “class AB” type and a “class A” type. The “class A” type is intended to be used in a CxC configuration with resistors onboard for CRC and pads for a choke to make it CLC. The “class AB” one is a standard unregulated design for class AB or D amplifiers that allows using both small 16/18mm radial capacitors and large snap-in types (up to 35mm). Here there are two versions, one for 2 off 35mm caps (or 8 smaller caps) per rail and one for 3/12.

The picture below is of the large class AB board. It’s actually the board from the previous post that has had some caps mounted in the mean time 🙂

How big are the boards?
The AB board measures 3.55” x 3.9” (app. 90 x 99 mm.) for the standard version and 3.05” x 6.1” (app. 77 x 155 mm.) for the XL version. The CRC board measures 3.15” x 3.95” (app. 80 x 100 mm).

What is the status of the boards?
Both of the “class AB” boards are in v1.0. The “class A” board is in v1.1 as I made a couple of tweaks (including the pads for off board R/L) to my original version. The original v1.0 is the board that I use in my “Green Monstre” amps.

Does it use any special/expensive/hard-to-find parts?
Nothing, really. You can go overboard with expensive capacitors if you want, but even if you have the money to put NOS Black Gates in your power supplies I’d still suggest you spend them elsewhere in the circuit 😀

Anything else I need to know?

  • Unless you are building very small amplifiers I’d recommend that the CRC and the small AB boards are used in dual-mono configurations with one PSU per amplifier channel. The large AB board can be shared across channels for a medium power class AB or D amplifier (meaning anything with a rail voltage up to around 55V and 63V caps).
  • The boards all include LEDs that indicate power and bleed the capacitors when no load is connected (albeit very slowly). The corresponding resistor footprints should be large enough to allow fairly high LED currents but remember to calculate the power dissipation.
  • The CRC board has space for two resistors in parallel per rail, either axial types (up to around 3-5W will fit) or MPC7x radial types up to 5W.
  • The rectifiers are GBU-types which are available from Mouser up to a 25A rating.
  • Input connections for the Class AB “XL” board are via FAST-ON tabs. All other input/output connections are via 5mm spacing screw terminals.
  • The capacitors on the class A-board can be up to 30mm in diameter. Since class A amps tend to get hot, I’d recommend 105 degree types here. As mentioned above, the class AB boards use either snap-in caps up to 35mm diameter or 16/18mm  radial caps with 7.5mm pin spacing.
  • Needless to say, all capacitors should be rated appropriately for your amplifier’s rail voltage.


Download design files here

Related information:
These are very simple circuits, but there’s some god background on PSU design for amplifiers over on Rod Elliot’s pages (under “power”)

Note: Always read the “intro post” for additional important information about my designs.