A new king?

Normally I spend a surprisingly low amount of time listening to the builds I finish, but this one is an exception. That’s because I finished casing my Hypex NC502MP class D module and as I have very little experience with the Hypex class D amps, I had to try it out.

The original plan for the module was to build a top-end “integrated” amplifier but I quickly abandoned that idea (however, I picked it up again later with this build). Instead I’ve simply cased the module in a basic Modushop case but added an 8mm thick piece of aluminium to the bottom. A small niggle is that I can’t seem to find the crimps for the signal connectors so I used the cables I had to get the amp working, but it would be nice to be able to put in a functioning mute switch and a power LED as well.

As you probably already know class D is very efficient and class D amps therefore run very cool – right? Not quite actually. The very high efficiency numbers are always measured at (nearly) full power and at low power the efficiency is typically quite unspectacular. The Hypex module here has idle losses of around 20W, which honestly isn’t far off what you might get from an 80-100W class AB amp with a traditional power supply.

The module does therefore run quite hot and don’t for a moment think that my “thermal design” here is suitable for anything except a limited home use application. Even so, it’s hotter than I expected and what surprises me most is actually that I measure very high temperatures on places like the output chokes – these parts are not heat sinked to the backplate and so presumably a better heat sink on the back would not make much difference?. In any case the few experiments I did were enough to break with my conventions and order a ventilated lid for the amplifier instead of the usual one I use, because running the amp “topless” did make a difference to the temperature of the board.

On to the listening then: The logical comparison is against my “new favourite” ICEpower amp, the 700AS2. However, initially I just hooked up the Hypex amp to my test speakers (a pair of 5” Tang Band full range drivers in small reflex boxes) and even then it was obvious that this is a high quality amp. I especially noticed that the small TBs actually managed to sound like they had some bass articulation, which definitely isn’t common. In fact, the very improvised “test setup” ended up staying on my temporary work-from-home desk for three days of near-field listening.

Moving the amp into the main system and the positive impressions continue – this really is a great-sounding amplifier. To make a long story short though, I still ended up returning to the ICEpower amp in my current system for two main reasons: One is that the ICEpower amp seems to give a slightly wider soundstage which I am honestly a bit of a sucker for, and the other is that the ICEpower seems a little leaner in the bass. Whether that is a good thing or a bad thing in absolute terms I am not sure about, but my speakers are quite bass-heavy already and any more just makes them boomy which I don’t like.

Be in no doubt that to me this is a very capable amp though, and as I have a suitable enclosure with a bit more heat sinking that would suit a dual-mono setup I’ll definitely be keeping an eye out for a pair of the mono NC500MPs 🙂

Building an(other) F5…

Although I recently built a new type of F5 amplifier, I haven’t completely abandoned the original F5 design 🙂 Hiding in one of my many boxes were a pair of half-finished F5 boards and some matching matching fan heatsinks that only needed the last bits of assembly and calibration. That honestly didn’t take long to do once the right parts showed up and I then managed to confirm the boards were indeed working.

The boards were originally bought from ebay and are more or less the same as my original F5 build – nothing special there. I have some matching PSU boards as well, only missing the last few parts which are now in the queue for my next order and that’s going to be a standard C-R-C type thing as well.

The mechanical design is from the same time as my JLH mono blocks, so the idea is also more or less the same. This heat sink profile is too large to fit in most enclosures though, so cracking what to do took some time but I think I have it figured out now. It’s also going to be monoblocks, but much larger ones than the JLHs. From my first tests during calibration of the boards I think a slow-speed fan should be enough to keep the heat under control, so hopefully they will be living-room friendly when they are done 🙂

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 🙂

PeeCeeBees in a box…

Well, almost. At least the box is ready for the PeeCeeBees, even if they are not quite ready for it yet 😀

Apologies for the stupid puns, but I managed to (nearly) finish the chassis for the PeeCeeBee amplifier boards. The basis is a small ebay-sourced enclosure with side heatsinks, but I have replaced the rear panel and fitted the insides with custom mounting panels for the PSU and the transformer/softstart.

The “upstairs/downstairs” layout maximises internal space and is something I plan to reuse extensively on other projects (even if the cost of the custom panels from Schaeffer/FPX does begin to add up…)

Still to do is some transistor matching (bleh!) before I can finish and test the boards and I also need to order a new transformer – the one in the picture is the right size, but not quite the right voltage.

First Watt F4 (part 1)

I don’t normally build class A amps in the summer because my apartment gets really warm, but this time is an exception. Partly because this summer in Copenhagen has been much more “class A amp friendly” (i.e. a lot colder!) than usual, and partly because this is a design I’ve been wanting to try for a very long time now.

The First Watt F4 is a classic Nelson Pass/First Watt design with JFET inputs and MOS-FET outputs. However, as with the other FW amps there is a twist here, namely that the F4 has no voltage gain. That means it’s essentially a buffer than can provide a full 25W class A output. What’s the point of that you might ask? Well, one point is that it can help get a better gain structure and that it’s possible to use some sources (such as DACs) which have a very high output. There are various other applications in the F4 manual as well.

Some will have spotted that the F4 boards are from the diyaudio store. They are good quality and a well-proven design, so I decided not to bother doing my own.

The chassis is sort of the usual from Modushop, but then not quite anyway. Partly because the heatsinks are predrilled 4U types from diyaudio (which did cost a bit more, but saved me drilling and tapping nearly 30 M3 holes) – because they match the boards 100%, and partly because I have decided to do a bit of “hacking” to make a non-standard size chassis (teaser! 🙂 )

So, in addition to the chassis hacking, I am also thinking about which preamp to choose to provide the voltage gain for this and obviously there are plenty to choose from, so it should be possible to come up with an intriguing combination for you guys 😀

Soundwise I also have quite high expectations because of my past experience with the First Watt F5 design – which I still consider one of the best sounding amplifiers I have tried in my home system – but let’s see if the F4 delivers on that front as well when it’s ready 🙂

PeeCeeBees in the wild…

First of all, let me apologise for showing yet another half-finished board, but there’s a reason for that which I will get to later. Secondly, apologies as well for the stupid headline, but unfortunately this is the name of the design so I did not choose it 😀

The PeeCeeBee amplifier is as far as I can recall a version of the VSSA (Very Simple Symmetrical Amplifier) developed by diyaudio-user LazyCat and a precursor to his “FirstOne” semi-commercial design. The VSSA is (as the name sorta implies) a simple amplifier based on Lateral MOS-FETs which are excellent for audio and the PeeCeeBee circuit has built on the concept.

The PeeCeeBee design has gone through several iterations, but this week I received my boards from the diyaudio groupbuy of the v4 design from Shaan in India. The group buy boards are black (which would not have been my first choice because you can’t see the traces very well), but they are 2.4 mm thick(!) and excellent quality so I couldn’t really wait to start putting them together.

Now the reason for posting this now is that there is a second run group buy which runs until the end of the coming week, so if you missed the first round there is still a little time to secure your own boards 😀

Still short a few passive parts for the boards, but I have the LAT-FETs on hand, I have a suitable chassis on hand and probably a transformer as well. I’ve never built a LAT-FET amp before, so really looking forward to hearing this one “in action” in (hopefully) a few weeks when the last parts get here.

More Naim clones…

Yep, I know I should be working on the HackerNAP instead, but I was just in the mood for building something else and as I had another Naim clone kit lying around, here we are 🙂

This is a NAP140 clone (or one of many actually) from ebay. I bought a cheap kit thinking I could get away with just replacing a few caps as usual, but I actually ended up replacing most of the resistors as well after a couple of them tested out of tolerance – hmm…

Also, while the listing said the 2SC2922 output transistors would be genuine after checking them I’m fairly certain they are not – at least the screen print looks wrong. The PCB is also much flimsier than usual, so actually this is one cheap kit I wouldn’t recommend that you buy 😦

Anyway, I know a couple of places that have genuine Sankens at a reasonable cost, so with a few of those and the last few caps (already on my next Mouser-order) then we’ll see if this one powers up 🙂

HackerNAP/HackerCAP

One of my (numerous) neglected projects is a version of the “HackerNAP” Naim clone amplifier. Naim is one of those brands that have a very loyal following, and many of their original designs have been analysed extensively by DIY’ers looking for improvements. The HackerNAP is one of those derivatives and the NCC200 from Avondale Audio is another – ebay is awash with other (more or less accurate) versions as well by the way.

Part of the reason why this project hasn’t been top of the list is that did not like the original HackerCAP PSU boards, so with a small delay (of around three years…) I decided to do my own version instead 😀

To be honest this isn’t how I would normally have done a PSU board – if had designed from scratch I would have made a larger board, used two full bridges and a full ground plane – but as the chassis are already drilled for the original boards I kept the physical size as close to the original as I could.

While the board size isn’t 100% the same as the original HackerCAP, I’ve retained the option to configure the design for both “normal” PSU usage and also for CRCRC or CLCLC configurations.

As the PSU boards are now done and tested, I can hopefully manage to do the rest of the assembly in less than three years 😀

Sunday morning chipamps…

It’s been some time since I did an ebay kit, but that doesn’t mean I have given up on them (in fact I bought plenty…) and a cheap kit is still a great thing to play with on a Sunday morning**

It’s a pair of power amps based on paralleled TDA7293 amplifier ICs in the correct “master/slave” configuration as per the data sheet (and this discussion on diyaudio). The TDA7293 and TDA7294 chips are among the few survivors of the “purge” of audiophile components and they should still be available. Unlike the LM38xx-series and its siblings, the TDAs have MOS-FET output stages which means they can run in parallel without resistors to limit current sharing between outputs. The parallel arrangement allows for more current into low-impedance loads, but as the TDA7293 will work on up to +/-50V rails having two ICs also makes for a fairly serious effective power output.

These kits are seriously cheap and although I’ve tried to use most of the components that came with the kit, some parts have been replaced for cosmetic reasons (because that matters to me, sorry!). Even with component replacements though, these kits are so cheap that there is no real excuse for not trying them – even if you don’t need new amplifiers at all 😉

No real sound impressions yet, but I know these chips can sound really good so I am looking forward to seeing how much of their potential can be unlocked for the same price as a takeaway meal 😉

**Yes I know it’s not Sunday today, but as Whit Monday is a holiday in Denmark it felt like Sunday morning 😀