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.

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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.

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 😀

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 🙂

 

Pass V-FET kits are here!

Forgot to post this a week ago when they arrived, but I managed to secure a couple of the Nelson Pass V-FET kits which I am quite excited about.

In short, this is a low-power class A amplifier based on some complementary Sony V-FET (SIT) transistors that have been out of production more or less since before I was born. The actual devices were bought as NOS (new old stock) by Nelson Pass himself and offered to the diyaudio community through the diyaudio store as a (more or less) one-off opportunity. I was lucky enough to register my interest early on and so managed to secure a couple of kits to keep me busy on those long Scandinavian winter nights when they come around 😀

There’s a big discussion thread on diyaudio and also an article on the FirstWatt website about the design, in addition to the information in Nelsons previous articles on SITs (also on the FW website). As usual, I don’t really need these and the class A heat is a bit impractical in a small apartment, but a limited-edition amplifier kit with unobtanium transistors that was developed by Nelson Pass himself was an opportunity I simply could not pass up (pardon the stupid pun 🙂 ).

The Firstwatt F5 is still one of the best amplifiers I’ve heard in my system so I have very high expectations for this new design. The lower power of the VFET could be an issue, but I’ll have to build it and try I guess – with my current speakers it should be OK and if not, I can always get a pair of very inefficient planar magnetic headphones instead :D.

vfetpcb-1

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 😉

An unusual clone…

Well, it isn’t actually that unusual when you look at it, but to most audiophiles these days cloning a Harman/Kardon amplifier doesn’t make a lot of sense – they’re nothing special. That used to be different though**. Before Harman became a big conglomerate, took over many other brands and positioned the Harman/Kardon brand as a middle-of-the-road consumer brand, they were actually quite a decent hifi-company. Especially their top-of-the-range “Citation” series became home to a few popular classics.

Small wonder then, than even Nelson Pass had a go at improving of one of these – go and have a look (or download pdf here). Admittedly it was a while ago (1981), but if Nelson’s had a hand in it I think it might be worth trying and so what you see in the pictures is actually a “Pass Citation 12” clone.

As for my contribution here it’s honestly quite limited – I bought the amplifier PCBs som time ago from diyaudio.com user Tazzz who always makes nice stuff 🙂 The power supply is mine though, but it’s just a bigger version of a previous design I did (as I recently upgraded to a different version of Eagle which can do bigger boards than the standard 80×100 mm.), so honestly that’s not much of a contribution either 😀

As the picture shows, I am stilling missing the main PSU caps but otherwise I already have most of the parts I need to finish this. I need an enclosure that fits as well though, so interesting project or not, it’s going on to my (already very long) list of half-finished projects 😀

**Fun fact: My first “real” amplifier and CD-player back in 1994 were the entry-level models from H/K. That set kept me in music for over 10 years and then did another few years of service with my brother when her moved into his own apartment for the first time. Unfortunately I don’t think the entry-level models from H/K of today are the same quality…

A Smaller Gainclone…

I have already done a couple of “gainclone”-type chipamp designs with the LM3875 amplifier IC, mainly here and here. Now there is a new one, this time based on the smaller LM1875 IC.

The smaller IC obviously means less voltage and less power compared to the LM3875 and LM3886 but unless you have a big room and/or very inefficient speakers (or you are having a party… 😀 ), the 20W or so that you can squeeze out of the LM1875 should still go quite far.

The circuit I’ve used is exactly the same as the standard one in the datasheet and also the same as the one used by chipamp.com in their kit. Some people might recognise the schematic as more or less a textbook example of how to make a non-inverting amplifier from an op-amp. That isn’t surprising though, because that is what the LM1875 really is – a power op-amp.

I have made the amplifier PCB as small as I could to make it possible to fit the amplifier either in a 1U enclosure or directly to a 50mm heatsink. The form factor of the board is a bit different than I originally intended, but layout-wise it’s obviously much better now than I could have managed by sticking to the original plan so that’s no big issue. In addition to the amplifier board I made a matching PSU board. This is a simple unregulated supply which is fine for this kind of application, but actually the current requirements of the LM1875 are approaching the range where regulation starts to be possible, so maybe I’ll do that some other time (in the future…).

The boards shown here are the prototypes with the mostly standard components I had available (and yes, the heat sink is for testing purposes as well). In the works is a more “boutique” version with better parts which is probably also the one I’ll end up putting in an enclosure. Testing confirms that it does indeed play music, but real listening tests I’ll hold off until I have the other prototype ready.

ICEpower 200AC Amplifier

A while ago I realised I still had a single pair of ICEpower 200AC modules left over as well as a suitable transformer – and why miss an obvious opportunity to make another power amplifier I don’t really need? 😀

The 200AC module is exactly the same amplifier section as the better-known ICEpower 200ASC only without the onboard power supply. The 200AC board is very compact at app. 55 x 107 mm per channel but will still put out over 200W into 4 ohms and because I had the transformer available I opted for a linear power supply. The transformer is a custom one I got from ebay (I think) with a 32VAC winding and a single 12VAC winding. This makes it perfect for the ICEpower modules as the dual-rail low-voltage supply can easily be generated via a voltage doubler. The main power rail is a bit lower power than I might have wished for (160VA), but not overly so, and the transformer is made by what I consider a quality manufacturer so it should be OK. 160VA is still more than 1/3 of the peak power which should work as a rule of thumb (yes, I know it is a bit more more complex than that but a good starting point as far as I am concerned).

The power supply board is a variation/update of a design I first made nearly ten years ago (when I started building with the ICEpower modules) and quite simple. I will publish the board files shortly as it might be useful for other users of the ICEpower AC-series and A-series modules without switching PSUs. I’ve used a dual-mono setup with separate PSUs mainly to be able to add a bit more capacitance to the mail supply rail (2 x 10000uF per channel) which shouldn’t hurt. The capacitors are very audiophile-approved “Gold Tune” types from Nichicon, not because I think it is audible per se, but because I like the look (yes I know, I shouldn’t admit to such things :D)

Apart from the amplifier boards and the power supplies I have added fuses on both the primary and the secondary sides of the transformer via a couple of my supporting PCBs. The secondary-side fuse board is the one I published here and the primary side fuse board is somewhere in the pipeline :). Obviously using these boards aren’t strictly required, but I wanted the fuses in the amp and especially the secondary-side board also makes for much neater wiring than would otherwise be possible for me to achieve.

I also wanted this amp to be fairly compact and unfortunately that took a few bits of custom metal work to achieve, namely a mounting plate for the modules and PSUs, another for the transformer and a small one for the primary fuse board (not fitted yet in the picture below). That obviously pushes the cost up a bit, but fortunately I have decided to ignore that part 😉

The back panel sketch is done and will be included in my next order with Schaeffer/FPX. Still to do is a front panel and some wiring, although I might actually hold off doing the front panel until later. That way I can match the looks of this power amp to an as-yet unspecified DAC/preamp/whatever to make a matching set 😀

200ac-amp-1

More JLHs…

Yeah I know, I should probably stop making these at some point 🙂

We’ll do this one quickly then: Standard JLH1969 Ebay-board with upgraded components and better transistors (MJ15003). Fan-cooled heat sink with temperature control (we’ll see how well that works…). Industrial-grade 10A switching PSU per channel. Monoblock configuration in Modushop GX288 chassis.

The PSUs (Artesyn NLP250) are overkill for this application but they were cheap (surplus items). And besides, more is better – right? Not necessarily here though, because some of these industrial-grade PSUs have a reputation for being extremely noisy at low power output. As a class A amp, the max. current consumption of the JLH should be twice its quiescent current (so app. 2.6A) and each PSU will deliver four times that before the limiter kicks in. Whether this is a real problem here or not I don’t know yet, but there are no audible artifacts at all so I am not overly concerned right now.

The heat sinks were also surplus items and I am not sure exactly what their rating is. At full speed the fans are a bit too noisy for my liking (the heat sinks add some flow noise as well) but if the fan speed is lowered a little I don’t think it would be really noticeable once the amps are seated in a rack. For the time being I have installed some small temperature speed control boards for the fans (hence the somewhat messy wiring) but depending on how well that works and how hot the amplifiers get, I may go back to fixed resistors. The PSU already has a dedicated 12V fan output so the resistor doesn’t need to drop a lot of power.

The heat sinks had a cutout in the side that was just too narrow for the angle brackets to fit into. The best solution would have been to mill the ends of the brackets to fit the cutout so there is only one contact surface. Unfortunately I don’t have access to a mill anymore so I had to find another solution: A copper “heat slug” to fill the gap. Just a piece of copper bar in the right thickness cut to size and with thermal grease on both sides and that should provide the best possible thermal transfer under the circumstances.

So, will I stop building these amps? Erm, no! 😀 I am out of the ebay-boards but I do however still have my own version of the 1969 JLH that isn’t cased up yet. This build has given me some inspiration for how I can build that into small monoblocks so while it might take a while to do at least I know what parts to keep my eye out for 🙂