Back from Japan…

I am now back again (physically at least) from two weeks in Japan. As the trip was a holiday and I could set the pace myself there was plenty of time to explore audio-related stuff :)

My credit card statement also tells me I have managed to take full advantage of the fact that there is a good selection of DIY parts shops in both Tokyo and Osaka – and while domestic prices in Japan tend to be lower than where I am that’s easily fixed by simply buying more stuff :D

Special thanks to Pete Millet for providing a useful page of links for where to go. Although I found most of these on my last trip to Tokyo, Pete’s page has been very useful to me both in Tokyo and Taipei so definitely worth a mention here.

As was the case last year, this year’s expensive souvenir was also pair of expensive Japanese-made headphones, namely these:


Past projects: Pass Zen v4

It’s been quite a while since my last one of these “past project” posts, because honestly there isn’t a whole lot of stuff left in the “back catalogue” that I find worth showing off :D

One of the exceptions is here, a version of Nelson Pass’ Zen v4 class A amplifier. I built the amp a couple of years ago and it worked but had terrible hum. I traced the hum to a combination of the transformer and my grounding scheme. I ordered a new transformer that was better suited (and higher quality) and then forgot all about it until a couple of weeks ago. After replacing the transformer with the improved one (an audio-grade model from toroidy) and wiring it properly, the amp is not only working but also completely silent :)

The PCBs are decent-quality clones from ebay but all the components are bought from reputable sources. The only exception is the softstart which is a premade module that is a bit illogical (= annoying) in that you must use the “standby” to turn the amplifier on, but you can’t use the button to put it back into standby-mode again….

The chassis is a 4U/300mm standard “dissipante” from modushop, albeit with quite a bit of mechanical reinforcement underneath to take the weight of the transformer. The 4U heat sinks are OK for this amp but only just, if left at idle I measure the hottest part of the heat sink to be around 35C above ambient.

My F5 is on loan to someone else at the moment, but when I get it back I plan to make a comparison between the two and see which one I like best. On second thought it might have to wait a few more months since both of these amps run a bit too hot for summer – even a Danish one :D

Second anniversary…

Yes, today is the second anniversary of the blog and when I started writing I honestly didn’t think I’d still be here :)

As this post also just happens to be number 100, it is the perfect opportunity to say thanks to everyone out there reading and post the obligatory stats:

  • 100 posts, more than 80% of which are on audio-related builds or project file posts.
  • Over 90k page views in all
  • Over 2k project file downloads in total
  • Visitors to the site now come from 116 countries and territories around the world

I am currently in Japan on holiday, so I hope to have some new audio-related stuff to write about when I get back. In any case, I can assure you there are still plenty of other projects in the “pipeline” back home.

Thanks again for reading – I hope to continue writing and celebrate many more anniversaries in the future! :D

Project files: Universal Triple-PSUs

What is it?
Two boards for general-purpose LM317/LM337 power supplies with three rails, useable for many low-power applications where both a +/- supply and an auxiliary voltage are needed. Examples include analog amplifier + digital/logic circuitry, microphone preamplifier + phantom voltage etc.
There are two versions, one where the +/- voltage is derived from a single AC-voltage via a doubler and one where it comes from a traditional two-bridge rectifier circuit. This design is virtually a copy of my GP-PSUs. I made some minor enhancements and added the extra rail, but it is the same basic design.

How big are the boards?
Both board versions measure 3.925″ x 2.6″ (app. 100 x 66 mm.) and they are mechanically interchangeable.

What is the status of the boards?
The “standard” board is in v1.0 and works fine. The voltage-doubled board is in v1.1 and also works fine. The two versions are completely identical except for the diode/bridge arrangement on the +/- supply. The difference in version numbers came because I originally prototyped a different (smaller) layout for the voltage-doubled version. After making the “standard” version that requires a bit more space for the rectifier bridges, I decided it was smarter if they were both the same size and then changed the layout of the voltage-doubled board to match.

Does it use any special/expensive/hard-to-find parts?
Nothing, really. As always with these circuits, you can use standard LM317/337 regulators or splash out on more expensive (low-dropout) types like the LT/LM/LD108x-series. My experiences with the latter parts aren’t the greatest though (instability), so unless your applications require the low-drop capability I’d just as well stick to standard 317/337-types from a reputable source. If your application requires higher performance than this, you are probably better off looking at entirely different circuits and regulators.

Anything else I need to know?

  • There is a jumper on the boards that links the ground on the AUX-voltage to the midpoint (0V) of the +/- supply. This is optional and probably not required for most applications but can be used for e.g. linking analog and digital ground in mixed-signal circuits.
  • The diameter of the main filter capacitors is 16mm on the AUX supply and 18mm on the main supply.
  • The DIP rectifier bridges exist in versions up to 2A rated current although anything more than 1A can be a bit difficult to find. Realistically though, if you plan on drawing more than 1A from either supply the SK104-type heat sinks are probably going to be a limiting factor anyway.
  • Mounting the regulators and heat sinks is a bit of a faff because there is not much space, especially if the heat sinks are 38mm or taller. My suggestion (as always) is something like this:
    1) Loosely assemble the regulator, the isolation components and the heatsink.
    2) Mount the combination on the PCB and solder the heatsink in place.
    3) Tighten the screw holding the regulator to the heatsink.
    4) Solder the regulator in place.

Download design files here

Related information:
Even though the regulators used here are generic types made by many manufacturers, there can be small differences in recommended parts values etc. I suggest you always consult the regulator data sheets from the specific manufacturer.

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

Project files: The Borbely Hybrid headamp

What is it?
This is my version of Erno Borbely’s tube/MOS-FET hybrid headphone amplifier. As discussed in a previous post I found this design a while ago and made plans to do my own board for it at some point. For a long time it was just another point on a long to-do list, but one random Saturday a couple of months ago I just somehow got started and managed to finish it shortly afterwards. There are only minor changes compared to the orginal. Apart from what is described below, it is mainly space for RN60-type resistors for all positions and use of bigger (and more easily available) heatsinks.

Note: I don’t really recommend building and using this as-is (see explanation below), but I decided to publish the board files anyway because I think it is still an interesting circuit. I am definitely not ruling out trying to make it useable at a later state with some soft of turn-on/turn-off delay circuit,. but for not that is not a priority for me.

How big are the boards?
Each mono board measures 3.2″ x 3.6″ (app. 81 x 91 mm.)

What is the status of the boards?
The board file is version 1.1. I have built version 1.0 and it works as expected (note the rather large caveat mentioned below though!!), but I had swapped the labels on Q2 and Q5. I also corrected the footprint for the two CRDs to make it easier to fit axial types which are the most commonly available.

Does it use any special/expensive/hard-to-find parts?

  • Power FETs: I decided to make the boards fit 2SJ313/2SK2013 FETs because they are mentioned as substitutes in original article and while still a bit difficult to get (watch out for fakes!) they are still easier to find than the original 2SJ79/2SK216s. This means that this layout is not useable with the original devices because they have a different pinout. You would however (most likely) be able to use IRF510/IRF9510 or IRF610/IRF9610 pairs instead. I haven’t tried this myself, but at least the pinouts match. If anyone want’s to have a go at this I’d be happy to donate one of my spare sets of boards to “the cause” – just drop me a line :)
  • Small-signal transistors: I replaced the originals (2SA872/2SC1775) with BC550/BC560 variants that aren’t quite as low-noise as the original types, but much easier to get. If you prefer “audiophile-approved” (near) unobtanium parts at all cost, then I believe the 2SA970/2SC2240 would work as well if they are turned 180 degrees to compensate for the different pinouts.
  • Tubes: You can pay a fortune for branded ECC86/ECC88 variants or you can use something cheaper, i.e. chinese/russian equivalents. I chose the latter and bought some 6N23P-types from ebay. These seem to work fine, but note that the 6N1P which is another oft-recommended substitute for ECC88 will not work in this application. Also: One of the tubes I tried gave me a steady-state DC offset of around 1V that I could not get rid of whereas the other channel was fine. I replaced the tube and redid the adjustment and then it was fine as well. This could be a fluke, but I think you should buy more than a single pair of tubes just to be on the safe side.

Anything else I need to know?

  • Important: As described in some of the diyaudio-posts I read about this design it has one major flaw and that is serious DC-offset at power-up and power-down. Both my boards are after adjustment within +/-10mV when they are fully warmed up and stabilised, but during power up they both swing the output to very close to one of the supply rails (meaning 20V or so) and stay for such a long time that I think it would be fatal for headphones. There are a couple of solutions to this, either an output capacitor or a delay circuit of some sort. I don’t have time to try either at the moment, but if you do so please report back.
  • The original circuit is differential input. However, my layout grounds the negative input as standard to make the inout single-ended only. I normally wouldn’t make a simplification like this, however it avoids a very long and unsightly trace through the ground plane. Since I expect that SE-input is how most people would use it anyway this was an acceptable compromise for me (but of course it might not be for you :) ).
  • When you mount components, note the resistor that is supposed to be mounted on the back of the board. This is much, much easier to do if you solder it before mounting the tube socket and not afterwards…

Download design files here

Related information:
See the original build article for more information about the design and a great walkthrough of component values etc.

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

J-Mo buffer/headphone amp

A couple of months ago I stumbled upon the discussion thread for Richard Murdey’s J-Mo Mk. 2 headphone buffer on Richard runs RJM Audio (which you should definitely check out if you haven’t already) and is also the man behind the Szekeres VE design that I built a while ago (see this post).

I am not sure why the J-Mo caught my eye, probably the simplicity of it, but it did. Richard already has a nice PCB for the design, but as I thought I could make it a little smaller, substitute some parts for more commonly available sizes and also improve the versatility a bit I decided to “roll my own” boards instead :)

I downloaded the eagle-files that Richard graciously provide for download, ripped up the original PCB file and got to work. The result is here in dual-mono format with amp and regulator on separate PCBs similar to the original. Apart from the revised layout my changes are relatively minor, mainly different component footprints where I thought it made sense and of course different heat sinks.

The rectifier bridge PCB is from my second Gainclone design and was perfect for making the unregulated DC voltage that the Zener regulator requires. The bottom plate in the pictures was just one that I had left over from another project and was suitable for mounting the boards. There is no wiring in the pictures, but the boards were wired up and it does play wonderful music (although feeding it with wonderful music seems to be required… :D)

As usual I didn’t really listen for a long time while it was sitting on my desk in “prototype mode”, but what I heard was good enough that I have ordered a proper mounting plate (i.e. one that fits in a standard enclosure), a transformer and some chassis part so I can give these great boards a “real” home :D

Project files: The EL2k headamp

What is it?
The PCB files for the EL2k headamp in the previous post (here)

How big are the boards?
The board measures 3.95″ x 3.0″ (app. 100 x 76 mm.) and contains one channel.

What is the status of the boards?
The files are v1.1 of the board. I corrected a few minor issues in the prototype such as the footprint of the input capacitor and the package dimension for the CRD.

Does it use any special/expensive/hard-to-find parts?

  • The Elantec buffers (EL2008/EL2009) that for the basis of the EL2k have been out of production for a long time. You can find them in various places online, both as pulls from scrapped equipment and as unused new-old-stock (NOS) ones. I bought a single pair of EL2008s from a long time diyaudio-user and member of the headphone community who was cleaning out parts so I have no doubts that mine are genuine, but if you do try to source from elsewhere always beware of fakes or substandard parts.
    That said, demand for 15-year old analog video buffers in TO-220 packages probably isn’t at an all-time high now, so I would judge the chance of getting genuine ones as quite good. Unlike various power transistors and small signal JFETs that are regularly counterfeited – even in channels where you would never suspect it – there probably isn’t a lot of money to be made from faking these in the first place.
  • The heat sink is not hard to find as such, but it must be a specific one (the SK68/75 from Fischer). It’s quite common in Europe with Reichelt and TME both stocking it, but I am not really aware of any other sources.

Anything else I need to know?

  • When you mount the buffer as shown, the heat sink will be grounded (because the tab-pin is grounded on the PCB). Not a problem in itself, but it does mean you should be careful of flying PSU leads :)
  • Mounting the buffer is a bit of a hassle, firstly because the electrolytics can get in the way unless you wait with mounting those (I didn’t…) and secondly because it doesn’t line up 100% true with the grooves in the heat sink. You can either have the buffer sit flush with the board as I did and use the M2.5 slot, or you can use the M3 slot and have it raised quite a bit above the board. In the first case, there is barely enough room for the screw and in the second it might be necessary to bend the buffer leads a bit to make them reach the holes. It works, but it isn’t as elegant as I would have liked :)
  • The PSU for this board should be +/-12 to +/-15V. 15V is recommended unless you are using an opamp that doesn’t tolerate 15V. In theory, the PSU should be capable of at least 2A output currents, but in any normal audio application 1A should be more than enough.
  • If used, the recommended value for the CRD is app. 2mA. I used a J508 because I had a pair left over, but there are other options out there. You can also use a resistor instead or skip this entirely. See this page about class A bias of opamps.

Download design files here

Related information:
See the two original posts for some more information and links.
Note: Always read the “intro post” for additional important information about my designs.

More old silicon – the EL2k headamp…

After my adventures with the obsolete BUF03 buffer comes a design with another discontinued buffer-chip – the Elantec EL2008 :D

The EL2008 is definitely an overkill-device for audio duty. It’s got high bandwidth, high slew-rate and a 1A current capability with a built-in limiter. Like the BUF03 it was originally intended for video applications and like the BUF03, it has also been discontinued for a decade or so. There is also an EL2009 with even more impressive specs for bandwidth and slew-rate if you want and since both ICs should work in this design coming up with the name was pretty simple – the EL2k.

The design itself is a fairly straightforward “buffered op-amp” circuit, the only “tricks” being a resistor between the opamp and the buffer (because the buffer needs a controlled source impedance) and a current-regulation diode (CRD) to bias the opamp into class A (something else that was very popular in diy headphone amplifiers 10 years ago – my age is starting to show here I guess…).

I’ve possibly gone a bit overboard with the heatsinking, but this was the type of layout I had in mind and it seems to work well (electrically at least, there are some mechanical niggles). The input caps are ClarityCaps ESA which probably also qualifies as overkill, but I am sure they do no harm :D

The opamps used are LME49710s because I had a pair to hand when I did the test. However, in my opinion the obvious choice for this build would be another one of “yesterday’s heroes” – the OPA627. Back in the day when the EL2k buffers were around, the OPA627 was pretty much the king of the audio-grade opamps so I think that match is sort of meant to be. The OPA627 also has a warmer, less clinical sound signature that might offset a bit of brightness here.

I have only listened briefly to this design so far, but the immediate impression is “detail, loads of detail” Whether this turns into listening fatigue in longer sessions I don’t know yet but we’ll see when I get some more time. In any case: the guy that sold me the Elantec buffers told me “to build something awesome with them” – not sure I succeeded, but I definitely tried :D

Project files: Little helpers – Alps PCBs II

What is it?
Not exactly the most complex designs ever made ;) A couple of PCBs for mounting Alps (or pin-compatible) potentiometers. Unlike the previous boards these ones have screw clamps for input and output, making them better suited to testing use and people with fat fingers (like yours truly) :D There are two versions, a 2-channel (for stereo) and a 4-channel (for balanced) amps.

How big are the boards?
The SE board measures 1.15″ x 1.975″ (app. 29 x 50 mm) and the balanced board measures 1.975″ x 1.975″ (app. 50 x 50 mm.)

What is the status of the boards?
I’ve called these version 1.5 since they are based on the previous boards of the same type, just modified with screw clamps for the input/output connections.

Does it use any special/expensive/hard-to-find parts?
Mostly there’s only one real part on the board and that is the pot itself which can be a bit expensive, so yes, I guess so :D

Anything else I need to know?

  • These are “preamp” style boards have a ground plane and a ground pad that can be used if you grounding scheme requires the shaft of the pot to be grounded. Use a piece of wire connected from the ground pad to either one of the screws on the back of the pot or soldered to a ring terminal wedged between the pot and the chassis.
  • The stereo board has a four-hole footprint to fit various pots that use that configuration, but the last set of pads isn’t connected to anything so will not work directly with a loudness tap.
  • The boards can also be used to make separate, passive preamps. In this case, a 10k potentiometer should be used.
  • The screw clamps are standard 5mm pin spacing types, but of course it is possible to solder bare wires to the boards as well.

Download design files here

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

As usual, please remember to consult the manufacturer’s datasheet as well if you use a different pot than the recommended type.

Going “retro”….

For the past few months I have noticed something: Most of my everyday listening is with a portable rig, either at my desk at work or during the daily commute. When I am at home, while I have my entire 800+ CD-collection ripped to lossless files and a whole dedicated setup for listening to it (dedicated Mac Mini with Audiolab M-DAC etc.) I was actually not using it a lot. It’s not that I don’t like the sound, but it is a bit of a faff having to turn everything on, wait for the computer to start up and then having to either turn on the TV to navigate or get out an iPad/iPod/iPhone to use the remote app etc.

After this (slow) realisation, I started thinking back to when I started playing music on my own. My first “real” system was a simple Harman/Kardon CD-player and integrated amp and I lived happily with that for nearly ten years. There was nothing to wait for, just two on-switches and a play-button and then there was music, and there was a bit more “tactility” to the process overall (if not much). I don’t think I’ll ever really go back to the CDs, but I have actually – slowly but surely – started playing a lot more vinyl at home.

Some would say that I have just succumbed to the first “wave” of accumulated nostalgia when you reach your mid-thirties, but it’s not as if I have a long history of actually using vinyl records. Of course I am old enough to know how they work ( ;) ) and I can remember playing records when I was younger on my parents’ stereo. But when I started buying my own music in the early nineties, CD was already the format of choice (and cassettes were still common as well, mainly for exchanging music with friends). The only friends that bought vinyl were a couple with older siblings that had turntables and even they switched to CDs very quickly. As a result, I’ve never really had that much affection for the vinyl format so I do challenge the notion that this is just misty-eyed nostalgia at work :)

To add to that, the turntable obviously has its share of downsides – I had for instance mostly forgotten just how short the side of a record seems when you are working on something and just playing music in the background. I had also forgotten just how much dust a record is capable of attracting and how annoying scratches can be. My turntable is nothing special (a simple Project Debut Carbon albeit with an upgraded cartridge and an aftermarket plexiglass platter), but even so – it sounds very good and it is definitely more of an “experience” or “occasion” to put on a record, lower the stylus and wait for music to come out of the speakers.

So, there we go – I said it: For me this hobby isn’t really about sound quality (at least not only) but also about the experience. Blasphemy to some audiophiles, but a revelation to others maybe? If nothing else, I guess it provides an explanation (or excuse…) for why I continue to design, build and buy a lot of gear that I may never really get to use :D



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