Sunday 20 December 2020

A new tow vehicle for Elena

My old pug that used to tow Elena became very unreliable, with crankshaft position sensor errors and other sundry issues cropping up regularly. Its age was such that we were going to have to do timing belt and particulate filter, and there was a fair bit of panel damage from an intimate encounter with a roo. So when rego came due last year we took it to the wreckers.

Since then we haven't had a car with a towbar.

I've been talking about getting a ute for ages, and recently my main car has been off the road (another roo), so we brought that forward. Top of the list was something that could comfortably tow Elena. I also wanted something that would be good for picking up piles of wood for the next boat. I decided something with a tray 2.4m long would be perfect, as so much wood comes in 2.4m lengths. Also I didn't want to spend too much, as it's a second car and will have it's arse dipped in the water occasionally.

So meet our new ute. It's a bottom of the range Mitsubishi Triton single cab, with a tray. It's a 2011 model, with 120,000km and is as simple as a vehicle can be. And it's just the ticket for towing Elena.

I've come up with a simple method of securing the mast so it doesn't scuff the floor, just by hanging it between the aft mooring cleats. I'll sew bags for the rest of the bits.

Tuesday 8 December 2020

AEM6000 Based 50W and 100W Amps

This is a design I've had in use for rather a long time. It started life as a design exercise to see if I could do a more space-efficient board for my original AEM6000 based amps, as I wanted something that would fit on a 50mm high heatsink. Along the way it changed a little from Tilbrook's original in topology, and rather a lot in component choice. It has better performance than my original design, both through a better tighter layout and also through the use of faster transistors.

I've built a bunch of these, using both Renesas and Exicon lateral MOSFETs, and subjected them to all manner of abuse. I had one fail, due to a leaky mica compensation capacitor (see noiseUnit speaker thread), but apart from that they've been rock-solid.

Lots of component substitution is reasonable. I like to use MELF resistors, but that's mostly just bloody-mindedness. An exception is the feedback divider. No, It won't work with cheap vertical MOSFETs.

The design is free for use for non-commercial purposes.

The 50W design is available on my Google drive

The 100W design is available on my Google drive

Thursday 19 November 2020

Tektronix TDS-340a CRO

A mansplainer on DIYAudio just told me my TDS-340a has an LCD, not a CRT.

This photo is to put him in his place.

Saturday 14 November 2020

Building the Per-Anders Sjöström QSXM2

I don't always just build my own toys. When other designers make really beautiful kit, I buy their PCBs and go to town.

Such is the case with a few of Per-Anders' designs. He and I share a common design rationalle, which can best be summed up as "components are cheap, if more of them makes it perform better, go for it!".

A perfect example is the QSXM2 phono preamp. Something like 200 resistors, 110 transistors, around 100 caps. It's really not mucking around. It's a preamp that leaves no stone unturned in the search for performance. I'm keen to see if I can improve on the basic phono pre in my NAD3240PE, and this one looks like a very good candidate. I've built some othe Per-Anders designs (mainly head-amps), and have been very impressed.

So I ordered a PCB from his website, downloaded the design doco, and started work:

I've set my work area up with a nice new A2 cutting mat, which protects it from the soldering iron and scratches. There's no need for the microscope for this guy, as it's all through-hole.

So far I've done all the resistors (I had comprehensive stocks, which will now need to be replenished), and I'm on to the caps, many of which I'll have to order in.

I'm looking forward to trying it out!

Sunday 8 November 2020

Annual HP 3585B stinky capacitor hunt

One of the hazards of using elderly test equipment, such as my HP 3585B, is old capacitors. HP loved using tantalums, which while having great low ESR, are also teensy little time bombs. Occasionally (typically at turn-on) there's a stink, and that's the sign that another one has let go.

So this happened the other day, and I spent a couple of hours sniffing the little blighter out, quite literally, as they're quite pongy and your nose is a great diagnostic tool.

This is quite a beast of a spec-an, weighing in at around 35kg. It's really beautifully made, with gold plated circuit boards. I started by pulling boards one at a time and giving them a quick once-over.

Eventually I found it, at the back of the input module on the underside of the unit.

This one is a little 2μ2 20V Kemet axial tantalum. Luckily I have a few in a drawer. So I whipped it out and popped a new one in, and now it's good as new (until next time).

Saturday 31 October 2020

NAD L70 receiver refresh

On the bench today is a NAD L70 receiver. It's a bit newer than the stuff I generally like to work on with NAD, but it was going really cheap, and is cosmetically pristine, so I thought I'd have a play.

There were two symptoms of bad behaviour. Firstly, a truly dreadful hum present in both channels, and secondly the CD/DVD player was really flaky, reporting "no disc" as often as not, and pausing and stuttering quite a lot while playing when I could get it to recognise a disc.

On opening it up it was really obvious what was causing the hum. There are 4 large capacitors on the top (CPU) board, that provide smoothing for all the lower voltage DC supplies. A couple of these were obviously bulging. So I whipped all four out and replaced them with 2200µf 25V 105˚ Panasonic electrolytics. While I was there I replaced a bunch of the smaller caps nearby.

That sorted the hum. Next up was the misbehaving CD/DVD player.

This is a real bear to get to, being underneath the CPU board. In order to get the transport out you have to first open the tray and unclip the oval NAD bit on the front. Then retract the tray again, open the cover, remove the CPU board, and it's pretty obvious.

The transport is an ATAPI/IDE one, made by Raymedia (RMC) part number RL-A700. This is common to a lot of CD, DVD, and SACD players of the period.

Once the transport was out, I started by popping the top cover off and giving the lens a wipe with a kimwipe and a little isopropyl. I cleaned the dried grease off the sled slides and gears, and relubed with Electrolube Special Plastics Grease (SPG), which is just for this.

Cleaning didn't help. The supplies were tested good, and this transport really has nothing to adjust, so I next ordered a replacement pickup. Part number for the pickup is SF-HD60.

It arrived after a couple of months, and I fitted it today, removing the anti-static solder blob after fitting.

This made a really big improvement, but it still stalls very occasionally and 2 or 3% of the discs I've tried today don't read. After repeating the clean, relube, reassemble, test cycle a couple of times, including pulling the spindle motor and giving that a bit of a spray of iso (did I mention that it's a pain to get to the transport under the CPU board), I've decided to bite the bullet and just order a whole new transport for it.

So that's where this one is at. It actually sounds really good, and with the exception of three useless channels will make a lovely all-in-one stereo. I think I'll set it up in my office at work once it's finished.

Tuesday 6 October 2020

Telegraph Roads - an objective comparison of Dire Straits - Love Over Gold in various formats.

I really do love Dire Straits. Perhaps my favourite Dire Straits album is Love Over Gold. There's a bunch of reasons I love it; it's melodically beautifully put together, there's a nice variety of different styles, and most importantly it was released in '82, when I was at the tender age of eleven, so I played it rather a lot as an impressionable teen. A whole lot of synapses in my brain are dedicated to this album.

So I've had it in various formats over the years. Originally in the '82 issue Australian pressed LP (Vertigo 6359 109/4), slightly more recently on the original Australian CD (Vertigo 800 088-2), the 1996 remaster (annoyingly also 800 088-2, but copyright '96 rather than '82) and most recently on the Japanese SHM-SACD (UIGY-9637) which is generally well regarded by audiophiles.

I'll stick to the very first track, Telegraph Road. It's 14 minutes 20 of really good music.

Before I start, all my versions sound pretty good. Telegraph road is one of the most engaging, haunting pieces of music I know of, and they're all good copies. My LP and original release CD, though old, are very well loved and looked after. My SACD version is brand-new. I cannot tell whether the original CD or SACD is playing, and I honestly can only tell the LP because of the pops and crackles. I can tell the difference with the 1996 CD though - it's louder. I've always really enjoyed the LP. It's probably simply because of the tactile nature of the medium, and the way I sit down in a nice quiet room to listen on a reasonably good stereo, but it has character that I enjoy. But these are subjective evaluations, not objective ones. They deal with my emotions, which are coloured by handling the album in the format in which I first played it. And subjective evaluations are easy to fake.

To evaluate the various versions I first import them into my mac. For that I use a variety of different things, and they are different depending on the medium.

For the LP, I play the LP on a NAD-5120 turntable (one of the later ones with a more conventional tonearm), with Goldring Epic-II moving magnet cartridge at 2.0g force. I run it through the phono amp and preamp in one of my NAD3240PE integrated amplifiers (why yes, I do have a couple of these wonderfully temperamental beasts), then to a Roland FA-77 firewire ADC, then to my mac. I run the ADC at 44.1ksps, 24 bit. The turntable, cartridge, and amplifier, while nothing to write home about, are representative of the better quality but not esoteric kit that was available in the 1980s. It's not the gear that I listened to the album on as a teenager. My parent's HiFi was a Kenwood one (with graphic equaliser!) and I actually only listened to the LP the once, while recording it to tape at 7 1/2" per second on our Akai cross-field reel deck. I was a weird kid, and I'm a weird adult.

For the CDs, I simply rip using itunes on the mac and a CD drive. I save the file as 44.1ksps 16 bit PCM, uncompressed.

I have no way of directly transferring the DSD stream from the SACD, so I go via analogue. I use a Sony UBP-X700 4K blu-ray player (which plays SACD contant), to a NAD D1050 DAC, then to my Roland FA-66 ADC, then to the mac. As with the LP, I digitise at 44.1ksps, 24 bit.

Let's work our way through the copies in chronological order. First, the LP. I started this expecting to see a gradual improvement with better equipment, but in reality it's quite a lot more subtle than that.

I've trimmed the track to 14 minutes, 22 seconds. The official length is 14 minutes 20 seconds, but I've left perhaps a second either side. When digitised, I kept the gain such that it never clipped. Then I used the Audacity amplify tool to amplify it to 0.1dB from clipping (3.6dB gain, for what it's worth).

The resulting audio reports the following dynamic range in the MAAT DR Offline Meter:

Dynamic Range: Left 12.52dB, Right 12.47dB
Peak: Left -0.70dB, Right -0.10dB
RMS: Left -17.87dB, Right -17.63dB

MAAT reports the DR as 12, which is generally accepted as very good. I've seen reports of 13 for this track on the original 1982 LP. I may be able to do better with a better cartridge and phono amp. Also I've done nothing yet to clean up the clicks and pops, which may be colouring the result a little.

So next the 1982 CD. I did nothing to the file. Just imported it into Audacity for viewing and ran it through the DR meter as-is.

This looks similar to the LP at this level of zoom, which is nice. I note there's a bit of a fade in applied to the first 20 seconds or so.

MAAT DR Offline Meter reports the following:

Dynamic Range: Left 13.40dB, Right 13.09dB
Peak: Left -0.11dB, Right over
RMS: Left -17.95dB, Right -17.06dB

This is a better result than the LP, with close to a dB better dynamic range.

Now for the 1996 "remastered" CD:

MAAT DR Offline Meter reports the following:

Dynamic Range: Left 10.34dB, Right 9.89dB
Peak: Left -0.00dB, Right over
RMS: Left -14.31dB, Right -13.96dB

It's pretty obvious to see why this isn't a well-regarded mix. It's certainly subjectively louder than the originals, but that's because of judicious use of compression. Alas the '90's were awash with this sort of awful treatment of audio.

Finally we come to the "definitive" 2014 SACD:

This is interesting when compared to the original LP and CD. Note the gradual increase in gain during the final instrumental passage, up to around 1.5dB for the finale.

MAAT DR Offline Meter reports the following:

Dynamic Range: Left 13.91dB, Right 13.68dB
Peak: Left -0.38dB, Right -0.00dB
RMS: Left -19.27dB, Right -18.50dB

I keep looking at the fiddling to the end of the instrumental passage. Could this simply be a cynical attempt to fudge the DR readings? Could the record industry really be that blatant?

What happens if I undo this? On a whim I applied a fade-out of 1.1dB from 11 minutes onwards (I actually added silence to 22 minutes, then selected the audio from 11 minutes to 22, and used the "studio fade out" effect in Audacity, then amplified back to -0.1dB peak:

So now it looks... Pletty much exactly like the 1982 CD. MAAT DR Offline Meter reports the following for my "un-tweaked" version:

Dynamic Range: Left 13.37dB, Right 13.18dB
Peak: Left -0.73dB, Right over
RMS: Left -18.55dB, Right -17.81dB

Which is very close (we're talking within 0.1dB) to the 1982 CD. Enough so that I'm wondering if perhaps this isn't the extent of the "remastering"?

So, what to say? In raw numbers, the SACD wins. But only, I feel, because they cheated. Discounting the cheat the 1982 CD is the winner.

So that's a "whole of track" view showing the really loud bits. One of the really engaging things about this track is the very quiet bits between passages. These don't affect the overall dynamic range figures terribly much, as they're derived by simply taking the difference of the whole-of-track RMS vs peak. If a quiet passage is a few seconds long, it won't have much impact on a 14 minute track. Sections of silence, or near silence, stretch the medium, and are a good indicator of a really good recording. CD should have an overall signal to noise ratio of 96dB, so we should be limited entirely by what the original (analogue) tapes could manage.

The bit I'm interested in comes immediately after the line "There's six lanes of traffic, three lanes moving slow" at about 5:10 into the track. It moves around a little on the various recordings due to small changes in speed, plus slightly varying start times. In any case, there's a very quiet passage, then some piano. Let's examine the second before the first piano note.

Again, we'll start with the LP:

I've simply used the contrast analyser (a power meter) within audacity to show the power in the second before the piano note. -49.36dB is pretty good. Remember this is a media that's full of pops and crackles, and I haven't removed these.

The 1982 CD:

Interestingly, significantly noisier than the LP version, at -46.45dB. Nearly 3dB. This is incredibly strange, as one assumes that CD is much quieter than LP. There must be something else at work here. Perhaps the original master tape has degraded somewhat between the LP pressing and the CD mastering?

The 1996 CD:

This result of -43.77dB is pretty much what you'd expect from something that's been compressed. The process boosts the quiet bits. Nice for listening to in the car, not really what you want otherwise.

Finally the SACD. I've gone with the version as recorded, with the slowly increasing gain at the end to fudge a better DR value:

Now this is interesting. It's -48.01dB, which is good (though not as good as the LP) on the face of it. However when we recognise that this bit of audio is essentially attenuated by something like 1.5dB, in reality it's about the same as the original 1982 CD. This lends some weight to the hypothesis that the SACD is simply the original CD with a slow increase in gain for the last few minutes.

Examining spectrograms of the quiet bit really throws the difference in noise levels among the different versions into sharp relief. First the LP:

The 1982 CD:

The 1996 CD:

And the 2014 SACD:

This is maddening. The LP version is obviously quieter than everything else, in between the pops and clicks! The 1982 CD version and SACD version are really the same thing, and the 1996 CD is garbage. Interestingly the liner notes for the '96 CD version go on about "super bit mapping", a technique using HF dithering to reduce the noise level for the lower frequencies. I'd expect to see an increase in noise towards the high frequencies, but I see no such thing. I'm guessing any dithering improvement is completely masked by the noise level of the source, which simply isn't as quiet as the source used for the LP master.

Wednesday 26 August 2020

Making the most of the dyneema - splicing rings for boom attachment points.

The 12 strand dyneema SK75 is really nice to work with. Much easier to splice than double-braid, and incredibly strong. I've been using it for all sorts of things on Elena; shrouds, outhaul, and also to fashion attachment points for blocks.

On my boom, I'm attaching the three blocks (two for mainsheet, one for vang) using simple loops. I simply make these by cutting a length of dyneema, then passing the two ends into the rope, while it's attached to the boom. it's extremely simple. With long tapered ends it's very secure under tension, and some lock-stitching (using waxed dyneema thread) holds it neatly while it's not under tension.

Here's a view while working:

And the finished result:

Tuesday 26 May 2020


Welsford’s plan for the Navigator shows a rudder with an up-haul and a down-haul. I’m not too keen on the idea of down-hauls, as if I hit things and the down-haul doesn’t release, then bad things happen.

So I figured I’d omit the down-haul, and instead weight the rudder with lead, similarly to the centerboard. Hey, every little bit of tighting moment has to help some, right.

This time with the lead, I just went and bought a pile of lead flashing. I melted it in an old cast iron pan outside, and poured it into a mold made from steel and aluminium.

I cut that into the rudder core, made from four 12mm thick jarrah planks.

And then glued on cheeks made from Tassie Oak, roughing it to shape with the bandsaw, power plane, and jack plane, then 40 grit in the sander.

I’ve added a pivot point (16mm hole with 12.7mm bronze bushes), and an eye for the up-haul, which I think will have to be 2:1 on account of the weight.

Tuesday 5 May 2020

I can stop any time

A picture of my frypan collection.

They’re all Le Creuset, mostly vintage. Two of them have had the enamel stripped and replaced with seasoning.

And the omelette process. We start with my favourite pan, a 23cm Le Creuset with the enamel stripped, seasoned with lard. When the seasoning is just so it’s a little glossy.

Ingredients for a basic omelette are a bit of butter, two eggs, some finely cut spring onion and a little grated cheddar cheese, with salt and pepper.

Chuck the butter in the pan and heat it until it’s foaming. While that happens go at the eggs lightly with a fork, and add salt and pepper.

Add the eggs to the pan when the butter quietens down. Then chuck the spring onion on top. Move it around a little with a fork to get the folds, and allow the runny egg to run onto the bare pan.

I like to add a teensy bit of grated cheese, which I melt with a torch. I used to pop it under the grill for a few seconds, but the torch is much more controllable.

Finally fold it in half with a fork, and slide it onto a plate.

Et voila. Bon apetite!

Sometimes I just chuck in whatever’s in the fridge. Pepperoni, chorizo, cherry tomatoes, mushroom, etc. But that usually ends in a thicker omelette that won’t fold.

Sunday 3 May 2020

Doodles towards a new boat

So these are the constraints I'm working to:

  • Beam of around 2300mm, to allow the boat to be stored behind my house (the gap between the fence and my garage is 2400mm). This will also allow for trailering without wide load placards, being under 2400mm.
  • Length of around 6000-6500mm. This is a bit more vague, as there's no specific constraint here, but the 6m length tends towards a 2300mm beam, so this is it.
  • Maximum draft of around 800mm. More than this makes trailer launching at boat ramps really hard. Indeed even launching a boat with an 800mm draft will be hard. Stability and cabin room is however directly related to draft, so there is a strong push to maximise draft at the expense of trailerability.
  • Maximum weight of around 1800kg unladen. The tow vehicle I am considering has a maximum towing weight of 2500kg. If we subtract 700kg for trailer, we end up with 1800kg for the boat. Stability constraints again push us upwards here, and trailerability constraints push us down. I think something around 1400-1500kg is probably reasonable. This implies a displacement of around 2000kg.
  • As much sailing ability as I can get given those other constraints. Ideally I want something I can sail across the Great Australian Bight in, so some measure of blue water capability.
Some of these constraints are directly contradictory. Trailerability comes at the direct expense of blue water ability. I think I can find a happy compromise that ends up in a boat that's enough different to Elena to make the exercise worthwhile.

I'm working on the premise of a 6m LOD, 2.3m beam, 0.6-0.8m draft boat with centerboard mounted in a trunk below the cabin floor. Katie comes pretty close, but the draft is perhaps a little on the shallow side, at around 0.48m board up. Pretty-much everything that's designed without a board has a draft of over 0.9m, which I think is just a little deep.

To find a better compromise, I thought I might try developing my own hull shape. I started with the table of offsets for Buzzard's Bay by Herreshoff, as published in Sensible Cruising Designs. I found the table of offsets to be surprisingly lumpy, so abandoned any attempt to stick to the table of offsets and instead just started drafting lines in Sketchup. The process was first to draw a profile (face), and overall plan view, to constrain LOD, beam and draft. The shape is similar to Buzzard's bay but I brought the bow up more vertically above the waterline, and increased the radius of the turn of the bilge, giving the rabbet a hard inflection rather than a smooth curve.

Then I drew waterlines and stations, got them to line up, drew buttocks, found they were miles off fair, edited the waterlines, edited the stations, edited the buttocks, and went around the loop half a dozen times, until the waterlines, buttocks and stations all intersect with errors of <1mm or so. I think the shape is reasonably pleasing.

Here's the profile:

Draft ended up 760mm, which is just shy of my maximum of 800mm. LOD is 6380mm. Beam is 2300mm. There is 750mm freeboard at the bow, dropping to 470mm amidships and raising again to 600mm at the transom.

The plan view is below:

After the issues I had with Elena getting the garboard plank around to the bow with a strong concave section, I kept the bow mostly convex, even down at the garboard. There is s reasonably strong turn to the bilge at the stern. This gives a nice shape to the transom and I think will also provide additional stability.

The rear view is also shown:

I haven't put any tumblehome in to the stations. I'm wondering if perhaps bringing the gunwales in a tad might make for more strength to the form, but also want a decent amount of room on deck to be able to get past the cabin, when I design one in. I may change things around a bit as I keep going.

Finally the quarter-view. I haven't sheeted the hull in sketchup, so it's just a bunch of lines.