Monday, 18 April 2016

Don't Let The Existential Dread Set In...

I saw this on Facebook the other day and it summed up perfectly how I was feeling at the time. I'm normally fairly resilient towards feeling down but a heavy cold, lack of sleep and busy family commitments prevented me from the usual antidote of getting out for a run or a ride.

The moment passes, music and tea always helps
"Bees" by Caribou

Wednesday, 13 April 2016

Peter's Phantom Powered Condenser Microphone Pre-Amplifier

Another imported page from my old website which I'm winding down.

This is being hosted on behalf of Peter Miles who designed this circuit for his church's sound system and used it for the basis of a presentation on SPICE simulation at work. The pre-amp is in regular use and has proved very reliable. Words and circuit design by Peter Miles. Any errors are likely to be mine!


An audio pre-amplifier designed to interface an electret condenser microphone to XLR balanced microphone input at mixing desk which provides phantom power.


  • Bandwidth, suitable for good quality speech 100Hz – 10kHz ±3dB
  • Gain, in range 12dB – 20dB
  • Low noise
  • Output impedance << 3kohms (to drive into 3kohms input impedance at mixing desk).
  • Transformer coupled balance output on to pins 2 & 3 of XLR audio circuit.
  • Powered from 48V phantom power coupled on to pins 2 & 3 of XLR audio circuit via 6k8 resistors
  • Provides DC bias in range 1.5V – 5V at input for the electret microphone module.
  • Construction, shielded inside metal box. Box to be grounded to pin 1 of XLR audio circuit.
Some useful information on powering electret microphones


2N5457 JFET           BC182 NPN

Neutrik NTE4 transformer datasheet

Bill Of Materials

ItemSupplierPart NumberDescription
VeroboardFarnell1201473CIF AJB16 RBP STRIP PROTOBOARD 100X160
Copper clad plain boardFarnell149054KELAN PCB, PLAIN S/S 100X160MM
Box for systemFarnell1171664BOSS ENCLOSURES DIECAST BLACK Length / Height, external:62mm; Width, external:112mm; Depth, external:31mm
XLR CableFarnell4259348LEAD, XLR MIC P-S 1.5M Connector A:3 Way XLR Plug; connector B:3 Way XLR Socket; Length, lead:1.5m;

Simulation Results

Simulations performed using Simetrix


Gain at 1kHz = 4.04mV / 500uV = 18.1dB
Measured performance on bench 9.9dB

Frequency Response

Finished Assembly Photos

  • Copper clad board on back of vero board to provide ground plane under the entire circuit
  • Circuit located inside diecast box by the copper clad board being cut larger than the veroboard and providing tabs that slide into the groves in the box inner walls

Monday, 11 April 2016

Team Spinach Ride Again: Open 5, Todmorden, March 2016

This weekend saw the last race in this winters Open 5 Adventure Race series, this time based out of Todmorden. Practically next door compared to other venues like North Wales and the Lakes. Emma was free that weekend we set the controls to Team Spinach!

Go team :-P tired but happy faces after the long run back!
Photo courtesy of Open Adventure.

Check out the rest of the (really good!) photos here, it really gives a great idea what it's like to take part in one of these events!

There had been a dusting of snow on the high tops overnight, which made for a nice drive over the moors, and a cloud inversion over Hebden Bridge as we descended.

We arrived in plenty of time so after a tea, a study of the map, getting ready, locating the car key, wheeling over to transition we had about 10 minutes left to get started.

Bike Stage

No battle plan survives contact with the enemy and our bike plan of not taking in the large obvious loop eventually went out of the window. We picked up the Mary Towneley Loop near Rodmer Clough and rode all the way round anti clockwise to Long Causeway. It looked slightly different going the other way from my previous expedition but some bits were very familiar. This is the first time I've ever had anything approaching local knowledge on an Open 5 event and it was welcomed!

It was a glorious day, blue sky, deep blue reservoirs, beautiful moorland colours, lapwings dancing overhead, nice riding temperature. Perfect. We both appreciated the bit of head space that this segment of ride provided.

Clever Google stitched this panorama without being asked!

Everyone coming the other way at Widdop res were telling us that control 24 wasn't to be found but we stopped for a look anyway.

Is it here? Or perhaps it is here? No?

But it didn't matter, we had a great ride over all different kinds of surfaces from fast bridleway, muddy steep descents, rocky climbs, bits of road and rutted stone sets. Definitely a good day to be out and about. We were also glad to not find the permissive bridleway that dropped down to the back of Cant Clough reservoir, it sounded like a right old miserable mud fest! Going the long way round worked out pretty well.

It wasn't long before we picked up on a bit of trail I recognised from the Haworth Hobble and we were bombing back down into Todmorden and back to the school. Emma is a good rider and I can just about keep up with her on the descents. A longer than preferred bike ride at around 3h 45m and 24 miles but crucially we had fun and sometimes that is what matters.

Run Stage

I refuelled with lots of water in transition as I'd dropped my water bottle on a bumpy bit of bridleway and lost the contents. We knew we didn't have time for many controls on the run so just went for the nearest ones, slogging up the wooded cliff (hill seems too kind) behind the school to pick up a couple of high points value controls.

I caaaan seeee myyyyy biiiiike froooooom heeeerrrreee!

We had one wrong turn on an overgrown path before we put ourselves right. Bumped into an ex colleague, Dave W, at this point who was racing. He let us photo his control description sheet as I'd lost mine on the bike ride and Emma left hers in transition. Ooops!

It was a right slog up this hill...

We picked up another well hidden control affixed to a railway bridge; the lack of the usual red/white warning tape that is normally affixed to the controls made a big difference in ease of locating them! Then the short steep climb up to Rake End where a marshal was stood holding the control for us to dib before hammering it back down the hill for one last control near a farm. At this point we knew we were going to be late back, the question was, how late?

Flying totally by instinct, I led us wiggling and winding down steps and snickets, mostly guessing what seemed like the best path through the Salford area of Tod, dropping us out by the Golden Lion pub on the canal.

We belted it back along the main road; I haven't run that hard for a while and was only just keeping going, Emma not far behind, with the finish in sight. The event clock was pointed away from us. Did we make it back in time?

The faces say it all.


We dibbed into the finish just three minutes late dropping 6 points, not bad considering I was expecting to be at least 10 minutes late. A couple who were descending from our next to last control turned up about 5 minutes after us with a puzzled "didn't we..." "how did you get back so quick?"

Downloaded, 384 points scored, happy with that! Should put us in the top half for the mixed pairs, I thought. Got changed, acquired a well needed cuppa and wandered in to the hall to catch the end of the prize giving.

We were pleased to have made 4th place in the mixed pairs but the scores from the lead guys and girls was really impressive, they must have cleaned up the entire course!

Also the prizes were being given out for the series with some very deserved wins. Even though the came second on the day by a whisker I was glad to see Rosemary (check out her blog) and Lucy win the Female pairs overall. We chatted with Lucy afterwards and said congrats. It never ceases to amaze me how many people in the AR community that Emma knows and that know her!


One shower later and I took the lovely Louise out for a tasty curry to celebrate a good race result and her having a successful wedding fair earlier that day. We were very hungry!

Monday, 4 April 2016

Pull Up Bar

My opportunities for climbing these days are a bit restricted by time and other activities. After a good winter climbing trip I'm planning to get out for more trad climbing this summer as I'm finding that I miss it. So as to not be utterly rubbish when I do get out I'm going to need to work on my upper body strength at home.

To this effect I've installed a pull-up bar in the garage. The idea is that when I arrive back from my cycle home I can do a full set of pull ups before I enter the house and find that motivation has deserted me. Five sets of pull up exercises a week should see some progression.

This was a slight technical challenge as the roof beams are a bit flimsy to have 85 or so kilos of Yorkshireman dangle from them and the headroom in the garage is a bit limited so I'm going to have to lift my legs up to get the requisite clearance! After a bit of thinking I ended up coming up with the below design.

Simplified view of the mounting method

Since its only in the garage I don't have to worry too much about it's appearance so the frame is made from rough sawn timber. A couple of lengths of 2400 x 100 x 50mm for the reinforcing beams from B+Q and the rest is made up of similar cross section lengths from an old pallet that I ripped apart. Recycling!

The pull up bar hooks into the arms for easy removal. I should have used a coping saw to cut the rounded ends but I confess I was too lazy so carved them out with a chisel. The hook base is reinforced with a few screws.

The arms swing up into the roof space for added headroom.

The M10 x 150mm coach bolts hold the arms tightly enough and the surface is rough enough to hold it in place. Penny washers spread the load and double nuts (I didn't have any M10 Nyloc) prevent loosening.

The bar is a 25mm galvanised steel conduit that was getting thrown out of work a while back that I saved. More recycling! I can always add some self amalgamating tape for extra grip if necessary.

Not exactly fine craftsmanship, but rough, ready and ultimately practical.

I've got this picture stuck up on the reinforcing beam that I look at when I've completed a pull up. Just a little something to keep me motivated!

Himmelswillen, VS 4c, Wharncliffe; Louise; Point Five Gully, V 5, Ben Nevis, the nippers.
There's some good suggestions for training routines on that internet and I'm intending to do the following for the first week to see how I get on. I'm starting from pretty much nothing, I can probably do one or two pullups unassisted. So I'll probably start with my feet on a chair and progress from there.

Week 1, daily routine
  • Standard pull ups, palm away from face, 5 reps
  • Straight arm hang, leg raises, 90ยบ knee bend, 5 reps (working core)
  • Lock off and slow controlled descent to straight arm over a few seconds, 5 reps
  • Push ups, 5 reps

I'll probably still suck at climbing!