james david low

live / work / play / worship

Fishman Aura Spectrum DI Preset Footswitch Mod

I’m a big fan of the Fishman Aura Spectrum DI. If you don’t have something like the Taylor Expression system on your acoustic, it can vastly improve your plugged in sound, particularly for live situations. If you have a piezo on an electric or slimline guitar, it does the same, but because of the more “neutral” sound, I’ve found you can use it to give you all sorts of different acoustic sounds. Fender even do this with their Acoustasonic Tele.

Since using it to give multiple sounds on an acoustic guitar, something I’ve wanted to be able to do is switch presets with a footswitch. I had a look at the circuit and figured out a straight forward way to do this. Warning: This will void your warranty and I am not responsible for any damage to your pedal.

How I did it:
1. Use pliers to remove the ring around the anti-feedback switch. The anti-feedback switch is a momentary switch and we need a latching one.

2. Use hex keys to remove the base of the pedal, and remove the battery clip as you do.

3. Locate the rear of the anti-feedback switch and remove the clip for that too.

4. VERY CAREFULLY use a sharp craft knife or scalpel to cut down each side of the switch to remove the plastic washer that stops you removing it. I found if I bent the switch to one side while I did this it made it easier. I’ve owned two versions of the Fishman Aura DI, and the older ones didn’t have this, so you could just remove the switch, if you do you’re lucky, this step took me a couple of hours!

5. Insert the new switch, I used some rubber washers to space it. Alpha’s small DPDT footswitches fit, and appear to be the same as what Fishman are using. They’re available on eBay: http://www.ebay.co.uk/itm/131175360378

6. Connect one pin of the switch to the 2nd pin of the 16 position rotary encoder (bit 1), and another pin to ground.
– There are multiple ground points, use the one that’s easiest, but I used the ground for the rotary encoder.
– From left to right the pins of the rotary encoder are: Input, bit 1, bit 2, bit 3, bit 4

How it works:
The 16 way preset switch is basically a rotary encoder counting from 0-15 in binary. As it counts, it connects each of the 4-bits to ground. We’ve connected the switch to bit 1, which means that it will increase any of the off positions (in binary even) by 1. So it will switch between preset 1 and 2, or preset 3 and 4, 5 and 6, etc. If you are on an even position (in binary odd), bit 1 is already grounded so the switch does nothing, i.e. positions 2,4,6,8 won’t be switched.

– The original Aura Imaging Blender seems to have had preset footswitches built in:

– If you could get access to the other side of the PCB, you could disconnect the input to the rotary encoder and switch that. This would give you a better switching system, where you always switched between preset 1, and what you had set on the preset dial. I didn’t feel confident disassembling things that much though, so elected for the simpler system.

– Here’s a list of my favourite Fishman Aura patches:

3:59pm / Feb 23rd / 15 Comments

Humbuckers with good single coil split sounds

I just found that Catswhisker Pickups #5 with in their S-Bucker pickups:

Recently been interested in changing the neck pickup on my guitar to a humbucker that has a coil tap that doesn’t seem to have such a large drop in volume. There seem to be a few different ways to do this:

1) Seymour Duncan and Dimarzio

Seymour Duncan seem to be have experimenting with this for a while. They had their Stag-Mag which is a humbucker made of two true single coils and The P-Rails which is a single/P-90/humbucker all in one:

Dimarzio had their DP157 Multibuckers which where two of their rails pickups in one. While both rails where humbucking, one was designed to sound like a humbucker, the other a single coil. Dimarzio discontinued it, and when I emailed to ask why they said “the parts used for it are no longer available”, I’m not sure why that should be in our technologically advanced age, but maybe its because of a legal dispute or something.

2) Mismatched coils

Lindy Fralin have their Unbucker pickup which has two heavily mismatched coils. When its coil split, it then has a higher output coil than a humbucker that is just split in half. It sounds pretty good, the disadvantage is that you don’t have full hum cancelling in humbucker mode:

3) Asymmetric coil tapping

Asymmetric coil tapping, doesn’t split the pickup in half like a coil split, it takes one coil and then a few extra winds from the other coil. The disadvantage here is that you don’t have a true single coil anymore:

4) Partical coil cancellation

Similar to the above, some people just put a resistor across one of the coils:

5) Add extra coils to single coil

Finally, this is an idea I had, how I think it should work though is mismatched coils like the Unbucker so that the coil split has more than half the winds, but also a coil tap of the overwound coil when in humbucking mode so that the coils are matched again and you get a proper humbucking tone and hum cancellation. I think it can still be done with a 4 conductor cable, but the connection points would be different than a standard one. Something like:

-------------------------- Single coil hot
       |    1.5K     |
Coil 1 ------------------- Humbucking hot
       |     4K      |
-------------------------- Single coil ground
Coil 2 |     4K      |
-------------------------- Humbucking ground

How it would work is that when you want a single coil you would connect the extra windings on coil 1 and use the middle point between the coils as ground. For Humbucking you would coil tap coil 1 it had the same number of winds as coil 2 and use the humbucking ground. In this example in humbucker mode you get an 8K true humbucker. In single coil you get 5.5K true single.

I also found out PRS are doing something similar, but I can’t say its exactly the same:

3:26am / Feb 2nd / 15 Comments

Fender Blues Jr. Fat Footswitch with LED

I recently bought a Fender Blues Jr. with Billm mods. I wanted a Hammond 1590H footswitch to fit on my pedalboard.

The Blues Jr. footswitch circuit has a 15V signal that is connected to switch the fat switch. Billm suggests that you could use a LED and resistor and then bypass it so that the LED is on when the fat switch is off. However other companies offer a footswitch with an LED that is on when the fatswitch is engaged. I did some testing and I found that, at least with the Blues Jr. III, even with the LED and resistor in the circuit it still switches, so you can just break the circuit to turn it off. I think I calculated that an 800ohm resistor was about right.

Here’s a picture with the LED indicating the fat switch is on:

5:57am / Jan 4th / 15 Comments

Custom Neunaber ExP (3 Switches and other variations)

I wrote a previous post about my custom Neunaber ExP controller that uses a counter to switch between the 4 effects with just a single button.

3 Switches
I’ve had a few requests about how to do it with just switches. I’ve drawn up a circuit, but don’t have time to build it, so I can’t be 100% sure it will work.


– Neunaber don’t cover warranty for custom ExP controllers, I can’t be held responsible if you break your pedal.
– If you only want 2 effects, you can leave off the 3rd LED and switch
– The logic of the switching in this configuration is more like 2 banks of 2 effects with 2 presets each. Switch 3 selects between bank 1 (effects 1/2) and bank 2 (effects (3/4). Switch 2 selects between either effect 1 and 2 or effect 3 and 4 depending on the position of switch 3.

Common Anode
Another variation depends on the the type of multi-colored LED you use. Some have common cathodes, some have common anodes. You have to connect the common pin to the rail, and the individual coloured pins to E0/E1 because connecting the common pin would join E0 to E1 which you don’t want to do.


This also changes which colors indicate which effect:

Q1 Q0 Effect LED
0 0 4 Orange
0 1 3 Red
1 0 2 Green
1 1 1 (off)

4:41pm / Dec 1st / 14 Comments

Fender Superchamp XD Line In/Mute Switch Mod

I recently did a popular mod to my Superchamp XD. I put a line/poweramp in so that you can just use the tube preamp, without any of the digital or solid state that comes before it. At the same time I also added a poweramp mute switch so I could use the line out and play when son is asleep in the house. The line in mod will also mute the speaker when a cable is plugged in, but I put the switch in as well because its easier than finding a cable and plugging it in.

Tube amps can be dangerous. Always observe tube amp safety:

3:28am / Nov 29th / 14 Comments

Changing Batteries on a Mobee Power Bar

I used a Mobee Power Bar to save money and the environment by not needing any batteries for Apple’s Magic Track Pad. I use in plugged in all the time, meaning that I never run out.

However this does eventually kill the rechargeable batteries inside, and meant mine would keep losing the bluetooth connection and need to be re-paired. Anyway, had a thought the other day and unscrewed it and used a spudger to prize it open gently. Its basically two AAA NiMH batteries inside a AA case. I replaced the AAA with new ones, and things seem to be fine again.

5:23am / Nov 22nd / 14 Comments

Custom Neunaber ExP Controller

I recently purchased a Neunaber Slate pedal for the amazing Wet Reverb effect. However all the v2 of their stereo pedal range support up to 4 effects, with 2 presets per effect. They make an external controller to control this, but its a little too big for my Pedal Train Mini. You can see a demo in the video below:

Neunaber Slate: http://neunaber.net/collections/pedals/products/slate-stereo-effect-pedal-v2
ExP Controller: http://neunaber.net/collections/pedals/products/exp
ExP Specification: https://docs.google.com/document/d/1dtP4e3Sp2izZ9LJ1SC9TPAYDjfYPpU8mbfK4Lh-GG54

Here’s the circuit I used to build it:

Q1 Q0 Effect LED
0 0 4 (off)
0 1 3 Green
1 0 2 Red
1 1 1 Orange

– Neunaber don’t cover warranty for custom ExP controllers, I can’t be held responsible if you break your pedal.
– While my pedal works, I’m not sure if I drew out the circuit exactly like I made it :P
– While I’ve used a counter so that I can cycle through the effects with a single momentary switch, the same could be achieved with 2 latching switches or a rotary encoder: http://www.fk-industrie.de/en/produktkatalog/P/D/E/A/27.html
– I’ve used an up counter which cycles the effects in reverse 4-3-2-1. Use a down counter if you want to go the right way.
– When the counter sets the effect inputs to high, it also turns on the LEDs.
– I used a two color LED for L1 and L2. Mine had a common cathode, some others you buy have a common anode and may need to be connected to the +3.3V rail, with the cathodes connected to Q0 and Q1.
– Power is provided through the ExP port, I’ve just labeled the rails for clarity.
– Since the supply is 3.3V, you need a HCF logic chip (Not HCT which is minimum 5V).
– I wired the RJ45 cable directly into the box to save space, but there are some nice panel mount sockets around.
– I’ve drawn a switches only circuit here: http://jameslow.com/2014/12/01/custom-neunaber-exp-3-switches/

Counter: http://www.maplin.co.uk/p/4024-cmos-logic-hcfhef-qx13p
2 Color LED: http://www.maplin.co.uk/p/5mm-multi-colour-led-yh75s
Panel Mount RJ45: http://www.gtcontact.com/Ethernet-RJ45-Plastic-Screw-Panel-DIP90.html

3:51am / Nov 15th / 14 Comments

World’s smallest true bypass looper

I recently built a bypass looper into a Hammond 1590H pedal enclosure so I was doing some research into this. If you wanted to use jacks, and not have the LED, I realised you could use insert cables and fit two stereo switchcraft jacks and one of the small 13mm x 13mm DPDT footswitches that are avaliable.



I ended up soldering the patch cables directly to the footswitch and used strain relief gromets because I wanted to be able to fit a 3PDT switch, 9V power, and an LED indicator:

8:21pm / Oct 17th / 14 Comments

Western Digital Black² in a Apple Macbook Pro 13″

The Western Digital Black² is a 120GB SSD with a 1TB 7200rpm regular hard drive in a single 2.5″x9.5mm case. I thought it would be ideal for both expanding and speeding up my MacBook Pro 13″ without needing to use a hard drive caddy and remove the DVD drive, which I still use from time to time.

I went ahead and got one without realising it wasn’t compatible with a Mac. Since the move to Intel almost everything is these days, so I just assumed it would be. Not wanting to give up, I did some Googling and found that AnandTech reports that once partitioned using Windows, it is readable on a Mac.

Annoyingly you have to install the Black² as an internal drive in computer, otherwise the automatic partitioning tool won’t recognise it. I din’t have a Windows PC I could put this in, so I had to install it in my Mac first, install windows just to use the partitioning tool, and then copy back over my Mac OS. This is all the steps I did to get it working:

1) Backup your existing drive, its important to do this often anyway, but especially since this is not supported, I or Western Digital will not be responsible for any damage or loss suffered to you, your hardware, or your files.

2) Remove your old hard drive and install the Black² in its place.

3) Install Windows (I used Windows XP, so I also had to remove a ram chip to leave it with only 4GB RAM).

4) If on Windows XP SP2, install Windows Installer 3.1, download it onto a USB drive first so you don’t have to install the bootcamp drivers to get the WiFi working.

5) Run the WD Black² partitioning tool.

6) Hold the Alt key while booting and boot onto your backup or original hard drive on USB.

7) The Black² should now have two visible partitions. Erase existing partitions so that you’re left with one big one.

8) Create 2 partitions, the first one 119.8GB, and the rest for the remaining. I experimented with different sizes, but 119.8GB left the right block sizes (see appendix).

9) (Recommended) Add an additional partition of 1GB to the end of the first (SSD) partition you just created. I then cloned by old recovery partition using the instructions here. Update: I’ve changed this from optional to recommended, since when I tried to upgrade to OSX 10.10 Yosemite it couldn’t install because it wasn’t able to create the Recovery HD. I also tried to create it with Carbon Copy Cloner as a 650MB partition and that failed too. I don’t know if its because my partitions weren’t quite right and were overlapping the SSD/HD but when I created the Recovery HD as a 1GB partition it worked, and Yosemite installed.

10) Clone less than 120GB of your original or backup hard drive onto the SSD. If you have more data, you may need to clone your home folder on to the magnetic hard drive bit.

11) (Optional) If you have too much data for the 120GB, clone your home folder to the magnetic hard drive partition, and after booting up, move your home folder location.

12) (Recommended) Enable Trim. You can use Trim Enabler (paid) or what I used Chameleon SSD Optimizer (free). If anyone is interested, there seems to be an extra hardware controller in between the SATA and the drives to make sure trim command only effect the SSD not the magnetic partition.

There has been one or two settings that have changed on my Mac. I’m not sure if this is a result of moving my user home folder, cloning the hard drive, or something else. It seems unlikely that it would be because of using the Black², but I’ll report back as I’ve spend more time using the system. The settings changed were:
– Custom screenshot location overridden
– Mac gatekeeper changed from “All” to “Trusted”

Also strangely Western Digital do have a firmware update tool for the Black2 that does work on a Mac. I haven’t tried it, and not sure if I will yet.

– I just tried to update to Yosemeti and realised it won’t install if the partitioning scheme is master boot record instead of guid. I updated above to include these steps.
– In searching to fix the partitioning scheme problem I found that someone else has done this before, and also turned it into a full fusion drive!
– I also found this article helpful for how to check out the partition sizes in detail.
– Also since doing this upgrade I’ve noticed I get the the “Disk too slow (recording) -10004″ error when using GarageBand. I’m not sure if its the hard drive, or making the upgrade to Yosemite on an older Mac, but now I have to record to an external hard drive (not the one that the OS is on. I used to be able to do this when I had a normal hard drive. The disk isn’t slow, my boot times are at leas 6-10 times faster, but it maybe “glitchy” in a way that GarageBand doesn’t like.

Partition Block Sizes using sudo gpt show /dev/disk0

After WD Black2 Tool on Windows + Converting to GPT. I really should have done this before converting to GPT for it to be more accurate. From this you can see that the last block of the 1st partition should of the 120GB SSD partition should be at most 234420417 + 63 = 234420480 to be sure its on the SSD. In addition the start of the 2nd block should be at least 234442752.

start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
34 29
63 234420417 1 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
234420480 22272
234442752 1953523712 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
2187966464 319
2187966783 32 Sec GPT table
2187966815 1 Sec GPT header

After deleting original partitions and formatting to two partitions using Disk Utility and the first set to 119.8GB. Apple creates the EFI partition at index 1, so now index 2 is the 120GB we will store the OS on. The last block of this partition 233984376 + 409640 = 234394016 which is < 234420480. Apple also intentionally creates a large gap after any user partitions. This makes the first block of the normal hd partition start at 234656160 which is > 234442752.

start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
34 6
40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
409640 233984376 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
234394016 262144
234656160 1953048472 3 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
2187704632 262151
2187966783 32 Sec GPT table
2187966815 1 Sec GPT header

After I used Carbon Copy Cloner to create the recovery partition on the SSD, this is what I get:

start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
34 6
40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
409640 231887224 2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC
232296864 262144
232559008 1835008 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
234394016 262144
234656160 1953048472 4 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
2187704632 262151
2187966783 32 Sec GPT table
2187966815 1 Sec GPT header

8:12pm / Oct 17th / 14 Comments

Third Culture Parent

Just letting the world know that my wife has started a blog parenting products and all the things we’re doing to try and be intentional parents: Attachment parenting, baby wearing, reusable nappies, elimination communication.


5:32pm / Sep 12th / 14 Comments
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Fishman Aura Spectrum DI Preset Footswitch Mod / Humbuckers with good single coil split sounds / Fender Blues Jr. Fat Footswitch with LED / Custom Neunaber ExP (3 Switches and other variations) / Fender Superchamp XD Line In/Mute Switch Mod / Changing Batteries on a Mobee Power Bar / Custom Neunaber ExP Controller / World's smallest true bypass looper / Western Digital Black² in a Apple Macbook Pro 13" / Third Culture Parent / Presonus iTwo with Garageband on iPad / Dumble in a box pedals list / Low cost made in China pedals / Small single-pedal sized multi effects / Pedal and amp list / Fulltone Fulldrive 2 Circuits / Ikea Standing Desks / Who I'd like to see in the dunk competition / Top 10 things I am missing about HK, enjoying about the UK / Simultaneous MIDI/Audio with Apogee ONE for iPad / iPhone Repair Bristol / Disable Git in Eclipse / A New Language for App Engine / iPhone Push Notifications with JavaPNS on Google App Engine / Midi Keyboard Velocity Curve Calibration With Pianoteq / Top 10 things I will and won't miss about Hong Kong / List Apps To Update After Moving iTunes App Store Countries / DynDNS via curl on Apple TV 2 / iOS-WebStack with Apple TV 2 firmware 5.2 (iOS 6.1) / Fast Track Ultra 8R in Mountain Lion / Google DFP with Appcelerator Titanium / Alternatives to Google Apps / Digitech iStomp and the new iPhone 5 lightning connector / The case for wired keyboards / Cornerstone vs. Versions vs. SmartSVN / Use of Foxconn and other manufacturers / iPhone Screen Setting / Pedal Board / New Family Friendly Homepage / Tip for efficient living / Detecting Quercus / Amazon S3 for WordPress with CloudFront / Database Read Replicas / Force User Login Multisite / Moving Church / Top 10 things I love about living in Ocean View / My Paper / iPhoto '11 No Place Smart Album / Creed / Random OSX Hacks / Getting Married :) / Diddy Feet / Very helpful error message / Apple LED Cinema Display with a PC / Simply Christian - N.T. 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