look Ma, I made a ... mess

buffer/5 band EQ/booster and headphone amp with aux line-in mix

https://plus.google.com/u/0/+VladimirPantelic/posts/DxDJwM945HT

just a simple A-B switch pedal

https://plus.google.com/u/0/+VladimirPantelic/posts/a3AaoJHW3Ek

Replacement bridge for my Samick Corsair MCR-1 mini bass

I have this wonderful 25" scale Samick Corsair MCR-1 mini bass (http://gregbennettguitars.com/guitars/electric/minis/minis-corsair-mcr-1/) that is awesome for e.g. taking on trips. I bought it used with the original strings still in place and there is sadly nowhere to buy replacement strings unless you custom order some.

You cannot simply cut down bass strings as they are tapered on the top end in order to wind easily around the tuner posts. People have resorted to cutting and splicing the ball ends or to soldering a short piece of tubing to create a replacement ball end at the right length.

I don't want to have to do a lot of work on the strings and I want to be able to try out different string gauges easily, so I came up with this "locking" bridge. Similar to the top piece of a headless bass, the string are clamped in place with set screws, just at the bridge end in this case.

The replacement bridge adds a locking section where each string is held in place by two set screws. As the screws that adjust the bridge saddles were in the way, I had to drill the screw holes at an angle. Also I tried to remove as much material as possible on the back which results in this V8 look.

For easy tapping I drilled the set screw holes all the way through. As to not create a string cutter, I closed them again with short set screws that I glued in place and milled down. 

All milling and drilling done on my coworker's mill, thanks again for buying it :)


https://plus.google.com/+VladimirPantelic/posts/c3JS9rmkB2T

http://www.talkbass.com/threads/sub-short-scale-talk.644956/page-23#post-16373686

DIY class D practice amp and 8" cabinet

I thought I'd share my DIY bedroom practice amp setup with you.

The speaker is an 8" Visaton W200S woofer in tiny cabinet, around 5-6l only. It is a HiFi speaker, so it's efficiency is only 88dB but it has a low fs of only 30Hz which helps in this small box. I did some simulations with Visaton's Boxsim SW for a vented design but that would have produced a too large maximum cone excursion. I had the speaker already, so it beat the alternatives by being free, if I had to buy one I probably would have picked the Visaton BG-20 instead.

The cab is made from thin 9mm plywood and cross braced internally to add some stiffness. the W200S has a large flange on the outside so I had to 3D print little spacers for the speaker grille clamps. The top of the cabinet has room for a half width 19" enclosure that just slides inside. 

The amp is a mashup from three major parts:

The preamp is a Behringer Bass Driver DI BDI21 PCB with some tweaks ~$25

The power amp is a TPA3116 2x50W Class D amplifier PCB from China ~$15 (eBay or Aliexpress)

a 24V, 5A, 120W switching power supply, removed from it's casing ~$15 (eBay or Aliexpress)

the half width 19" case I got from eBay, it was for a wireless mic receiver initially, so I added new front and back bezels to cover the existing holes.

The back has a 2nd input and the XLR DI output of the BDI21 preamp. The green jack is a direct input to the power amp so that other preamps can be used.

All the front controls are the original BDI21 ones, the two slide switches are well known BDI21 tweaks that remove the midrange scoop and the speaker simulation filter from the signal chain. the BDI is powered from a 9V linear regulator and has the footswitch permanently engaged.

I have neither golden ears nor an acoustic measurement setup, so I can only say it sounds good enough to me to play and practice at modest volumes. With 2x50W and more efficient speakers, the amp can get quite loud but I have not tested that much yet.

http://www.talkbass.com/threads/diy-class-d-practice-amp-and-8-cabinet.1105507/

"activating" an OLP MM2 bass

I have a first series OLP MM2, the one with the passive treble and bass control. when I bought it, all three potentiometer axes were broken off and instead of getting new pots for this passive setup I decided to make it active.

The circuit is the original Stingray 2-band EQ. I did not want to route a hole for a 9V block battery holder, so the tiny 9V battery will do. I made a battery holder from a cut down AAA holder and a 3D printed frame to hold it together. The stingray EQ asks for a 1M reverse log pot for treble, I just put a 1M linear instead.

http://www.talkbass.com/threads/activating-an-olp-mm2-bass.1121539/

the "P" in P-bass stands for "PCB" of course - custom pickguard build

The woman in the Chinese electronics market stall offering PCB production services could not understand why I wanted to buy her random display PCB and not order one made to my schematics. Paying $10 for it I said "it's for art" but I'm sure she still thought I was a plain crazy foreigner.

I cut the PCB down to the approximate outline with a scroll saw, wearing out 4 blades in the process. Then I routed it down to the final shape with a copy bit. Since the PCB is quite thin, I did not chamfer the edges but left them square. I did countersink the screw holes though.

the bass is a Japanese Seiwa Century Royal from the late 80's

http://www.talkbass.com/threads/the-p-in-p-bass-stands-for-pcb-of-course-custom-pickguard-build.1128422/#post-16847139