Mottlefeeder

As an alternative to converting battery power to mains and back down to amplifier supply rail voltage, you could consider a car booster amp. These are designed to work from a 10-15V supply, contain a dedicated voltage converter, are built to withstand harsh treatment, and have a sensitivity that allows you to connect an active bass to them and get something approaching full power without needing a preamp. £70-80 will get you 75W into 8 ohms or 150W bridged into 4 ohms. All you have to do is bolt it to a piece of plywood, connect speakers, power and input jack socket, and you are good to go. The amp even has its own fuse so you don't have to provide one. The amp on the left is Class AB as described above. The amp on the right is Class D, giving 35+35W into 8+8ohms or 90+90W into 4+4Ohms - it's 4 amplifiers wired as two bridged pairs. David

I bought a convertor block to clamp normal strings, and it gives me a much wider choice of strings. It might be worth investigating. I'm using D'Addario Chromes on a Hohner 5 string headless. David

Why it is 440Hz - a bit long winded, but fascinating. David

The picture below shows: On the left, a Class AB stereo car amp bolted to a piece of plywood, and connected in bridge mode to give 75W RMS into 8 ohms or 150W RMS into 4 ohms. With the 7 AHr battery shown, it gives about 2 hours of playing time. On the right, a Class D 4-channel amp which I use as 2 bridged pairs, each giving 35W into 8 ohms, or 80 W into 4 ohms. Using the 7AHr battery, I busked for nearly 5 hours and it was still going. The mixer I use is the Behringer 1002B, which runs on mains, or two 9 volt batteries. https://www.andertons.co.uk/behringer-1002b-battery-powered-analog-mixer-000-a0401-00010?utm_source=google&utm_medium=organic&utm_campaign=surfaces&gclid=Cj0KCQjwtrSLBhCLARIsACh6RmgidspbWPV-o7EHRGp4bv5UzMbTzEJSkdUOqxtAMiEnW3izZmrxuAMaAgUrEALw_wcB Not a combo, but less than half of the price of a street cube if you use an existing smallish speaker cab. David

The problem with inverter + mains systems is the standing current drawn by the amplifier. It may only be 12 watts which is insignificant on mains, but that alone is 1 amp continuously from the battery, and that assumes that your inverter is 100% efficient. My amplifier plus inverter takes 1.5 amps before it produces any sound. A better route is to use a car audio amplifier connected directly to a 12 volt power pack - less voltage conversion eating up your battery power.

I carry the bands spare mixer. We mainly plug into mains or generator supplies, so I went for a small mixer that could also run on batteries. We've needed it twice in the last couple of gigging years, both times because of generator problems.

The string clamps sold by a US independent have a bowl ended screw pushing the string into a bowl shaped recess. This clamping mechanism pinches the string windings against the core so that the string will not unravel when the tension is increased, nor when the tension is released and the clamp is removed. That works for my steel flatwound strings, but may not work for nylon. David

The three kits are different. The diamond shape of the 4 pots rotates from kit to kit. David

In my defence your honour, I was just following orders. The supplied instructions referred to fixing the module using the supplied screws or cable ties, and made no mention of the need to earth the case, which has no discernable earth terminal. Having avoided cheap far-eastern modules because they have a reputation for being noisy, I assumed that a major brand would have incorporated whatever was necessary into the module. Having said that, to be fair to them, a bass pickup is a lot more sensitive than anything likely to be fitted in a car, so it is probably fit for purpose in their eyes. One learns (or is reminded of things one has forgotten). David

A quick update - Checking out mains power supply options, I noticed that I was getting a high-pitched buzz through the speaker. I rejigged the earth connections to get as close to a single earth point as I could, but then noticed that the noise varied as I moved the bass around, so it was probably radiated interference. With a bit more testing I discovered that the amplifier case isn't connected to earth. Connecting it to the earth star point cured the problem completely. David

I think you mean connected in parallel. Cabs in series would increase the impedance and draw less power from the amp. David

Out with Loose Change Buskers on Sunday, playing at a Makers Market - a 5 hour shift with a front line that changed every hour or so. Also the first serious outing with my combo lockdown project, the "Joe Bloggs Briefer Case". About 150W, but smaller and lighter than a PJ Briefcase - build thread here. https://www.basschat.co.uk/topic/445027-combo-lockdown-project/ Our audience was anyone passing, or queuing for food stalls within about 30m of us, and our PA volume was loud enough to be clear, but not so loud that the audience had to raise their voices as they talked. I was pleasantly surprised to find that the "Briefer Case" was plenty loud enough to be heard throughout our catchment area, and the built in battery was still working after nearly 5 hours of playing time, so I now have a viable small rig, and an emergency backup to the larger rig. David

Portable appliance testing is used to ensure that equipment containing dangerous voltages continue to be safe. If your pedal is mains powered, test it: if it is powered from a 9/12/15/24 volt brick, test the brick. David

There may be some confusion here between amplifier ratings, current drawn on start-up and current drawn in use. An amplifier rated as 100W output will deliver much less most of the time - an average power of about 1/8 of the peak power is possible for bass guitar, and the peak power here will be 100W. To deliver that 12W average power, the amplifier may draw 100W if class A, 48W if class AB (25% efficiency at low power), or 13W if class D (90% efficiency most of the time) During switch on, a large transformer can draw *6 of its rated current in the initial fraction of a second, and a switched mode power supply can be worse, or can be designed to have a slow start to limit the inrush. When you connect several bits of kit to a single socket, you should switch them on in sequence so that the switch-on current pulse does not take out the fuse. It is unlikely that your class AB amps and class D amps will draw more than 13 A, but your lights might. David

My cab came in at 7kg I think - I'm away for a couple of days, so I can't weigh it. I'll let others comment on whether you can swap speakers.

Might have been this one? https://www.basschat.co.uk/topic/322103-battery-powered-rig/?tab=comments#comment-3959658 David

I've just looked on the Eminence site for their recommended enclosure designs, and the links don't work. Searching by product type does not bring up B102, and a search for B102 finds it, but when you click on that product, the link takes you elsewhere. I'm not sure if that is a fault on the website, or an indication that the product in no longer available, but either way it doesn't move us forward. David

An RCD at the switchboard/fuseboard will not require an earth to operate correctly, but many plugtop RCDs require an earth before they will switch on. David

Depending on what it is you are trying to adjust out, a neck shim might allow you to back off the truss rod tension David

Odd - it has an electronic crossover, but only one speaker according to the website, and no mention of battery operation, which would help it compete against the likes of the Rolland Bass cube. David

Thanks @basstone, but I've already done my modification - fixed gain of 10dB and a switched passive attenuator of 10 dB between the instrument and the input capacitor. It has the advantage of dropping the input impedance for high gain active basses. The gain switch click is now a lot quieter, as is the power on/off click, so I think I'll stop there. So, what have I achieved? The positives - It's small, battery powered, loud for its size and plays a low B without farting. The amplifier is rated at 90w x 2 into 4 ohms x 2 with a 14.4 volt battery, but it is not clear whether its power supply compensates for lower battery voltages, so it could be down around 100W or worse, but it's still pretty loud. At a recent band rehearsal in someone's garden it was still going after 2 1/2 hrs, but that was at a relatively low volume. The negatives - Twin speakers means two ferrite magnets, and a lead acid battery, so it weighs 9.7kg, which is a little heavier than I had hoped. Secondly, small speakers are less efficient, so it uses four times the power to generate the same volume as my neo Eminence Basslite 1 x 10 cab. Having said that, where I need a small loud combo, this will do the job. A few pictures and a couple of sound clips to finish off. For the sound clips, instrument EQ was flat, HPF was at 30Hz, and for the Yamaha, pickup blend was 75% neck, 25% bridge. The recorder is a Tascam guitar trainer which I assume has reasonable microphones on it. Ibanez acoustic.mp3 Yamaha solid body.mp3

I think the main advantage to a manufacturer is that all their fretboards are cut the same so they save on a bulk order. They can then put in frets or lines. David

Finally built the new circuit with the switched gain on veroboard. I didn't finish working out the layout before a trip to see family in the North, and I didn't finish the build before a trip to see family in the South. Add in some self isolation between visits, just to be on the safe side, and that's a month gone. The circuit has enough gain, which was the reason for the redesign, but the gain switch causes a loud 'crack' when operated, so I'm not out of the woods yet. I'm now looking at a fixed gain preamp, with a passive attenuator on the input. More rework... Definitely reached the point where I wish I had not started this. David

Back in the 70's, Barkley James Harvest had a hit with 'Mocking bird'. When I saw them at the Hammersmith Odeon, they had a neon tube prop that they only used once, for that song, on their 5th encore - they planned 5 encores? David