JapanAxe

Blimey!

What were the circumstances that led to this?

I think the @Chienmortbb is hoping there won't be smoke

Marked, punched, drilled and de-burred all the holes in the top surface of the chassis. That's a lot of holes! Also fitted the grommets for the transformer lead holes. Oh yeah, fitted the feet to the bottom plate.

DIY Ampeg B15 head into a BF One 10. 22W of vintage tube tone in my music room, although the Origin Bassrig ‘64 has been getting a lot of love lately.

Valve socket holes cut and mounting holes drilled.

Last night and this morning have been all about metalwork. Never my favourite subject at school but it just has to be done. The big challenge here was cutting a rectangular hole in the rear panel (0.91mm steel - about 28 gauge for our US friends) to fit the IEC mains inlet. I started with a 6mm hole inside each corner, then took out the bulk of the material with a 20mm panel hole cutter. I managed to remove some more with a hand nibbler (yes it's a thing!) before defining the edges with a cutoff disc and a grinder on my Dremel-a-like tool. I'm pretty pleased with the result. That's all the front and rear panel holes done, plus the mounting points for the eyelet board.

My current bass heads include Class AB (both valve and solid state) and Class D. Each is a good example of its type and I enjoy playing them all. I see no value in generalisations based on personal preference. If something works for you, that’s a win so go with it.

Made some progress on the board: (1) Covered the board with sticky paper recycled from an eBay label and marked out all the positions of eyelets, mounting holes, and bias pot. (2) Drilled all the holes. (3) Set the eyelets. I ended up moving one because I thought it was a bit close to its neighbour, given the 720V between them! (4) Fitted the stand-offs and the bias pot, straightened some copper wire and soldered the earth bus in place.

In 30 years of using it I have come across a no-earth situations 3 times. In 2 of these the solution was to run an extension from a good socket. In the last it was an outdoor stage so I got the organisers to create an earth by running a wire form an earth pin plugged into one of our socket strips, to a lamp iron driven into moistened ground next to the stage. It worked and the show went on.

I always carry a ring main tester (a few quid from you local ToolFix ScrewStation). Plug it into a socket and if all 3 lights come on you’re golden. Anything else indicates a fault, most commonly live and neutral reversed (be afraid) or no earth (be very afraid). In those (rare) situations the venue should be made aware as it their potentially lethal problem to fix.

Yes I'm aware of that. I use the PDI09 with valve amps rated at no more than 30W and always with a speaker connected. I'm wondering if it will roll off too much low end to be useful for bass, but there's only one way to find out!

I use this plugged into a speaker output of my guitar combo but never tried it on bass. Time to experiment…

There's been a bit of a hiatus in this build for a couple of reasons. First off I had a run of 4 gigs and 3 rehearsals, followed by a 2-day trip up to Liverpool to play the first ever David Bowie World Fan Convention! Secondly, the PT secondary hits 360V AC unloaded, which would translate to about 509V DC. The standby arrangement leaves power applied to the first filter cap, which is rated at 500V, so I have obtained some smaller 450V caps to use in series (with balancing resistors) like Fender did in amps such as the Twin. The original JTM45 design employs 32uF filter caps at the first two nodes, whereas this design has 100uF at each! Two 100uF caps in series will give a total of 50uF at the first node, so I bought 4 in the hope of doubling that. I can only fit 2 on the board but if the smoothing turns out to be inadequate (unlikely!) I can possibly piggy-back them on the 2 that I'm installing (left of the circuit board). Today I finished drawing the layout. I'll check it again tomorrow, then start marking the eyelet board.

I find that even 1 pint affects my concentration noticeably, and hence my playing and my driving. On gigs I stick to soft drinks or tea/coffee if available.

One gig was about 2 hours away, the others no further than an hour. No chance of a medal for me then?

You lightweight Tim! Thursday - guitar with a Stones tribute Friday - rock’n’roll guitar Saturday - country bass Sunday - rock’n’roll guitar Monday (tonight) Tuesday Wednesday - Bowie tribute rehearsals (guitar)

On lead guitar again with a Rock’n’roll band. During setup the drummer found that the jack socket for the trigger cable had fallen inside the body of his electronic cymbal. I opened it up (14 screws!) and managed to gaffer-tape the PCB in place. This got us through the rather excellent gig, after which I nipped home with the cymbal and fixed it properly with a nut from my spares stash, and Mr Drummer picked it up on his way home. I love a good kit fix!

I used the 'headphone trick' to work out the best position of the OT in relation to the PT: I connected the 240V PT primary to a mains cable while all other leads were safely parked in a chocolate block connector. Then I connected a set of headphones to the 16ohm secondary of the OT and listened for hum while I positioned the OT. No surprise that the hum was least when the transformers were at right angles at opposite ends of the chassis. I marked the transformer positions onto a piece of paper. I also tweaked the eyelet board layout with the actual components to hand for their sizes, and drew in some under-board HT runners (red dotted lines). The pink circles are where the mounting stand-offs will go.

I can honestly say I don’t have a number one bass, I pick up the one that I think is the best fit for what I want to play, just as if I were picking one out to take on a gig.

Depends! My build will come out at about £450. That might buy you a used Ampeg PF-50T - I had one and liked it a lot. I don’t think there’s much else around in the way of 50-100W valve heads in a package that will sit neatly on top of a Barefaced One 10, except the Handbox WB-100 at about £1,000.

The iron has landed! Michael at Modulus Amplification wound me a JTM45 OT with a 6.6k primary. The PT is sold to fit a JCM800 but has the right voltages for my build and by default is in stand-up format. All the rest of the bits arrived with the same order. Woot woot!

Am I right in thinking that in bridged mode there is no earth connection to the speaker output because each terminal is fed by a ‘hot’ connection?

I carry enough stuff that, if any one thing fails, I can get through the gig. What this equates to will depend on whether I’m on guitar or bass and varies from gig to gig, but the show will always go on.

I voted for the Markbass Nano, only because I have one so it’s the obvious choice for me. Also good for one-trip rehearsals, but for gigs it is relegated to backup as I find it too clean and uncoloured. Mine once did the job of power amp for one side of the PA on a gig.