JapanAxe

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.

I doubt that a YouTube video of Jim Lill reading a book wood get many views though!

It's pentode. I've gigged a 50W valve head (Ampeg PF-50T) in a 3-piece rock/pop covers outfit and it was plenty loud enough.

Some more bits have arrived today, including a pair of KT66 valves. Those things are monsters, they dwarf the 12AX7s from my stash - I'll have to space them a bit further apart on my layout!

No influence at all. When I started out I wanted 2 pickups and active electronics as I thought it would be a plus to have plenty of tonal options. I found from experience that I prefer P basses and passive controls. It so happens that James Jamerson and Duck Dunn (who are among my favourite players) are linked with Precisions but at no point did I think, ooh I must get a P bass so that I can sound like those guys. As a Bowie fan I also appreciate his various bassists’ playing, but between them they have been seen with almost every imaginable bass!

Absolutely. I use a bullet journal to plan 2 or 3 things to progress each day so that I stay on top of all the material I have to learn. I’ve never been the guy that turns up to rehearsal and says, ‘Sorry, haven’t had time to look at this.’

First draft of my board layout. I will revisit this tomorrow and check that it makes sense! That may not be its final position within the chassis, that will depend on where the transformer bolts and cable holes end up.

I only work 3 days per week at my day job.

Thinking about my current gigs: Bowie tribute - hell yeah, I’ve loved the music since 1974 Country covers - yep, I love country Rock’n’roll covers - not my favourite but quite fun Various other general covers bands - mostly stuff I like I also find that I grow to like music that I’ve learned for bands.

The enclosure arrived yesterday but I won't start any drilling or cutting yet because I have only just started work on the layout. I draw the layout at 100% scale to make sure no component fouls any other. You can see I have made a full size 'footprint' of the PT. That board will get chopped around a bit. The input grid stoppers will go as I am only having one and will mount it straight to the valve socket. I will also be adding the filter caps next to their respective stages, rather than using cap cans. I may have to move the bias circuit to a separate small board. I already have a few bits in my stash, the rest is on order. Things like power switches soon add up in cost so I use what I've got. With resistors I tend to order extra so that I always have a stock for mods. Bottom right you can see my home brew bias pot. Fender ones retail at £6 but I found an old 10k pot, carefully undid the clips, took out the shaft, and cut enough off so that it no longer projects from the threaded portion. There is a screwdriver adjustment slot on the back of the pot.

Following the success of my B15-ish build I have decided to go for a giggable 50W head. I was originally looking at something based on a 60s Fender Bassman but then I came across a MojoTone 50W bass amp kit. Although it's discontinued you can still access the schematic and the layout. It's based around the iron from a Marshall JTM45 and runs two KT66s in the power amp, two 12AX7s in the pre, and a solid state rectifier. I'll be housing mine in a Hammond steel enclosure with a mesh cover as I want it to sit neatly on either of my BF cabs - overhang makes my teeth itch! Here's a video from a happy chap who built one of the kits: EDIT: Links removed as they now point to a Bassman kit build.

Thank you so much for that. I may be confusing this with SMPS cap failures in TVs, having watched a couple of YouTube videos where people have repaired these.

Cheers, that's good to know! I think my Demeter head has an ICEPower unit (700W?) in it. I've been gigging that on and off for about 7 years now. Ironically that amp did go flakey on a gig but it turned out to be the bridge rectifier used to create a DC supply for the valve heaters. Fortunately I was able to fix that myself!

I don’t think any of us end users are qualified to assess the reliability and failure modes of different amp types as we have so few examples (i.e. amps owned) to work from. Amp repair people are much better placed to comment on this simply because they see so many on their work benches. So here’s a question for them - are the caps in the SMPS sections of Class D amps their weak point?

Cŵl!

Are you a Hobbit?

I love playing live, at its best the stage is my happiest of happy places.

Well thanks for the encouragement chaps! 😆 To the OP - sorry for the thread derailment!