JapanAxe
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Everything posted by JapanAxe
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I don't think anybody's going to be moving this around when I'm not there, so I can't see two side handles giving an advantage over one top handle. Plus I can carry something else in the other hand. It doesn't feel any heavier than my Fender TB600 head (although I haven't weighed it).
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Well that was fun! It is in fact a working amp, with a huge range of tones on tap. As ever when I'm trying out my builds at volume, I get a lot of buzzes and rattles in the room that make it difficult to hear whether there is distortion from the amp, so a blast in a hall or something would be an advantage. Background noise is acceptable with just a little 100Hz hum. I can hear no effect from the bright switch on the normal channel because I have the channel volume up a fair way, so I might turn that into a channel selector instead. There's now way too much negative voltage available on the bias circuit so I'll experiment with component values and maybe add another filter cap in there - who knows, that might reduce that hum a little. For now I think I'll work out the best place to fit the top handle and get it installed, although I think it may be a challenging one-handed lift!
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It lives! Last night I was trying to work out which HT node the excess curent was coming from. The various components up to the third node (C+) all tested ok but I was measuring 121k from C+ to ground where it should have been open circuit. Before I turned in for the night it occurred to me that I should look for leakage in the coupling caps. While I was falling asleep (in the hypnagogic state, no less) I kept thinking that there were resistors where there should be capacitors, but when I woke up I realised that was just daft. This afternoon I checked over the circuit diagram and worked out there are just two 100nF capacitors which, if leaky, could allow positive voltage onto the control grids of the 6L6s, thus messing up their negative bias. I found them on the layout, but when I looked on my eyelet board, there was a 100k resistor fitted in each spot! I had written '100n' (for 100nF) on my layout but misread it as 100k (100kΩ). Consequently there was a straight resistive path from the anodes of the phase inverter to the control grids of the 6L6s, with no capacitors to block DC. I took out the resistors, fitted the correct caps, and was able to bias the amp to a healthy place. I gave it a quick test through the guitar speaker cab that I keep in my music room, and all the controls seem to work as they should. Tomorrow I'll give it a try through my BF Super Twin while Mrs Axe is at work
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Here we see @Sean demoing (1) the new pickups in his Precision, and (2) what an all-valve 22.5W amp sounds like when driven to the max!
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Definitely the busiest bash I've been to! Always nice to meet other players, many of them coming from very different places in terms of the music they pay and/or the kit they favour. Of particular note - @Wolverinebass and his amazing John Entwistle-style bass; @MichaelDean and the passive tone mod on his Dingwall NG2 - why didn't I think of that! Can I also add my thanks to @scrumpymike and all those who assisted in making the day such a great experience.
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Hope it's ok to mention this here... The self-built all-valve B15-inspired head that I brought along last year will be with me again, this time with a FOR SALE sign on it! I mention this because, while I am really trying to slim down my kit (honest), I am also not completely averse to a trade, and you might want to bring something with that in mind. If the head sells/trades at tomorrow's bash I will donate 5% of the net proceeds towards the Bash running costs. Of course you are welcome to try it with your own bass and/or cab without obligation of any kind - that is part of the fun of a Bass Bash!
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Yeah I can do that.
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I've made sure the documentation reflects what's in the actual amp, ready for Sunday's SW Bash -
Any interest in having your valves tested? If so I’ll bring my Orange Valve Tester. It tests most types of preamp and power amp valves commonly used in guitar and bass amps, but not rectifiers.
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I did actually (and I occasionally do so) but I seem to recall members being encouraged to host their images elsewhere. I understood there was a fairly low limit on how much each member could upload - every so often a member would complain of being unable to upload, and it was usually because they’d reached their personal limit. Also I want some of the photos to be visible on other sites e.g. in for-sale threads. I could just directly upload here and then link from other sites, but it didn’t seem quite right to me. Maybe I’ve massively overthought it and I should just crack on! -
Will likely do that then!
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Yes I’m well aware of this. I’m probably going to self-host using Dropbox but it all takes time!
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I'm bringing this to Sunday's SW Bass Bash. Although I'm really trying to slim down my kit, I'm not wholly averse to a trade with cash my way... If it sells, I'll donate 5% of the net proceeds to the Bash running costs.
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For anyone who wants to see these pedals in the flesh, I'll be taking them along to the SW Bass bash on Sunday. If any sell, I'll donate 10% of the proceeds to the Bash running costs.
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Well this is both annoying and encouraging. Today I rebuilt the bias board with a voltage doubler, giving me a range of -56V to -36V. I still get a positive voltage at the control grids when I apply HT, and this time I got some sizzling and smoking from around V4. I wasn't able to determine exactly where, and there are no crispy components, but it's a start. I then removed all 4 output valves and dropped the mains to 180V. With the amp in standby, I measured around -14V on the HT downstream of the standby switch, and it changes as I move the bias adjustment pots. There should be no way for DC to make its way from the HT to the bias circuit. There's either a short or a leaky capacitor. I'm off to play sone music now to soothe my brain but I'll come back to sort this another day.
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I think there’s a general lack of ‘fun money’ in people’s pockets at the moment.
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Depends. But always remember - you can never be too smart on a gig. There are few worse feelings than that of being inadequately attired.
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Not a scam but you’re not the only one to experience frustrating delays: https://www.thefretboard.co.uk/discussion/287054/
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My frends really awful band - advice needed
JapanAxe replied to Uncle Rodney's topic in General Discussion
I’m a big fan of the sh!t sandwich. Start with something positive, then deliver the bad news, finish with another positive. But only if you’re asked. -
Well that's annoying. I rebuilt the bias board with the correct component values but the result is the same - the bias voltage disappears when HT is applied. With 450V of HT there should be about -37V on the control grids accordoing to the 6L6GC spec sheet. I'm pretty certain that the tapping I am using for the bias is a completely separate secondary as I checked continuity when I first got the transformers out of the Bugera. It has a centre tap (unused) but the HT secondary doesn't as it went to a bridge rectifier (which is what I'm using on this build). I'll check that again, and then consider the following options: Voltage doubler on the 41V AC secondary. It may be that it just can't produce a high enough negative bias without this. Creating negative bias by dropping the HT with a potential divider. Merlin Blencowe goes into all this. Sadly it's looking less. likely that I'll have the amp ready for the SW Bass Bash
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Yes. Yes it is.
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How many hours do people practice?
JapanAxe replied to Bassbooksbikes's topic in Theory and Technique
Probably at least 2 hours per day, but I am retired and either a member of, or dep with, a ridiculous number of bands. Not many days go by that I’m not practising something or other, and sometimes I spend pretty much the whole day at it. I recently worked out that I was working on learning some 65 songs: - 15 jazz or similar numbers on guitar for a one-off charity gig; - 32 rockabilly and country songs (again on guitar) for a first rehearsal / audition - now joined that band! - 18 West Coast rock numbers on bass for a theatre tribute dep. -
I love depping, although I frequently end up biting off more than I can chew! A lot of my opportunities have come through musicians who I’ve already played with, but if my diary is looking thin I put an ad on Bandmix. A couple of my long-term dep relationships have started that way. I always try to be the person that solves problems rather than creates them, whether that’s singing a couple of numbers, digging out cables from my spares bag, or giving a lift to another band member. Finally, I always thank the band for the gig, even if I have silently sworn to be unavailable next time they call - I’m pleased to say that’s a rare occurrence!
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I’ll bring a roll of wide masking tape - have at it!
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Well that's interesting. I've discovered that, when HT is applied, my nice negative bias voltage all but disappears, leaving the output valves to go full-on Fukushima. Which bit of this circuit is not a tried-and-tested design, but my own concoction? Yep, the bias supply. I consulted the writings of good old Merlin Blencowe, and discovered that my choice of component values may have left the output valves with too high a grid leak resistance. Time to re-design the circuit!
