Firstly, a fix-it. When fitting the chassis I noticed that it was rather resonant. Nay, more than resonant: the bastard rang like a bell. They're not meant to do that, so I had a good, close look at this thing and discovered that at one end the spot welds were missing from one side of the chassis! I kid you not. They were present at the other end of the chassis, but not this one.
Not happy, Jan.
I'm not a welding kind of guy, but reasoned that this was what it needed. So I headed on down to the Fremantle Men's Shed, and one of the fellas there tack welded it in a couple of minutes:
That bastard would've buzzed and rattled very badly indeed. That's a Weber chassis, by the way.
But enough of my bitching! Here's a pic of the test fit I just did tonight before I cover the speaker baffles. I just wanted to make sure the drivers fit the baffles and that the baffles fit the cabinet with the drivers on board.
It's all good. Everything seems to be fitting properly, so I'll just keep my fingers crossed and hope it continues that way.
I said this may take some time, and I wasn't kidding! But here's an update of sorts. Well, it's an update on what's been keeping me from this V-front thing, anyway. In mitigation, all I can say is that at least the distraction is amp-building-related.
I've been building a cab for a friend for a 5E3 style amp. This time around I've modified the cab design a fraction to make it easier to build and - hopefully - a bit stronger. The main change is here:
As you can see in the pic, I've run the facia the full width of the cab. The blueprint I've found has the facia only the width of the interior distance between the cab sides. I've always thought that was wrong: it just couldn't be strong enough. When I made mine I routed a channel in the side panels as well as the top and bottom. The facia was then an insert. But this was frankly a pain in the arse.
So this time I just routed the channel the full width and it's not just simpler, it looks neater, too (in my view).
So the whole bloody thing is nearly finished, and it looks like this:
I'm reasonably happy with it as a piece of rough carpentry. I reckon by the time I've made another four or five I'll be quite decent at it.
But I did make some progress on the Most Awful and Dread V-Front. I've basically finished the carpentry on this monster now, and I'm only awaiting some hardware from USsia. But I did do a full test fit of the speakers, mounted on the baffles, mounted in the cab:
Resurrecting this old build thread after more than six years (ermmagherrrd!). A quick summary of what happened with this project seems in order.
Firstly, I did build the amp. It was based on a tweed V-Front Super (5C4), which I thought was an interesting old circuit. I like 6L6s, and I like the sound of them in cathode-biased class AB, so the ancient Super was good start. I also like 10" speakers, and I was really curious to play and hear an amp with a paraphase driver (paraphase phase inverter), and with preamp tubes that are grid-leak biased. It was also interesting because all the tubes, including the preamp, are octal based.
I was also interested in making this amp a real blues monster. I figured that it wouldn't be difficult to add tremolo to this circuit. There were plenty of Fender circuits to use as a starting point, so how hard could it be, right? I picked on the tweed Tremolux 5E9A as my model circuit because, among other things, that amp also used a paraphase driver. It was a good match.
So that's what I built: a 5C4 Super, with tremolo (from a 5E9A circuit), all shoe-horned into a cab that is as close to a vintage V-Front cab as I can make it without having an example from which to take measurements. I took the meager data available on that cab, and combined it with analysis of online photographs to calculate the dimensions of the vintage cabs. I reckon it's pretty close.
How did it go? Not well. It turned out that I wasn't as clever with my redesign as I'd thought, and the bloody thing didn't work. So I did a bunch of trouble shooting and got it going, but without the tremolo. Then I discovered a subltle parasitic oscillation. I hunted for that bastage, but I couldn't nail it down. In the end I rebuilt the amp, and to keep it simple to help with the trouble shooting, I eliminated the trem. and just built a Super. Oscillation was still there. A couple of other people had a go and couldn't find it either.
So at that point I put it away. It was working, and it sounded great except for that bloody parasitic. It was frustrating to say the least, but I had to move onto other things. I put this amp on ice, and let my subconscious work on the problem.
Well, after six years of other projects and events, yesterday I finally started the resurrection of that amp project. I'm aiming to get what I wanted in the first place: a 2 x 10" combo, driven by a pair of cathode biased 6L6s, with tremolo, all octal.
So I've taken out the board, ripped out the heater harness, and I've depopulated and cleaned up the board. I'm just going to replace some of the turrets, then I'm going to be into my least favourite part of an amp build: the heater wiring.
This time I'm using teflon coated multistrand cable. I am done with single solid core wire in cloth insulation. Sure, it's easy to work with and it looks cool, but cable is more robust than wire, and modern insulation handles everything (heat, cold, moisture, etc) so much better than cloth it's just not even worth comparing.
Very interesting, Spattle101...crafty you are!
I am going to try my hand at the non-trem version of your amp, basically a 5D4 but with 6v6 instead of 6L6
so I'd really love to hear (and see more of) your amp as you progress.
The preamps have arrived! That's the only parts outstanding, so we're away.
This amp will take three tubes in the preamp, all twin triode valves. The preamp will use one, with one triode valve for each channel. The phase inverter will take one tube. It's a paraphase phase inverter, so it'll use both triodes. The third tube is the oscillator for the tremolo, and it'll use both triodes, too.
This is one of the changes I've made from the old Super circuit. The oscillator requires the two triode valves to be completely independent. The old 5C4 amp used 6SC7 tubes for the preamp, which are twin triodes with a Mu of 70, transconductance of 1325 uMohs, drawing 2 mA on the plates. Unfortunately, the two triodes share their cathode so it's not a suitable tube for the oscillator.
I've therefore decided to go with 6SL7s. These are part of the 6SN7 family and are widely used as audio preamps. They're pretty similar to the 6SC7, too. They've got a Mu of 70, transconductance of 1600 uMohs, and draw a fraction more plate current (2.3 mA). Importantly, each triode valve has its own cathode. I reckon they're good substitute on paper, and I'm pretty confident they'll do at least as well as the 6SC7s in practice. When I built this amp first time, I went through a big bag of 6SC7s to find three that weren't badly microphonic. Not an encouraging experience so I'm not sad to see the back of that tube, to be honest.
I bought four of them, because tubes. I intend to use the three JJs (above right) when the amp's all up and ready to go, and use the Sovtek (left above) as a spare / troubleshooting tube.
The Sovtek tube has the old Reflektor symbol etched into it along with some Cyrillic text (the Sovtek info is stamped on the other side in black ink). I'm wondering if it's old pre-New Sensor production. Do they still use that Reflektor symbol?