TG "The Loudspeaker" Build (Sort of)

[simon]

Me four.

I've not seen Vitiux before but thought it looks interesting and I'd have a play with it. Unfortunately the virus checker picked up a threat with the download but didn't give a clue as to what. Probably some kind of embedded minor spyware, but I binned it anyway.

[MistyBlue]

Thanks Guys!

That's really sweet of all of you.

Although the full scope of what I have taken on is really starting to dawn on me.......but I'm up for it, and will have help from within the household (WAF is luckily amazing!).

Tony - I haven't forgot about the PCM2DSD/RTZ build. Got a new microscope (a surprise prezzie) for the QFP soldering to make it a bit easier than trying to do it through a PC screen. I'm waiting for some practice boards to be delivered before I attempt the Spartan 6.

The speaker build itself will be slow starting because I have a few things to sort out first. But I'll post progress reports as they happen - warts and all!

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[andrew Ivimey]

Four!

[MistyBlue]

Apologies for a slight detour. I have been putting this off for a while and things are starting to overtake it.

I want to keep my options open regarding crossover design and implementation, with an eye on possible changes that could happen in future if we decide to try something out. Before I bought the drivers and designed the cabs, I had already simulated quite a few options involving active / passive and combinations of the two using TGs measurements and measurements from other sources that were relevant. My current setup is a straight single amp with passive crossovers built into separate enclosures from the speaker cabs themselves (the two veneered boxes either side of the 2A3SE amp). The amp is built as an integrated (simple rotary input selector switch and stepped attenuator) but has an added complication of a system remote control based on a simple Arduino/GBRL cnc board with steppers crudely adapted to operate the 2 switches and some very basic code I wrote (my coding kung fu is not strong). The amp and DAC (I never got round to integrating the PC) have Arduino relays that operate from the 5VDC line of this controller. No 5V – no amp or DAC (the latching power on/off pushbuttons on the front of the amp and DAC enclosures are overridden by this system).

I’ve just done a quick job by replacing one of the connectors for another GX20-12, so I can transfer the attenuator/input switch and steppers to a new chassis. I will probably revisit this at some point in the future, so I can switch on all amplification related devices at the same time. This will do for now.

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I have been making a new enclosure chassis with my usual flamed maple/sycamore veneered plywood front and rear panels for the attenuator and input selector that can house an active crossover, primarily for bi amping. The Hypex amps that TG uses for the bass seem like a great idea, especially with the DSP, but I am aiming to eventually bi-amp them with a MoFo that I have been meaning to build for a while (I’ve had the parts for ages), or one of a few power amps I have in storage. I bought a Pass DIY 6-24 JFET active crossover ages ago to do this.

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The holes on the front panel look worse in the photo than they actually are at this angle, I did those with a milling cutter and cranked the speed up on the mill. Unfortunately, not with the sharpest cutter. I used the same technique for the recesses for the phono sockets etc on the rear panel. I recently discovered that the crossover kit was on offer over on DIY audio and bought a second kit just in case in the future I want to go for a 3 way active system. I’ll take a view on replacing the attenuator value later if needed.

The dual shaft steppers have a machined aluminium housing on the back which covers the flexible shaft coupling to the switches. It works quite well, even if has stuck at times on the attenuator, probably due to a slight misalignment. My plan here is to remove the housings and run coupling rods back to close to the rear panel. I machined a new aluminium plate between the crossover board and the rear panel to take the switches.

I wasn’t really happy with the half round gap in the plate for the wiring to the phono sockets, so I milled a bigger one. I also needed another shaft extension for the input selector stepper.

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[MistyBlue]

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[pre65]

Nice nail varnish.

[MistyBlue]

Thank you, kind sir!

It doesn't last very long though, and not my usual colour.

[simon]

Lots of interesting stuff here that would probably stand their own thread. I'd be particularly interested in the whole remote control and preamp setup.

[MistyBlue]

Lots of interesting stuff here that would probably stand their own thread. I'd be particularly interested in the whole remote control and preamp setup.

I almost always have something audio related on the go. I am happy to share anything I can, although I must admit to being a bit overwhelmed with the current speaker build. I will probably do a thread on that when I can. In the meantime, if you have any specific questions that are urgent, drop me a PM.

[Morgan Jones]

Nice toolholder on the lathe. What's the lathe? Looks pretty substantial with a 200mm chuck.

[MistyBlue]

Nice toolholder on the lathe. What's the lathe? Looks pretty substantial with a 200mm chuck.

Hi, lathe is a 1976 TOS SN40B, we spent 2 years restoring it, full bed regrind and gearbox rebuild - long story, but a great piece of kit and very useful. Toolpost is PeeWee Tools multifix. Sadly Trens (manufacturer) as it became has just gone bust. The mill is 1996 KRV2000 - also restored.

[MistyBlue]

It's just occurred to me that I havent shared the CAD drawing. Doh!

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Cutaway showing bracing, although I might add more.

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[MistyBlue]

Active crossover/passive preamp is now done far enough so that the system is ready for the crossover design stage and get my system back up and running. I will return to it later to stuff the board. Having to modify the 2A3SE amp on the lounge floor is playing havoc with my back and I need the room to start sorting out and marking the plywood for processing, but both the 2A3SE and the crossover won’t fit on the bench and the 2A3 is best manoeuvred when two of us lift it.

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[MistyBlue]

Just when I thought things were going well.......

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[MistyBlue]

Nice toolholder on the lathe. What's the lathe? Looks pretty substantial with a 200mm chuck.

Actually, I seem to remember part of getting into the whole metalworking thing years ago was because I was doing an amplifier chassis and refered to a section in a book entitled "Metalworking for poets".