valve5425

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About valve5425

  • Rank
    Advanced Member

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  • Location
    West Yorkshire, UK
  • Interests
    Nearly finishing audio projects. Trail running.
  • Headphones
    Stax SR-303
  • Headphone Amps
    Stax srm-313
  • Sources
    Ariston RD80 deck, Dell laptop
  • Other Audio Gear
    300B Monoblocks, RTPC3 pre-amp, Castle speakers. Geek Out 720 DAC, Pulse Infinity DAC.

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  1. Very stylish, neat build! Like your graphics.
  2. Looks like you worked it out yourself! I guess you could populate the board normally and fasten it upside down to the top panel of your chassis. Then use short wires from the bottom of the board to tube sockets bolted to the underside of the top panel. However that raises the problem of adequate heat sinking as they don't tend to work too well upside down! Maybe you could use something like a http://uk.farnell.com/amec-thermasol/mhp-1220a-100a/heat-pipe-ultra-flat-1tx100l-mm/dp/2290468 to replace the big sinks, (you'd need to size that appropriately) fastened between regs/mosfets and the top panel. But then it's getting complicated and you'd probably be better just getting modified boards made, or use connectors like I did!
  3. @charlo89. I've used MPSA's (06 and 56) in mine, no problem.
  4. Here are its innards! http://knob.planet.ee/amps/stax/stax.htm
  5. I've slept on this and now recall that when I initially looked at designing the case, there was also the problem of heat sinking if I flipped the boards. I did consider pushing the heat sinks through holes in the top cover but decided it would be messy. One solution of course would be to bolt the TO-220's directly to the top and fasten a fancy heat sink on top. (But then I guess if you wanted to use a 3mm copper lid, it would have sufficient mass to negate heat sinks!) Fastening directly also gives you the problem of having to re-seat the TO-220's every time you take the boards out for tweaking/repair. Just a thought I had after I'd built this, was to place the 24V zeners on the bottom of the PSU board. (Wish I'd thought of it before I built!) As they are designed to blow if disaster strikes, then they would be easier to replace. If anyone's doing a re-design then it should be possible to position them on the outer edge of the board and not tucked between the heat sink and caps. However, with the current board, future builders may want to consider them underneath.
  6. Thanks Blueman2! No reason really, just figured this would give best access to the boards without taking all the case apart. Also, I didn't like the idea of all those electrons upside down! Good luck with your build. Cheers. Hmmm. I could send you some photos of it completely naked if you want?
  7. Finished!! Running at 375 volts, (I like to be different) and 10ma. 1K3 cathode resistors with the 1k0 trimmers. 42° C at the heat sinks (psu around 32° C) with the top barely getting warm, so no heat issues. PSU is actually putting out -377.37V and +376.16V when warmed up. There's less offset without the servo, around 200mv, so jumpers are out. I've designed the chassis base to enable access to the boards from below. Also the brass valve platforms are removable, so balance and offset trimmers can be accessed without removing the full top cover. Signal wiring is 4n silver foil, everything else 600V PTFE. Power lines twisted and heater wires run along the top of the chassis, so no hum. All grounds to star earth located near to the filtered mains in. The volume control is an LDR kit (4 boards in the rear right hand corner) which I thought I'd try. I know the potential issues with these but it doesn't seem to be having any negative effects. I fancy playing around a bit more with LDR's to see if there's any mileage in them, but if I get bored with them I've got room for a conventional attenuator, so I'll see how it goes. I know I said it was finished, well, almost. Just need to re-etch my relay/delay and 12V supply board for the LDR's which will slot in where the terminal blocks and small board sit next to the main psu board. Slight printing error, that I hadn't spotted, meant it had shrunk the image horizontally. Dooh!! TBH, it's not really needed, but it gives me something to do. It's been 12 months from the design stage but well worth the effort. Oh, and did I mention that it sounds bloody fantastic? I guess that now I'll need to upgrade my SR-303's. Thank you, Kevin Gilmore, Spritzer and anyone else responsible for the design of this amp. Now, did someone mention a T2?
  8. Hate to mention them here, but have you considered posting this on diyAudio site as well? A 1000's an awful lot of pots to shift and I guess you'd get quite a bit of interest there! On a different note, some info here from Fairchild on heat sink mounting. (Apologies to those that have already seen it.) It includes optimum torque settings and differences between thermal grease/no thermal grease and washers/no washers. (Great if you're a bit OCD like me!) Recommended torque for the Aavid 7721-* washers is 0.565Nm to 0.678Nm (5.76 kgf.cm to 6.91 kgf.cm) which ties in nicely with the settings here for the TO-220(F). Mounting packages-torques.pdf
  9. Neat! Looks like there's more than a few hours gone into that. As UFN said, looking forward to the finished item.
  10. Thanks! Hmmm, hadn't considered motorising it. No bending involved. They're just 10mm, end feed, 90 degree joints, used in plumbing. I just loved the shape of them, plus I figured they'd stop too much dust getting inside the chassis whilst letting some heat out. Brass block was drilled to same diameter, joints push fit and epoxy glue to fix. I dismissed soldering them in as tidying up the solder joints on the top side would have been a nightmare. I polished the parts with a buffing wheel on my pillar drill before gluing, and again when the piece had set Yep, a bit of a problem! Wiring the top to the B+ would solve that. (Only joking folks)
  11. Maybe if I crank up the current regs I could get some steam out of the vents. I'm looking forward to seeing it all lit up. As you may have gathered, I don't rush these things, so I'll aim for Christmas and get some pics posted. (This Christmas!!!)
  12. @‌G600 and UFN; Cheers! A few more pics here. http://s283.photobucket.com/user/valve5425/library/KGST (The aluminium base has been polished since the photo was taken)
  13. Thanks for the kind comments folks.
  14. AAAgh! That top was a pain in the butt. It's 3mm copper sheet which has been polished, buffed and then waxed with Renaissance wax. Should last 12 months between waxing and the wood can take the wax as well. (The elm was oiled with Tung oil before waxing.) I did consider lacquer but apparently you can't get the depth of shine. However, you only need to look at the top and it scratches, so I'll see how it goes and may lacquer it at a later stage. The plan is for the top to unplug from the PCB's, and the heat vents and valve bases all unbolt, so it won't be as complicated as it seems to take it apart later. The piping is just 10mm copper plumbing elbows set into a brass block.
  15. From a plank of elm I've had sitting around for the last 15 years.