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High Rollers
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About oogabooga

  • Birthday 02/04/1981

Profile Information

  • Location
    Ontario, Canada
  • Gender
    Not Telling


  • Location
    Ontario, Canada
  • Interests
    Computers, BBQ, cats
  • Occupation
    Pulse jockey (NMR)
  • Headphones
    SR-007 Mk1, Lambda Pro, Lambda NB, SE535
  • Headphone Amps
    SRM-323s, SRD-X, SRA-3S
  • Sources
    Concero, Gamma2

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  1. I've always found Backblaze's stats/reports to be a well written and useful: https://www.backblaze.com/b2/hard-drive-test-data.html
  2. Created HV bias from 603V B+ into a 23K-390K-390K voltage divider to get 585V measured just before the 5M1 ballast resistor. The plug-in card refurb will wait until I've enjoyed the amp for a bit :-) Thanks again for your suggestions Spritzer. I used lubricating contact cleaner on the pot, and ended up finding enough shielded wire from the previous stuff to run the audio. Oh - as to that 'side' mounting, after poking around a bit, I'm convinced that the giant 50K resistors are a major reason Stax designed the amp on it's 'side'. They get DAMN hot and would probably melt if they were under the PCB. I measured the frequency response using a sine wave generator on my Mac and the AC Vrms reading of my Fluke via the headphone sockets. I set the volume pot so that a 1 kHz wave was 250 Vrms and measured at 19 frequencies on both channels. Attached log plots shows was normalized to 0 dBV @ 1 kHz. The bass rolloff is slightly more than I calculated for 0.22 uF caps into a 145KOhm impedance load, but -2 dB @ 20 Hz is more than great for me. The high frequency rolloff is about 4x stronger than on my SRM-323 and is probably why this amp sounds less fatiguing than the SRM-323 with my Lambda Pros :-) Almost makes one think Stax designed the Lambda Pro to go with a tube amp... PS - I recreated the circuit in falstad.com: http://tinyurl.com/zlxjj9d The simulator seems to work (better) if I replace the the triodes with N-mosfets, but the output signal still looks screwy. That being said it's still a great website for smaller circuits.
  3. I used VMware at my last job to run Windows NT, XP, 7, and Centos 6. It works very well. Seamless integration, excellent speed. Features like drag and drop sharing, shared clipboards and folders, and the like all worked well. Only gripe is that one usually has to do a paid upgrade to VMware if they do a major OSX update. They don't seem to care much about maintaining compatibility IMHO. At my current job I've used Virtualbox to run WinXP. The VM works fine, although I cannot get drag and drop sharing to work at all - the VM crashes whenever I try. Printing had some growing pains, too. It's also noticeably slower to suspend/restart a VM. That being said, it does the basic job and is free. If you have the money, I strongly recommend VMware. Haven't used Parallels in many years so I can't comment on that.
  4. Thanks Spritzer, catscratch, and MrSneis, I was able to get the housing off (the adhesive had 'melted') and indeed all is as you describe. I'll scrape off as much glue as I can and wipe the rest down with 100% isopropanol (if anyone knows of a better solvent please do share!). When I repaired my Lambda Pros, I used Double Sided Hercules Tape. The only kind of PU glue I know of is Gorilla Glue - is there something better out there?
  5. Used a rotary tool for the first time and wondered why I didn't buy one 10 years ago.
  6. PSU done! With no source connected, the "A" line (aka B+) is running a bit high at 603V, the "B" line measured ~56V, and normal bias is ~260V, measured before the 5M1 resistor. In the original design, the 10K input resistors are soldered across the contacts of the input selector switch. I'm not using the selector, so I put new resistors on perfboard and stuck that into the plugin slot for the Mag PU card. Connected a source and played a 1 kHz sine wave: maxed out at ~380Vrms output to the left and right channels. Played some music and the distortion I had before is gone! Pot is no longer scratchy, either (contact cleaner). Next step is to redo the input/pot audio wiring. Stax used shielded wire but the ends look like crap and the wires are too short to trim, so it's all got to go. Will single conductor pick up anything from inside the amp? Also, why the heck did Stax design this amp to lay on its 'side'? It just seems like sub-optimal cooling for the tubes...
  7. I found 100% isopropanol to work well, and wiping it off while still wet like muskyhuntr says helped eliminate residues.
  8. Refurbished my SRA-3S PSU board today (except the HV caps that I'll place tomorrow after putting it back together). Three copper traces were already in a bad way when I started, and I broke a few more. Ran the blue 22AWG teflon-coated wire to fix. I've attached a picture so you can make fun of my soldering skills. I left a few mm on the component leads in case I need to reseat them... there'll be enough room in the case anyways thanks to those Rikens. For reference, I ended up replacing: diodes with 1N4007s, the five PSU resistors with Vishay BC PR02/PR03 2W/3W the three bias resistors with Vishay BC VR37 1/2W three LV PSU electrolytics with Nichicon VX 22-47 uF (the HV caps will be 180 uF 400V) four output film caps with Panasonic ECW-F(L) 0.22 uF 630V
  9. You're right! Traced the paths - the two arrows connect to pins on the Mag PU card slot. There's a jumper bridging the two pins on the card, so when it's plugged in, the 63k resistor is parallel with the 47k.
  10. Prepared for my university's 'annual power shutdown' happening tomorrow. The critical stuff we can't unplug goes on diesel generator backup... (i.e. crappy and surge-y power), and in two days, I find out what didn't survive!
  11. Removed all the PSU caps, to find two resistors in the PSU (circled in red) looking terrible. One has it's casing blown clear off! The Vishay BC PR01 metal film resistors (1W) I have are much smaller than what Stax used. Is 3 W enough/safe here? I figure the voltage is 280V here, so that 47k resistor should top out at 1.7 W if it's other end was ground. Bias resistors are also cracking, going to replace these with 1/2W Vishay BC high voltage, ditto for the pro bias. I hope that's it for parts - one more order from Digikey and I can start putting it all back together! Thanks everyone for the help (Does anyone know that the two 'double arrows' just above and to the right of that red circle are? Never seen that symbol before and I can't find it on the board, or on Google.)
  12. Thanks all for the suggestions, I've got a few choices now. Been avoiding eBay mostly because of delays with customs in Canada, but it looks like I can either have it cheap or fast... George - the offer is much appreciated but I'm gonna just buy a spool and get it over with
  13. How normal is it for LNS drivers to be off-kilter? I just received a pair and the left driver looks fucked up. I removed the four screws on the driver to try and get a closer look, but I wasn't able to pull the driver/back plastic apart (didn't want to use too much force) - not sure if a previous owner glued em on. FWIW google turns up other LNS's that look like this: http://www.ebay.co.uk/itm/RARE-STAX-LAmbda-NOVA-Signature-/141886669059
  14. 1Password can store the initial two-factor authenticator key and generate one-time passwords just like Google Authenticator. However, it can also be backed up and syncs across devices (I have 1P on my Mac and iPhone) so I can get a one-time password from either. Perhaps its slightly less secure, but its a small penalty to pay for a lot of convenience.
  15. I was afraid you'd say that. A 100 ft spool of 22 AWG teflon-insulated wire costs ~$75 at Mouser. So much for doing this repair on the cheap! For the 5k1 - is a 2W or 3W resistor about right? Buy 25 and match 2 pairs by hand? What's a mini SRA-3S?? How the heck can they make that thing any smaller!!
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