Thursday, January 04, 2007

A little fix me up

The big rig needed a little TLC. There's a circuit correction for the transcendant that was never done (is now), not to mention, swapped out the horrid heater diodes for the driver stage (1N4007, awful noisy nasties) for uF4007, a 25c drop-in much lower noise replacement.

Nice gain in smoothness and clarity, a little better transparency too. Don't know how much came from which, but I've always had impressive results replacing noisy diodes in the past. I also had to make a fix in the linestage (12AY7 based circuit, simple plate amp running at about 190V and 3mA.), the grounding on the attenuator (chinese 24 step stereo 100k ladder) had worked it's way loose, so it was intermittent, and jiggling around causing the loss of the shunt element..... drivers with 0.3mm xmax aren't meant to jump around! Good thing they weren't hooked up to a big class D amp, but rather the OTL.

Next Victim on the repair list: A finnicky LP12. Also have a passive preamp to rebuild for a customer, and my own big Phonostage/Preamp. After that, looking like open baffles, probably with 4 8"s ..... perhaps with a horn midrange! How strange! Still working out the details of the horn, probably a 400Hz or so round tractrix.

If anyone's reading this, comment so I know!


At 10:56 AM, Blogger Chris the test engineer said...

What was up with the LP12?


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