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Posts by AudioCats

*SRM-212 modification   (still in testing stage, trying various upgrades.... pay no attention to the large motor caps)       power supply section: 1) C31 change to larger value low-esr cap. 2) C36 change to larger value low-esr cap (using tantalum 150uf/16v, barely fits) 3) C39/C40 are +/- rail reservoir caps, change to larger value high ripple current caps. Voltage rating needs to be at least 250v. (stock cap value is 22uf/250v). 4) C4/C5 change to more...
looks like I just bought a  002 system (base model) ..... Guess it will finally be the real "002 mod thread".   Thanks mods, for removing the "?" in the thread title.
* SRM-212 modifications   my first encounter with the 212 was in the form of a SRS-005 (sr-003 baby stax + 212 amp combo) about 10 years ago. At the time I did not have other pro-biased phones so the only thing I used the 212 with was the baby stax. The result was disastrous, I could not handle the major "listening fatigue" from the combo, the sound was just too hard for my taste. (The baby stax is already mid-centric, I'd guess the 212 has a bit of mid-range burn of its...
b) Amp section: the Xh has direct DC coupled output so there is no output caps needing upgrade. And there is no adjustments to make. That leaves the only the signal input section to be modified. The stock volume control pot is a generic round 50k Alps, which is not bad, and there is not enough room to change it to a square Alps blue RK27, so I left it alone.   However there is still a lot that can be gained at the volume control section: convert it to shunt type (google...
Starting a thread about modifications on smaller Stax amps (SRM-X, X pro, Xh, 212, 252, etc).   *** warning: these amps have high voltage supplies inside. Before doing any work on the circuit board, always unplug the power and confirm HV rail voltage is at 0 (usually drops to 0 within a minute) .       First up, some mods on a SRM-Xh (to drive a pair of 303, for work use)   The Xh board looks pretty simple, a lot less components comparing to the later models such...
how big is the conference room?
if you bring the mpx3 to the meet maybe we can take a look under the hood. from what I have read, the safety concerns on some of the singlepower amps are: -- undersized transformers, overheats easily. probably easy to tell by feeling the transformer cover to see how hot it gets. -- power caps wired in series to get higher voltage rating, without balancing resistors. should be easy to tell once the amp is open. -- low voltage switch used in high voltage circuit, should...
Someone I know will likely bring a pair of Oppo PM3, which is closed.   you can demo Oppo PM phones at ListenUp audio in Boulder, if you don't want to wait till the meet.
I should be able to make it.   electrostatic phones: Stax sr-003 (baby stax) Stax sr-303 Koss ESP950 HeAudio Jade   electrostatic amps: Stax SRM-xh (upgraded with blackgates power caps) maybe a Stax SRM-212 as well Stax SRM-1 with teflon output caps Stax SRM-1/mK2 with power caps upgraded to paper/oil motor caps WOO audio WEE (probably will be driven by a small gainclone amp) Transformer box with Lundahl transformers (LL1627 if I remembered...
Bottlehead kits come with good step-by-step assembly instruction (usually in PDF format on a CD), suitable from someone new to building tube amps.         macm75, great idea on using cisco supplies in series, I might give it a try in my up coming "space warmer" headphone amp project.
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