ComradeTexan

Glad to hear your thoughts! My 727 also runs notably warmer after the feedback mod, but it's constant whether its idling or driving two pairs of Lambdas. It worried me at first, and I've thought about adding a cooling fan, but mine's run continuously for six months and the only problem is keeping my cat from discovering this new warm thing she could sleep on and get her fur shoved down into. Agreed about the value of the pot bypass, I don't use mechanical pots at all in the signal path if I have any choice. The 727 uses a version of the Alps RK27 that was never sold to consumers AFAIK (the key feature is the dual knobs, one per channel). The RK27 has a beautifully smooth feel, but even the cheap 21-way DACT switch I made into a preamp provides superior sound quality. I'm about done building an LDR-based preamp volume attenuation device that I expect to sound even better. @padam what does NFB mean, and what mods are done on your Lambda Signature?

You've got a normal bias jack on your 727? If so, that's awesome! I'd love to do that to mine so I can get in on this NB Lambda Signature action too. Where do you see a 4 V rms limit on the XLR input? The owner's manual just says 30 V and doesn't specify a particular input, which seems to imply it refers to both. Anyway, I once had that notion that higher input might change the sound characteristics in some way, but the more I learn, the more I fail to imagine how that could be. That in itself doesn't mean much, but then with the fact that nobody with a better understanding than me has explained this phenomenon either… Until someone can explain otherwise I don't think it makes a difference. I chalk it up - like so many other ideas I'm unlearning - to some combination of tribalism and wishful thinking meeting in an echo chamber. I call this monster Trifucking!

I'm pretty sure it's the 404 itself that rolls off the lowest of the low end. I always thought of "synergy" as a purely subjective thing, I don't think you can attribute an objective effect to it. I assume you're using an 404 and a Lambda *PRO* Signature? If so, cool! That's my setup exactly! I think the two sets of headphones compliment each other quite well, any time I get tired of the sound of one, the other is always exactly what I want to change to! I was under the impression that the 727 gain mod made the amp unstable and it wasn't recommended, but don't put a ton of stock in that until someone else can confirm. If you're using an active preamp, the stock 727 can handle enormous amounts of power, so if you really need more gain, you can put it upstream easily enough. I'm using an ODAC -> passive attenuator -> 727, and I haven't once needed or wanted more gain than I have; I suspect that might become a concern when I upgrade to an SR-007 in ten years after I've saved up enough! I do think you will like the results of the feedback mod based on your description, since your negative impressions are exactly what the mod fixes, subjectively to me at least. It's a really easy job, assuming you have soldering/de-soldering experience. I did it in a half hour, after getting over my nervousness about working on something so expensive and so critical to my day-to-day life.

My 727A mod is successful I dealt with the glued pieces by digging underneath them with an xacto blade, then broke them off a half at a time. Just getting the first one took longer than the other three combined. It was probably about 90 mins of actual work. I'm trying not to worry too much about the differences and trying to just listen and enjoy it for now. It takes me anywhere from two weeks to to two months to truly evaluate gear, and rushing usually does the opposite of help xD

Thank you Arthrimus for posting all of this about your bias mods! I haven't learned enough to even think about trying it myself (I can follow most of it, but I wouldn't have thought about grounding the cases together, for example). It's great being able to see what's possible if I put in the work to get better. A year ago you'd have lost me at "bias voltage"

Wait of course they're just in series. I can see that on the other side! I'm going to go do something else for awhile If anyone has any ideas to deal with the glue, I'm all ears still. It would be a lot easier to just cut the resistors in half and worry about making it look nice later

Long time lurker, first post here Did I mess up my Stax 727A feedback mod? I think I'm okay, R21 and R22 are in series, correct? As long as I didn't tear off an essential trace where the top of R22 was I know where to go next. I have the old boards with the resistors glued on I figured I might destroy that resistor during the removal, and I have a replacement already on the way. Any tips on dealing with the glue on the other three I still have to pull?