Stax SRM-727 Voltage Input
May 13, 2017 at 11:19 PM Thread Starter Post #1 of 3

Peter_S

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I am aware that there are two current versions of the 727, the 727ii (USA verson) and the 727a (Japanese version). I just purchased a 727a that was modified for 115v by Justin at Headamp (when the unit also received the feedback mod). My understanding is that the unit should now be suitable for US voltages. However, I am told that the Stax equipment is very sensitive to excess voltage. My wall outlet is currently reading 122v, and I've seen it slightly higher than 123v. While this is reportedly within the NEC specifications for residential voltage, I am concerned that it might be too much for the amplifier. I'm hoping that Stax aficionados can weigh in here to answer the following questions:

1) Is a power modified 727a the SAME as a 727ii (the modification based solely on switching wiring on the power transformer)?

2) Assuming yes, should both units be able to work within the standard range of US residential voltage (e.g. 123.6V to 116.4v)?

3) If the answer is no, what range should a power modified 727a work in? The seller told me it was modified for 115v, though I suppose it was modified for whatever the transformer would allow.

Thanks in advance Stax aficionados!

Peter S.

PS - I prefer not to use a stepdown transformer, as my experience with them is that they are noisy (hum)
 
Dec 11, 2017 at 9:37 AM Post #2 of 3

DJ The Rocket

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Sorry I can't address your main question, but I'm using this cheap stepdown transformer with a 727A as I type this, and I can't detect any noise whatsoever (either in the signal coming from my amp, or physically putting my ear on the box) :)

I don't understand all the negativity around this amp. Or maybe I do, considering it's a power amp, not an integrated amp, and I have the impression that most users aren't using preamps. I didn't realize I needed one at first either, until I hooked up a Magni 3 and immediately noticed it sounding better than ever before! Your results may depend on what source you're using, though. Using an ODAC, the Magni took the 727 from "pretty good, but with some obvious problems" to simply "transcendently good." Using a Modi Multibit (or the line out jack on an HM601), it sounds identical to me whether I go through the Magni preamp outs or plug directly into the 727. Note that this is impossible if you set the internal switch to "Direct."

Even though I love the sound, I'm still planning on trying the Spritzer feedback mod to see if I like that way better or not. The ODAC -> Magni 3 -> 727A -> Lambda Pro is already the best sounding headphone system I've ever heard. Granted, that does mean that I don't know what I might be missing with something "better," but again, it is the best sounding system I've ever heard :)
 
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