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plaurids

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About plaurids

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  • Interests
    Trying to be an audiophile with a tight room and a tight budget...
  • Location
    São Bernardo do Campo
  • Gender
    Male

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  • Occupation
    Adjunct Professor of Mathematics at UFABC
  • Headphones
    Stax Lambda Signature SR-407, AKG K701
  • Headphone Amps
    Stax SRM-T1S
  • Sources
    Fiio X7II DAP, M-Audio ProFire 610

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  1. Another improvement I've seen people around (e.g. spritzer) suggest on the SRM-T1 is to replace the RCA input jacks and input wiring, but judging from pictures it seems that there is some improvements made by Stax on that area from the T1 to the T1S - the RCA jacks definitely look beefier and the input wiring looks nice enough (actually better than the output wiring)... but again, that's only a visual impression. I wonder whether it's sonically worth the trouble to make these upgrades... Anyhow, I'm using the XLR balanced inputs in my SRM-T1S for now, so this makes upgrading the RCA input jack
  2. I've found a potential problem concerning a possible future replacement of the bias trimpots (TVR1-2) in the SRM-T1S. I couldn't find 2kOhm trimpots with at least 0.6W power rating as recommended by JimL above with the same PCB footprint as the original trimpots (three pins forming an equilateral triangle - 3 x 60 degrees). The closest PCB footprint I could find for these is with three pins forming a right isosceles triangle (2 x 45 degrees + 1 x 90 degrees - e.g. Bourns 3345W single-turn). Ideally, were I to replace the bias trimpots, I'd use multiturn parts to make the rebiasing easier as re
  3. Now, regarding tube replacement / rolling... I am pleased with the sound of my Gold Aero / Sylvania 6CG7 tubes (they probably can use some rebiasing, though, but that will wait for after recapping), but I have nothing to compare them against, and as I said above it's good to have spare tubes when mine decide to die out, at least. JimL forwarded above advice hirsch and spritzer gave on other threads about Japanese short plate tubes sounding best with the SRM-T1(S) circuit. Digging deeper on these threads revealed that Toshiba 6CG7's seem to be preferred, and that some of these have been re
  4. Just a summary of what I have learned on planning the recap of my SRM-T1S unit - a bit on the TL;DR side and probably repeating a lot of boring stuff well known to experts in the forum (specially ones with little or no patience for capacitor esoterics - yeah, I did notice that the latter is a thing in the audiophile community 🙄 ), but it may be useful to others (or at least to me) in the future to have everything in one place. I still have a few doubts, though (those only interested in that may skip to the last paragraph below)... Thanks again to all who helped! My current (stock) configu
  5. Ok, indeed I didn't know the current through the bias trimpots either... Thanks!
  6. Hmm... Do you mean just the four big snap-in caps, or all ten of them?
  7. Thanks again JimL, I've measured the lead spacing of the big snap-in power caps (100 uF, 400V) and it seems to be 12,5mm, but I've seen people saying that in this particular case snap-in caps with 10mm lead spacing should also fit because the holes in the PCB are wide enough to allow for such lead spacing (indeed, there is a lot of solder in those holes). I don't think the other dimensions will be a problem. Do you know the remaining specs of the bias adjustment trimpots (power rating, tolerance) apart from its maximum resistance (2 kOhm)? I couldn't find that in the schematic, and I need
  8. That makes sense... I'm (clearly) not that familiar with power amplifier designs (something I'm currently trying to overcome) but I did help my father build a couple of passive loudspeaker crossovers back in the day, and electrolytic caps were a big no-no in such devices if you sought quality sound (he used big polyester / polypropylene caps). I guess this is a general principle... As far as I could understand from the SRM-T1(S)'s schematic, all of its electrolytic caps are in the power supply stage. So no such cap is used in this design for coupling, right? On the other hand, I've also s
  9. By the way, if one of the TVR pots goes bad during rebiasing and needs replacement, which are the part characteristics (power rating, tolerance, etc.), apart from having 2k Ohms (total) resistance (according to the schematic)? Thanks
  10. OK, so for example, if I replace the four big 100 uF, 400V, 85oC power caps by, say, 330uF, 400V, 105oC caps with compatible physical dimensions, the amp should be fine, yes? Does the same apply to the other electrolytic caps? Another thing: I've noticed on the Mouser website that some cap brands (e.g. Nichicon) have so-called "audio grade" capacitors: https://br.mouser.com/ProductDetail/Nichicon/LKX2G181MESA50?qs=TI%2F9gtmDCEEsSiejfUzVag%3D%3D Is there any real sonic advantage in using these, or is it just marketing? What I can tell is that the "audio grade" caps usually have s
  11. I see... If that's the case I have no problem with (de)soldering components on a PCB and I do have the necessary tools (fine soldering iron, standard multimeter). Do you have any particular brand/model recommendation for the electrolytic caps, apart from your previous voltage rating / size / lead spacing instructions? For instance, are the choices made in this particular recap example OK? (granted it's a SRM-T1, not a SRM-T1S, but it's also a B-type serial number like mine and the PCB arrangement looks similar - I'll have to check my precise cap parameters, of course) https://www.head-fi.
  12. Thanks for the reply JimL. How do I know (apart from sheer age) that the electrolytic caps are reaching the end of their lifespan, particularly in terms of sound quality? Moreover, if I replace some (or all) of the electrolytic caps, do I need to rebias the tubes, even if I manage to keep the capacitances and voltage ratings the same for the new components? As for the tubes, the manual says that the end of service life of the output vacuum tubes is signaled by a decrease in output volume at the same volume knob adjustment. In other words, you start to feel the need to turn the volume knob
  13. Thanks spritzer, I think I figured out what's beneath the 100V sticker by now even without removing it, just by looking at the manual... 😁 I wonder why Stax did that... Is it because the unit was meant for sale in Japan and therefore it was pointless to provide other voltage options, but at the same time to strip the voltage selection feature from the power supply was not worth it in terms of production cost (that is, it's cheaper to slap a tiny sticker on the back of units meant for sale in Japan than to produce units with two different power supply designs)? I understand why they k
  14. Well, what do you know? It did have a voltage selection jumper behind the bottom panel... I hadn't bothered to check the first time due to the warning in the back panel, I'd inferred it would be a fool's errand. Moreover, the manual PDF doesn't describe how to reach the voltage selection jumper. Thanks thebrunx and spritzer! In due time: is it safe to change the jumper to (say) 117v and drop the step-down transformer for use with a 127V power outlet? Is changing the jumper enough, despite the warning at the back panel (it seems to be just a sticker on the metal back plate, but even so)? T
  15. Thanks for the reply. Unfortunately, my SRM-T1S has no voltage change jumpers at all. The back panel clearly states "100V only" (50/60Hz). I wasn't expecting otherwise when I bought it (even though the manual PDF available on the internet describes a variant where voltage changes are indeed possible), so I bought the step-down transformer right after I ordered the unit. Good thing I did that...
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