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Posts by alphaman

Migoul67 ... we've repeatedly read your comments about how much you like the TekMOD ... and your sig lists several source components that may be used in compare/contrast tests with T51. This would be useful ... even if source components are not exactly in same "category". E.g., TeKMOD vs. iBasso D7, etc. BTW: Your equipment (if sig line is correct) is hardly "poor" ... both in dollar value or audio quality.   
Without detailed schematics or better (more updated details or photos) you're all talk.  I've tried various tweaks with the T51 and CK4 on a breadboard, bench and with o'scope.My advice to those looking to bring the T51 to very high quality is simply replace the stock LPF opamp with an AD8066 or AD8397. That's mostly all one really needs to significantly improve over stock. And it's something most people with basic soldering skills can easily handle. 
As long as there is plenty of current, the TPA6120 works fine with one volt below its spec'd minimum (this is where actually testing the device -- measuring distortion, etc -- instead of just going off the datasheet pays off.) About your comment "I am not going to publish all details about the modification, it isn't necessary for me." It would be to your benefit to do so, as other DIYers from player.ru already have -- as I noted earlier, you seem to have only repeated...
The THS4222 may have "excellent data" (PUBLISHED specs) but  ...(a) those are specs done by the manuf. (or did you personally bench spec them, burnwaygta?); and (B), in any case, good specs do not always equal better sound. A good example of this is vacuum tubes vs. solid state.I have compared the THS4222 to the TPA6120 and much prefer the latter. I design by ear and  manuf. specs and my own oscilloscope measurements. The manuf. datasheets of opamps publish full and...
Not saying you will ever encounter the worst-case scenario but in the case of DC, it's not what you HEAR that will kill your IEMs ;)Is this what you're using for the TekMOD HO and/or LO opamps?Why not use purpose-built headphone amp ... also from TI? E.g., TPA6133A2. I think your customers would like this, but you'll have to solder at SOP level. Or you may also try a class-D amp for experiment.
That's a lot of effort ... and now, the TekMOD produces even greater transients?!! Well, we all NOW know what the risks are ... so those that may be affected have been properly warned ;)
F2K (v1.19) wasn't CPU overloading any more than 2-3 days max before I upgraded to v1.29. That's not that long and I trust my "audio memory" for what CPU-normal v1.19 and v.1.29 sound like/different. And as I noted ... it was quite a big improvement, so my appraisal confidence is high. I never use Foobar for any DSP -- but I still made sure none was active as I was troubleshooting. Nada.I don't know what caused my 9-year-old Win XP PC to suddenly misbehave with F2K v1.19....
Now that I think about it, most modern DAPs and smartphones and iPads, etc. do not have output protection. A few years ago, home components (CD/DVD players, etc) had output protection transistors (and a lot of DIYers removed them for improved sound). I think output protection is old-school thinking ... back when something blowing was more likely and would cause DC on the output (e.g., tube stuff) Today, QC and component reliability has gotten good enough that we can bypass...
If the output is direct coupled and the headphone or LO output on the T51 is not servo'd or carefully tweaked, you could be passing hazardous DC to your delicate IEMs!! This may damage them. IIRC, the original T51 used no output (DC blocking) caps, but was carefully tweaked so output voltage never went too high. Of course, in the event of a RARE accident, the original (non-modded) T51 could also pass DC. To get both decent sound and protection you really need to go this...
About the comment ... "Such changes should not have audible effects - let alone obvious large ones "... Yes, I thought so too, along these lines ... but that was years ago ... freshly minted from BSEE ... when I was an objectivist spear carrier ... in fact, I used to be much harder-core HA camper than even most narrow-spectrum HAphiles currently are ... but as I got older, the universe gets larger and clearcut mindsets and beliefs get swamped in complexity ;) I have an...
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