Encontre una pagina donde un tio dice que solamente Strobo stomp de Peterson es true bypass y hace un review de algunos.
Non-pedal tuners: Here we have all those that you can plug your guitar into, but don't have a switch and/or come in pedal form. These tuners ofthen has an output jack, for sending the signal on to the amp/pedals. Even though they don't have any bypass system at all, their operation is similar to the half-assed bypass system, but with both lines open (instead of passing through a switch, the "bypass" line goes straight to the output jack, possibly through a buffer section). The Boss TU-12 is a prime example of this type of tuner.
Boss TU-2: This is more or less the industry standard pedal tuner - even though I've seen too many reports of erratic tuning behaviour from it to feel comfortable recommending it. Like any other Boss pedal, it uses FET (electronic) switching, and shouldn't affect the sound any more or less than any other Boss pedal does. It is most definitely not true bypass, in any case.
Korg DT-10: The new kid on the block - this one has the legendary Korg tuner preciseness about it, and a large mute switch. There are two output jacks - the one labeled "output" mutes when you press the switch, and the one labeled "bypass" is always active, regardless of the switch (in essence, it is bypassing the mute switch). The signal passes through a buffer amp before it splits to the "bypass" jack and tuner section/"output" jack. No true bypass here, then, but a great tuner nonetheless (if possibly a bit big). Also, it is possible to modify it for true bypass, if you should want to.
Sabine NEX-5000: Advertised as "true hardwire bypass", which has led many to believe that it is true bypass. This is not the case, sadly. The tuner is constantly active (tuning at all times), and the switch only mutes or un-mutes the sound. That in itself is enough evidence - as we just concluded above. Again, the half-assed bypass system makes an appearance, this time in mute only form.
AKAI DT-1: Originally advertised as a true bypass tuner, AKAI has now pulled all ads using that terminology and rewritten the manual. Like the Sabine, the tuner is constantly active, regardless of the mute switch, and therefore it has the same system as the Sabine. No true bypass there either...
Guyatone MT-3: Easily the smallest of the pedalboard tuners out there. It has a buffered system with electronic muting, and the tuner is constantly active. No true bypass, but a neat little tuner that can be modified for true bypass. Because of that, it is currently my personal favourite among the pedal tuners, although I prefer the Boss TU-12 overall - I love real needles!
Fender PT-10: Like the Korg, this one also has two output jacks. One is affected by the mute switch, while the other isn't. But I don't know if the mute switch does anything else - if it switches the tuner in or out as well, or if the tuner is constantly active. So this is in fact the one tuner I'm not 100% sure isn't true bypass - I'd have to check the manual, or try it out in person, to know for sure. But I'd hedge a bet that it isn't - if it was, they would definitely advertise it...
Peterson StroboStomp: The first true bypass pedal tuner available! For those who don't know what "strobe" means in the world of tuners, let me just briefly say that it is a completely different method of measuring pitch, compared to "regular" tuners, and that it is a lot more accurate. This particular specimen is of the "virtual" strobe variety, which means that it doesn't use the actual moving parts a real strobe tuner has, but the readout (which is what we're tuning to) works the same way. As if that weren't enough, this puppy has true bypass switching too (allegedly - I haven't opened one up yet, but I'm inclined to believe them).
Planet Waves just introduced a new pedal tuner which has the words "true hard bypass" attached to it. In my experience, every time a manufacturer has stuck something in between the words "true" and "bypass", the pedal has turned out not to be TB... It's to early to tell on this one, but I remain sceptical... more on this one here (scroll to the bottom).
