I don't understand Apheared's 47 output resistors

[amb]

Quote:

Originally Posted by doctorkelsey I think (correct me if I am wrong) the TLEs are actually rated at 30mA maybe even 20mA.

They are rated to source or sink 20mA.

Quote:

my A47 with two opa2134s gain 2 at full volume into my grado sr-80s sucks about 45-50 mA and a no load current of 20mA. So, I think eventually if I didn't have a buffer, I would fry a TLE. Now with a cmoy, much less current is needed, so I can see maybe using a single unbuffered TLE for that- but it still isn't ideal current output.

When the amp is idling, the quiescent current goes from the positive rail to the negative rail, not through the TLE2426. So it' not going to fry. On the other hand, when you have a low-Z can connected and have the volume turned up, then the ground return current will go through the TLE2426 if it isn't buffered externally. Fortunately, what we're talking about here is music (bursts of current rather than a steady state current), so it would be much easier on the TLE. No question, though, that letting the TLE2426 bear the full return current is not the best thing to do, and this is the primary reason why the cmoy is basically a toy, and is what differentiates between, say, the MINT and the Pimeta.

 

[doctorkelsey]

thanks for the good info amb!!

 

[moeburn]

Quote:

Originally Posted by doctorkelsey moeburn, I think (correct me if I am wrong) the TLEs are actually rated at 30mA maybe even 20mA. My A47 with two opa2134s gain 2 at full volume into my grado sr-80s sucks about 45-50 mA and a no load current of 20mA. So, I think eventually if I didn't have a buffer, I would fry a TLE. Now with a cmoy, much less current is needed, so I can see maybe using a single unbuffered TLE for that- but it still isn't ideal current output.

I... disagree!



My A47, unbuffered 3-pin TLE splitter, i've ran it for hours with no problem. Now I'm not using high impedance headphones, 32ohms, so they don't suck alot of current, but I'm pretty sure grados don't either.

 

[doctorkelsey]

hmm,

well as amb has pointed out, my current readings on my A47 measured some current which was not going through the TLE, therefore, when at full volume I measured 45 mA, only 25 mA was going through the TLE. Also, this is not a continuous 25 mA (it varies with the music playing). This makes a much better case for the TLE being capable of supplying the A47 without a buffer (as you have said you're doing). My understanding is that generally speaking, headphones with low impedence require more current, or atleast at a given output voltage, will have a higher current than higher impedence headphones.

With all the new information, especially knowing that the quiescent current does not go through the ground, I feel comfortable using a TLE to power a cmoy.