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Old 11th September 2009, 04:51 PM   #11
jcx is offline jcx  United States
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if these are the 600 Ohm monitors with 90 dB/V sensitivity then I certainly wouldn't settle for +/-15 drive - bridging gets closer but a discrete output with +/-45 Vsupply would be needed to drive them to 120 dB SPL without clipping

of course the transistor choice is still an order of magnitude too big with only 70mA required by the headphones


AKG K240 55 Ohm "Studio" version would seem to be quite simply served by something like the TPA6120
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Old 11th September 2009, 08:20 PM   #12
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K240 produces 104 dB at 1 V =>10 V rms = 124 dB, QUITE LOUD
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Old 11th September 2009, 10:38 PM   #13
tomchr is offline tomchr  United States
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I have gotten really good results with the LME49600 and a LME49710 used as a DC servo. The circuit is outlined in the applications section of the LME49600 data sheet.

Eventually I'll get around to actually measuring the darn thing and post schematics and such.

~Tom
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Old 14th September 2009, 12:18 AM   #14
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Quote:
Originally Posted by peranders View Post
An idea would be to design a really small amp.
Do you mean a headamp or 498xx power amp? I am planning to do the later: a low power (<50W) 498xx + ThermalTrak amp on compact single board.
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Old 14th September 2009, 04:37 AM   #15
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I meant a physically small amp.
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Old 14th July 2010, 10:27 PM   #16
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Quote:
Originally Posted by peranders View Post
I meant a physically small amp.
HERE is one example, but what takes up room is really the power supply itself, specially if you got a few high capacitance caps in there and a half decent toroid adds to the weight too
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Old 15th July 2010, 01:14 PM   #17
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Default LME vs. LM 6245

Quote:
Originally Posted by ttan98 View Post
Why not try using LM4562 and output buffer like BUF634 or better HA-5002?
AFAIK is LME the high voltage version of LM (+-24V vs. +- 15V).
You could couple the LMEs parallel ( 22 Ohms in each output to compensate the differences in gain - I did this in a preamp to drive a 600 Ohms output transformer (Jensen)).

G
Peter
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Old 16th July 2010, 02:50 AM   #18
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Quote:
Originally Posted by ttan98 View Post
Why not try using LM4562 and output buffer like BUF634 or better HA-5002?
BUF634 in 5 pin configuration is $12 on digikey where as MJE15030/31 $1.72
Imax is 250mA VS 4A for the MJE's

ANd whats makes it even better is i have 4 pairs on hand along with 3 LME49810's :P
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Old 5th April 2013, 08:57 PM   #19
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Nice idea and good results. I was googling for this kind of headamp after some reading on the lme drivers IC.
Panson, Could you post the complete schematic with values? About 4x gain and 100mA+ for each output transistor is very close to my needs.
I'm trying many different headphone amps this year
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Old 5th April 2013, 09:38 PM   #20
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Wow, old thread. You can find the schematic in the LME49600 datasheet. Just change the feedback resistors to get the desired gain. I'd be surprised if 12dB is actually needed, though, and probably neither is a high current buffer like the LME49600 (my earbuds run plenty loud on MAX4477s).

Quote:
Originally Posted by Adrculda View Post
BUF634 in 5 pin configuration is $12 on digikey where as MJE15030/31 $1.72
LME49600's a bit cheaper. LMH6321 is almost identical to the 49600 and half the price. And somehow I'm not sure having headphone amplifier with a 4A output current is a feature.

Quote:
Originally Posted by tomchr View Post
I have gotten really good results with the LME49600 and a LME49710 used as a DC servo. The circuit is outlined in the applications section of the LME49600 data sheet.
What tomchr doesn't mention is his DC servo, as I recall, uses a JFET op amp instead of the LME49720 shown. I've commented on this in other threads but the LME49720's input bias and offset make it, like most any other BJT op amp, a horrid choice for a DC servo, especially on with a 1M tank impedance. I have no idea what National's apps engineers were thinking. The TL032 and TL072 are good defaults for servos and the LME49880's worth a look if one wants BOM bragging rights.

Last edited by twest820; 5th April 2013 at 09:42 PM.
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