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Post by videoguy on Dec 27, 2014 20:39:29 GMT
Last fall I decided to try some improvements to the SCHA I was building. My phones are highly modified AKG K340, dynamic driver paired w electrostatic element for the tweeter. These phones have a reputation of being hard to drive; hence the mods.
1. Use the LME 49860NA opamp from Texas Instruments; (This replaces the metal can version & requires no heat sinking).
2. Use a power transformer that is rated at least 20 - 20 vac @ 400ma.
3. Set the regulators for 20vdc + & -.
4. Change the 4.7 ohm 1/2 watt emitter resistors to 3.9 ohms 1/2 watts
5. Aside from the above mods, build the board using Sandy K's modifications.
P.S. For R.G. members that want to do another build or a first build of the SCHA, I can supply PCB's foe both the amplifier & the combined regulated supply/ripple eater circuits.
NOTE: I do not have a price on the boards as of this date but will post it here in the next week.
If you have any questions PM me for answers.
Bill W. (I am located in the U.S.).
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jc
Fully Modded
Posts: 5,417
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Post by jc on Dec 28, 2014 11:30:11 GMT
Hi Bill,
Could you explain/quantify what you meant by,
Being such an easy mod to do I'm interested in what you think the improvement is here.
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Post by videoguy on Dec 28, 2014 17:48:23 GMT
Hi CJ: It gives slightly more output current.
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jc
Fully Modded
Posts: 5,417
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Post by jc on Dec 28, 2014 18:32:32 GMT
Hi Bill,
Yes, I realised that to the case electronically, what I failed to ask clearly was, does it from its own merit add a discernible change to sound quality/response?
Chris
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Post by videoguy on Dec 30, 2014 5:02:28 GMT
Hi Chris: The answer is, no it does not change the sound quality.
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