By-passed input amp. Is this OK?

nelsonvandal · 21st December 2006, 08:45 PM

I have a Xenos OHA-REP headphone amp. Originally there was an OPA2134 as input amp and two LMH6543 as output stage (now LMH6654). The sound was a bit dull and congested. I've rolled some input op-amps: LM4562 - too artificial and unfocused but sparkling and fun, AD8620 - too harsh treble and thin but great control and soundstage, AD746 - too soft and a bit boring and high noise level but very neutral balance and soundstage. Now I'm awaiting AD823 and 8058.

I got bored with AD746 and removed it. I soldered input cables directly to pins 1 and 7 (used for output from the op-amp). Still using the output stage. No more noise, no more dull sound, no DC-offset. Now it's fun again. Neutral tonal balance (maybe a bit bright), great dynamics, fun. Can you really do this? Do I need an input op-amp? What can go wrong? Is there any op-amps that doesn't colour the sound to use with 9 V battery supply?

odysseybmx414 · 4th January 2007, 10:49 PM

hey if its workin with no offset and the chips arent heating up why wouldnt you be fine? also i like the opa134 not sure about the psu voltage for this chip tho

21st December 2006, 08:45 PM	#1
nelsonvandal diyAudio Member Join Date: Nov 2006	By-passed input amp. Is this OK? I have a Xenos OHA-REP headphone amp. Originally there was an OPA2134 as input amp and two LMH6543 as output stage (now LMH6654). The sound was a bit dull and congested. I've rolled some input op-amps: LM4562 - too artificial and unfocused but sparkling and fun, AD8620 - too harsh treble and thin but great control and soundstage, AD746 - too soft and a bit boring and high noise level but very neutral balance and soundstage. Now I'm awaiting AD823 and 8058. I got bored with AD746 and removed it. I soldered input cables directly to pins 1 and 7 (used for output from the op-amp). Still using the output stage. No more noise, no more dull sound, no DC-offset. Now it's fun again. Neutral tonal balance (maybe a bit bright), great dynamics, fun. Can you really do this? Do I need an input op-amp? What can go wrong? Is there any op-amps that doesn't colour the sound to use with 9 V battery supply?

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4th January 2007, 10:49 PM	#2
odysseybmx414 diyAudio Member Join Date: Feb 2005 Location: Watertown, NY	hey if its workin with no offset and the chips arent heating up why wouldnt you be fine? also i like the opa134 not sure about the psu voltage for this chip tho

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