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# The Opamp thread - Page 273

All components that is added will affect SQ in my experience.  I would be providing documented compensation as this is a start.

FWIW with capacitor bypassing and compensation, latest findings in a Silicon Chip article of there latest M3 100W power amp with On-semi output devices have "discovered" that removing all ceramic capacitors that where used for compensation and stability, reduces distortion in the audio frequency path.  This is contarary to there statement made on the use of MKPs and in this article they have opted to use MKPs throughout the design.  Very differernt direction compared to there previous offerings and discussions.

In the NAD M51, they are using polystyrene capacitors throughout for compensation on there LME 49990 balance output stage.

Hi FritzS!

Quote:
Originally Posted by FritzS

Are using JLH ripple eaters between lithium-ion battery pack and amp are a way for you to solve this problem?

Or a lowpass filter with choke coils and caps?

The AD797 oscillation problem (in the buffer stage of my PB2) was solved when I unplugged the XP8000 battery pack from its charger, so I don't really need a solution, now, but I do appreciate the links.

Thank you!

Mike

Well, got my HD800s and Matrix M-Stage and they sound fantastic! I also got my LME49990s through the post and tried them out... they're definitely better in the Auzentech sound card, the sound became clearer and more detailed, but I found when I put the second pair in the M-Stage, it was clearer still but I was getting quite a lot of background noise. I wasn't a fan of that so I've put the stock opamp back in and I'm happy. I was surprised at the background static though, has anyone else experienced this?

Perhaps you did not insert it correctly.

I got no additional noise with LME49990 and my M-Stage.

Edited by electronicmaji - 7/10/12 at 4:39pm
Quote:

Perhaps you did not insert it correctly.

I got no additional noise with LME49990 and my M-Stage.

I just tried re-inserting them and I get the exact same sound and background hiss as before. It's not crazy-loud but it's quite noticeable. Could a faulty chip do this?

There's actually a little bit of hiss with the LM45625na, just not as much. This is present even when I have nothing plugged into the amp's inputs. Is that normal?

Edited by Jimlad - 7/10/12 at 3:54pm

I found a decent current-out / passive IV NOS DAC to experiment with, any thoughts on anything special to look out for when rolling op-amps in an amp connected to a NOS DAC?

Quote:
Originally Posted by zilch0md

Given that both you and qusp like the 49990, I'm sure I'll be happy with it. I can't afford to do any wild experiments. I'm content to follow in the footsteps of your experience. :-) Mike

The 4x LME49990s arrived today.

I popped them into my PB2 and I've been listening for about an hour. I'm using them with the HA5002 buffers and my first thoughts were that they sound brighter than even the OPA1612s but they're smoother in the highs, and not at the expense of detail. The OPA1612s can be just a tiny bit edgy or harsh with my Sony PCM-M12 line out as source - which is known for being bright.

So I like these LME49990s more than the OPA1612s because the smoothness comes without throwing a veil over everything.  Tons of detail without an edge.  Beautiful!

Surely, I'm imagining all of this.

Mike

Ah, so the OPA1612 has more detail / edge than the LME49990?

Quote:

I just tried re-inserting them and I get the exact same sound and background hiss as before. It's not crazy-loud but it's quite noticeable. Could a faulty chip do this?

There's actually a little bit of hiss with the LM45625na, just not as much. This is present even when I have nothing plugged into the amp's inputs. Is that normal?

Perhaps the issue is something else.  Have you tried going through the M-Stage thread?  A number of issues have been covered there.

Alternatively, you can try using google, just make sure to add "site:head-fi.org" (without quotations) at the end.

Quote:
Originally Posted by kiteki

Ah, so the OPA1612 has more detail / edge than the LME49990?

It depends.

Edited by Mad Max - 7/11/12 at 12:29am
Quote:

Well, got my HD800s and Matrix M-Stage and they sound fantastic! I also got my LME49990s through the post and tried them out... they're definitely better in the Auzentech sound card, the sound became clearer and more detailed, but I found when I put the second pair in the M-Stage, it was clearer still but I was getting quite a lot of background noise. I wasn't a fan of that so I've put the stock opamp back in and I'm happy. I was surprised at the background static though, has anyone else experienced this?

I have this on a couple of my amps. Fortunately the amp best suited is my Fi-Quest which has bandwidth limiting switches. Not sure if that helps but at least you know it's not just you.

I'm happy people actually talk about real differences in sound in this thread unlike most others on h-f.  I just started an anticipation / review thread for a Vsonic IEM and then people start spamming the Fiio E6 is the only amplifier ever necessary and it's better than a lot of sound-cards due to low $\scriptstyle Z$... =/

Those tiny Fiios are jokes.

Quote:
Originally Posted by kiteki

Ah, so the OPA1612 has more detail / edge than the LME49990?

I'm pretty sure I didn't say that.  I think they're neck-and-neck for detail - it's hard to say, from my perspective - but the LME499990 is smoother - not quite as edgy with my already bright source, the Sony PCM-M10.

In my limited experience, "smoothness" comes at the expense of detail, but that's not the case with the LME499990. I'm thinking the OPA1612 has the same detail, but they're just not as smooth in the highs.

The bass seems to be tighter, too, with the LME49990, but it's not dark, warm, or colored in any way - the LME49990 is neutral - very neutral - it's doing what an audio amp is supposed to do - increasing the gain without adding or subtracting to the traits already in the signal.  It's extremely transparent.

These LME49990s are going to spend a lot of time in my PB2!

Mike

Edited by zilch0md - 7/11/12 at 11:58am
Quote:
Originally Posted by zilch0md

I'm pretty sure I didn't say that.  I think they're neck-and-neck for detail - it's hard to say, from my perspective - but the LME499990 is smoother - not quite as edgy with my already bright source, the Sony PCM-M10.

In my limited experience, "smoothness" comes at the expense of detail, but that's not the case with the LME499990. I'm thinking the OPA1612 has the same detail, but they're just not as smooth in the highs.

The bass seems to be tighter, too, with the LME49990, but it's not dark, warm, or colored in any way - the LME49990 is neutral - very neutral - it's doing what an audio amp is supposed to do - increasing the gain without adding or subtracting to the traits already in the signal.  It's extremely transparent.

These LME49990s are going to spend a lot of time in my PB2!

Mike

Sounds the same as my experience. I likened the 49990 to a high end tube amp because of the great resolution and detail. Anyone that has experienced a decent tube amp will understand that there is a fullness to the sound, micro details without glare, just magical....

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