[Change is Good]

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I'm having a bit of an issue with my unit, which I have narrowed down to the OP-AMP. I've got an Audio-GD moon, and after 4-5 hours of being on, I get a low level hum that doesn't go away with a power cycle, but does go away after it cools down. Any ideas on what might be wrong?
 
Also, what's the bees knees on opamps? Is everyone going for a OPA627 with a class-A bias mod? I'm really in love with the Moon OPAMP, and I'd like to figure out what's going wrong here. It's a very full sounding opamp and really improves over stock. 

 
I've had the same low level hum with all op-amps I've tried. I think it's a issue within the M-Stage or a ground looping issue. Some input on this would be appreciated.

 

[Chris J]

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I've had the same low level hum with all op-amps I've tried. I think it's a issue within the M-Stage or a ground looping issue. Some input on this would be appreciated.

I only hear a low level hum when I use IEMs with the M Stage.
 
I don't hear a low level hum with Q701, DT880, etc.
 
The Bees Knees with Op Amps is the LM4562......'cos that's what I use!

 

[LugBug1]

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The Bees Knees with Op Amps is the LM4562......'cos that's what I use!

+1 

 

[Lohb]

Hi there !
 
I'm looking to drop a custom opamp in a Matrix DAC M-stage soon.
 
I've been told that OPA2209, OPA1642 and OPA602BP are nice upgrades from a fellow member but not specifically for synergy with the Hifiman 400's. ....some members mentioned LM4562 recently in the thread is that upgrade dual or single opamp ? I had it already in an altoid tin and it was very detailed....
Was also told that 627's and 637's not  good drop-in opamps for Matrix hardware even though a lot of ebay sellers offer them as rolling options in their listing....something to do with a mis-match in speed design I believe (?)
 
 
My aim if possible is to tame the treble a bit at the amp stage. I may also upgrade to the Hifiman 500's in future, therefore trying to find an opamp that would be good for the 400's and 500's....and I read bumping the M-stage +10 gain is OK for the 500's so I do like the flexibility of this amp.....(opamp rolling and gain control)
Though given how cheap the dual opamps are, I could buy one more suited for the 500's later if there is no bridging opamps given the different SQ's of these cans.

 

[elwappo99]

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I've had the same low level hum with all op-amps I've tried. I think it's a issue within the M-Stage or a ground looping issue. Some input on this would be appreciated.

 
Strange. Mine is definitely OPamp dependent. Trying various opamps the only one that gives off any hum is the Audio-GD one, after many hours of use. 

 

[elwappo99]

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The Bees Knees with Op Amps is the LM4562......'cos that's what I use!

 
I do like the LM4562, and I get no issues with it, but it just doesn't have the full body and warmth of the Moon OMPAMP.

 

[Lohb]

Would these chips (dual LM4562) and socket work with the M-stage .....?
They seem like a better alternative to M-stage ebay sellers' opamp rolling choices in
compatibility and price.... (627A or B/637A or B)

 
 

 

[LugBug1]

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Would these chips (dual LM4562) and socket work with the M-stage .....?
They seem like a better alternative to M-stage ebay sellers' opamp rolling choices in
compatibility and price.... (627A or B/637A or B)

 
 

You only need one LM4562NA as it is a dual opamp. You would use the adaptor for two single opamps such as the opa627. But yes both will work with the m-stage

 

[Lohb]

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You only need one LM4562NA as it is a dual opamp. You would use the adaptor for two single opamps such as the opa627. But yes both will work with the m-stage

Ha, of course.........never picked up on that DUAL info in the ebay title....well, I can just buy these 2 and drop the second LM4562 opamp in my BSG portable amp as the current opamp is a bit muddy as it is...
 
Thanks LugBug1.

 

[Chris J]

Hi there !

I'm looking to drop a custom opamp in a Matrix DAC M-stage soon.

I've been told that OPA2209, OPA1642 and OPA602BP are nice upgrades from a fellow member but not specifically for synergy with the Hifiman 400's. ....some members mentioned LM4562 recently in the thread is that upgrade dual or single opamp ? I had it already in an altoid tin and it was very detailed....
Was also told that 627's and 637's not  good drop-in opamps for Matrix hardware even though a lot of ebay sellers offer them as rolling options in their listing....something to do with a mis-match in speed design I believe (?)


My aim if possible is to tame the treble a bit at the amp stage. I may also upgrade to the Hifiman 500's in future, therefore trying to find an opamp that would be good for the 400's and 500's....and I read bumping the M-stage +10 gain is OK for the 500's so I do like the flexibility of this amp.....(opamp rolling and gain control)
Though given how cheap the dual opamps are, I could buy one more suited for the 500's later if there is no bridging opamps given the different SQ's of these cans.

I've rolled in a few different OpAmps, no matter which one you install in the M Stage, it still sounds like an M Stage.
If you really want to tame the treble you may want to try a tube amp, or, (oh no!) try different headphones...
Or use an EQ.
How nasty is the treble?

 

[Lohb]

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I've rolled in a few different OpAmps, no matter which one you install in the M Stage, it still sounds like an M Stage.
If you really want to tame the treble you may want to try a tube amp, or, (oh no!) try different headphones...

Or use an EQ.
How nasty is the treble?

You make the M-stage sound like it is so-so no matter what you do...! Is there a better one for the same price range you are using ?
Hifiman 400's are known for bright treble spikes in certain EQ regions.....so much so that there is an earpad mod (Jergpad) by one member on the thread over there for the 400's / 500's that targets that aspect among other isssues with these headphones.

 

[Chris J]

You make the M-stage sound like it is so-so no matter what you do...! Is there a better one for the same price range you are using ?
Hifiman 400's are known for bright treble spikes in certain EQ regions.....so much so that there is an earpad mod (Jergpad) by one member on the thread over there for the 400's / 500's that targets that aspect among other isssues with these headphones.

I think the M Stage is a very fine amp for the money.
A lot of Q701 owners use one, the Q701 is known for being a rather bright sounding headphone.
All I'm saying is that rolling in another Op Amp will not change the sound of the M Stage much.

 

[Lohb]

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I think the M Stage is a very fine amp for the money.
A lot of Q701 owners use one, the Q701 is known for being a rather bright sounding headphone.
All I'm saying is that rolling in another Op Amp will not change the sound of the M Stage much.

 


I see. Thanks.
 
I wonder how many watts the Hifiman 400s and 500's get from this amp...
Given that the Hifiman really shine through the Emotiva....worried the watts might be underpowered with the 500s I hope to get in future.

 

[Chris J]

I see. Thanks.

I wonder how many watts the Hifiman 400s and 500's get from this amp...
Given that the Hifiman really shine through the Emotiva....worried the watts might be underpowered with the 500s I hope to get in future.

I don't know much about the HiFiMan stuff, sorry!

 

[LugBug1]

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I see. Thanks.
 
I wonder how many watts the Hifiman 400s and 500's get from this amp...
Given that the Hifiman really shine through the Emotiva....worried the watts might be underpowered with the 500s I hope to get in future.

The 400's will work better than the 500's with the M-stage as they are more efficient. But the m-stage doesn't give a full watt into any cans, its designed more for high impedance hp's or headphones that are known to have impedance swings such as the K70X. 
 
It wasn't a great match with the HE500's or LCD2's when I tried them. They didn't sound bad, but I know they sound better with other amps that give out a lot more current such as the Audio gd line or Schitt amps. It's all about the matching in this hobby, I'm not saying the m-stage isn't good enough for those orthos as I highly recommend the m-stage as a great starter amp with the HD800's. Its purely a spec thing.