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Rockhopper M³ Background Noise. Please help troubleshoot.

post #1 of 4
Thread Starter 

Greetings Head-Fi folks,

 

I bought a Rockhopper build M³ from a member here years ago. Recently I have been switching up my equipment and have run into some noise issue with the amp.

 

Details on the amp here:

http://www.speed-freak.ro/?page_id=161

 

Old DAC was a MisterX built Gamma2.

 

Using a Massdrop ODAC:

https://www.massdrop.com/buy/massdrop-odac

 

Also using a Schiit Modi 2 Uber:

http://schiit.com/products/modi-2

 

Also have a Schiit Magni 2 Uber:

http://schiit.com/products/magni-2

 

When using the Schiit DAC and amp I can turn the volume all the way up on the amp and not hear any background noise. When using my M³ I can hear hissing or background noise when I turn the volume up past about 1/4. I never noticed this with the old Gamma2 DAC because I did not need to turn the volume on the amp up much. With both the ODAC and Modi I get background noise when i turn the amp up to listening levels.

 

I am not an electrical engineer. I can not solder worth a damn. I have and can use a volt meter and swap equipment around. I can swap surface components like socketed OPAMPS. I assemble computers so stuff that just assembles I am good with.

 

What troubleshooting steps can I take to try and diagnose the issue?

post #2 of 4

The M3 looks good.

 

Do you know the gain on it? R3 and R4 values. Noise is often a result of of a high gain.

The wiring looks good and doesn't seem to be an issue.

 

Can you describe the noise? Is it a hiss or hum? Is it fluctuating in a regular pattern? Does it change in proportion to the volume?

post #3 of 4

I agree that hiss is a gain-related issue and FA's response is a good one.

 

I'm just still curious about why it worked before, but not now.  I don't think the output level from the Gamma 2 should be that different from an ODAC or Modi.

 

Likewise for me, can you describe the noise?  Could it really be a high-level hum, perhaps, and maybe there's ground loop issue going on?

post #4 of 4
Thread Starter 

Thanks for the insight guys. I got a chance to play with the amp. Have it plugged in to the same UPS as the Magni. No input plugged in. Cans plugged directly in to the amp (was using a extension before). No noise at 1/4 or 1/2 volume. At about 3/4 you begin to hear a faint hiss. As you get to full volume you can hear a distinct background hiss. The noise is not fluctuating, as in changing frequency or intensity. High frequency no real bass to it like a hum. Your insights sound probable where a gain is set to high because this is the same hiss you get with mobile audio when amp gains are up too high.

 

Now how do I check the gain?

*runs off to the AMB website*

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