resonance at 500 Hz using headphones - maybe need a different DAC?

I'm primarily a headphone listener (Audeze LCD 2 pre-fazor) and I've been troubled by a resonance around 500 Hz that seems curiously dependent on my digital source. I'm looking to troubleshoot this resonance.

Note that all my equipment has modifications by a technician in the N.J. Audio Society. He adds bypass caps, damping, and ERS fabric.

I was using a modified iFi Nano for a while and liked it (with linear 5V power supply). Then I purchased a Gustard x20pro DAC, had the guy tweak it out. I noticed at first that the sound was much improved compared to my iFi Nano, in terms of an immediacy, transient power, dynamics (micro- and macro-), and so forth, but I was getting something undesirable, which was a resonance in my headphones on certain notes.

I have a musical keyboard and piano synthesis software on my MacBook, so I played different piano notes along with a spectrum analyzer plugin and a parametric EQ, and determined that the main resonance was happening at approx 500 Hz. (C above middle C). There was another resonance an octave above that.

This resonance is particularly noticeable on choral music.

Furthermore, I've made several improvements to my digital sound, like adding a better power cable to the Gustard, experimenting with an Aurender N100 music server, and experimenting with an iFi Zen Stream with different power supplies.

Whenever I tried something that improved the USB source (like adding a better power supply on the Zen Steam, putting a better power cord on the Aurender, etc.) the sound from the Gustard became even more immediate, involving, dynamic etc. But the more of this I was getting from the Gustard, the worse the resonance became. 

I tried two other DACs I had lying around. I went back to the iFi Nano. I also tried a Beringer 24/96 DAC from a long time ago (it's modified, runs off battery supply and is actually pretty good). Both of these DACs had much less resonance or maybe none. But they were less dynamic, transient speed, involving, etc. than the Gustard. Very dynamically tame compared to the Gustard and that's a bit disappointing were I to go with these DACs long term.

So I may want a new DAC if this is the fault of the Gustard, But that's what I'm trying to determine... could a resonance be related to some general good quality of a DAC, like transient speed? Or is a fault in the Gustard?

Before I decide that I want a new DAC, I just want to debug this resonance. If anyone has encountered something like it or has a theory where it comes from, I'd like to know.


I am quite familiar with the technician you used. Unfortunately, he is retired, otherwise, I would suggest that you have him investigate. I owned the same Beringer DAC that he modified. It was an excellent DAC, and I only replaced it because I wanted to go beyond 96/24. I don’t do much listening with cans, but I have never heard any frequency peaks from this DAC, or, for that matter, my turntable, which he also modified. Perhaps there is an impedance curve mismatch between your headphones and the DAC? Also, it could be some issue with the USB receiver. Not sure how you can address this with the fellow being retired. You could still contact him. He might find your issue puzzling enough to take a look at it. If you need contact info, private message me.

There is a resonance starting right around 500 Hz on the LCD-2's - see


Could be a bad solder joint that's causing some distortion and making the problem worse. Might be a good idea to have your modder listen to your setup and check over his work.

Have you tried this test on a real piano? Possibly you are experiencing a temporary sensitivity in that range. This happened to me and it soon went away.

A tone from an open string bass guitar, or guitar, tends to sound louder than a closed string further up the neck. Some DACs seem to give this fundamental sound more preeminence than others. But maybe not relevant for choir music ca 500 hz.