Pairing Sensitive IEMs to a Powerful DAC/Amp

[metaleggman]

Hi,

My current setup for my PC is an iFi Zen DAC (using iFi's power wart) connected via a Pentaconn to XLR cable to the Drop THX AAA 789 amp; the Zen DAC is set to fixed output. I was using the Drop XLR to 2.5mm balanced adapter at first, but I just got my Hart Audio cable set in, so I'm still using the XLR input mostly, just without as much danger to my poor 2.5mm ended cables. I use this setup for gaming, movies, etc., but in terms of music I'm either using Foobar w/ASIO or the Tidal desktop app. The cans I rotate through are the Hifiman HE4XX, Senny HD6XX, Senny HD280 Pro, and Shure SE535. For the former-most three, this setup gives ample power even on the lowest gain setting, but given the sensitivity of of the Shure IEMs, I'm at a bit of a conundrum: even using a SE interconnect and the lowest gain, the AAA amp is just too powerful. At best I have maybe 10 degrees of volume pot that's useable before it gets just far too loud.

Is there anything wrong with using the variable output of the Zen DAC, or using variable output to begin with? I believe the review/test posted on here only showed the results for the fixed output; I realize that generally the consensus is to use a fixed output when sending something to an amp (e.g. that's what I set my Bluesound Node to in my Hi-Fi setup), but I can't for the life of remember the exact reason.

If I were to use the variable output, is there a certain sweet spot that might be "best" in terms of the Zen DAC's volume knob? I'm currently testing it out with the iFi DAC pot at about 12 O'Clock, and it gives me a decent amount of range over the SE output from the THX amp.

The biggest reason I'm looking into this is because I like to juggle around cans, and it's just unsafe using the IEMs as I was (Fixed, completely balanced). One wrong move or slip up, and my ears will get blasted. So far my testing with the variable output is positive: sounds good! However, one of the things that attracted me to this forum is that people are generally attempting to discuss these audio issues in more objective ways, and not about how "danceable" the newest power cord is (though I'm sure we're welcome to dance if we want to). So if anyone can provide some concrete reasons against using the DAC with variable output, I'm all ears, as well as to any best practices when using a DAC with its variable output.

If anyone can think of other solutions I'm missing, let me know. From what I've read so far on this and other forums, some people use something like the iFi IEMatch, but I'm not sure that'll do much past what I can accomplish with the DAC's knob and is more for something like a DAP.

PS. The main reason I bought the iFi Zen DAC was mostly because it was the cheapest way to get MQA and balanced output from a DAC. It's obviously not without its faults, and I'll eventually update once more options come out to market (I look at stuff like the Mytek and while it seems impressive, I'm just not sure I'm that wedded to MQA, Tidal, or any particle DAC chip yet to spend that much lol). This is why I can't just lower the volume in Windows or the Tidal desktop app; to use MQA on Tidal, you have to use the DAC in exclusive mode and that sets it to a fixed output, in terms of what's over USB. In Foobar, I can just lower the output a few dB and it's a-ok. The Drop amp, though, is great so far; not really sure when I would need to upgrade it, unless it breaks or I want to burn a hole in my pocket.

 

[maverickronin]

Honestly it would probably be best to just use single ended RCA cables between your DAC and amp instead of using the balanced output of the headamp. You'll skip an extra layer of amplification, the amp won't get as strong a signal, and you'll get more room with the volume pot on your THX.

There's nothing inherently wrong with using a DAC as preamp in for a headamp but it's probably not the best in your situation. That's because the volume potentiometer on the ifi probably doesn't track any better than on the THX and using the balanced out from the ifi doubles the voltage right off the bat. If you had a different DAC it could work just fine though. I have a run a balanced DAC into my Massdrop THX with the THX's volume all the way up, but my DAC has built in digital volume control so the tracking is perfect at any volume level.

If you do want to keep that arrangement then something like the IEMatch would be your next best bet. It uses a small resistor network to somewhat isolate the IEM and the amp from each other and has less impact on the frequency response of the IEMs than a simple inline resistor.

If you're handy with a soldering iron @solderdude has and article about how to make one yourself on his website.

 

[metaleggman]

Honestly it would probably be best to just use single ended RCA cables between your DAC and amp instead of using the balanced output of the headamp. You'll skip an extra layer of amplification, the amp won't get as strong a signal, and you'll get more room with the volume pot on your THX.

Heh, funny enough, I forgot to even try this. Or maybe my brain skipped it out of laziness; I recently just hooked up my monitor's headphone out to the SE input on for when I watch movies on my Fire Stick. I originally had the DAC connected to the amp both balanced and single ended. I'll have to try that. I had the SE plugged in because there seemed to be, perhaps, impedance issues between the Zen and THX that went away when both were connected at the same time. Should check if that's still happening too, out of curiosity's sake (coincidentally, I planned to ask about it as my first post a while back, but the issue more or less is resolved).

There's nothing inherently wrong with using a DAC as preamp in for a headamp but it's probably not the best in your situation. That's because the volume potentiometer on the ifi probably doesn't track any better than on the THX and using the balanced out from the ifi doubles the voltage right off the bat.

I presume this is why I'd be best off finding a way to keep the DAC in fixed output? Better to lower the voltage than have the amp of the Zen muck about with the signal? This is one of the bits I'm curious about from the technical side of it, since I'm still learning about the actual, how might one describe it, electrical engineering that goes on in Hi-Fi? When you say tracking, what do you mean exactly?

If you're handy with a soldering iron @solderdude has and article about how to make one yourself on his website.

I'm not, but the last time I tried using one was as a child haha. This could be a fun project, especially to make a balanced one that's compatible with my Hart Audio cables (mini 4-pin XLR in and out).

Appreciate the help so far.

 

[maverickronin]

I missed a couple things when I was checking on the Zen's product page. I didn't notice the switch for the volume knob to control the line outs and I didn't notice it was using a pentacon as a balanced stereo line out either. I thought you were using the balanced headamp out on the front.

for myself...

I presume this is why I'd be best off finding a way to keep the DAC in fixed output?

It doesn't really matter either way. Just have one cranked and use the the other to control the volume. Having both partway up can add more overall noise to the signal. This would pretty much just be in the realm of measurements with most headphones, but with something as sensitive as the 535s you may actually hear it.

Better to lower the voltage than have the amp of the Zen muck about with the signal? This is one of the bits I'm curious about from the technical side of it, since I'm still learning about the actual, how might one describe it, electrical engineering that goes on in Hi-Fi?

Really the primary goal is just to make the output voltage lower since the 535s are so sensitive. Each device is just controlling the volume with a poteniometer. Once you turn it all the way up, it's essentially bypassed so it's that not that big of a deal to leave it in the signal path.

Assuming you use the RCA out on the ifi you have two good options.

You can set the RCA outs on the ifi to fixed and control the volume on the THX.

You can set the RCA outs on the ifi to variable, use it to control the volume, and keep the THX turned all the way up.

Either way should lower the overall gain of the whole system and give you more play on the volume knob.

When you say tracking, what do you mean exactly?

How well the two separate channels of the pot(eniometer) match up. They very rarely stay well matched near the bottom of the range and can cause the channel balance to shift back and forth until you get into hearing damage territory with an efficient IEM. I was just assuming that was also an issue for too since it's very common. It's a problem I've had with my old 530s and every amp with volume pot I've ever plugged them into.

If you're still using the 535s with the THX whenever you upgrade your DAC and important feature to look for would be digital volume control. Then you can use the DAC to control the volume and get perfect channel matching at any level.

You could also do this in software on your computer in the operating system or player software, but I wouldn't recommend it on anything but a dedicated streaming box since misbehaving or unstable software can mess with the volume or just output noise at maximum level which will not be good for your headphone or ears.

 

[metaleggman]

Awesome! That's a lot of helpful information. I just tried the SE output, and for now, it works well. I love that the amp has the option of both. Still might make the attenuation adapter just for fun though; I really need to get into soldering and it seems like a fairly simple project, and would make a fantastic addition to my cable set!