Why Use a DAC/Amp with IEMs? EPZ P40 + TP35 Pro Setup Guide

People often ask a simple question: “My IEM already plays from my phone/laptop—why would I add a DAC/amp?” The honest answer is: you don’t always need one. But for many setups, a small USB-C dongle DAC/amp can make your IEM easier to drive, more consistent across devices, and less dependent on the quality of a built-in headphone output.

In this guide, we’ll use the EPZ P40 paired with the EPZ TP35 Pro as a concrete example, and focus on what changes in real-world listening: output quality, control, and headroom.

1) What a DAC/amp actually does (in plain words)

A DAC (digital-to-analog converter) turns the digital audio stream from your phone/PC into an analog signal your earphones can play. That’s the “translation” step. A headphone amplifier then provides the electrical drive needed to move the drivers in your IEMs cleanly and with control.

If you want the formal definition, Wikipedia describes a DAC as a system that converts a digital signal into an analog signal. Source (Wikipedia)

2) Why IEMs can benefit from a dedicated dongle DAC/amp

A) Cleaner and more consistent output across devices

Phones, tablets, and laptops vary widely in their internal audio circuitry. Some are excellent; some are “good enough,” and some are simply noisy or weak. A dedicated dongle DAC/amp can give you a predictable baseline: one device that you plug into different sources and get similar performance.

EPZ positions the TP35 Pro as a portable USB-C DAC/amp for noticeably improving sound quality from mobile/tablet/computer sources, with dual CS43198 DAC architecture and high-res support up to 32-bit/384 kHz and DSD256.

B) More headroom (useful when your source feels “strained”)

Headroom isn’t just “louder.” It’s having enough drive so peaks don’t feel compressed and the presentation stays controlled when the music gets dense. On paper, the TP35 Pro lists up to 112 mW (3.5mm) and 262 mW (4.4mm) at 32Ω, which is typically more than many built-in outputs.

For the P40, EPZ notes it works well with phones and dongle DACs, and also explicitly says that for best detail and dynamics, a “clean dongle DAC” is recommended.

C) Output impedance matters more than most people think

Some sources have higher output impedance, which can interact with the varying impedance of earphones and (in certain cases) alter frequency response. This isn’t a “marketing myth” — it’s basic circuit behavior. Texas Instruments’ headphone amp design document notes that output impedance is important because it indicates how varying headphone impedance can affect frequency response. Source (TI PDF)

D) Better control tools (when you want to tune, not just listen)

If you ever find yourself thinking “this is slightly too bright” or “I want a touch more body,” simple EQ can go a long way. TP35 Pro is positioned with configurable sound profiles through app or PC control, which is handy if you like saving different setups for different IEMs or use cases. If you want to explore tuning tools, start from the official downloads page: WalkPlay / Web Tuning & Driver Downloads.

3) EPZ P40 + TP35 Pro: a straightforward setup

Step 1 — Decide 3.5mm vs 4.4mm

• Use 3.5mm if you want maximum compatibility (phones, laptops, most adapters).
• Try 4.4mm if your source supports it and you want extra headroom. It’s also convenient if you already use balanced outputs on other gear.

Step 2 — Connect in the “quiet” order

1. Lower your system volume first.
2. Plug the P40 into the TP35 Pro output (3.5mm or 4.4mm).
3. Connect the TP35 Pro to your phone/tablet/PC via USB-C.
4. Start playback, then raise volume slowly.

Step 3 — Keep it simple for the first hour

If you’re testing whether a DAC/amp helps, avoid changing five variables at once. For the first session: keep your music app the same, keep EQ off, and just listen. After you get a baseline, then consider small EQ or filter adjustments.

4) A/B test: how to compare phone output vs TP35 Pro (real-world method)

If you want an honest comparison (and to avoid placebo), use a simple A/B process. You’re not trying to prove one setup is “better”—you’re checking whether the differences matter to you.

What you need

• Your EPZ P40
• A phone/laptop output you normally use (or another dongle)
• TP35 Pro
• One 60–90 second music segment you know well (same track, same timestamp every time)

Step-by-step (10 minutes)

1. Turn off EQ/processing on both paths (no system EQ, no DSP, no “sound enhancer”).
2. Match volume as closely as possible. This is the #1 source of “false wins.”
   A practical trick: start with the quieter path, raise it to a comfortable level, then switch and adjust the other path until it sounds equally loud.
3. Use the same plug type for both tests when you can (e.g., compare 3.5mm to 3.5mm first). After that, you can try 4.4mm as a separate test.
4. Listen for 3 specific cues (write a quick note after each switch):
   • Dynamics/headroom: do loud hits feel more controlled or more “flattened”?
   • Background cleanliness: do you hear hiss/noise during quiet parts?
   • Separation: when the track gets busy, can you follow vocals and instruments more easily?
5. Repeat two short cycles (A → B → A). If you can’t reliably describe a difference on the second cycle, it may not be meaningful for your use.

5) Who benefits most from using a dongle DAC/amp with IEMs?

You’ll likely notice the benefit if you…

• Switch between multiple sources (phone + laptop + tablet) and want consistent sound.
• Feel like your current output is “thin,” “flat,” or runs out of control at higher volumes.
• Care about small improvements in separation, dynamics, and low-level detail.
• Like the idea of saving different sound profiles for different IEMs.

You may not need one (or may notice less) if you…

• Already use a device with a known high-quality headphone output and you’re happy with it.
• Listen quietly in simple setups and never feel limited by volume or control.
• Prefer “set and forget” and don’t want an extra device/cable in the chain.

6) Practical notes (small things that make a big difference)

• Volume headroom ≠ listen louder: use headroom to keep peaks clean, not to push unsafe SPL.
• If you hear hiss or noise: try a different USB port/cable/adapter, and reduce system volume before reconnecting.
• Tip fit matters: before judging “bass” or “treble,” make sure the seal is good. A tip change can outweigh a hardware change.

7) Quick links (so you don’t lose your place)

If you’re building the same pairing: EPZ P40 product page and EPZ TP35 Pro product page. If you want tuning/driver resources, here’s the Downloads page. And if you want a broader look at the lineup, you can browse Shop All.

Need a recommendation for your device and listening style? Send your phone/PC model and what you want to change (e.g., “less sharp,” “more sub-bass,” “clearer vocals”) here: Contact us.