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New Member
Jan 30, 2024
By doing it this way, you're most likely boosting the Zero's bass response a lot.

Nothing wrong with that if it suits your preference, but something to be aware of nonetheless.

The SU-1 is designed exclusively for plugging into external Amps.

If you're looking for a compact DAC that's actually built to drive IEMs directly, then take a look at the Topping DX1.

That one will reproduce the Zero's tuning as intended by the designer.

Edit: Sorry, my mind jumped to the Truthear Zero. It's the Truthear Zero whose bass will be boosted when used directly from Line out.
The 7Hz Zero OTOH should stay pretty stable WRT frequency response.

Whether the SU-1 can cope with the increased current draw due to a load which it wasn't designed for, is another question.
Thanks. I also have a smsl m300se, which has an actual headphones amplifier. My daughter took over the m300se because it takes bluetooth as an input.

The Zero:2 are very sensitive. The SU-1 drives them more than adequately, at least from a volume standpoint. I'm listening to this setup right now and any volume above 40/100 in the PC is too loud for my taste. Anything above 50% is probably not safe for my ears. The bass sounds excellent, not overly boosted. Sound is extremely transparent. I will report if I blow up the SU-1, but I doubt it at this point since I've using the setup for hours a day for a few weeks.


Feb 3, 2020
DX1 should be perfect for use with IEMs as per measurements by L7audiolab
Especially the 50mv dnr is fantastic, so no noise at all with sensitive iems, unless some leakage in usb like @solderdude said, that can happen with any device.
I don't own the DX1 but i see it as a great all-in-one solution for IEM having the great convenience of a volume pot. Alternative is a good dongle (moondrop dawn pro, tanchjim space or space lite, truthear shio or even a 20€ jcally jm20) possibly with a usb volume control if you value it.
I would already have bought a DX1 if I wouldn't already have an old external sound blaster that i adapted as a usb volume control for my good dongles.

Completely agree.
I've read good reviews of SMSL SU-1, but cannot compare it to DX1 as i don't own SU-1.
I own Topping DX1: DAC with Headphone Amp - highly recommend if you can live without SPDIF inputs (especially if it's on sale).
Versatile, compact, inexpensive quality solution for any IEM or standard size headphones (if not power hangry).
Works great with my laptop, PC via USB output or mobile device (i replaced USB stock cable) - excellent no distortion sound
output to my amps, vintage gear, etc.
No noise at all as no external power supply and my laptop USB output is very clean too with better cables.
Optimal ChiFi solution for me for minimum investment from well-known brand i can trust.
(of cause Topping makes much more sophisticated devices if willing to invest).


Jan 8, 2024
I am using SMSL SU-1 with Crinacle Zero:2 IEM, both highly thought of here. The SU-1 is connected to the PC via USB. I'm using one of these (https://www.amazon.com/Connector-Female-Amplifier-Speakers-Theater/dp/B07DNXZBW4) to connect the RCA output of the SU-1 to the IEM. Sounds fantastic. Volume control using the PC.
You can use adapter RCA to female 3.5mm to get sound from RCA port. But it is not the best way to use a DAC like this.
In my opinion, you should pair SMSL SU-1 with a Headphone amplifier. Because SMSL SU1 has only RCA output, there is no 3.5mm in this device.
As you know, RCA has high output impendance. Meanwhile, Headphone (or IEMs) requires very low output impendance.


Addicted to Fun and Learning
Nov 28, 2020
Essex, UK.
Hi everyone,

I have been looking for my first DAC (or combo DAC/Pre-Amp) recently and found that SMSL SU-1 is highly recommended by some members.
Because I am a newbie so I don't have much experience in this area. My purpose is quite simple, I want to listen to music by IEM headphone.
And I would like to ask members in here several questions. I hope you can help me to make a final decision.

Q1. Which solution produces the best sound quality?
- Option 1: DAC + Heaphone Amp. Example: SMSL SU-1 + Douk Audio U3 or Topping D10s + Douk Audio U3.
- Option 2: Combo DAC/Pre-Amp. Example: Topping DX1

. Which entry-level DAC have the same price and sound quality compare to SMSL SU-1?
- I found in the internet that Topping D10s or Topping E30 II lite have the same price and sound quality, but I do not know other brands.

Q3. Which reasonable Headphone Amp have the same price and sound quality compare to Douk Audio U3?
- Someone suggest that Douk Audio U3 is a good Headphone Amp. But I still need your advice.

Thank you in advance.
Got the Douk U3 for a bargain price from Temu. As soon as it arrived I rigged it up and plugged in my Sennhieser 560s. For anyone buying this little budget amp don't let the initial sound quality put you off it. While it is decent out of the box it still can be better with changing the op amp. Initially with the NE5532D op amp the cymbols were very splashy which is what people mean when they say it has 'glare'. I rolled a couple of op amps which completely killed that 'glare'. The Muses 8920d, 8820, Oracle 11, opa1622 and the BB2604. My personal favourite is the BB2604 (CERAMIC VERSION) it has a deep wide soundstage with a very full and well controlled sound signature with clear vocals, nice tight high end and full bass, the BB2604 always packs a punch in everything i put it into. Next was the opa1622 (the most technical and flat sounding) which has a very balanced sound with tight drums, and a very clean overall sound and dark background. The Muses 8920 was a little mashed in regards to over instrument separation and not as clean as the others including the 8820 which is far cleaner and with a good soundstage. So, the U3 is a very decent small headphone amp. There is a tiny bit of background noise when idle but not enough to complain about and for the price the U3 is a bargain! It is a big step up from my Creative Audigy FX2 soundcard and puts some real power into my 560s and with the BB2604 op amp, the U3 is definitely staying put for a while.

UPDATE: This morning I put the BB opa2134 in the Douk U3 and used a QED performance audio 3.5mm jack to RCA from the Audioquest Dragonfly Red/Jitterbug FMJ that is plugged into my PC (HP Prodesk 400 G6, Intel i7 9th gen, 16gb ram, Windows 11) running Spotify. In my opinion the BB opa2134 superseded the BB opa2604 by a marginal but notable difference. I have used the 2134 in other amps but never found it particularly appealing possibly due to the rest of the chain but in this set up with the Sennhiesser 560s, it's actually very impressive! It really goes well with the rest of the components. The sound quality is more detailed than the BB2604 and a fair bit more engaging. I left the desk but couldn't wait to get back to it! A very, very nice sound and a highly recommended system match from me!
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