Excellent build quality and form factor, linear sound, good driving power and dynamics for a micro, Case friendly with remote support
3.5mm jack is slightly finicky, Faint hiss, >1-ohm output impedance
The DD TC35B nails the fundamentals of a great source, representing an immediate step up over laptops and manufacturer included dongles with a similarly unobtrusive form factor.
DD HiFi burst onto the audiophile scene just a few months ago and have enjoyed great visibility online due to their innovative accessories that have filled an important yet previously unfilled niche. The TC35 is their first electronic development and the world’s smallest USB-C to 3.5mm adapter. This will surely be very exciting for smartphone users as most modern phones have axed the jack even including Samsung’s brand new S20 line. At $39 USD, this isn’t the most affordable option but is a far cry from the premium options out there. As such, this surely represents a high-quality one with a stunningly compact form factor. You can read more about the TC35B on DD’s product page and on HiFiGO.
I would like to thank DD very much for their quick communication and for providing me with the TC35B for the purpose of review. All words are my own and there is no monetary incentive for a positive review. Despite receiving the adapter free of cost, I will attempt to be as objective as possible in my evaluation.
Tech Specs –
USB Codec: ALC5686
THD+N: < -92dB
DNR: > 110dB
SNR: > 120dB
Output Power: 30mW@32ohms
Drive Ability: 16-200ohms
Frequency Response: 20Hz – 20 KHz
PCM Sampling Rate Support: Up to 32bit/384KHz
Dimensions: 18.8 x 11.2 x 10.2 mm (excluding Type-C plug)
“Smaller than small” is the first descriptor on DD’s website and that doesn’t truly sink in until you see the adapter in person. This is possibly the smallest an audio adapter could be made. The benefits extend beyond pocketability, longevity is also benefited by the short housing that puts less stress on the USB-C port. Meanwhile, a one-piece 316 stainless steel housing shields the circuit board from interference while providing great structural integrity. Though it’s the machining and finish isn’t on the level of say Campfire Audio’s earphones, the brushed exterior combined with bronze faceplate is a delightful combination.
The design is thoughtful too. For instance, a small step near the connector gives it clearance for phone cases. It fit perfectly into my Pixel 4 with Moment Lens case, which is definitely on the thicker side. The USB-C connector is also of the high-quality kind, extruded rather than pressed to promote continued connection stability as seen on their TC05 interconnect cable, high marks! As a final note, the 3.5mm plug is a touch tight due to having a power switch inside as well. As such, it’s a good idea to plug the earphones/headphones in before connecting to the source to avoid putting strain on the Type-C connector.
Using the TC35 is as easy as plug and play. There’s a windows driver on DD’s website, however, the adapter worked on my Windows 10 laptop including windows volume control without installing anything. It also worked perfectly on my Pixel 4. The adapter automatically powers on when headphones are plugged in and turns off when they’re removed to save power. I didn’t notice huge power drain when listening to music, it was similar to being paired to a BT receiver. The TC35B also supports CTIA-standard in-line remotes and will pass through play/pause and mic to the player which is especially handy for calls and commute.
Unfortunately, Apple headphones are not supported, however, this makes sense as no Apple phones or tablets are using Type-C at this time and the camera kit defeats the purpose of such a compact device. The little touches are also very encouraging. There’s essentially no pop when plugging in and unplugging the adapter with headphones connected and connection itself is prompt and effortless. I can imagine some users purchasing multiples to keep permanently attached to their headphones.
I think with a product of this kind, it’s most important to firstly keep our expectations in check. I’m not expecting great driving power or a huge soundstage but it’s important to nail the essentials; a linear frequency response, low-output impedance and minimal hiss. In the following sections, we’ll determine how good this adapter is as a source objectively, then compare with similar alternatives to gauge price/performance.
Frequency Response –
Testing Methodology: RMAA via Startech External Sound Card
The TC35B has an almost perfectly linear frequency response with no bass roll-off as can be observed on certain lower-cost sources. This is am excellent result. Due to the quality of my sound card, I am unable to reliably test other measures such as distortion and crosstalk so they will be used as a personal reference only. Qualities here can impact the sound in subjective listening.
Output Impedance & Hiss –
Testing Methodology: SPL volume matched comparison through an inline splitter to JDS Labs Atom + Khadas tone board to Campfire Audio Andromeda
The Andromeda is wildly sensitive to output impedance where it quickly loses bass quantity. From the TC35B, I did hear a slight roll-off in the bass and bias towards the midrange. As we can observe from the above frequency response, this is not a result of colouration from the signature of the source itself, confirmed also with flat-impedance earphones. From the level of deviation, I would estimate a lower output impedance that is above 1.5-ohms output but certainly not much higher, making the TC35B suitable for most multi-driver IEMs. That said, those with an especially low impedance that are sensitive to output impedance will sound noticeably different.
The Andromeda is also incredibly sensitive and picks up hiss on most sources. With such a sensitive IEM, I was comfortable on low volumes with the very lowest being perfectly audible to me. At such a low volume, a very faint hiss was present that didn’t scale with WiFi or Bluetooth activity of the phone. I didn’t personally find it obtrusive nor should low volume listeners as it isn’t noticeable when music is playing and it cuts off shortly after the music is paused. The hiss also doesn’t increase with volume so those that tend to listen at medium volumes or higher won’t notice it at all. I can only imagine this being irksome to those listening to classical on highly sensitive monitors where it may be apparent during quiet passages, otherwise, hiss is a non-issue here.
Testing Methodology: SPL volume matched comparison through an inline splitter to JDS Labs Atom + Khadas tone board to Custom Art Fibae 7 (flat impedance)
What I’m hearing from the TC35B is a balanced yet lightly warm and smooth sound. Sub-bass has good extension, lacking a little solidity by comparison to more powerful sources but tight, nonetheless. Meanwhile, I hear a lightly lifted mid-bass instigating a warmer tone and smoother texture through the low-end. Control is moderate, not too high, and no doubt a contributor towards these qualities. The midrange is balanced and linear with an accurate vocal reconstruction in terms of size. That said, it carries a lightly warm tone from the low-end in addition to an uptick of fullness.
As such, the TC35B doesn’t sound as separated and layered here as more reference sources, of course, one would not expect that given its size and power output. Highs possess a touch of additional crispness within the lower-treble with slightly accentuated note attack and slightly thinner instrument body. Nonetheless, this is subtle and, therefore, sibilance is no more of an issue than with other sources. Detail retrieval is good, providing an engaging listen while the background is dark and clean. There isn’t a huge amount of resolution and extension present which filters down to a rather intimate soundstage with limited separation. Imaging is retained, however, with a solid centre image and sharp directional cues crafting a keen sense of directionality.
Driving Power & Suggested Pair-ups –
The TC35B outputs 30mW into a 32ohm load which doesn’t sound like a lot on paper but is way more than most dongles and Bluetooth receivers before getting into a higher price category. As such, it reliably powers IEMs well and easier to drive portable headphones. That said, this obviously isn’t suited for full-size headphones, but there is plenty of power on tap for high listening volumes and good driver control.
Moondrop Starfield (122dB, 32 ohms): A sensitive and easily driven earphone with good driver quality, the Starfield reached comfortable listening volumes for me at around 10% volume. The TC35B drove them very well, bass was extended, controlled and defined delivering great pace and timing similar to the Atom. The overall transient response was a touch smoother on the TC35B delivering a more natural presentation where the Atom is sharper and more resolving. Highs were clean and well-detailed with ample extension. The soundstage was more intimate but well-separated with pleasing directionality. The soundstage is likely the most limiting factor with such a small form factor where isolation of each component is difficult and, as such, its presentation is a bit more muddled than larger sources. Nonetheless, a balanced performance with good control.
Final Audio E5000 (93dB, 14ohm): The E5000 requires a good amount of volume and driving power to reach ample listening volumes and tighten up its bass. I was comfortable at around 50% volume. Being a single DD, the signature was identical. As expected, my Khadas/Atom desktop combo was noticeably more controlled with a bit more sub-bass power. That said, the TC35B wasn’t too shabby, with moderate definition through the mid-bass and good pace overall. The sound was cleaner on the desktop setup with quicker transients and more separation, aided by its larger soundstage. The TC35B is more intimate with a little less bass power and resolution but is coherent, dynamic and well-detailed up-top otherwise.
Hifiman Sundara (94dB, 37 ohm): I’m a low volume listener but was pushing around 60% volume to get the Sundara to a comfortable listening volume. Compared to my desktop setup, which represents the ideal conditions for the Sundara, I was quite surprised that the TC35B did a reasonable job driving this headphone. That said, the TC35B was definitely showing signs of strain here, delivering a brighter sound with reduced bass presence throughout. Bass remained tight but there was noticeable roll-off with softer sub-bass slam and rumble and reduced body. Mids also lost body, sounding clearer but thinner and the headphones weren’t as warm or powerful sounding overall. The soundstage lost dimension and scale. Obviously, headphones such as these aren’t the prime target for such a compact DAC/AMP, but it’s encouraging to know there’s a decent amount of power here that will do in a pinch.
Google Pixel Adapter: The TC35B provides a much lower output impedance, especially noticeable with low-impedance multi-driver IEMs that are perfectly listenable on the TC35B but very wonky on the Google adapter. Both have a slight hiss, the Google adapter is slightly quieter due to its higher output impedance. Otherwise, the TC35B represents a noticeably cleaner and more linear sound. The Google adapter is slightly vivid sounding to my ears with a thinner midrange and boosted clarity, it also has a loose low-end and substantially less driving power.
Gigabyte Aero 15: I’ve never liked the audio jack on my laptop, the Aero 15 has a substantially higher output impedance and very low current output. It has high max volume but poor control and dynamics, producing a very droll sound. Otherwise, the sound itself is linear when enhancements are turned off. The Aero also has a prevalent background hiss, not unbearable but always noticeable. The TC35B is a breath of fresh air here, transforming it to a much more listenable experience with high-end IEMs with no additional USB cables required, I think this sort of application will be very popular too.
LG V30: The V30 has a slightly lower output impedance at 1.5ohms on the dot and higher driving power. The V30 is slightly more resolving to my ear with a bit more control and cleaner transients. It has a slightly larger soundstage with better separation. Both have a slight background hiss of similar degree. As such, the TC35B won’t provide a noticeable upgrade here but with smartphones axing the headphone jack, unfortunately, we not get to see such quality native implementations in future and products like these will inevitably grow in popularity.
Fiio BTR3 ($55): Slightly more expensive and substantially larger, the BTR3 has slightly less output power but a 0.3ohm output impedance and Bluetooth connectivity over which I felt most appropriate to test the Fiio device. The BTR3 is a slightly warmer source. It has similar driving power and a bit more bass heft at the cost of definition and control. The high-end has a bit more air on the BTR3 and the soundstage is slightly larger. I hear no hiss on the BTR3 and its lower output impedance makes it ideal for sensitive monitors.
I have been very impressed with the sound quality of these receivers recently, they’re clean and balanced with none of the noise and jank of past BT devices. That said, the treble extension is clearly limited to my ears and there isn’t quite the background cleanliness and resolution of non-wireless sources. Still, it is to me, the superior sounding device over the TC35B if by a smaller than expected margin. You are mostly paying for the wireless connectivity and associated circuitry here.
From the outset, I set to analyse this source in 3 key domains; linearity, hiss, output impedance. In all regards, it performs well if not quite perfectly. When taking the price and form factor into account, this is still an excellent result, representing a huge step up over smartphone dongles and the generic audio implementations in most laptops. That said, a smartphone with well-implemented audio circuitry such as the LG V30 will do just as good a job with a bit more power and separation on top. In terms of my subjective listening tests, the TC35B performs just as admirably so long as our expectations are kept reasonable; this is made by an enthusiast company with heaps of experience making sources, but it is still limited by size and the output power of the smartphone’s port. Accordingly, the soundstage is intimate, the driving power is only suitable for IEMs and, at most, portable headphones and it is slightly warm. Otherwise, this adapter provides good dynamics, great balance and ample cleanliness with a well-organised stage. Resultantly, the TC35B makes for another great buy from DD, suiting smartphone users listening to all but very low-impedance multi-driver IEMs that would benefit from a slightly lower output impedance.
The TC35B is available from on Aliexpress and HifiGo (International) for $39 USD at the time of writing. I am not affiliated with DD, Aliexpress or HiFiGO and receive no earnings from purchases through this link.