Just about to pull the trigger on Pontus 15th ...

@lanx0003 I wasn't aware of the Denafrips output Z but that is indeed pretty high for a dac, source, of even most modern tube preamps. 

I only received the unit a couple days ago on Monday..which was quick considering I received an email it was being shipped from China at midnight on Thursday. But since I've been concentrating on "breaking in" the Pontus I haven't given it the rounds on multiple preamps I own. I initially plugged the Pontus into this old Assemblage L1 one tube preamp that's been upgraded to the gills with high end parts & bypass caps thru in thru. I just had to mention this unknown preamp because I find it stupid good & it makes me question some more expensive pre's I have. But anyway, I haven't a clue of any of its specs. I only used it for maybe an hour & didn't notice any frequency, noise, or other issues I've encountered with impedance mismatches in the past. 

I've been running the Pontus with an Icon Audio LA4 MKiii Sig tube pre ever since; as I was thinking this is the preamp I'll be trying to pair long term. The LA4's input Z is spec'ed at "Greater than 50k ohms".  I've been inside this preamp but didn't take notice to what's going on after the input jacks or volume pot reading. I haven't detected any issues of mismatch but I've been focusing on other things when listening to the 15th. I also have only used the single ended outputs on the Pontus. 

I honestly don't think I've ever experienced a mismatch between a source or dac & preamp before. I've definitely encountered it between preamps & amps in the past. I've actually seen a YouTube reviewer & a commentor somewhere else complain that the Pontus was kinda bright...lacking some bass. Makes me wonder if they were maybe having mismatch issues? 

I do have some other issues with this dac I can complain about & share. First off the unit has 3 feet..which are kinda rough & definitely able to scratch things due to this Dac's hefty weight. She is solid. The dac comes with these little rubber pads to push into the bottom of the feet. My pads don't stay in..2 of them fall out whenever I lift the dac to move it. Not an issue when it gets to its final resting place. But I guarantee they will fall off & get lost at some point..pretty crappy for a $2k device. 

This next issue is a little bigger & one I haven't gone to the next step to fix. The RCA outputs on the rear. None of my regular sized RCA cables will push all the way in for a proper fit. It just won't push in all the way like something is blocking it..the grounding clasps of the connectors is only getting maybe a quarter way on. I found some Blue Jeans connects I had from back in the day. Ones I never really liked as the have the long connectors/longer cinch with a shorter pin. So the rca connectors on their Pontus are not going to work for me. I'm going to have to address this with Frips people. Another pain in the ass & unacceptable for a $2k device. I've only experienced this RCA jack issue once before..with a Chinese manufactured brand. I had to replace the jacks..the plastic inside the jacks weren't evenly bored out. Lame. 

My 3rd issue is a sound quality one..though this is with the rca coaxial input. Now I use a Neotech NEVD-2001 cable. Not overly expensive but I'll just say that after experimenting with digital cables cheaper & more expensive I highly recommend this Neotech model. It's proper good. You can buy the cable itself from a couple different sellers but the Neotech manufactured cable comes with some impressive connectors. I wish I could find them for DIY cables. 

Also I've only used the Pontus with a streamer & it's coaxial input. I've tried probably 12 different streamers over the last couple years under the $1600 mark..looking for a budget standout. The Zen Stream & Primare Prisma NP5 are the 2 I've held onto. I've only used the Zen Stream with the Pontus. I have 3 12v power supplies..an Sbooster, IFI Elite, Super Farad 3. Farad sounds the best with the Zen but I use it elsewhere now so I've settled with the IFI PS with the ZEN. 

Granted this dac hasn't broken in. But with coaxial input I'm not impressed. Veiled & dark. Some decent depth & stage but overall sound is meh. I chalked it up to break in period. But this morning I figured I would tried a USB cable. Completely different dac. The blanket was lifted. Everything from top to bottom, inside & out is better. Clarity & high frequencies. Dac at least is showing some good promise. Now I've never had issues using the coaxial on the Zen Stream in the past & honestly it's my output of choice on it. But I will try the Prisma later. I think it sounds better anyway but I also know that the coaxial output on the Prisma is a little hotter. I've had to dial back the input on it with my pro audio dac. So maybe the Denafrips just needs more juice going into it's coaxial. But so far the coaxial & USB input seems like 2 different dacs. 

The USB allows the dac to use its superior clocks if I understand things correctly. But I don't recall the Zen ever sounding that bad with other dacs & coaxial connection. It could be this "break in" that I've been warned of..& that I shouldn't even critically comment on this dac til at least a couple weeks of heavy usage. USB sounds good. But I'll comment more in a couple weeks if interested. I need to see about these RCA jacks. I'll take a closer look at it when I get a chance..pop the top on this joker & see what's doin'. If I keep this thing long term I'll probably invest in a streamer with i2S output instead of a DDC. I'll have to see how this plays out. 

@mattw73 Thank you for sharing. If your preamp has an output impedance of 50k ohms, it should not have any matching issues with the Denafrips DAC, whether using RCA (625 ohms) or XLR (1250 ohms). I was referring to my own preamp, which has only a 10k ohm output impedance and might have some issues since the ratio is less than 10. I was surprised to hear that the RCA input of the Pontus does not perform well.

@lanx0003 yeah I understood your question & concerns but I ended up babbling on about my situation. My experience with impedance matching has only been with preamps & amps as far as close calls & definite issues from mismatches. I have a 10k input & a 12k input amps. I've been as close as an 8x's difference between the 2 & didn't notice any meaningful issues. I've had preamps in that 5k range & probably higher depending on frequency where noise & brightness occurs. Stuff like my old PAS preamps caused issues with all my modern day solid state amp. 

I've run my MTK kit preamp which can be as High as 1800ohms sound quite nice with my 10k amp. Not exactly the same situation between dac & preamp though. Maybe someone else will chime in with something similar to your exact question. 

Wow, no apparent issue from 10k to 12k! Maybe I, along with many others, have been overly concerned. But here’s my experience: I used a preamp with a 5k output impedance into an amp with a 20k input impedance, and the sound felt restrained. However, this particular preamp was well received by some, if not the majority. I tend to attribute this to a matching issue.

I had been eyeing Denafrips for a long time, but its high output impedance was always a hurdle that kept me from pulling the trigger. Then the Harmony DAC had the same design—until this micro DAC came along, seemingly designed to address matching concerns. I don’t know. I guess I’ll never know until I try, right?

Yeah my 2 lowest impedance amps are an Arcam PA240 at 10k & a Rotel RB-1582mkii at 12k..this is their single ended inputs. Not an issue with solid state but I favor tube preamps. When I bought the Arcam I was unaware of its input. I had a Arcam SA30 & liked the amplification of it so much when I saw a deal on the PA240 I grabbed it. At the time it was an issue for my favorite preamps & I regretted buying it. It was very disheartening. 

With preamps you can compensate a little by upping the value on the output caps which most tube preamps have. But when the match is really bad it's like you said..less drive/gain. I'd have rolled off bass & hot treble. If the match was really bad it will add noise into the system. Also a lot of times what the manufacturer specs isn't always legit. It could be a 1k output at 1khz with the volume full blast..with the impedance actually being much higher at other frequency's & volume levels. 

My kit amp that is 1600ohms at its highest & that I said paired well with the 10k Arcam was actually rated at 800ohms by the designer..which he measured at 1 frequency. 

In your situation without knowing for sure how the Pontus would match I would probably try something like the micro first. Then if maybe you don't care for the micro you could go for the 15th. Personally I'd like to hear your thoughts & opinions on the Harmony model. I'm going to give the Pontus a lot more time but I'm not really impressed with it thus far. I've been strictly using my Icon preamp & Fritz REV7 SE speakers but switching amps every couple days. I work from home & listen to music 6 or 7 hours a day..with at least an hour of it sitting between the speakers. I listen to a lot of music. When I'm not playing music I have the TV going thru the dac. It still hasn't even been a week though so I'll pump the breaks on criticizing it more than I already have. 

I think that Harmony uDac looks pretty cool. I like that one has the choice to use their own power supply. The guys at Vinshine think it's a great value piece..which is usually the stuff I'm always interested in. It's getting good reviews but then all these R2R's seem to get that..but this unit is under $1k before tax. No impedance issues either.