Koss Porta Pro-Unofficial Thread

Is it worth upgrading the Koss Porta Pro?
What do you get with upgrades?

Background

The Koss Porta Pro retails for $50 as of 2022, and can often be found for around $35. It has been a mobile audio standard since 1984, and remains respected by many serious enthusiasts. To my ears, its mid range sounds quite good, but it has significant flaws and limitations. First, I describe it as “thick in the middle with no highs or lows.” The Porta Pro cannot generate real bass. It has a loud lower-mid hump, but this is not true bass. Male voices tend to be too loud and husky. Overall, its timbre is warm and comforting but not accurate.

A second and more troubling issue is that the Porta Pro tends to whine and whistle at a specific high frequencies. While the Porta Pro cannot generate true highs, it sometimes puts out unpleasant noises. This seems to happen when the drivers cannot generate an intended sound – they appear to convert notes to the driver’s natural resonant frequency. Imagine a dentist’s drill playing at random parts of a song. Fingers on the chalkboard. For more information, see the frequency charts for the in-line control model at Rtings.

The $35 Porta Pro brought to mind my experience with painful high frequencies from the $300+ Sennheiser HD-600. It too has loud and scratchy treble with a bad or incompatible DAC/amp setup. I learned to greatly improve its performance by upgrading my DACs, and using tube or balanced amps. With the right setup it becomes a smooth, easygoing, all-round performer. Without getting the treble under control I’d rarely use either product.

Enter my Porta Pro upgrades

Setups Tested

  • iFi ZenDAC (V1) – Balanced versus single-ended output on the same device
  • FiiO Q5 – Balanced versus single-ended output on the same device
  • Bifrost 2 → Drop THX AAA 789 (balanced tested, but even that was bright, edgy, and awful)
  • Bifrost 2 → Rebel Audio RebelAmp (single-ended, only option)

Test Tracks: A condensed 20 song edition of my standard fatigue-evaluation playlist. I could generally tell how well a setup performed upon reaching the awful recording Californication, but not always. The whining was consistently worse with my problem tracks (see the last third of the list).

Findings

  • Yaxi pads are worth it for all songs and sources. They smooth out the high frequencies and reduce the Porta Pro’s scratchy, random hiss. They are also larger, softer, and more comfortable than the factory pads. They come in multiple colors, making it hard to confuse left versus right.

  • The amp matters and the DAC matters, but the Porta Pro doesn’t scale much. The Porta Pro has firm limitations, but a warmer amp will sound warmer while a smoother and warmer DAC will not make its inherent flaws worse. It’ll always be thick in the middle with no highs or lows. The ZenDAC is warm and doesn’t extend very far into the treble, so it was my clear favorite (balanced mode). The Q5 (AKM 4490 DAC) was good but not great in balanced mode. It was often whiny in single-ended mode. I used the Bifrost 2 to feed the THX AAA 789 and RebelAmp. I’d avoid the 789 with the Porta Pro. Not good. The RebelAmp competed with the Q5…the Porta Pro just doesn’t scale much.

  • A balanced setup matters, and was required to minimize or eliminate the Porta Pro’s treble artifacts. In comparing the ZenDAC and Q5 both in balanced versus single-ended modes, balanced was better and I was able to finish my playlist with little discomfort. The timbre remained identical, but the phantom whines were controlled by balanced.

Should I upgrade the Porta Pro or buy something better?

When I reviewed the Sennheiser HD-58X, I made a ludicrous comparison table ranging from the Porta Pro ($35) to the Focal Utopia ($4K+). My Porta Pro upgrades were an effort to see how much I could improve a $35 product. The answer is…not very much… It remains a pleasant, light weight, and affordable product with serious treble dangers. I’d happily use the Porta Pro in mobile situations, at least with a warmer balanced amp. However, if given the opportunity I’d choose the HD-58X ($125 to $190) in a heartbeat. It has better bass and treble extension and sounds more natural overall. It performs better out of the box, with the factory pads and cable, and with a single-ended amp.

The table below adapts and expands some of the information from my HD-58X comparison table. A higher price gets you “more” of something but its doesn’t scale with the dollars spent. The Porta Pro is in the lowest quality tier never rises above. It delivers just some of the facts, ma’am.

Quality Tier Rough Cost (2022) Sample Products Character Summary
C: Obvious Flaws $35 to $100 Koss Porta Pro, Beats consumer products, many bundled “free” headphones and IEMs Exaggerated frequency bands, abruptly cuts off frequencies, creates artifacts such as whining, scratching, or buzzing
B: Solid Fundamentals $125 to $200 Sennheiser HD-58X, many airplane-oriented noise canceling products Reasonably accurate in the midrange, but limited details and little or no ability to reproduce the air, room, or the recording environment
B+: Hints of Nuances (good enough for many people) $200 to $500 HD-6XX, HD-600 Subtle aspects of audio start to be heard, but not all. Generally unable to produce sound all the way from deep bass to high treble. These products can require strong amp/DAC support to perform acceptably.
A: Audiophile “Fine” $1,000 Focal Clear (Original) Reasonable dynamics, wide and accurate frequency reproduction, no glaring flaws. “Clear” ability to distinguish between primary notes and secondary sounds (e.g., room echoes, breath, etc.).
S: Superior or Specialized $1,500+ to $6,000+ HD-800S, Utopia, RAAL, ZMF, Audeze, Rosson, Abyss, etc. Either technically superior or specialized in a way that appeals to dedicated users. These are not necessarily better or always hearable versus A tier products, but they are sometimes stunning. Low production numbers with little relationship between price and value.
8 Likes