TL;DR Summary: If all you need is a pure analog headphone amp, get the Corda Jazz. It has all the clean neutrality of the JDS Element, but richer, sweeter, more refined. If you want the flexibility of having a DAC and analog RCA inputs and outputs too (even if you won’t always use them), get the JDS Element.
Cost: Both cost the same (about $350).
Provenance: Both are built by very small independent companies. Both are designed and built with a no-bullshit engineering philosophy.
Sound Quality: Both have excellent reference-quality measurements and great subjective sound quality. Differentiating them in a properly done level matched DBT is possible, but requires careful listening.
Gain: Both have adjustable gain separate from the volume knob–a switch for high vs. low gain. This enables them to drive anything from efficient IEMs that only need millivolts and milliwatts, to big power hungry planar magnetics.
Power: Both have > 1 watt max continuous power output, enough to drive almost any headphone on the planet, except for electrostats which need a dedicated voltage step-up transformer.
Reliability: I’ve used both near daily for more than a year with no problems.
I believe any pragmatic audiophile (myself included) would be happy with either one, so long as he valued sound quality and neutrality over fancy knobs, glowing displays and the exclusivity of limited production boutique equipment. Actually, each of these does provide some of the latter exclusivity despite their low price, being less common than mass-produced gear from major manufacturers. When people see one on your desk they ask, “What the heck is that?”
DAC: Advantage: JDS Element
The Element has a DAC; the Jazz doesn’t. The Element’s DAC is clean, but USB-only and does not run in async; it relies on the source (your computer) to clock the data. JDS claims async mode doesn’t provide any audible benefit, and their measurements support that claim (though that doesn’t necessarily make it true). I do note, when using the Element’s DAC from my computer, occasional (once every few minutes) “tics” or brief drop-outs that are not in the source material and occur seemingly randomly. These don’t happen when bypassing the DAC and using the analog input. This behavior is consistent with the notion that the clocks (computer source vs. Element DAC) are slightly different and it occasionally re-syncs. This may happen less frequently or never on other computers.
Flexibility: Advantage: JDS Element
In short: in addition to being a headphone amp, the Element also has a DAC and can serve as a preamp. The Jazz is only a headphone amp; it has no DAC and cannot serve as a preamp.
If you need a DAC that can drive line-level analog output (for example to a different device), and also a headphone amp, the JDS Element does the job. You can use the Element with any computer or device having a USB connection; you don’t need a fancy sound card.
Both the Element and the Jazz have unbalanced analog RCA input jacks and can be used as a simple analog headphone amp. In the Element, this bypasses the DAC.
The Element also has analog RCA line-level output jacks, which the Jazz lacks. This makes Element quite flexible as a line-level DAC, an analog headphone amp, or a preamp. When turned off, the DAC is still on and it routes the USB input to the analog RCA outputs. So you can use the Element as a DAC with line output, and as a headphone amp, leaving both plugged in at the same time. However, it will only drive one or the other, depending on whether it’s turned on. Put differently, think of the Element as “always on” for DAC, line input and output, and its power switch controls the headphone amp.
The Jazz is nothing more than a pure analog headphone amp. It has no analog RCA outputs to drive another analog line level device. It can’t be a DAC, nor can it be a preamp. That’s because of the Jazz’s active balanced ground drive.
So what is active balanced ground drive? More on that below, but in short, it improves the S/N ratio. The drawback is that the – output carries part of the signal, so an unbalanced analog input shunt this signal to ground. This makes the Jazz attempt to drive a 0-ohm load, which can blow the fuse or damage the amp. Use the Jazz only to drive headphones — not other audio components!
Volume: Advantage: Corda Jazz
The Element has an analog potentiometer volume control. It’s a very good one: smooth, wide range, well balanced, but still a pot. The Jazz uses a stepped attenuator triggered by an analog pot; there is no pot in the signal path, only metal film resistors. It has about 30 steps, each about 1.5 dB apart. One can argue whether a stepped attenuator makes any audible improvement, but there’s no question it’s a superior design: cleaner signal with perfect channel balance at all volumes, and unheard of at this price.
Imagery: Advantage: Corda Jazz
The Jazz has a mode to artificially create a more natural stereo image from normal (non-binaural) stereo recordings. It’s a switch that blends channels with phase delay depending on the difference in L / R channels. I’ve used these before and they’re usually gimmicky. Meier’s is not a gimmick. It’s the only one I’ve heard that improves the image while getting out of the way of the music being otherwise sonically neutral or nearly transparent. I said “nearly” transparent. It does make the tone a tad less rich, a small emphasis in the upper mids to lower treble. I usually leave it off, except on recordings with extreme L-R separation, where for example a singer or instrument is entirely in one channel or the other. These are hard to listen to on headphones, and this switch fixes that.
Signal Isolation: Advantage Corda Jazz
Both amps have unbalanced analog output to the headphones. But the Jazz adds a twist: active balanced ground driving. Signal ground to the headphone is not the 0 V frame ground that it would be with standard unbalanced. Signal ground contains some of the L and R signal combined, such that the net signal at each speaker of the headphone (difference between + and -) sums to pure L or pure R. Because the ground contains some L and R signal, the net field around the cable is near zero (not exactly zero, as it is with balanced). This isolates the signal better, immunizing it to hum or other electrical interference, improving the S/N ratio. Some might say this also makes the load easier for the power supply to drive, but the power supply is already over-engineered with its 10 W toroidal transformer.
Build Quality: Advantage Corda Jazz
Both have great build quality, but the Jazz is a small step higher both inside and out: the case, switches, knob, power supply and other internal components. The Element is by no means cheaply made, it’s a pleasure to view and handle. But the Jazz is a step up.
Sound Quality – Subjective Listening
Both sound great: clean, neutral, detailed and fast without brightness, deep bass without being bass-heavy. Both are dead silent even at high gain full volume – no hum or other background noise. Both have excellent measurements comparable to professional reference gear. Not having a DAC, the quality of the Jazz depends on the source. I compared the Jazz & Element using an Asus Xonar DX sound card to drive the Jazz, and driving the Element with a USB bit stream. I used Audeze LCD-2 headphones (with the 2016 drivers) and extremely high quality recordings of a variety of music, mostly acoustic.
In this configuration, I preferred Jazz in overall sound quality, which countered my expectations since good solid state amps are so hard to differentiate in blind listening tests. The Jazz has the same level of clarity and detail as the Element, yet at the same time sounds slightly more rich in the bass and sweet in the mids and treble. Call it more musical, yet without any loss of neutrality or clarity. I emphasized the word slightly because the difference is subtle. Upon first impression they sound identical, though I feel well trained experienced listeners using excellent recordings would detect the difference consistently with careful listening in an ideal quiet environment. Indeed, the differences were big enough to overcome my expectation bias that there would be no differences!
That said, if I needed the flexibility that the Element provides–listening to music from a laptop where I must stream bits over USB because I can’t install a high quality sound card, or I needed to use it as a preamp in addition to a great headphone amp, or I was using great but less than reference quality headphones like Sennheiser HD-600 instead of the Audeze–I would grab the Element without hestitation. To put some meat to that statement, I purchased my Element and it’s not for sale.
By comparison, the Oppo HA-1 is the best of both worlds and more. Its analog amp equals or exceeds the Jazz, which is a high bar. Its Sabre ES9018 DAC is fantastic and has coax, toslink and USB inputs. It is fully balanced with both line level and headphone outputs, yet also has a single-ended outputs. It also has great flexibility with numerous inputs and outputs. The only feature it lacks is the Meier’s headphone image circuit, but I only miss it on those rare recordings with artificially extreme L-R separation. But the HA-1 is big and bulky, weighs about 15 lbs, costs 3x the price of the Jazz or Element and is no longer made.