Exogal Comet DAC Review

A standard headphone jack is located on the right side of the unit. The Comet has a 5-Watt, respectable sounding internal headphone amp. I did a comparison between my Kingsound King M-20 Headphone Amplifier and KS-H3 electrostatic headphones to the Comet driving a set of Sennheiser HD-800 ESL cans. While the Kingsound was meatier and had a touch richer presentation, the Comet and Sennheiser setup was tighter, more technically thrifty and warmer.

It is difficult to draw a sweeping conclusion regarding the performance of the Comet’s headphone output, except to say that with excellent headphones it should suffice for anyone who does not wish to delve into the world of headphone separates. But, there is exciting news on the horizon! Exogal will be introducing a dedicated headphone amp called the Meteor, which will be able to drive high impedance headphones, and will be compatible with the “Exonet,” the proprietary connection used by Exogal between components! According to Jeff, the design of the Meteor will allow for system expansion by adding an Ion amp, discussed below, and thus play music through external speakers. Exogal has not set time of availability of the Meteor.

The Ion amp (estimated $3,250 with standard power supply, and $4,500 with optional upgraded power supply), is a digital amp along the same architecture as the Comet. Exogal is wrangling with the Android app due to a variation in Bluetooth 4.0, but this beauty of similar appearance to the Comet will bear 125wpc into 8 Ohms and 250wpc into 4 Ohms. I will be assessing it in conjunction with the Comet. It is connected to the Comet by the aforementioned Exonet connection, so it will be entirely proprietary. This Exonet connection uses an HDMI type wire, but is not an HDMI connection. Refrain from experimentation with such devices, as that is not its purpose. According to Jeff, the Comet will not be hurt by accidental attachment of an HDMI cable to a device, but the Comet will simply not function.

Finishing the physical description of the Comet, the backside from right to left has 12V power supply plug, Exonet Input and Output sockets, USB, SPDIF on 75Ohm BNC connector, Toslink, and AES/EBU on XLR inputs. Both single ended and balanced outputs are supplied and have identical gain.

I had the opportunity to try both the RCA and XLR outputs of the Comet, and both performed admirably, though to my ear the XLR offered the best results for system building. Occasionally, my lighting system produces a ground hum, which usually can be ignored. When using lower-powered amps or less efficient speakers, the hum is negligible. However, when a Kilowatt amp is introduced, or even more difficult, when one is used with a more efficient speaker, the hum reaches an annoying level. How delightful it is to banish it completely with the XLR outputs! Features like these are worth their weight in gold for a person who is building his best rig. As my Legacy Audio XTREME HD Subwoofers also have both RCA/XLR low-level inputs (as well as speaker level inputs), I can swap outputs around to suit any amp while using the subwoofers, if I wish.

Enter the Red Dragon

When I first received the Red Dragon S500 stereo amps, I hooked them up to run them in mono mode via the XLR connections to the Exogal Comet. I took great care setting up the rig, as I always do, knowing that one false connection can spell trouble. There was no signal passing from the Comet to the amps. I checked and re-checked the connections; everything was correct, or so I thought! I called Jeff at Exogal and discussed the situation, wondering if they had seen any bad units with faulty XLR output. Jeff seemed surprised but immediately offered to replace the unit. The complete lack of hesitancy to offer a full solution in customer service was exemplary and should hold Exogal in good stead with customers.

I decided to go over the connections one more time, whereupon I saw it. The unusually angled lines on the busy backside of the Red Dragon amps indicating the inputs for the Mono configuration led to the other input jack. In order to see where the line terminated, I had to lie on the floor and use a flashlight. It was a simple “missed connection” which was rectified in seconds. The Exogal Comet had been passing the signal, and now the system sprang to life.

It seemed more like a lift off, as the synergy between the Exogal and Red Dragon amps set a new record for dynamic power and presence. With a super-clean volume control, a super-refined signal from the DAC and 1,000 Watts of crystalline clean power, I had discovered a new reference sound! I will share more about this in a moment.

Worthwhile upgrade power supply

There is an upgraded power supply for the Exogal Comet, costing $500. This regulated supply is well worth its cost. To explain how important this power supply is to the fullest performance of the Comet, early on Brian Walsh of Essential Audio in Chicago visited and brought the Comet for a listen. While clean and tidy as heard with the stock, wall wart power supply, it was just good enough to think it interesting for a review. Later, when the review unit came along with the upgrade power supply, I revisited the stock unit’s performance and again was not overwhelmed.

Putting the better PSU in place made “all the difference,” elevating the performance to a far superior level. Only in cases of fiscal hardship should the upgraded PSU be neglected. If so, buy it for yourself as a birthday or Christmas present and you will be well rewarded. A final footnote to the power supply, the umbilical is upgradeable! Wywire and Clarity Cable both offer an upgrade to the umbilical, which according to Jeff can be replaced in the field. Speak with these companies regarding pricing, and to Exogal if you have questions about the umbilical change out.

As a dedicated DAC

The Exogal Comet can be used in a more simplistic fashion as merely a DAC, but this does not take advantage of its full design capabilities. One might be tempted to think that a fine, external preamp would lift the overall sound quality of a digital front end with the Comet, rather than using the Comet’s internal preamp function. I put this idea to the test using the analogue outputs of the Comet and the TEO Audio Liquid Pre, an exceptionally resolving passive preamp. For comparison, I alternated DACs by switching out the Comet with the much-discussed Eastern Electric Minimax DAC Supreme with discrete opamps rolled in for extra effect.

The results were surprising in that the Exogal Comet did not show as well as when it stood alone. The Owner’s Manual warns of this, or rather encourages the use of the Comet’s own volume control for best sound quality. Indeed, with the TEO Liquid Pre, the Minimax DAC Supreme came fairly close to the performance of the Liquid Pre and the Comet.

However, there are two caveats: 1. The Liquid Pre and the Comet together presented a duplication of attenuation circuitry, a redundancy that occluded some of the performance of the Comet. 2. The outcome with the Minimax DAC Supreme was maxed out, as in terms of system configuration no further improvements could be elicited. The Comet showed itself clearly superior in all respects when returned to use of its own internal preamp function. It’s digital volume control is exquisitely fine and seems perfectly lossless in terms of information conveyance; there seems to be no easy and economical way to best this combination of ultra-smooth DAC and digital preamp in one package.