Be warned.. This Meridian USB DAC has an output impedance of around 47 ohms!!!
This is generally not a good thing for earphones as it means that the amp essentially applies a headphone-dependent tone control (equalization curve) to the sound you hear. It will 'wooly' the bass and roll off the highs far more than an amp that is accurate. The effect will be more pronounced on low/medium impedance headphones, and most pronounced on low impedance IEMs with multiple drivers and crossover networks.
Be warned.. This Meridian USB DAC has an output impedance of around 47 ohms!!!
This is generally not a good thing for earphones as it means that the amp essentially applies a headphone-dependent tone control (equalization curve) to the sound you hear. It will 'wooly' the bass and roll off the highs far more than an amp that is accurate. The effect will be more pronounced on low/medium impedance headphones, and most pronounced on low impedance IEMs with multiple drivers and crossover networks.
In early February 2013 Meridian released it's new USB powered DAC/headphone amp with much fanfare. By the end of the month, Head-Fi.org member Purrin had found its performance in listening tests underwhelming and had measured the output impedance of the Explorer at about 48 Ohms. This is not good.
Fortunately, Meridian had already received feedback from early units delivered to dealers and distributors, and had got wind of the problem when driving the low impedance headphones commonly used in portable applications. An engineering change was put into motion. Unfortunately, the wheels were already turning and the product introduction continued on schedule with the original product going into production. From what I could gather, a few thousand Explorers were shipped before the running change could be made. The first run of modified product has just finished production (about March 13th 2013), and is currently in shipment to dealers. I'm told the Explorer is selling very well, and dealers have little stock on-hand from previous production runs. I expect it would be safe to place an order now from any retailer that is currently out of stock, and am fairly certain that the unit received will include the changes.
I received the revised version a few days ago, and measured the output impedance:
With 0.1988Vrms out open circuit, I get 0.1922Vrms with a 150 Ohm Load for a calculated 4.99 Ohm Output Impedance. With 0.1988Vrms out open circuit, I get 0.1723Vrms with a 32 Ohm Load for a calculated 4.92 Ohm Output Impedance.
Bottom line: The revised Meridian Explorer now has a about a 5 Ohm output impedance.
In early February 2013 Meridian released it's new USB powered DAC/headphone amp with much fanfare. By the end of the month, Head-Fi.org member Purrin had found its performance in listening tests underwhelming and had measured the output impedance of the Explorer at about 48 Ohms. This is not good.
Fortunately, Meridian had already received feedback from early units delivered to dealers and distributors, and had got wind of the problem when driving the low impedance headphones commonly used in portable applications. An engineering change was put into motion. Unfortunately, the wheels were already turning and the product introduction continued on schedule with the original product going into production. From what I could gather, a few thousand Explorers were shipped before the running change could be made. The first run of modified product has just finished production (about March 13th 2013), and is currently in shipment to dealers. I'm told the Explorer is selling very well, and dealers have little stock on-hand from previous production runs. I expect it would be safe to place an order now from any retailer that is currently out of stock, and am fairly certain that the unit received will include the changes.
I received the revised version a few days ago, and measured the output impedance:
With 0.1988Vrms out open circuit, I get 0.1922Vrms with a 150 Ohm Load for a calculated 4.99 Ohm Output Impedance. With 0.1988Vrms out open circuit, I get 0.1723Vrms with a 32 Ohm Load for a calculated 4.92 Ohm Output Impedance.
Bottom line: The revised Meridian Explorer now has a about a 5 Ohm output impedance.