交流一个DAC-1的性能提升方法

fgpgp · 发表于 2007-2-4 15:34:49

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Posted by Ned ( A ) on July 17, 2005 at 17:51:23

There is a very significant upgrade that can be done for the Benchmark DAC1 -- and it's free! The ugrade is really an adjustment using the various switches which are part of the unit. For me, and several others, the improvement has been remarkable.
Background -- At CES in Las Vegas earlier in the year, several guys from a well-known W. Coast amp manufacturer (which shall remain nameless) were "playing" with a DAC1 and were very very impressed with its performance. However, they also tried various combinations of the switches and controls and discovered one which seemed to make a substantial improvement. I later found out about the improvement. The guys were planning to market a special cable connection (interconnect) for the upgrade but later found that the improvement didn't seem to work in all systems because, they surmised, it was impedance-related. It worked in some but not in others and their cable connection would therefore not be commercially viable. So, I'm describing the upgrade here. Some of you may remember that this was briefly discussed, but only partially, on Audiogon earlier in the year, in Digital discussion.

The upgrade-- OK, so here it is:

1. Use the HEADPHONE JACK on the front instead of the RCA or XLR outs on the back, to connect to the preamp or direct to the amp, using a cable connection described below.

2. IMPORTANT: Place the three position toggle switch (Ouput Level Switch) on the back of the unit to the MIDDLE position.

3. Cable connection from the headphone jack -- There are several possibilities:
a. Use Radio Shack Y-adapter cable #42-2546 ($3.99), which is a 1/4" headphone jack splitting to 2 RCA's. This cable really sucks and is only 6 inches long or so but the improvement is still very noticeable and substantial. You may have to extend the Rat Shack cable by attaching to your regular RCA-terminated interconnects with other adapters.
b. Use an Ipod Y-adaptor made by Monster, Signal Cable and some others, which has a mini headphone jack splitting to 2 RCA's. Connect the mini jack to the Benchmark headphone jack using a mini to 1/4" headphone jack adapter
c. Use a custom y-adapter like the Radio Shack but better quality longer cable. Possibly one can be made up by some cable companies which already make the IPod cable. I found a custom solid silver teflon-coated cable already made up and it blows away the Rat Shack cable.

Why does this work? The "upgrade" uses the built-in headphone amp instead of the RCA or XLR outs, which are muted by having the toggle switch in the middle position. Unlike the RCA or XLR outs, the Benchmark headphone amp has an amazing ZERO ouput impedance (as per the manual) and is a fine high current buffered amp delivering the full rated performance of the DAC1 (and perhaps more?) Perhaps the improvement is impedance related and will be apparent in some systems and not others. Benchmark itself says this method should not make a difference. I don't know why there should be an impedance issue with my system but, for me, and others who have tried it, the improvement was profound.

My system --FWIW, I am using the Benchmark DAC1 directly into a Hafler Pro 9505 Transnova amp, which has a standard 47,000 ohm input impedance, via the custom silver cable described above. The improvement also worked when going to a Reference Line Preeminence One passive preamp and then to the amp using Nordost Red Dawn. After the amp: Nordost Blue Heaven speaker cables to Magnepan 3.6's.

I hope some of you may try this and post your results. Regardless, the improvement has been amazing for me and I will certainly continue to use it in this manner.

Good luck.
Ned