Music in the Round #47 Page 3
Parasound Halo JC 2 BP preamplifier with home-theater bypass
This is not a multichannel product per se. I want to tell you about it because it helps bridge the gap between the mostly digital world of multichannel listeners and the mostly analog world of two-channel listeners. Many of the latter reject the former because they believe that multichannel digital pre-pros and AVRs will compromise the purity of their beloved analog systems, and their budgets and/or living arrangements can't accommodate two entirely independent systems.
Such is the justification for what has become known as the home-theater bypass, which permits the hybridization of a traditional analog two-channel system with a modern digital multichannel system. It is predicated on the assumption that feeding the front L/R channels of your multichannel signal through the fixed-gain input/output of a stereo preamp and power amp is entirely, or at least subjectively, transparent. It demands a very high quality of preamplifier, but really, unless this were the case, you could simply let a decent pre-pro handle the stereo and multichannel duties.
Parasound's Halo JC 2 should be familiar to Stereophile readers. It was reviewed by John Atkinson in March 2008, when he reported that its performance with music and on the test bench were beyond reproach. It remains listed in Class A of "Recommended Components" to this day.
The Halo JC 2 BP ($4500) looks almost identical to the Halo JC 2, with only the Bypass LED on the front panel and the letters "BP" added to the labeling front and rear. In fact, the greatest visible change is the new remote control, on which the trigger and polarity buttons are moved to the bottom to replace the now-missing tuner controls, the channel-selection buttons are elevated to their proper place near the top, and two new buttons are added for the BP function. (Since JA's only cavil with the Halo JC 2 was with its remote, perhaps he should see about a swap.)
You might think that such a bypass requires only that you tap off a signal before it reaches the volume control and connect it to a rear-panel jack, much like a tape monitor output. But as Parasound's founder and CEO, Richard Schram, explained to me, it was necessary to do a fair bit of engineering to ensure that the bypass was indeed sonically transparent and glitchless in operation, and that the excellent performance of the original Halo JC 2 was preserved intact. So when I saw the photos of the JC 2 BP's insides on Parasound's website, I was surprised to find that they looked identical to the JC 2'sand that the images, in fact, had the same file names.
There are, of course, differences. Schram explained: "The visible change is the separate circuit board on which the volume-control pot and the L and R trim pots reside. The board was modified with four double-pole relays that short out the controls (which equals full gain), followed by resistors that pad the full output back to exactly unity gain. There are also B+ and control-circuit connections on this board that didn't exist before. The changes in the front-panel control board are many because there are more control lines and there is now a bypass LED. Since the bypass function is active, the JC 2 BP must be powered up for the bypass to work."
Any one of the Halo JC 2 BP's inputs can be assigned as a bypass, which means that the source connected is passed to the main output with unity gain. Appropriately, Parasound warns the user about the dangers of connecting a source that lacks its own volume control to such an input. Since the JC 2 BP offers both balanced RCA and unbalanced XLR inputs (along with both types of outputs), I chose XLR input 2 as the bypass, and inserted the JC 2 BP between the L/R outputs of the Classé CT-SSP pre-pro and the McIntosh MC-303 amplifier. When the JC 2 BP is set to Bypass, the volume control on the remote is inoperative, nor can you change the volume with the knob on the front panel. However, if you do turn that front-panel knob, while you'll hear no change in volume, you will indeed have changed the volume setting, and will definitely hear the new setting (and possibly damage your speakers) if you then switch to another source. Despite this useful caution, there is little chance of this happening: When the Halo JC 2 BP is set to bypass mode, the user should manipulate the system via the pre-pro.
After telling you all about how the Halo JC 2 BP does this, I have little to report about the results. I could hear no difference at all between a direct connection from pre-pro to power amp and a connection via the JC 2 BP's bypass function. Zilch. Nada. If you have a Halo JC 2, Parasound will upgrade it to BP status for $500. But don't take only my word for itif you're not sufficiently convinced to buy a Halo JC 2 BP from this writeup, read JA's review and measurements of the Halo JC 2.