Greg Smith

December 1997

Z-Man Audio Signal Enhancer Followup

[Z-MAN] When I looked at the Z-Man ASE earlier this year, I found it to be effective at taming overly bright systems but in a manner that isn't necessarily an improvement for everyone. The stock tube in this unit is a capable but inexpensive performer, and accordingly Z-Man has looked into better sounding but more expensive New Old Stock tubes. I spent some time comparing performance with the more hefty tube they selected, an upgrade from Mullard, to the one originally provided.

This time around, I constructed a different system that I found to be a bit too bright (the ideal situation for applying the ASE to). I used my Rotel RCC-940AX, disconnected from outboard DAC for the first time in many moons, connected to an NAD 1600 preamp and NAD 2400THX power amplifier. Speakers were the (out of place in this system) NEAR 50ME, while all cables were from DH Labs. This combination could use some smoothing out, and as usual the regular Z-Man provided that when connected after the CD player via 0.5M of Kimber PBJ. In addition, the resulting sound seemed more dynamic and many string sounds were really brought out of the mix on recordings I listened to with the ASE in place. At the same time, some of the "thump" was attenuated, with really deep bass seeming less prominent.

Switching to the Mullard tube was a noticeable improvement. The sense of dynamics was considerably improved. The soundstage was bigger, and low-level details were better defined. It was a more enveloping presentation all around. The level of resolution on high-frequency material was more precise without bringing any of the brightness back.

If you've already got a Z-Man ASE, I highly recommend a NOS Tube upgrade. It's definitely worth an extra $50, and I'm told that as a bonus it's likely to last longer than most modern tubes will. The upgraded ASE really is better, but I don't think the improvement is enough that it's now appropriate for a larger audience than the stock unit was. It's not a fundamental change to how the unit sounds, it's more a case where the things the Z-Man unit had been doing right it now does even better.

.....GS (

The Mullard tube reviewed here was provided by Vintage Tube Services; call (616) 454-3467 for information about what they have for Z-Man upgrades. As with any rare item, pricing and availability are volatile. A typical cost range for one of these tubes would be $30-$70 depending on quality and grade. Z-Man also recommends the NOS Telefunken Diamond Bottom variant of the 12AX7, and says that either of these should last five to eight years in the ASE circuit. For those looking for new tubes that can make an improvement, the Yugoslavian Ei ECC83 is suggested as one upgrade that has been working successfully for many people. Note that none of these upgrade tubes are available directly from Z-Man.

Opening the ASE case to swap tubes should only be done by those familiar with the safety requirements of high-voltage circuitry. If you don't know how to make sure a capacitor is safely discharged, you should not try to swap tubes without some help.