Threshold FET Nine/e preamplifier System and setup
Sidebar 1: System and setup
My audio system has evolved somewhat since I described it in "A Matter of Taste" (Vol.12 No.6). The analog front end consists of a Linn LP12, now with Lingo power supply, Ittok, AudioQuest AQ 7000 replacing the Talisman S, and a Bryston TF-1 stepup. Digital source is a Philips CD650 (internally damped and otherwise messed-around-with), now feeding an Aragon D2A via MAS masTER LINK digital interconnect.
My PV5 has been re-tubed; the phono-stage tubes have AudioQuest tube dampers on them; the balance pot and mode switch have been bypassed, and the unused inputs have shorting plugs. A Dahlquist LP-1 crosses over to a Luxman MQ 68C, driving original Quad ESLs, and a Bryston 3B, driving Cizek MG-27 subs. The Luxman amp is a rather rare bird: designed by Tim de Paravicini, it uses made-only-for-Luxman 50CA10 output tubes, and has a zero and a 16dB negative feedback mode. (I prefer the sound in the zero-feedback mode.) The electronics are all plugged into a Tice Power Block.
The Quads' original connectors have been replaced with Tiffany-style binding posts, yielding a significant improvement. (Note to Quad owners: You must replace those pitiful banana jacks if you want to know what your speakers can sound like.) The Quads' front and back grilles have been removed, as has the absorptive material behind the woofer panels (but not the felt behind the tweeters), and the original flimsy AC cord has been replaced with 14-gauge wire (another inexpensive and very worthwhile improvement). The Quads are sitting on the subs in a tiered arrangement, with Sims Silencers between the Quads and the subs to reduce inter-speaker vibration transmission, and Tiptoes under the subs providing a mechanical anchor.
The Silencers (I hope all you Matt Helm fans are noting this) are also at work providing vibration control under the CD player and preamp, and the Luxman power amp is sitting on a Mission Isoplat. Speaker cable is van den Hul 352; interconnects include van den Hul D-102 III, Randall TX, and AudioQuest Lapis. I'm also the proud owner of a set of Stax Lambda Signature headphones, driven by the SRM-T1. (Yes, they're as good as Bill Sommerwerck said they were.) All equipment, including the tested preamps, had the AC plugs oriented for minimum chassis voltage (this sometimes required use of a cheater plug); contacts were cleaned with Cramolin, but, at the cost of tremendous internal struggle, I refrained from performing any additional tweaks on the tested equipment. A man's gotta do what a man's gotta do.
The preamps under consideration were subjected to listening tests over a two-month period. Some of the listening was of the informal "plug in the thing and listen to a bunch of CDs and LPs" type, but I also conducted tests where an attempt was made to control listening level and to explicitly compare the sound of specific recordings at a standardized listening level (footnote 1). To lend greater generality to the findings, some of the listening was done through a Muse 100 amplifier, the same unit reviewed by Corey Greenberg in Vol.14 No.4. (TJN also sent along a pair of the VTL Tiny Triodesagain, CG's review pair, same issuebut, unfortunately, they suffered shipping damage.)Robert Deutsch
Footnote 1: A The 1kHz warble tone on the Stereophile Test CD (track 20) and a similar tone on the ancient Stereo Review Test Record were the signal sources; listening level was measured with both a Radio Shack Sound Pressure Level meter at the listening position and a Realistic voltmeter at the speaker terminals. I was not able to match levels to an accuracy of much better than about 0.5dB (footnote 2), but, in any case, I think the importance of this sort of level-matching has been overrated. I agree that if you do comparisons involving a rapid switchover, the ear might very well be fooled into judging whichever sound is louder as better, but I can't believe that a slight level difference is a major determinant of evaluation in a prolonged listening comparison. If it were, then any component/system could be improved by just playing it 0.5dB louder!
Footnote 2: My preferred technique is to use the 1kHz sinewave on the Stereophile Test CD and equalize the measured voltage at the speaker terminals. It is possible to get repeatable matching within 0.1dB in this manner, but it has the disadvantage for some comparisons that frequency-response differences displaced from 1kHz can result in subjective loudness differences.John Atkinson