Sidebar 3: Measurements
The output impedance of the Woodside SC26 at its line output measured a high 2.1k ohms at the maximum setting of the level control, decreasing a bit to 1.7k ohms at unity gain, then returning to 2k ohms at the 9 o'clock setting. The SC26 will therefore be quite sensitive to the loading effects of cables and the input impedance of the power amplifier used; both of the latter should be chosen with care—preferably low-capacitance cables and amplifier input impedances of a minimum of 20k ohms, but the higher the better.
The SC26's line-input impedance measured…
My "Musical Cultural Literacy for Americans" write-in competition seems to have been a smashing success. I received 65 entries, and only a very few missed the mark. A few more were obvious, so-so, or lacking in passion. Many were good. But a score or more were of enviably high quality. Choosing the top 12 was tough. At the end, who won a prize and who did not was entirely my own subjective decision. The winning entries are posted in full on Stereophile's website as an appendix to my April column. Here are the points I made online in announcing the results:
"Here's an idea:…
A letter in response was published in October 2007 (Vol.30 No.10):
Don't lose that number
Editor: Regarding John Marks' call for the "extra-credit essay question" about Steely Dan's "Rikki Don't Lose That Number": No essay required, as your editor, John Atkinson (a fine bass player himself), already knows. The bass line for the tune has no relation to Coltrane's piece but is, in fact, a quote of the bass intro to Horace Silver's "Song for My Father," the Blue Note sessions for which occurred just a month and a half prior to Coltrane's Impulse! recordings.
Sorry, just couldn'…
The most important change made to the system was one that held up the writing of my review of the Mark Levinson No.23.5 power amplifier for several months, such was its anticipated impact. Though my listening room is well-equipped with wall sockets, there are actually only two 15A circuits serving these outlets. Ever since I had converted what had hitherto been our house's master bedroom into my listening room, I had intended to run new circuits to it.
Somehow, there always seemed to be more urgent jobs that needed to be done around the house—new roof, new main drainage, new bathroom, new…
I still have fond memories of my first Krell amplifier, a KSA-50. Back in those days (date purposely omitted), my principal source of audio equipment reviews, aside from Stereophile and The Absolute Sound, was Hi-Fi News & Record Review, which I read voraciously from cover to cover every month. One fateful day while sitting by our community swimming pool, I happened upon an enlightening review of the KSA-50 written by none other than our own John Atkinson, editor of HFN/RR at the time. His words describing "the steamroller-like inevitability of the bass with this amplifier" haunted me…
During one particularly heated listening session, we had a vividly divided camp as to which amplifier best represented the musical performance. Bob Kraft, bass trombonist, and Ken Harbison, percussionist, both felt that while the KSA-250 was more "dynamically impressive," it didn't have enough "meat on the bone," and lacked the immediacy and warmth of the ML No.23. Their priorities, and desired perspective, leaned more to "I want to hear it from the stage." They both felt that while the Krell had more impact, along with broader, higher, and deeper soundstaging, its leaner harmonic character…
Sidebar 1: Lewis Lipnick's Setup
In order to control the listening experiment as tightly as possible, only one component in my reference system was changed at a time. Initially it was the amplifier. The KSA-250 was substituted for the Mark Levinson No.23, with the rest of my reference system intact: a Theta Pro (balanced) Generation Two digital processor and Mark Levinson No.26 line-stage preamplifier, all operating in balanced mode, using Madrigal HPC interconnect. My B&W 801 Matrix Monitors were bi-wired with the same AudioQuest Clear speaker cable I've had for about a year (not…
Robert Harley also wrote about the KSA-250 in January 1991 (Vol.14 No.1):
It's somewhat unusual for two reviews of a product, by different reviewers, to appear in the same issue. However, JA asked me to relate my impressions of the Krell KSA-250 for several reasons: I'd been listening to the KSA-250 as a basis for comparison with the comparably priced Threshold S/550e amplifier (see review this issue), and I'd spent some time with the KSA-250's predecessor, the KSA-200, in the same system and room. The KSA-250's performance could thus be put in perspective with the older unit, as well…
Sidebar 1: Measurements
There is some diversity of opinion over whether an amplifier under bench testing should be supplied with whatever AC power comes from the wall (as it would see during normal use), or if the voltage drop should be compensated for by a Variac. The former argument asserts that the amplifier's measured performance with raw AC power is more indicative of its behavior under the conditions in which it will be used: the customer's home. The latter position holds that since AC power quality varies from location to location, one should measure the amplifier's intrinsic…
Sidebar 3: When is Class-A Class-A?
A contentious subject is exactly how much of the KSA-250's power delivery is in pure class-A, which is when both "upper" and "lower" sets of output transistors are turned on all the time. By contrast, class-B is when the upper transistors are turned on only during the time the output waveform lies on the positive side of ground potential and the lower transistors only during the time it lies on the negative side of ground. Class-A/B, which applies to the vast majority of solid-state amplifier designs, involves a small standing bias current to ensure…
