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What Happened in the Last 30 Years?

Way back in November of 1989 (nearly 30 years ago) Stereophile heavily
panned the Waveform Acoustics loudspeaker designed by Paul S. Barton
(PSB Speakers) and built by cabinet maker John Otvos. Reviewer Larry
Archibald said:

> the Waveforms "disappear" the ambience. I suspect it has to do with crossover design...
> That's the not-so-bad part. The really bad sounds came from any records
> that were less than superbly recorded... Yet, for me, hi-fi is about
> enjoying the music you like to listen to, not grimacing at it.

Pretty bad review, eh?

In the "Measurements" section John Atkinson decided the most likely
culprit for the bad sound was the electronic crossover which used
Signetics op-amps:

> Finally, I looked at the Waveform's electronic crossover
> characteristics. The crossover circuitry and all the in/out sockets are
> carried on one large printed-circuit board, with a small transformer
> supplying AC power to a pair of solid-state voltage regulators. All the
> filter circuits are based on Signetic NE5532 dual-op-amp ICs, and the
> response-shaping networks are carried on plug-in DIP headers to allow
> for easy modifications. Good-quality components are used throughout,
> including Bourns pots for the two controls, but the unit as a whole
> would seem a little outclassed by the amplification the Waveform
> speakers are likely to be used with, in my opinion.

> Yes, the sound of a circuit using op-amps will be dependent to a large
> extent on the way in which the designer has implemented the power
> supplies and other ancillary matters, as well as by the characteristics
> of the particular IC used. However, it is fair to point out that the
> 5532 is some 10 years old and there are a number of op-amp ICs now
> available that offer significant improvements in both subjective and
> objective performance. That LA felt the Waveforms to have overall
> rather non-involving nature could well be due to the crossover
> circuitry, I feel.

www.stereophile.com/content/waveform-loudspeaker-measurements

Now, almost 30 years later, JA apologizes for all of the (British! - except for HRT)
companies that still use Signetics op-amps in their design:

In Reply to: RE: There is this: posted by Charles Hansen on October 16, 2017 at 06:49:03:

> Just look at the analog circuitry in any piece of Meridian kit. They still
> use the 30 year old Signetics 5534 op-amp they've been using since they
> were founded.

At the risk of trying to teach my grandmother to suck eggs, Meridian aren't
alone in still using this chip. It can be found in products from LFD, Musical
Fidelity, Cyrus, and HRT, as well as Meridian. I was told that this is because,
when properly used, this op-amp can drive low-impedance loads with very
low static distortion. Of course, this begs the question of whether an
integrated circuit op-amp, which relies on a high amount of negative
feedback to work, is a justifiable choice to use in a high-end audio circuit.
~~~~~~~~~~

NB: The keen-eyed will note that the first article referenced the Signetics 5532, while the forum posting referenced the Signetics 5534.
What's the difference? Both are in 8-pin packages. The '34 allows the user to trim the DC offset manually, while the '32 omits that feature to allow
two op-amps in one package. The datasheets for both are at www.ti.com and have simplified internal schematics that are virtually identical.

In 2007 a poster on DIY Audio asked if there were any differences. One replied:

"The dual version's paralleled input transistors are both used
by the single version - hence the lower input noise of the single.

"At line level differences are not much, but at lower levels and more
gain, e.g. a MM phono amplifier the single's advantages can be used.

"For active filters, buffers, low gain line stages etc, not much in it.

For audio performance / price nothing gets near them."

(NB: Paralleling identical input transistors will yield an extra 3dB of S/N ratio. Maybe that's why these guys post on DIY forums - they don't really
understand that a phono stage needs a bit more than 3dB less noise than a line stage that typically operates with a 50dB larger signal...)

There you have it - you can get the best performance in the world for only around $0.35 - your choice of single or dual!
Ya gotta love those thrifty Brits! No need to actuallly design any of those pesky circuits - just buy some chips
and stick 'em in a fancy box!


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Topic - What Happened in the Last 30 Years? - Charles Hansen 00:18:33 11/2/17 (167)
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