[sdiy] Memorymoog opamp advice...

[harrybissell]

3080A - do not replace (its the best version)

CA1458G =  4558  (low noise version)  maybe a NJM4558

TL071 / 72 = pass

H^) harry

"James R. Coplin" wrote:

> Sorry, no c/c++/oop content... ;)
>
> I'm starting in on the voice card overhaul of my Memorymoog. I scored a
> whole ton of gold plated machined IC sockets at my local surplus yesterday
> so I'm stoked. The opamps are all socketed so replacement is trivial. What
> do people suggest for the following? I'm only interested in direct
> replacements, I don't want to have to custom wireup and adapt-a-socket kind
> of things.
>
> 3080A
> TL071CP
> TL072CP
> CA1458G
>
> Or should I even bother? Also, if anyone is interested in new sets of ribbon
> cable for their Memorymoog let me know. I'm going to have a custom cable
> supplier build me a couple sets of replacements with gold pin connectors.
> I'll have a better idea of costs once I know how many sets I need built. Let
> me know!
>
> James R. Coplin
> ***************
> If anyone asks of my whereabouts,
> simply tell them i've gone out the window
> for a spot of tea and am not
> expected back any time soon.
> ***************
>
> > -----Original Message-----
> > From: owner-synth-diy at dropmix.xs4all.nl [mailto:owner-synth-
> > diy at dropmix.xs4all.nl] On Behalf Of Czech Martin
> > Sent: Wednesday, February 04, 2004 3:01 AM
> > To: Thomas Dunker; synth-diy at dropmix.xs4all.nl
> > Subject: RE: [sdiy] Dynamics and speakers, was:Advice
> >
> > ok to everything, but:
> >
> > even a midrange horn with fc ~ 500Hz
> > has insane dimensions, about 50cm long and 80cm wide.
> >
> > This is very uncomfortable for home use, and also
> > for small events.
> >
> > A real bass horn that can deliver the lowest tones
> > of a church organ has dimensions that exceed 10m.
> > Folding causes some trouble, and shortening too.
> > Resulting in a response with lots of ripple.
> >
> > So there are reasons for lower efficiency speakers:
> > weight and space.
> >
> > I'm currently building a small system for synth performance,
> > and not surprisingly the woofer will be a closed system
> > with extra addad weigth for the membrane.
> > Double unefficient. But it will be able to go down to 25Hz
> > in a 45x45x45 cm^3 box.
> > Since weigth and space is the prime goal.
> >
> > There has been some advance in technology since 1940, though.
> > There are speakers with stiff membranes, stiff baskets,
> > low partial resonaces, strong permanent magnet and long Xmax.
> >
> > m.c.
> >
> >
> >
> > > -----Original Message-----
> > > From: owner-synth-diy at dropmix.xs4all.nl
> > > [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Thomas Dunker
> > > Sent: Mittwoch, 4. Februar 2004 00:53
> > > To: synth-diy at dropmix.xs4all.nl
> > > Subject: Re: [sdiy] Dynamics and speakers, was:Advice
> > >
> > >
> > > On Tue, 3 Feb 2004, Richard Wentk wrote:
> > >
> > > > The real point of compression is that given the limitations of most
> > > > speakers, there's no point trying to accurately reproduce
> > > the peaks anyway.
> > > > Studio monitors can reproduce peaks accurately (more or
> > > less) but nothing
> > > > else in the world can, so that headroom is effectively wasted.
> > >
> > >
> > >  Hey, couldn't resist commenting on this since the reproduction of
> > > uh..."life-like" dynamics has been my quest as a DIY audio nut for the
> > > past 10 years I have spent a great deal of time trying to
> > > figure out what
> > > it is the audio industry actually wants us to believe. Some
> > > of the most
> > > able speaker technology in terms of dynamics (or dynamic
> > > linearity to be
> > > more precise) just happens to be the oldest, and in domestic
> > > hi-fi terms
> > > also the "most obsolete" - namely horn speakers. Wherever
> > > horns are used
> > > in the pro audio industry today (SR rigs, stadiums, movie
> > > theatres etc.)
> > > it's precisely because they have vastly better dynamic linearity
> > > (distortion vs. output SPL) than most alternatives. Horns are
> > > also used a
> > > lot specifically for other primary reasons, like dispersion
> > > control, but
> > > they got me interested because of the dynamic potential.
> > >
> > >  Anyway, the sad story goes something like this: Ever since the direct
> > > radiator speaker came about (circa 1928, by Rice and Kellogg
> > > in the US who
> > > beat P.G.A.H. Voigt to the patent office - Voigt also had working
> > > prototypes at the time), an ongoing trend has conspired to effectively
> > > remove "lifelike dynamics" from most people's criteria for
> > > "high fidelity"
> > > reproduction. The first theater sound systems had speakers
> > > with something
> > > like 50% efficiency (modern hi-fi speakers have something
> > > typically around
> > > 0.1% efficiency, which probably explains the fact that efficiency is
> > > represented by a decibel figure at 1 watt input, yielding a more
> > > impressive number) and were powered with sub-10W triode amps.
> > > This would
> > > fill an entire movie theater with sound of unprecedented
> > > fidelity for the
> > > time (1930s).
> > >
> > >  Movie sound was developed into the forefront of audio
> > > technology during
> > > the 1930s, and advanced to give birth to multi-track studio recording
> > > techniques and fantastic analog reproduction systems by the end of the
> > > thirties. This is exemplified by the Fantasound system
> > > developed for Walt
> > > Disney's picture Fantasia by Hollywood sound engineers like Howard
> > > Tremaine, along with speakers and amps by RCA and Altec, and the
> > > three-track optical stereo soundtrack developed by Bell Labs.
> > > This optical
> > > sound track utilized a proprietary system called TOGAD (tone operated
> > > gain-adjusting device) which formed the basis of what must
> > > have been one
> > > of the very first "companding" schemes for recording. Separate gain
> > > control voltages for each of the three main channels were
> > > modulated onto
> > > different frequency carriers that were mixed and recorded as
> > > a separate
> > > track that ran along the three audio channels. These four tracks were
> > > recorded onto a dedicated 35 mm film that was syncronized
> > > with the picture
> > > film. During playback, the gain control voltages were
> > > recovered from the
> > > TOGAD track and fed to VCAs (!) in conjunction with the
> > > playback preamps.
> > >
> > >  Believe it or not, but this optical recording system enabled
> > > the Fantasia
> > > score to be recorded and reproduced with about 90dB of dynamic range!
> > >
> > > THAT'S ANALOG RECORDING STATE OF THE ART IN THE YEAR 1940
> > >
> > >  During the Fantasia recording sessions, multitrack recording
> > > technology
> > > as we know it was invented, except they mixed it down to
> > > three discrete
> > > channels (left, center, right). Orchestral "sound effects" were also
> > > worked into the mix and triggered by the TOGAD system to be played by
> > > various speakers placed around the theater, so even surround
> > > sound is a
> > > 60+ years old technology.
> > >
> > >  The speaker technology used reflected the demands of the
> > > recording/reproducing chain. The specs were insane for the
> > > time, something
> > > like 120dB peak in the rear of the theater, with 6dB of
> > > headroom. Huge,
> > > balanced class A triode amps powered bass horns and HF horns. A few
> > > theaters were equipped with insanely expensive Fantasound systems, but
> > > there was also a portable system complete with diesel generators,
> > > projectors, cables and everything.
> > >
> > > Read more here:
> > >
> > > http://www.widescreenmuseum.com/sound/Fantasound1.htm
> > >
> > > (I got a lot of first hand dope on Fantasound by one of the aging
> > > engineers who worked on the system in the 1940s, a guy named
> > > Jack Strayer)
> > >
> > >  OK, this is megalomaniac triode-age movie theater HI-FI madness, but
> > > demonstrates how we should probably be a little careful using
> > > phrases like
> > > "the state of the art" today, realizing that the actual state
> > > of the art
> > > TODAY is very far from reaching into most people's experience with
> > > reproduced audio.
> > >
> > >  And that's because of how amplifiers and speakers have
> > > developed since
> > > the days of triodes and horns. Triodes were replaced by
> > > pentodes, making
> > > amp power cheaper, causing some idiot to think hey, what do
> > > we need this
> > > kind of speaker efficiency for, and along come smaller, less efficient
> > > speakers. Pentodes were eventually replaced by transistors and by the
> > > 1970s typical "hi-fi" speaker efficiency had settled somewhere around
> > > 87dB/1W/1m - or somewhere below 0.1% relative efficiency. (Or 99.9% of
> > > input power directly converted into HEAT and other losses, rather than
> > > sound).
> > >
> > >  Specifying the efficiency in decibels is useful some times. The most
> > > inefficient speakers, like LS3/5As, Magnepans and such, are around
> > > 85dB/1W/1m. The most efficient speakers (big/horn based systems) can
> > > easily be around 105db/1W/1m. Most people don't realize how
> > > much a 20dB
> > > difference is in terms of amplifier power. If the speaker is 20dB LESS
> > > efficient, it needs 20dB or A HUNDRED TIMES MORE POWER. Think
> > > about it:
> > >
> > >  If you drive the 105db speaker with a humble 10W amp, comfortably
> > > below the speaker's max power rating, with 115dB peaks, you would -
> > > theoretically - have to have a 1000W amp driving the 85 dB
> > > speaker to get
> > > to the same max SPL or useful dynamic range - EXCEPT the 85dB
> > > speaker's
> > > voice coils would begin to self destruct at a mere couple
> > > hundred watts of
> > > input. No matter how much you up the amp power, the
> > > bottleneck will be in
> > > the speaker's power rating - BECAUSE OF ITS ULTRA LOW
> > > EFFICIENCY. It is
> > > therefore impossible to entirely compensate for inefficient
> > > speakers by
> > > increasing amp power as far as dynamics are concerned.
> > >
> > >  Next time you see a monster amp driving tiny speakers, don't be
> > > impressed, be sad.
> > >
> > >  Okay, so speakers can be more or less efficient, but it's
> > > not as simple
> > > as that. I brought up how 99% or more of the input power is
> > > converted into
> > > heat loss in the speaker. This has brought us fabulous
> > > innovations like
> > > high temperature cements and coil former materials allowing the
> > > low-efficiency insanity to escalate. An often overlooked fact
> > > is that when
> > > a piece of copper wire gets HOT its resistance increases. In
> > > a speaker it
> > > can typically imply that the impedance of the speaker may DOUBLE at
> > > "highish" input power, still well below max power rating. Since the
> > > industry has also decided that speakers - inherently current
> > > controlled
> > > devices - MUST ONLY be driven by low output impedance (undistorted
> > > voltage) amplifiers, another no-brain industry standard -
> > > this gives rise
> > > to what we call "POWER COMPRESSION", well known in the pro
> > > sound industry,
> > > but obviously a taboo in the "hi-fi" branch.
> > >
> > >  Quantitatively, power compression can very easily amount to something
> > > like 6dB loss of dynamics, give or take some. This
> > > compression will also
> > > be subject to unpredictable effects as the copper coils in
> > > different drivers
> > > will have different thermal time constants. Consider passive
> > > crossover/filter networks and you have the textbook definition of "A
> > > MESS". Not even the Q parameters or the actual efficiency of
> > > the drivers
> > > can be constant if the voice coil resistance isn't. A matter
> > > of speaker
> > > effciency and/or applied power.
> > >
> > >  I have spent years reading about all kinds of  distortion effects in
> > > speakers and the amp-speaker interface, so it's a little hard
> > > for me to
> > > get off the soapbox when I'm at it. But, the single most
> > > important thing
> > > to understand is that the harder a speaker must work (the
> > > more the cones
> > > move, the more power it tries to get rid of etc.) the more distortion
> > > (relative to the input signal) it makes. It's not cool that the woofer
> > > cones move an inch, it tells you you're probably listening to
> > > 20-30% THD
> > > and intermodulation distortion and horribly distorted transients too.
> > >
> > >  The subjective perception of music dynamics has to do with
> > > more than just
> > > SPL ratios and dynamic distortion. It also has something to
> > > do with the
> > > reproduction of transients, which typically has to do not just with
> > > amplitude levels, but also with time domain stuff. Like, how
> > > well are the
> > > system resonances damped? A bass reflex speaker is incapable of
> > > reproducing transients without some degree of periodic "overshoot",
> > > because the whole idea is that the resonance should only be
> > > damped to a
> > > certain degree so we get a little extra "bass" for cheap out
> > > of speakers
> > > that are too small. This is another "standardized" type of distortion
> > > typical in speakers.
> > >
> > >  Summed up, "state of the art" speakers and the amps that
> > > drive them are
> > > not suited for really big dynamics. Even most studio monitors
> > > except maybe
> > > Westlakes, UREIs, TADs and nice big old JBLs. Not the undersized stuff
> > > they tend to use today.  It should be quite possible - with
> > > the right speakers -
> > > to hear more of the recorded dynamic range than the recording engineer
> > > did when listening to the final mix.
> > >
> > >  It's not the recording industry's fault that the consumer
> > > audio people
> > > turn out so much misengineered junk, but it's sad how it's defined
> > > lifelike dynamics out of the "hi-fi" world. It's like they
> > > try to bring it
> > > back with amazing new digital media - WHY, IF THE SIGNAL WILL BE
> > > COMPRESSED DOWN TO 30-40dB DYNAMIC RANGE ANYWAY. What do we
> > > need all this
> > > dynamic resolution for then? You *can* get more dynamic range recorded
> > > onto 33 1/3 RPM vinyl than is common in most CDs out there.
> > >  How cool is it to have 24 bit resolution and 120dB S/N ratio when the
> > > recorded signal ends up being compressed to the dynamic range of worn
> > > cassette tape - or worse. Why are we supposed to get all excited about
> > > THAT? What a joke!
> > >
> > >  Still, the most dynamically capable speakers can make even the most
> > > awfully compressed recordings come alive, I know from experience, that
> > > only proves how much compression the average speaker ADDS. I
> > > had no idea
> > > until I could hear it for myself. Never would have happened
> > > at the hi-fi
> > > store.
> > >
> > > Pardon the ramble and off-topicness...
> > >
> > >
> > > Thomas Dunker
> > >
> > > Trondheim, Norway
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >