Is anyone interested with the Z80?

Did you know that the Z80 has different memory access timings for instruction fetches and standard memory accesses?

I worked at Mostek maintaining the Fairchild Sentry testers used to test the Z80s when they first began to manufacturer them. The second computer I every

built (parts, pcb, solder) was the SDB-80 which was the Mostek Software Development Board for the Z80 with 16K bytes (8 - MK4116 16K bit) dynamic RAMs

which Mostek also made. The first wire wrap board I ever made was a 48K byte dynamic RAM board also using MK4116s that worked with the SDB-80. I can

tell you there were a bunch of happy technicians when we were told that Mostek would be second sourcing the Z-80 and even happier when we were told we

could buy SDB-80 kits and build them ourselves! Those were really fun days. I still have a Zilog Z80 in a ceramic package that says it was manufactured in

Dallas even though Mostek was actually in Carrollton a suburb in Dallas County just north of north-west Dallas.

Hi COMPACT,

My son has a binocular microscope for his cartridge repairs/mods - tried it, didn't work for me alas (btw: there's a not-so-steady-anymore hand

to take into account as well). Thanks anyway for the uplifting tip.

I've read enough disturbing reports by pro circuit designers to stay away from SPICE and the like. My WYSIWYG-like statement lacked nuance,

that's true, but transitional phenomena e.g. are difficult to be measured correctly, and consequently just as difficult to predict/calculate/simulate.

And my experiments were on so called linear PSUs; btw: there's practically nothing 'linear' really in the operation of these classic power supplies.

As a result they are noisy, and hard to tame. Your average designer, however thinks, an overkill of microFarads + 'tripods' will easily cure this ...

Audiots frequently spend big bucks on external power supply 'upgrades' - on top of the just mentioned cure, these contain big transformers

with rediculous VA specs. While this might make sense for a power amp with underrated internal PSU, such upgrade PSUs for phono-amps are

outrageous ! We have performed in-depth listening tests here, and concluded that the advertised pros - improved bass response and dynamics -

didn't make up for the apparent loss of overall-quality: the music seemed robbed of its liveliness. Some team members stated: "As if an elephant

is sitting on the sound".

If you would want to consider RCA's Dynagroove technology* as a kind of early dithering, I would be with you, but calling RIAA equalisation

distorting the signal ... Changing the tonal balance in no way fits the definition of distortion. It is in fact a perfectly rational adaptation to the medium.

Its primary objective was optimizing playing time - so maybe one could call it a form of (physical) compression. The second aim, however is to

diminish and limit distortion - i.e. tracking distortion ! The famous ADC XLM cartridge from the sixties arguably was one of the most agile ever,

but it was not free from tracking distortion, of course. Here the question arises, how one is to discern between distortion caused by the vinyl

registration process, and distortion from the cartridge tracking the groove with its needle.

My son has done quite a bit of research in improving suspension in phono cartridges; he was surprised to find, how much there still is to be

gained in terms of tracking distortion this way - the experiments were done with state-of-the-art commercial carts.

(to be continued)

Ray

* dynamics at the end of the Pink Panther theme by Mancini e.g. really are impressive, but ... sure, it's just an effect - no HiFi.

Rather than perfect technical reproduction, modern audiophiles try to recreate a sense of being there at the original recording. To achieve this serious audiophiles place their speakers about 6-12 feet from walls and bevel or curve all orthogonal corners of the listening room and use sound absorbent materials as necessary. Even the stylus adds its own colour and audiohphiles usually have a collection of different ones to use for different recordings.

My Uncle is a really serious audiophile. He sends his used stylii cartidges to Switzerland to have them refurbished at $1,000 each, his pair of speakers cost about $500,000 and I'd hate to think how much he paid for is exotic Tube/Valve amp.

For those who aren't so as rich,  a pair of ELAC Navis ARB-51 Active Speakers designed by Andrew Jones is getting great reviews.  These $1,000 speakers are devoid of any Digital Signal Processing.

For me, I'm just happy to listen to my 1984 Sony D-50 Discman with headphones which still works today.

Hi COMPACT,

"Like oscilloscopes, sound should be sampled at about 5x or more than the desired maximum bandwidth", COMPACT wrote.

This ex-Tektronix test & calibration engineer couldn't agree more, but ... at the time of development, this was technically way out of reach for the

people working on e.g. the quadrophonic sound registration on vinyl, as well as those working on the Red Book standard.

Nowdays, cartridges with a frequency range of up to 50 kHz are available, serving people who have been convinced that they need super-tweeters

at the other end of their music reproduction chains ...

"And how does one get a speaker to playback perfect square waves?", COMPACT asked.

Peter Walker of QUAD Mfg fame came pretty close; in fact it was his ultimate way of testing (300 Hz) his almost single-handedly developped ESL

(Electrostatic LoudSpeaker; (fifties). Ever auditioned one ? You will never forget the listening experience ! We've also enjoyed Martin Logan's CLS

very much; of the electrodynamic units, Manger and Dynaudio probably have the best pulse responses. With ED speakers one tries to avoid square

waves because reproducing the top part would mean sending DC trough the poor unit(s), which very few would survive eventually. Furthermore,

audio is about reproducing natural sounds, not technical noises*; and music is the most complicated of sounds. Faithfully reproducing it means

getting the rise and fall right - these coïncide with the attaque of the musical instrument played, and the decay of the resulting sound. The most

demanding instrument attaque-wise, in terms of amplifier slew rate, turned out to be the harpsichord (& family), which is easy to understand once

you look at its playing mechanism. The same cousin who introduced me to electronics via his self-built Xtal receiver, made replicas of famous old

European harpsichords, together with his father (my godfather). I quickly grew to like the sound, that many audiophiles loathe. A possible cure might

be listening to the first chords of Bach's Italian Concerto in a harpsichord rendition (as it was meant to be) - it sings so much more that way than on

the piano ! (Try Glenn Gould's fifties recording vs. his almost anemiatic eighties registration by Sony).

(to be continued)

Ray

* I know, that same Peter Walker in an interview made a statement in relation to his ESLs that seems to argue otherwise ...

Hi COMPACT and Garry,

(Better late than never:) I'm sorry, if I have provoked replies that to me read like a kind of vinyl bashing ... won't go into that, because the

arguments are mostly too well-known to make a discussion in this day and age still worthwhile. I've been used to these arguments in audio

circles, but didn't expect them here, to be honest. And the worn-out objective vs. subjective discussion - culminating in head vs. heart ratings -

better be left alone, too, wouldn't you agree ?

Never mind; I was in fact just closing off some musings with an anecdote, but perhaps it would have been wise to present it with a bit more

context. Here that is yet.

The show was during the vinyl revival in the nineties, and we only had a speaker brand plus hi-grade vinyl at the time - all the rest was borrowed

from friendly colleague-importers. A high-grade CD-player was part of the demo set, but only used on request from our visitors. Btw, we didn't

do analog vs. digital comparisons.

The purpose of the shredded Mona Lisa poster was to show in a (simplified) pictorial manner, what digitizing is in essence. Apart from a good deal

of laughter, we als got recognition by colleagues referring visitors to our demo room. Only Philips was 'not amused' (and that was long before we

demoed the CD Clarifier the next year, thereby proving their slogan - "Perfect for Ever" - wrong; but that's an other story).

I also like to make an other point: as an importer of high-grade audio, I had to audition/listen to numerous gear/sets. With a few exceptions

the equipment was not 'my cup of tea', and I was pretty sure that I wouldn't be able to enjoy my music through it. Most of the time I tried to

imagine however, what enthralled the owner/seller. And by doing so, I often succeeded in 'hearing his point' ...

To prevent allegations that I'm living in the past, and that vinyl is obsolete, let me turn my eyes to the future* for a change: after virgin, HQ, and

Quiet Vinyl, vinyl lovers recently were treated to (the promise of) the Holy Vinyl Grail: HD-Vinyl. Multi millions have been invested in this project

that stems from the country where mr. Adolf H. was born, and that is frequently mixed up with your beloved 'Down Under', COMPACT. At the

risk of being judged too critical this time (and even because the concept is basically on digital), I think it's a mad men's scheme, and am certainly

not alone in that: https://www.analogplanet.com/content/hd-vinyl-exciting-concept-its-last-years-news .

Cheers

Ray

* the commercial product has been announced several times - yet have seen nothing so far ...

Take a look at this - I think it is impressive!

http://www.fagginfoundation.org/biography/

I do like your down-to-earth way of enjoying your music, COMPACT !

As audio advisors, we've always aimed at improving someone's music enjoyment for reasonable money. In the age of streaming, and what have you,

it's hard to pin-point that to a fixed amount, but in the nineties we felt, you could not expect the average customer to be willing to spend more than say

$ 5.000 on a decent player, amp, and pair of speakers (cable-mania was not yet wide-spread then). Of course, this statement immediately raises the

question: what is 'decent' ?

Objectively: equipment, apart from reliable and user-friendly, should be free of apparent flaws like hum/hiss, disturbing 'plops', or distortion levels that

were considered acceptable before the seventies. Furthermore limited performance is less of a problem than a lack of balance*.

Subjectively: equipment should raise the enjoyment level of the customer at least to 'content', but we were only really satisfied, when he reported

"having heard details in his music, he had never heard before", "discovering his music anew" - that sort of thing ... (one customer even declared:

"You have enriched my life" - he has become a friend). Best proof of having succeeded in improving matters came from the wife, though. If she made

a spot-on remark while removing the emptied coffee cups, we knew we had hit bull's eye. Why ? Because women just listen without any prejudice,

while men (audiophiles) are busy trying to hear what they have read ... ; sadly, didn't do much for the WAF (Wife Acceptance Factor).

Cheers

Ray

* that is a.o. why 2-way mini-monitors (not the Bose crap !) can be so very satisfying - certainly if they've been designed by Andrew Jones

P.S.: thank you for the Faggin-link, COMPACT - I'll dive into it

Sorry but those are easily provable deficiencies in vinyl recordings/turntables.

COMPACTS claim that audiophiles want the sense of being there at the original recording is a classic example of subjective.

How do they have the slightest idea of what the acoustics were at the original recording without actually being there? How

do you objectively reproduce something you've never heard?

The whole audiophile experience is subjective.

Our universe conspires to prevent perfect recording and playback and audiophiles are passionate of what constitutes a great sound.

I wish that some Astronauts would set up some speakers and microphones outside the International Space Station to see how well they work.

Here is one audiophile's take on things. Have a listen for 90 seconds.

The Australian company RODE is successful making microphones and associated paraphernalia. The recorded sound may not be technically perfect but it sure does sound crisp and clear.

Their latest offering is a wireless Lavalier microphone transmitter receiver combination for digital cameras. ("Go") which is very convenient.

"The whole audiophile experience is subjective."

That was exactly my point, aimed directly at Ray.  The problem with subjective interpretation of audio reproduction is

that it is always "in the ear of the beholder".

"and audiophiles are passionate of what constitutes a great sound"

They just can't explain in objective terms what constitutes that great sound. And there is clearly such a thing as being

too passionate. That is one reason why the ear of the beholder is not a good thing.

"The recorded sound may not be technically perfect but it sure does sound crisp and clear."

There are a few acoustic instruments that produce sound that is not crisp and clear, a muted horn is a good

example. Various kinds of distortion are widely used with electronic instruments and some of these also produce

sound that is not crisp and clear. Does a crisp and clear reproduction of these instruments constitute great sound?

It does not represent a faithful reproduction of the instrument's sound in the acoustic environment where it was

made (being there as you previously put it). And to me that faithful reproduction is what constitutes a "great sound".

It's just not possible to do, at least for now, no matter how much technology, subjective audiophile BS, or money

thrown at it.

The questions you've raised are certainly worthwhile, albeit far from new ...

First of all, there is broad consensus, that audio is the art of reproducing sounds, recorded in one acoustic environment, in an other - usually totally

different. As a (recent) result, room acoustics have become a hot item; with DSP prices coming down, ever more components in the reproduction

chain - both amps and active speakers e.g. - are equipped with some form of electronic adaptation. While this may seem progress, oldtimer audio

buffs (like us ?) probably wonder, what has become of good (?) old tone controls, or - a bit more sophisticated - equalizers ? The 'tilt control' on the

QUAD 34 pre-amp, beloved in the eighties (and not much unlike RIAA equalization, COMPACT), springs to mind. DSP-based room-correction

circuitry is said to spare you fysical adjustments, like COMPACT described; I don't think I'm convinced.

As to equalizers, in the nineties we were allowed one afternoon to 'play' with the famous Cello Audio Palette, originally intended for studio-use, and

the wet dream of many an audiophile. Although we really had a great time at the circular controls of that gem, we had second thoughts afterwards:

had we not in fact been indulging ourselves in 'bettering' recordings of top-notch mastering engineers ? Who did we think we were ?! Our host had

'encoded' the favourite tracks on his discs with the letters of the controls and the corresponding numbers of the scale settings ... (audiot).

Live vs. recorded comparisons were popular in both the UK and USA during the fifties, aiming at answering the question: how close have we come

with HiFi ? It was reported frequently that even highly experienced audiences (regular concert visitors) sometimes had trouble discerning one from

the other. But this only works in the same room, with the speakers exactly positioned, where the instruments/vocalists were before (and everything

else also kept constant, preferably). So there's not much hope of ever bridging the gap from concert hall/studio to listening room ... And "Bringing

the concert hall to your living room" a bluddy (marketing) lie !

The 'being there (present)' experience /illusion is in fact the last frontier in high-end audio. When auditioning a Cello set with Martin Logan CLS,

a much more experienced audiophile commented: "Ah, this is precisely the sort of set that enables you to hear a fly fart on the rear wall of the

recording studio !". That made us think: are we chasing ultra resolution in sound reproduction, or is our real aim musical satisfaction ? It took some

time to cure ourselves of 'audiophilia nervosa', but we have since been enjoying our music via much more down-to-earth equipment.

Stereo is btw. as much an illusion (and this goes as well for 'glued-together-again' digital signal samples, in an attempt to mimic analog sound).

I believe, though, ultimately most people do not care that they are listening to illusions, nor how far off they are from reality - they've simply come

to like them !

I hope you see my point: this kind of discussions is in fact a thing of the past, and when repeated all the same, bound to be ... pointless.

The questions you've raised are certainly worthwhile, albeit far from new ...

First of all, there is broad consensus, that audio is the art of reproducing sounds, recorded in one acoustic environment, in an other - usually totally

different. As a (recent) result, room acoustics have become a hot item; with DSP prices coming down, ever more components in the reproduction

chain - both amps and active speakers e.g. - are equipped with some form of electronic adaptation. While this may seem progress, oldtimer audio

buffs (like us ?) probably wonder, what has become of good (?) old tone controls, or - a bit more sophisticated - equalizers ? The 'tilt control' on the

QUAD 34 pre-amp, beloved in the eighties (and not much unlike RIAA equalization, COMPACT), springs to mind. DSP-based room-correction

circuitry is said to spare you fysical adjustments, like COMPACT described; I don't think I'm convinced.

As to equalizers, in the nineties we were allowed one afternoon to 'play' with the famous Cello Audio Palette, originally intended for studio-use, and

the wet dream of many an audiophile. Although we really had a great time at the circular controls of that gem, we had second thoughts afterwards:

had we not in fact been indulging ourselves in 'bettering' recordings of top-notch mastering engineers ? Who did we think we were ?! Our host had

'encoded' the favourite tracks on his discs with the letters of the controls and the corresponding numbers of the scale settings ... (audiot).

Live vs. recorded comparisons were popular in both the UK and USA during the fifties, aiming at answering the question: how close have we come

with HiFi ? It was reported frequently that even highly experienced audiences (regular concert visitors) sometimes had trouble discerning one from

the other. But this only works in the same room, with the speakers exactly positioned, where the instruments/vocalists were before (and everything

else also kept constant, preferably). So there's not much hope of ever bridging the gap from concert hall/studio to listening room ... And "Bringing

the concert hall to your living room" a bluddy (marketing) lie !

The 'being there (present)' experience /illusion is in fact the last frontier in high-end audio. When auditioning a Cello set with Martin Logan CLS,

a much more experienced audiophile commented: "Ah, this is precisely the sort of set that enables you to hear a fly fart on the rear wall of the

recording studio !". That made us think: are we chasing ultra resolution in sound reproduction, or is our real aim musical satisfaction ? It took some

time to cure ourselves of 'audiophilia nervosa', but we have since been enjoying our music via much more down-to-earth equipment.

Stereo is btw. as much an illusion (and this goes as well for 'glued-together-again' digital signal samples, in an attempt to mimic analog sound).

I believe, though, ultimately most people do not care that they are listening to illusions, nor how far off they are from reality - they've simply come

to like them !

I hope you see my point: this kind of discussions is in fact a thing of the past, and when repeated all the same, bound to be ... pointless.