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Atari 800 Audio - Line Level?


ckrtech
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"I'm sorry; the number you have reached is not in service, or temporarily disconnected. The number you have reached is not in service at this time. This is a recording."

Edited by TheTIGuy
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If you mean designed to be in compliance with other

audio devices that use standardized line level inputs

and outputs, then probably not even a consideration

done by Atari. So just attenuate it to your liking

and then it will be. Just guessing here but maybe

try 500 ohm shunt to ground and if still too loud then

lower the ohm rating for the next attempt. Exact ohm

rating won't usually be in decades so just something

close that's available to you would work. 470 ohm for

example would be a fine place to start with.

 

https://www.amazon.com/Decade-Resistance-Box/dp/B00ALLDB86

 

One of these decade boxes would help find the proper

resistance a bit faster? I got mine off eBay a long time

ago for a little less but they are not there anymore and

the atlanta-robotics site seems to be offline so there may

be a chance that the cheap way can't even be had anymore.

 

Resistor substitution box is another search term to

use if this method appeals to you over just pick one

and try it method.

 

IIRC line level is standardized to be 600 ohm impedance

so 75 ohm attempt by Atari shows the level of detail

that made it to the design board - in other words nada.

They didn't care enough to even look it up. More foggy

recollections 1 V maximum peak to peak at 600 ohms?

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Hmm. Interesting.

 

I have an audio switchbox (homemade) to switch between two inputs (normally two modern computers) as well as two outputs (computer speakers and 64ohm headphones). The Atari seems a bit hot as barely a small increase in volume from 0 results in a rather sudden "appearance" of boomy sound.

 

So, I figured the Atari output its audio with a bit more oomph - possibly due to the hardware (built-in speakers in a monitor?) of the time.

 

IIRC line level is standardized to be 600 ohm impedance
so 75 ohm attempt by Atari shows the level of detail
that made it to the design board - in other words nada.
They didn't care enough to even look it up. More foggy
recollections 1 V maximum peak to peak at 600 ohms?

 

And that 75 ohm resistor was apparently supposed to be on the main board but isn't if I am properly reading what sup8pdct wrote.

 

I suppose I could look into generating a tone from the Atari and hook it up to an oscilloscope, etc., etc., (would be my first time messing with sound on a scope, actually)., but I am more likely to throw some resistance at it.

 

I thought perhaps some of the Atari mod guys might know the proper/relative values offhand.

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Hmm. Interesting.

Uh huh (the hell you say, tee he he he)

 

I have an audio switchbox (homemade) to switch between two inputs (normally two modern computers) as well as two outputs (computer speakers and 64ohm headphones). The Atari seems a bit hot as barely a small increase in volume from 0 results in a rather sudden "appearance" of boomy sound.

Can we be sure that the sudden appearance of boom isn't due

to Fletcher Munson curves designed into your rendering

equipment though? Just a possibility I'm throwing in the

air to see if you'll shoot at it or not. In my experience

they shouldn't have made the Fletcher Munson volume control

as set by some arbitrary tap point because it's wrong where

it's placed and it's not adjustable when it needs to be.

 

Needs both amount of boost applied and where to apply it.

First one is simple, another volume control added, the

second issue will never be as easily solved as the first.

I'm constantly needing to tweak mine depending on the

source and even content, so I assume 'engineers' are

tweaking it before it's even laid down for my consumption

too. The result can then only be crazy making for the

consumer.

 

So, I figured the Atari output its audio with a bit more oomph - possibly due to the hardware (built-in speakers in a monitor?) of the time.

 

And that 75 ohm resistor was apparently supposed to be on the main board but isn't if I am properly reading what sup8pdct wrote.

Negative on the first one would be my stance, we are

lucky they put in composite video out and I've never

had a religious experience rocking to the tunes on a

color TV that was most of the time the viewer for

Atari back in the day. I do remember the experience

of 'stereo' as implemented by TVs back in the day,

their artificially recreated right channel seemed to

come from about 30 feet away which cause me to holler

at the cat to get off the counter so many times when

the cat was somewhere else entirely. Poor cat had to

live with insane people yelling at her for things she

wasn't doing. No wonder she never paid us much

attention.

 

Can't know because I'm not him, but I'm assuming he

was thinking about the RF side where audio is

combined with the video signal coming out.

That's a wrong design point issue too, but not this

one. Looking it up myself just now to know what

line level actually is shows several opinions on

the subject with the main takeaway being that it's

not a matched system as RF lines should be, but the

mismatch is there on purpose to maintain fidelity

as the primary issue. Output around 100 ohm, input

around 1K ohm with no spec talked about as to

voltage level but I have seen 1 volt listed on the

back of a Sony minidisc player/recorder for example.

They did mention 600 ohms but that was the first

thing tossed into the hamper after they stuck a knife

into matching lines are required for audio frequencies

deal. Lot of murder and mayhem in general and no small

small amount of conflicting opinions too.

 

I suppose I could look into generating a tone from the Atari and hook it up to an oscilloscope, etc., etc., (would be my first time messing with sound on a scope, actually)., but I am more likely to throw some resistance at it.

 

I thought perhaps some of the Atari mod guys might know the proper/relative values offhand.

You are the very first by my count to even approach

the Line Level subject from an audiophile's viewpoint.

I would expect the output to vary from machine to machine

so much that you'll need to cook up another matching

network for every one have in your stable too.

 

I've taken to calling my homemade A-B switch, a

breakout box because it has so many talents. But

they used to be called A-B switches where you only

had two choices of two inputs A or B and a single

output. Mine is still single output but does have

a return loop using the front to back fader so that

I can boost a weak source if need be. Recording jacks

on all inputs with a chicken head four channel selector

on one side and TV input on the other. Has simplified

my life by a vast amount where I used to have to find

and untangle all those lines to hook them up manually.

Jeebus, what a Godsend.

 

Knowing what I know about it, throwing some resistors

at it is by far the better way to go and don't be

surprised when you need to throw some more at it

later either.

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