Article View: comp.sys.amiga.tech
Article #9511Re: how to improve sound capabilities
From: Michael Grau see jimt
Date: Mon, 15 Aug 1988 19:12
Date: Mon, 15 Aug 1988 19:12
182 lines
7623 bytes
7623 bytes
In article <8808100911.AA07219@decwrl.dec.com> carli@munich.dec.com (Bernardo da Vinci - the Amiga genius) writes:
> Has anyone the Amazing Computing issue (april?) with an article
> how to improve the sound capabilities of the amiga?
> (ya know that nasty filter that won't pass any frequences higher
> than 7kHz...)
> I'm desperately seeking for a cheap solution to set the cut off
> frequency of the filter to 14kHz or higher. It shouldn't be a hard job,
> but without any printsets it isn't a simple task (for me).
> Maybe someone tried it allready - I don't want to reinvent the wheel.
> As far as I know can this filter be turned off on newer A500 or A2000
> with the LED PD-Programm. So CATS, what do I have to do ???
>
> Any recommendations would be appreciated.
>
> Bernhard
>
Well here it is, the hardware fixup for the A1000 from Amazing Computing V3N4.
PAULA
----- |------|
| | | |
| | |TL084 |
| | TL084 |-|\ |
|AUD|-----|\ 2| >--@-------->>--- L
| A | 13| >---X--R90--R98--R97--R96--R89-@--|/ 1 |
| | |--|/ 14 | | | | | 3 |
| | | 12 C110 C106 C109 C105 C104 |
| | | | | | | | |
| | | GND | GND | GND |
| | | | | |
| | | |---------@-------------|
| | |
| | |
| | | |------|
| | | | |
| | | |TL084 |
| | | TL084 |-|\ |
|AUD|-----|\ 6| >--@-------->>--- R
| B | | 9| >---X--R87--R91--R92--R93--R88-@--|/ 7 |
| | |--|/ 8 | | | | | 5 |
| | | 10 C107 C101 C108 C102 C103 |
| | | | | | | | |
| | | GND | GND | GND |
| | | | | |
| | | |---------@-------------|
| | V Ref
| |
| |
| | A1000 Audio Schematic
-----
PAULA
----- |------|
| | | |
| | __________________________ |TL084 |
| | TL084 / \ |-|\ |
|AUD|-----|\ | | 2| >--@-------->>--- L
| A | 13| >-@-X--R90--R98--R97--R96--R89-@--|/ 1 |
| | |--|/ 14 | | | | | 3 |
| | | 12 C110 C106 C109 C105 C104 |
| | | | | | | | |
| | | GND | GND | GND |
| | | | | |
| | | |---------@-------------|
| | |
| | |
| | | |------|
| | | | |
| | | __________________________ |TL084 |
| | | TL084 / \ |-|\ |
|AUD|-----|\ | | 6| >--@-------->>--- R
| B | | 9| >-@-X--R87--R91--R92--R93--R88-@--|/ 7 |
| | |--|/ 8 | | | | | 5 |
| | | 10 C107 C101 C108 C102 C103 |
| | | | | | | | |
| | | GND | GND | GND |
| | | | | |
| | | |---------@-------------|
| | V Ref
| |
| |
| | A1000 Audio Schematic Modification 1
-----
PAULA /RES========================================< L #2
----- / | |------|
| | / GND | |
| | / |TL084 |
| | TL084 / |-|\ |
|AUD|-----|\ | 2| >--@-------->>--- L
| A | 13| >-@-X--R90--R98--R97--R96--R89-@--|/ 1 |
| | |--|/ 14 | | | | | 3 |
| | | 12 C110 C106 C109 C105 C104 |
| | | | | | | | |
| | | GND | GND | GND |
| | | | | |
| | | |---------@-------------|
| | |
| | | /RES========================================< R #2
| | | / | |------|
| | | / GND | |
| | | / |TL084 |
| | | TL084 / |-|\ |
|AUD|-----|\ | 6| >--@-------->>--- R
| B | | 9| >-@-X--R87--R91--R92--R93--R88-@--|/ 7 |
| | |--|/ 8 | | | | | 5 |
| | | 10 C107 C101 C108 C102 C103 |
| | | | | | | | |
| | | GND | GND | GND |
| | | | | |
| | | |---------@-------------|
| | V Ref
| |
| |
| | A1000 Audio Schematic Modification 2
-----
RES - 4.7 Kohm 1/4 Watt
R90,R87 - 750 ohm
R98,R97,R92,R91 - 3.3 Kohm
R96,R89,R93,R88 - 36 Kohm
C110,C107 - .047 uf
C106,C109,C108,C101 - .01 uf
C105,C102 - .0047 uf
C104,C103 - 220 pf
TL084 - UG5 on the board
< - phono plug (must mount a new set for Mod 2)
X - Test Point
@ - connection
= - shielded miniature cable
Modification 1 : Simply locate chip UG5, and solder an insulated wire
(22 - 24 Gauge) to connect pins 14 & 3 and 8 & 5.
Modification 2 : Solder the resistors to pins 8 & 14 of UG5. Solder
the resistor to the center wire of the shielded
cable and cover with heat shrink tubing(to protect
from accidental contact). Drill two holes in the
back of the A1000 and fasten the two new phono
plugs. Run the shielded cable along the ground
traces on the board avoiding chips susceptible to
noise, use black plastic electrical tape to
fasten cable to board and run to back of A1000.
Fit the cable between the two connectors for the
original audio connectors on the motherboard.
There should be only enough slack to feed the
cable around and no more. *** note: also a .0047 uf
capacitor can be connected to the gound and main
wire of the shielded cable to form a simple low
pass filter (outside ground better). ***
Before completely finishing any modification, check it over to see
if there are any problems (loose wires, gounds touching
connections,...) then test it before completely closing up the
machine. By the way, UG5 sits underneath the kickstart board and
therefore it must be removed.
Mike
--
DCIEM - Summer Employer
(does not bear the responsiblity for this message.)
{utzoo|mnetor}!dciem!dretor!mjg
Technical Details
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Path: arc1-ca.pugleaf.net!utzoo!dciem!dretor!client1!mjg From: mjg@client1.DRETOR.UUCP (Michael Grau see jimt) Newsgroups: comp.sys.amiga.tech Subject: Re: how to improve sound capabilities Message-ID: <917@client1.DRETOR.UUCP> Date: 15 Aug 88 19:12:51 GMT Article-I.D.: client1.917 References: <8808100911.AA07219@decwrl.dec.com> Reply-To: mjg@client1.UUCP (Michael Grau see jimt) Organization: D.C.I.E.M., Toronto, Canada Lines: 182 Summary: better then 5.5kHz sound