K5synth

Pulling the DG from the boards not PSU board(Impossible, without removing a bridge rectifier), I've already used the PSU without the big brown connector full of wires for power and ground of the boards.

They connected the non-inverting(+) input(if I'm right) to the DG?!?
Well, sure it will make noise, if that ground is that much noisy, that would be like to plug a phono playing in the input and wondering why you hear it.(Well, that's what I think)

What's the VCA's ground?

Also, they put two mono DACs for 4 channels, so (My theory) the analog sound is passing thru a kind of flip-flop that switches rapidly the input from 1 to 2 to 1 ... and the other with 3 and 4. As I only have a part of the output board, the opamp section and the PSU(Thanks, 


"nelsonj_sce" <nelsonj_sce@...> wrote:

>
>Antdes,
>Ok, I still have more work to do but I did look more at the schems
>while on a plane today. Some thoughts...
>1) DO NOT simply remove the DG ground on the power supply and reroute
>it to the AG (black transformer wire).  If you do this the inverter
>for the backlight (as well as several caps and part D6 WILL NOT BE
>GROUNDED.  Basically the DG does not terminate on MI-010, rather
>MI-010 needs the connection <CN1> in order to be grounded.  I am still
>looking at things but it seems the main ground for the MI-003 &MI-004
>comes from where they are screwed in to the K5 case.
>
>2) Although I am not 100% sure, it appears that for some reason, on
>board MI-004 the DG and AG are actually connected.  Board MI-003 is
>all digital so the ground is pure digital.  If I am correct, and the
>AG and DG grounds are not separated on MI-004, this may be the source
>of the noisy ground.  The bad news is that there is no quick way to
>separate the grounds on MI-004.
>
>3) Part U4 (the op-amp right after the VCA that we have both replaced)
>has my attention.  It has four inverting op-amps, where the "+" of
>each amp is connected directly to the dirty ground.  It is possible
>that the dirty ground is basically injection noise to these amp.
>
>I think we both have replaced this op-amp and it is now in a socket. I
>plan on taking out the amp(this is a total hack but if it works I can
>make it look nice later), and then bending connections 3, 5, 10, 12
>(the grounds) out so that they do not connect to the socket/dirty
>ground on board MI-004. Then, I will wire these connections directly
>to the K5's case to try and get a clean ground.
>
>4) If that does not help lower the noise, I am looking at lines g0-g7
>that feed the op-amps U8 and U9.  These are the only analog signal
>lines that have Faraday shielding.  These are low level lines early in
>the analog signal chain.  If nosie gets in to these lines, the nosie
>will get amplified in each of the following amp stages.  Perhaps there
>is a way to improve the shielding on these lines or to change the
>grounds related to these singal paths...but I have to think about how
>to do it.
>
>Anyway, I will let you know what happens after I reground U4.
>
>
>
>
>--- In k5synth@yahoogroups.com, antdes45@n... wrote:
>> That's it, AG is analog ground, DG digital ground, +A6V dc analog
>6v. . .
>> The kind of fork for the analog ground is an other sign for ground,
>maybe they mean different connection places, as the fork like is used
>for antenna too. But I think it's just a country/continent difference.
>>
>> "nelsonj_sce" <nelsonj_sce@y...> wrote:
>>
              . . . Cut the file, was 62k.

-- 
Antoine Desch\ufffdnes
aka DragonMaster
http://thehotcom.deep-ice.com/
Files:http://angelfire.com/ca7/hotcomcenter/


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