K5synth

You told a couple of replies before "I suppose you now have socketed 
opamps, like me", well I don't have some, I forgot to ask them at the shop.

"U1 if you use MIX"
I only use MIX output and headphones. I don't have time/want to build 
some 4 ½ m wires. And my mixer is 8 channels : 2 for the first Roland 
D110, 2 for the second one, and 1 for the K5, if I would do that, I 
would lose all the 3 other inputs, which I use sometimes. Also, I don't 
use the K5 for recording or anything else, I modifiy it even if I'm just 
playing it when I've got nothing to do. The K5 is just a kind of toy for 
me(And my father owns it, and uses it rarely to use it as a controller 
in Finale).

nelsonj_sce@... a écrit:

>
> You wrote: "They connected the non-inverting(+) input(if I'm right) to
> the DG?!?"
> Not directly.  The schem show that the (+) is connected to the AG, but
> it appears from the wiring board layouts that the AG and DG have
> ground planes that connect in several places.  So basically, there is
> no physical seperation of the AG and DG ground planes on board MI-004.
> As a result the (+) is connected to this single ground plane that has
> both A and D parts on it.
>
>
> You wrote: "What's the VCA's ground?"
> The same dirty AG/DG ground as that of U4.  The VCAs are parts IC6 and
> IC7.  The ground is pin 3, there is also a ground through a cap on on
> pin 5 but this look like protection rather than ground.  I am not sure
> if pin 3 is the third pin from the top or from the bottom, but pin 4
> is -A6.  It can't hurt to move the VCA's grounds to a clean ground
> also.  Note that it looks to me that the VCA's do not play the role of
> traditional synth VCAs, but rather the are connected directly to the
> main volume slider via pin 5.  They don't seem to have any other
> control voltages so my guess is that all the VCAs do is control the
> overall volume of the keyboard.  If that is the case, I am note sure
> that a dirty ground will inject noise.  But again, it can't hurt to
> make sure they have a clean ground.
>
> So here is my plan: Step 1 is change the ground on U4 (and U1 if you
> want to use the Mix output).  Step 2 is change the ground on the VCAs.
> Parts U8 and U9 are set up as non-inverting amps and do not have any
> direct connections to ground so no grounding to change here, but they
> have that shielding that we may be able to improve as Step 3.
>
> I may be able to do step 1 tonight - it all depends on how sleepy my
> baby is!
>
>
> --- In k5synth@yahoogroups.com, antdes45@n... wrote:
> > 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@y...> 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 Deschênes
> > aka DragonMaster
> > http://thehotcom.deep-ice.com/
> > Files:http://angelfire.com/ca7/hotcomcenter/
> >
> >
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-- 
antdes45@...