MUFF WIGGLER Forum Index
 FAQ & Terms of UseFAQ & Terms Of Use   Wiggler RadioMW Radio   Muff Wiggler TwitterTwitter   Support the site @ PatreonPatreon 
 SearchSearch   RegisterSign up   Log inLog in 
WIGGLING 'LITE' IN GUEST MODE

MaxiKORG DV800 CV/Gate mod ?
MUFF WIGGLER Forum Index -> General Gear  
Author MaxiKORG DV800 CV/Gate mod ?
kaoss
Does any of you DV800 owners have a CV/Gate mod on their MaxiKorg?

There was a Japanese company offering mod schematics but it seems like they are not in business anymore. The only other option I found is this DIY guide.
Has anyone tried it out or are there any other options?? Thanks.
Reese P. Dubin
Mine had them when I got it in '98.

As afr as I have ever been able to determine they only affect the pitch and gate, with no effect on the performance controls, which is where most all of the magic is.

Maybe there is a different mod that brings them into play, which I would shift to in about one second.
kaoss
Reese P. Dubin wrote:
Mine had them when I got it in '98.

As afr as I have ever been able to determine they only affect the pitch and gate, with no effect on the performance controls, which is where most all of the magic is.

Maybe there is a different mod that brings them into play, which I would shift to in about one second.


there's a 'modular mod' by Analogue Solutions but it's just for MiniKorg not Maxi. I just emailed AS asking if it can be also used on or adapted to the MaxiKorg.
ndkent
I bought the Analogue Solutions mod for 30 pounds or something. It wasn't a total ripoff but I wouldn't recommend it (if it's still available).

It's a Hz/V instrument. I think everyone knows that up front, right?

As I recall it's pretty clear on the pCBs where CV and gate goes if you are moderately good with mods. So the kit mostly is pre-soldered sockets, a label and a xerox telling you to solder the leads there, there and there. So you get 2 CV ins, 4? filter ins (I'm forgetting, and some Maxikorgs already have a DIN connector for a Traveller pedal) and 2 gate ins

Bad news is quirky old Korg seems to use +-10v for the filter or something super wide meaning when I plugged in the filter mod to a doepfer LFO it just wiggled a little, anyway that's not great but not unsurmountable.

Another annoyance with anyone's mod is as far as I know you either have to build a new circuit board or hold down a key on some or all Maxikorgs for the pitch CV to work. Maybe it has to do with the duophony or something. Anyway, on mine if I don't tape down a key, it won't respond. Not a super big deal, I think the mod I have breaks the now normalized keyboard when a plug goes in so you don't hear the held key, if you follow, it does work properly, you just need to tape down a key.

The kit mentions nothing of the hold down a key or build a circuit board, I learned that on the net. Not sure what the deal is, maybe some units, like the one ASolutions tested the kit on are different in multiple ways. There are definitely differences in units. Mine has traveler DIN i/o so I dumbly drilled more holes than I needed. Also the fairly useless pass through feature on mine should have been used for the mods. The best I understand it Korg thought it was useful for bands without a mixer? You can mix an external signal with the synth. It's not like running audio through the filter and VCA, nahhhh, that would actually be useful. Anyway I'm just pointing out yours may have IMHO useless plugs on the back.

The one mod ASolutions omits is running audio through the filter. That would be a useful mod to have, no question.
kaoss
ndkent wrote:
I bought the Analogue Solutions mod for 30 pounds or something. It wasn't a total ripoff but I wouldn't recommend it (if it's still available).

It's a Hz/V instrument. I think everyone knows that up front, right?

As I recall it's pretty clear on the pCBs where CV and gate goes if you are moderately good with mods. So the kit mostly is pre-soldered sockets, a label and a xerox telling you to solder the leads there, there and there. So you get 2 CV ins, 4? filter ins (I'm forgetting, and some Maxikorgs already have a DIN connector for a Traveller pedal) and 2 gate ins

Bad news is quirky old Korg seems to use +-10v for the filter or something super wide meaning when I plugged in the filter mod to a doepfer LFO it just wiggled a little, anyway that's not great but not unsurmountable.

Another annoyance with anyone's mod is as far as I know you either have to build a new circuit board or hold down a key on some or all Maxikorgs for the pitch CV to work. Maybe it has to do with the duophony or something. Anyway, on mine if I don't tape down a key, it won't respond. Not a super big deal, I think the mod I have breaks the now normalized keyboard when a plug goes in so you don't hear the held key, if you follow, it does work properly, you just need to tape down a key.

The kit mentions nothing of the hold down a key or build a circuit board, I learned that on the net. Not sure what the deal is, maybe some units, like the one ASolutions tested the kit on are different in multiple ways. There are definitely differences in units. Mine has traveler DIN i/o so I dumbly drilled more holes than I needed. Also the fairly useless pass through feature on mine should have been used for the mods. The best I understand it Korg thought it was useful for bands without a mixer? You can mix an external signal with the synth. It's not like running audio through the filter and VCA, nahhhh, that would actually be useful. Anyway I'm just pointing out yours may have IMHO useless plugs on the back.

The one mod ASolutions omits is running audio through the filter. That would be a useful mod to have, no question.


interesting..., thanks for all the info!

my MaxiKorg doesn't have the DIN connector but a pair of "TO ACCESSORY" and "FROM ACCESSORY" inputs and outputs, which are basically FX loop In and Out.
kaoss
ndkent wrote:
Bad news is quirky old Korg seems to use +-10v for the filter or something super wide meaning when I plugged in the filter mod to a doepfer LFO it just wiggled a little, anyway that's not great but not unsurmountable.


could it possibly be that one of the filter knobs works as an attenuator when controlling the filter externally? when i tried to control my Pro-One's filter with external CV i was always getting similar results (less than impressive that is) until i read the manual and found out that VCF's Keyboard Amount pot also double-functions as a Filter CV IN attenuator.
andrewF
Mine is modded with all the E-lab circuits (a Japanese synth DIYer). E-lab site has gone now. I have posted all the schematics in a thread on electro-music (its down at the mo' so will add the link when its back up or I will turn on the old pooter and post them here).
It doesn't get any easier to control with CV/gate but at least for me I could 'play' it as the keyboard was buggered on mine.

as I said in the keyboard thread, I could design a PCB with all the CV/gate subcircuits onboard and get some made. Probably would work out to $20 a board.

Sometimes I think about cloning the whole 800DV into a set of modules, its such a growling beast of a synth, all I need is a spare month or so!
dougt
andrewF wrote:
as I said in the keyboard thread, I could design a PCB with all the CV/gate subcircuits onboard and get some made. Probably would work out to $20 a board.!


This would be great! I have 2 Maxis, 1 without a keyboard...
kaoss
andrewF wrote:
as I said in the keyboard thread, I could design a PCB with all the CV/gate subcircuits onboard and get some made. Probably would work out to $20 a board.


that'd be great, i'd definitely buy it!

please update this post if you do so
andrewF
just so this stuff is all in one place. the zip contains DV800 schematic, block diagram, CV and gate mod circuits (you will need two of each), pictures of where to alter the Korg circuitry to implement the mods plus a VCA replacement circuit if your VCAs are dead. Plus VCF inputs and more. This is all from the now defunct e-lab page.

I will make a little PCB, including a regulator to get +15V. It will be about 2 months away as it will be done in a batch with some other boards i am doing.
kaoss
andrewF wrote:
just so this stuff is all in one place. the zip contains DV800 schematic, block diagram, CV and gate mod circuits (you will need two of each), pictures of where to alter the Korg circuitry to implement the mods plus a VCA replacement circuit if your VCAs are dead. Plus VCF inputs and more. This is all from the now defunct e-lab page.

I will make a little PCB, including a regulator to get +15V. It will be about 2 months away as it will be done in a batch with some other boards i am doing.


amazing, thanks again!!
kaoss
andrewF wrote:
I will make a little PCB, including a regulator to get +15V. It will be about 2 months away as it will be done in a batch with some other boards i am doing.


hi, just wondering if you're still planning on making the PCB at some point
andrewF
Yes I have a PCB made up which contains two external CV input circuits and two gate input circuits (for gating the EG/vib/bender, repeat and S&H)
Managed to keep it fairly small - about 1" x 5.5"
sorry its taken so long, tend to have about 20 projects running at once.
It will be included in my next PCB run, which should be sent off in the next 2 weeks.....so xmas?

You will only need 1 board, will get probably get 20 made, 1 for me, 19 for sale, expect $20 including shipping to anywhere.
b3nsf
would this work on the minikorg?

looks fun! 8_)
andrewF
They are very similar synths but looking at the CV input cct for the 700S on Cykong shows a few differences, mainly the CV input is turned on and off by a FET.
So the 800dv board might work, but if you are going to go thru all the trouble of building a CV/gate input, use the proper circuit to suit the 700S.
This page is pretty detailed:
http://www.cykong.com/Synths/Korg%20700S/Korg700S2.htm
b3nsf
Thanks, AndrewF,


Cy's mod here we GOOoooo.... eek!
kaoss
b3nsf wrote:
would this work on the minikorg?

looks fun! 8_)


probably the most hassle-free solution is to get a HzV/Gate/Filter retrofit kit from Kenton. I have it installed in my 700S - works great!
kaoss
andrewF wrote:
Yes I have a PCB made up which contains two external CV input circuits and two gate input circuits (for gating the EG/vib/bender, repeat and S&H)
Managed to keep it fairly small - about 1" x 5.5"
sorry its taken so long, tend to have about 20 projects running at once.
It will be included in my next PCB run, which should be sent off in the next 2 weeks.....so xmas?

You will only need 1 board, will get probably get 20 made, 1 for me, 19 for sale, expect $20 including shipping to anywhere.


fantastic news!! thank you! ... and obviously count me in
kaoss
Dead Banana doublepost
b3nsf
kaoss wrote:
b3nsf wrote:
would this work on the minikorg?

looks fun! 8_)


probably the most hassle-free solution is to get a HzV/Gate/Filter retrofit kit from Kenton. I have it installed in my 700S - works great!


Do you have to hold a key down for it to work? I remember that being the problem...
kaoss
b3nsf wrote:
kaoss wrote:
b3nsf wrote:
would this work on the minikorg?

looks fun! 8_)


probably the most hassle-free solution is to get a HzV/Gate/Filter retrofit kit from Kenton. I have it installed in my 700S - works great!


Do you have to hold a key down for it to work? I remember that being the problem...


No, you don't hold down a key.
You chose between internal keyboard and external CV/gate with an included switch.
So the new stuff that gets installed on MiniKorg's rear panel are three inputs (cv, gate and filter) plus the switch.
b3nsf
Cool, I'm gonna try the kenton one, thanks!
andrewF
Hi guys
I have actually placed the order for these PCBs
.....only 6 months later oops
Just getting 20, 1 is for me, so 19 available.
You will only need 1 PCB for 1 800DV, each PCB has 2 CV circuits and two gate/trigger circuits.

The PCBs will be $20 including shipping to anywhere.
If you want one, just say so on this thread (you can of course change your mind) and I will let you know when they are tested & ready to go.

Given all the hoohaa with xmas & new year I expect they will arrive in mid-Jan.
kaoss
andrewF wrote:
Hi guys
I have actually placed the order for these PCBs
.....only 6 months later oops
Just getting 20, 1 is for me, so 19 available.
You will only need 1 PCB for 1 800DV, each PCB has 2 CV circuits and two gate/trigger circuits.

The PCBs will be $20 including shipping to anywhere.
If you want one, just say so on this thread (you can of course change your mind) and I will let you know when they are tested & ready to go.

Given all the hoohaa with xmas & new year I expect they will arrive in mid-Jan.


I'll take one
dougt
I want one.
schmidtc
One for me please.
andrewF
got boards in
built one
dragged my old 800dv out of the corner where it has been sitting unused since 2005 (just a panel & pcbs - no case or keys)
turned on the 800dv to find all the switches have corroded and need replacing (same as cykong had to do). Lower VCO doesn't work at all.
I suspect i will have to replace all the pots and electros too w00t to be honest it isn't going to happen for a few months.

so I tested the board by hooking it up to the PSU, feeding it CV and gates, then monitoring the outputs with my oscilloscope.
It all works as expected and is the same as the original e-labs design. The only difference is I used BC transistors instead of the Japanese ones specified. For this kind of circuit any general purpose trannie will do.

Each PCB has 2 CV circuits and two gate circuits, ie one PCB for one 800dv.
$20 each including shipping anywhere, pm if you want
andrewF
boards sent today to

schmidtc
ndkent
kaoss
dougt

sent 11/1/12
jkjelec
a100user
a100user
Out of curiosity, does anyone know if the 900PS uses the same circuitry and therefore this mod would work with that synth?

I beleive the 900PS predates the mini & maxi by only about a year.

Thanks
andrewF
They both have the same VCO chips, although the 900ps circuitry around the chip is a bit different. It looks like there is a 680 Ohm resistor in place of the 1k Coarse tuning pot on the 800dv (which is where the external CV is injected)
The 900Ps also has a similar trigger circuit to get the EG and whatever else to tick over.
So yes it would be do-able, just you will have to experiment to find the best way to do it.
a100user
Thanks for that.

So can I have a board please?

Thanks
andrewF
no worries
pm'd
dougt
Could half of it work for the 770?
andrewF
I am sure you could make it 'work', the question is how well?
Tho I remember when my 800dv did work the CV/gate mod circuit was great fun but difficult to tame.

It looks like the 770's "remote" input is a gate or trigger input, at least to trigger the EG. Otherwise, the gate sections on the mod PCB have three types of outputs (one follows the incoming gate, another is inverted and the third connects to ground when the gate is high) This covers all the usual types of requirements for gates so one of them should suit your needs.

you could try to use the two CV channels on the mod PCB to control the VCOs.
My suggestion would be to use an oscilloscope and monitor the likely points around the tuning pots to see where the voltage changes as you press keys up and down the keyboard. On the 800dv this ranges from 1V for the lower F key up to 12V for the top C key.
You could check this with a multi-meter if you do not have a scope, just hold the key down until you get a good reading. Once you have found a likely node, cut it, install a switch to select between keyboard or external input and give it a whirl! Not sure how good your electronics skills are, don't be shy to ask here or on the diy forum.
andrewF
here is the BOM and wiring info for the PCB
If there are any errors or anything is not clear, just ask
CaptainZilog
Great board !

Do I need 2 of them if I want to control Synth1 and Synth2 independently ?

Thanks !
pm sent
andrewF
Hi Captain
Welcome to Muffs
i sent you some email
w00t
Rqckmounted
Hi everyone

10 years ago I was walking in the street and suddenly I have fund a Maxikorg 800 dv in the garbage !!
The keyboard was very ugly and painted in christmas green color. The synth has been put in storage since

now that I can across this nonlinearcircuits pcb board I am so excited to make this mod.

I have a basic knowledge in electronic so I would like some guidance please if someone can help.!

This is a list of the components / parts that I assume is needed, if there is anything else I need to get or to know please let me know.


100 nf capacitor X 6

100 k resistor X 10

10 k resistor X 10

1 k resistor X 2

diode 1S1588 OR 1N914 X 8

1x3 (AVR ISP header) X 4

1x2 (AVR ISP header) X 2

10u Capacitor X 1 what is the voltage ??

op-07 op-amp 78L15 OR 7815 X 2

10 k trim pot X 2

nun and pnp transistors, what are there values ??
andrewF
Rqckmounted wrote:


10u Capacitor X 1 what is the voltage ??

op-07 op-amp 78L15 OR 7815 X 2

10 k trim pot X 2

nun and pnp transistors, what are there values ??


Hi
The capacitor can be 35V or higher (50V okay). I always buy 50V rating. This is just the minimum operating voltage for the cap.

Transistors are
NPN - BC547 (need 4)
PNP - BC557 (need 2)
any general purpose types will work, but be careful to check which way to insert them on the PCB. The PCB is designed to take the BC series

The 78L15 is a regulator, you just need one of these. Note the 7815 is a 1A version and is bigger with a different pinout to the 78L15 which is the 100mA version.

The two op-amps are TL072, many dual op-amp ICs will work fine.

http://www.taydaelectronics.com/ are a good cheap place to get almost everything
Rqckmounted
Hi Andrew

Thanks for the info, I will take my time to do this mod, I will let you know of the progress.

Best regards

Dave
analoglsd
I'd like to buy one of the PCBs if they're still available.
Thanks.
andrewF
pm'd
8 left!
Though once they are gone I will probably get more, its a small PCB and easy to tack onto other manufacturing runs.
Rqckmounted
OK everybody

Now I am ready to order my electronics components, please note that I have put more quantity than need to be shure to have spare parts to keep…

here is my list:


BC547 Transistor NPN 45V 0.1A x 5

BC557 Transistor PNP 45V 0.1A TO-92 BC557B-KEC/P x 3

10uF 50V 105C Radial Electrolytic Capacitor 5x11mm x 2

100nF 0.1uF 100V 5% Mylar Film Capacitors x 7

100K OHM 1W 5% Carbon Film Resistor x 20

1N914 Small Signal Diode 200mA 100V x 9

L7815CV L7815 7815 Voltage Regulator IC +15V 1.5A x 2

TL072 LOW NOISE J-FET DUAL OP-AMP IC x 3

10K OHM Trimpot Variable Resistor 6mm x 3

40 Pin 2.54 mm Single Row Pin Header Strip x 1

10K OHM 1W 5% Carbon Film Resistor x 20

1K OHM 1W 5% Carbon Film Resistor x 10

L7815CV L7815 7815 Voltage Regulator IC +15V 1.5A x 3





Question no 1

The 100 nf capacitor I have found are in Mylar or Polyester material, I wonder if it make any difference if they are not in carbon ( Beige brun color ) !??

Question no 2

Is 1 watt are ok for all the resistors in my list ?

Question no 3

I did not found the 78L15 regulator so I will use the 7815, I am not able to see the pin out difference (only 3 pins) ??




Stay tune for the progress work

have a nice day
andrewF
Hi
1. the 100nF capacitor is just for decoupling, it keeps the power supply smooth. A ceramic (beige colour) is fine for this job, it is also fine to use mylar or poly. These types are better quality.

2. definitely not ok. You need 1/4W (0.25W) resistors. The 1W types will work but be too big to fit on the PCB. Sorry I did not state this oops
You can use metal film or carbon resistors, metal film are better, but seeing as the 800dv uses all carbon resistors (metal film used to be expensive) it will make no difference.

3. The 7815 will have to be installed backwards to the 78L15. Also the 7815 pins will probably be to large to fit in the thru holes, so you will have to solder it standing on the PCB, trim off the pins a bit so it is not too high, but don't trim off too much so that you cannot solder it easily. Remember if you use a 7815 it will not have a strong mechanical connection to the PCB so do not bend it around - be gentle with it 8_)
rude66
i'd like one of these pcb's if you still have them.. would be great to use my 800DV again!
andrewF
Hi & Welcome to Muffs

still have a few
will send you a pm (private message Mr. Green )
GlennVS
I would like to order a PCB to modify my DV800. If I'm correct I only need 1 PCB for 2x cv and 2x gate?

Grtz
andrewF
Hi
Welcome to Muffs

yep one pcb does the job

sent you a pm
Rqckmounted
hello again

This is what I have received :

http://www.taydaelectronics.com/capacitors/polyester-mylar-film-capaci tors/0-1uf-100v-5-mylar-film-capacitors.html

I was able to solder them on the PCB but they are touching each other (tightly) with the 7815 and the other black capacitor.

Should I go on or order smaller beige ones ? ( Can seem to find some beige caps )

Thank you in advance

Have a nice day
andrewF
if you mean the bodies of the components are touching, that is fine.
Just be sure there is no metal to metal contact.

Post a photo of them if you like.
Rqckmounted
OK Thanks

I think I have figure it out.

Now I have just realize that I forgot to order 2x 47 ohm resistors.

47 OHM 1/4W 5% Carbon Film Resistor

just to add on the list for other users.
Rqckmounted
Hi Everyone

The upper section w the nonlinearcircuits mod ( CV & Gate ) is done, it is working only if I press a key.

any clue if it is possible to make it work without pressing a key ?

Please note that I have only connect/solder the CV 1, Gate in 1 & EG ( 2nd pin on the pcb )

Have a hot & nice day
andrewF
good to hear the project is making progress w00t

It should be wired up so the keyboard is switched out of the circuit when using the external inputs and would have no effect at all.
Which is "Gate in 1"? Do you mean the S&H Gate or the Repeat gate?

I guess try wiring in all 3 gate connections.
Rqckmounted
aahhh ok

now it is working

I have realize that the SH is need to be solder to make the full gate usable.

now I wonder if I need to solder the 2 rpt ( one for each cv ) together on the same RPT Mod wiring .??!
andrewF
Rqckmounted wrote:
aahhh ok

now it is working

I have realize that the SH is need to be solder to make the full gate usable.

now I wonder if I need to solder the 2 rpt ( one for each cv ) together on the same RPT Mod wiring .??!


good to hear (read)
I suggest using a toggle switch to select which gate will control RPT.
Check pg1 of the build doc, there is a pic showing how to do it
Rqckmounted
ohh ok right

I guess I have learn the hard way ( didnt know there was a manual )

What could happen if I connect the 2 RPT on the same distination.,, could it overload the voltage.?

The problem is that my Maxikorg repeat function doesnt work on the upper section , only the lower and only 1 mode is working..

I'm wonder if it is really worth to make it work since I will control it with external Control voltage.and gate

thanks
Rqckmounted





VOILA

now I only need to figure out how and where can I place the pcb inside this monster beast,..

As you can see I have cut off the keyboard off by hand with a metal saw (made alot of muscles !!smile)

If you look the 3rd picture you can see that there is some traveller control input so I guess I could control them via cv if I change the connectors..

Now I need to finish the body & paint the woodside panel and then I am very happy

I am able to control cv with my Doepfer MCV 24 but the tracking is not scaled correctly, I have tried to get some info but it seems that the MCV 24 is not able to make the proper convertion in Hrtz...


Stay tuned..
[/url]
andrewF
good to see

thumbs up
Duchemole
Hi,
Do you have at least 1 left, please (ok, 2 would be even better)
Thanks
andrewF
Hi
yes, a few left
You only need one PCB per 800DV

will send you a message
Reese P. Dubin
Makes me sad seeing one of my favorites all hacked up confused
redragebrian
Hi, I'd like to buy one of these boards from you. Do you have any left?

Regards

Brian
andrewF
yes 2 left...........1 left - sent you a pm

edit - sold out
I will get ten more in about 2 months
Rqckmounted
Hi andrewF


Still have a Maxikorg mod pcb left ? or does your new batch is ready ?


Regards
andrewF
boards are back in stock
Spacetrader
Can I order 2 ?
( I have several maxis)
Greg
andrewF
sure can
pm sent

Welcome to Muffs btw Champagne
Sir Ruff
Someone sell me their maxikorg so I can add cv/gate to it! 8_)
Spacetrader
https://www.facebook.com/Korg800dv
Yip2
Switched-On just put one up for sale on their site:
http://switchedonaustin.com/products/korg-maxi-korg-univox-korg-800
Sir Ruff
Yip2 wrote:
Switched-On just put one up for sale on their site:
http://switchedonaustin.com/products/korg-maxi-korg-univox-korg-800


Thanks! But pricewise, ouch! Never seen one go for that much.
conno
andrewF
HI there AndrewF,
I'm new to muffwiggler. Been a vintage synth tech since '79, mostly in Los Angeles. I was wondering if you still have info on modding the Maxi Korg to have a decent version of a cv & gate retrofit ?
Thanks
Tim
andrewF
Hi conno
welcome to muffs

All the info is in a zip from HERE zip 1.9Mb (or see the post halfway down page 1 of this thread)

Also Cykong's page contains the same info and other mods, HERE

Pretty sure I still have some PCBs left, if you need some, send a pm and I will have a look in the shed. Build notes for the PCBs are HERE
conno
Hey again AndrewF
thanks. I'd like to take advantage of this already being made up, so yes, I'm interested. What kind of $ do you need for it? Can you accept a Paypal ?
Thanks again
Tim
mmp
Whoops... meant to send PM..
andrewF
conno wrote:
What kind of $ do you need for it? Can you accept a Paypal ?

$20 (includes shipping anywhere)
yes to paypal
spinning
Atlas Torso
Hey AndrewF,

Do you still have some pcb available ?

Many thanks and great work Andrew,really !
andrewF
PCBs are back in stock w00t
rimeroni
Hi Andrew,

I just started building this and just want to make sure,
I used BC556 & BC550 instead of BC557 & BC547, as I had them laying around. These should be ok right?
andrewF
Should be fine thumbs up
asrvegas
need a maxikorg cv gate mod
asrvegas
Any left?
andrewF
asrvegas wrote:
Any left?


Yes - still got some w00t
Parnell Paul
kaoss wrote:
andrewF wrote:
Hi guys
I have actually placed the order for these PCBs
.....only 6 months later oops
Just getting 20, 1 is for me, so 19 available.
You will only need 1 PCB for 1 800DV, each PCB has 2 CV circuits and two gate/trigger circuits.

The PCBs will be $20 including shipping to anywhere.
If you want one, just say so on this thread (you can of course change your mind) and I will let you know when they are tested & ready to go.

Given all the hoohaa with xmas & new year I expect they will arrive in mid-Jan.


I'll take one


I'd love to order one board also!!!!!
andrewF
pm'd
elmegil
I have some detail questions that I'm unclear on even after reading the doc and cykong's site and looking through the bundle of images.

Cykong cites a 3PDT and 4PDT switch, but it's not clear at all how he wires those up. I can see a 4PDT for CVs/Gates, and a 3PDT on-on-on for repeat (gate 1, gate 2, stock), but that leaves out the S&H gates??

How did you wire yours up? There's only the one switch listed in your doc (for the repeat gate), and from the way I read that it goes to where there's yet another switch in the list of GIF/JPG diagrams.

The other question is where did you mount it? Cykong's stripboard has holes that line up with the screws in the voice board, but the holes in your PCB don't. They *almost* line up between one of the voice board screws and one of the brown PCB screws, but it's off by about a mm or so which leaves me concerned that the mounting won't work well there. Suggestions?

Thanks....
andrewF
The PCB just goes either in the floor of the case or my original one (on veroboard) was mounted to the back of the case. I never planned it to line up with any mounting holes, there is plenty of space to mount it under the PCBs.

Sorry it is not clear but the wires from the mod PCB to the various points on the Korg should go via switches, so you can select external gate/CV or original Korg setup. I used to have a spdt switch for each one....forget maybe 6 or 8, all on the back of the case. I replaced the socket panel with one of my own.

As my 800dv no longer has a keyboard I no longer have any switches and the external inputs are always 'on'.
I'm not entirely sure what cykong is doing with those rotaries either, I pretty much stuck to the e-lab design.
elmegil
Great, thanks for the info smile
elmegil
I'm still scratching my head over the switch layout. I'm not entirely clear on how the S&H and repeat functions work on this synth (owners manual... less than clear smile ), so I'm going to bounce my ideas here if anyone wants to let me know if they make sense, or if I'm way off in the weeds.

So:

Switch 1: 4PDT, both CVs, both EG/Bend/Vib gates, basically on or off for the the external capabilities. Could conceivably do two 2PDTs if I wanted to do upper and lower separately.

Switch 2: DPDT on-on-on (aka 3PDT on-on-on), repeat gate, up connects in the upper voice's external gate, center is normal, down connects in the lower voice's ext gate.

Switch 3: DPDT on-on on, S&H gate, up connects in the upper voice's external gate, center is normal, down connects in the lower voice's ext gate.

I don't see any good way for me to combine switches 2 & 3, and I think the main thing that is confusing me is whether it makes sense to have the repeat & S&H gates separate from the EG gates.

Thoughts?
elmegil
I just got the first switch described above completed last night (had a delay due to a bad switch and no spares), and external is really really weird. If I hold a key on the keyboard, it works as expected. If not, I get whatever the last note the external played repeated with the incoming gates.

This prompted further review of the mods and the circuit and I think I realize what the problem is, and the switch model I describe above will absolutely NOT work.

The repeat and S&H gates are integral to each voice ( first of all ) and so independent. And the S&H gate in particular is just the internal hold of the last key's voltage. Lack of familiarity with the keyboard had me confused on that point.

So for external to work correctly, *all three gates* have to be hooked in for the voice in question.

So the right way to wire this for independent upper/lower external control is two 4PDT switches, one for each voice. Each switch then has CV, key gate, rpt gate, and S&H gate enable or disable.

I plead unusual architecture and weird gate routing in my defense for not understanding how it works prior to this. smile


EDIT: And I still have it slightly wrong there. The S&H is per voice, but the repeat gate is not. So I've wired that so that the non-mod internal gate wiring goes to both of the 4 pole switches for the "off" position, and the center on that pole goes to an additional SPDT switch to select whether the repeat gate is fed from the upper or lower voice.
demian
If you have one more pcb, i'd like to buy it.
andrewF
yes, still have

pm sent
chiasticon
has anyone tried the Kenton cv/gate kit? seems well done. wondering how difficult it is to install; the manual's not online. it's also not cheap.

kenton 800dv cv/gate kit
RAW2019
Hi Andrew,

If you still have i like to buy one also.

And does anybody know where the performance tools are inserted into the system? Is that after the keys and before the vco? I love to use those when using cv/gate.

Thanks!
andrewF
yes still have
sent you a message

all the files for mods are
HERE - DV800 mods

and

HERE - PCB build info
emTu
Hi !

Great job. I want one PCB too.

Thanks !
andrewF
emTu wrote:
Hi !

Great job. I want one PCB too.

Thanks !


Welcome to MUffs

message sent w00t
modularrydavid
andrewF

Hi Andrew. Can you refresh my memory on what your 800DV board controls? To be clear, it can control the repeat rates?

Sorry, viewing thread on my phone so hard to read. Let me know if you have any available still. Thanks much.
andrewF
Yes in stock, US$20 including shipping by regular airmail.

they have 2 CV inputs for the 2 VCOs
and 2 gate inputs which trigger EG/Vib/Bender, S&H and repeat gate.

Not on the PCB, you can also mod VCF cutoff, but this is just a 22k resistor from the jack to the circuit
kipervarg
Does someone have their Maxikorg easily accessible and can measure the length/width? Planning a rack to hold it and it's not yet in my possession.
jabberwalky
I'm about to dive into the project. How is everyone doing the sequencing? I'd ultimately like to sequence both Upper/Lower independently. I thought the Korg sq1 would be a cheap option, but it is unable to convert midi to hz/v (only works via the usb from what I understand) and it also only converts 1 channel.

I also have a Paia midi/cv that's part of my 9700s. As far as I know it doesn't natively output hz/v though. Anyone have experience doing that?

Thanks and happy new year!
wiperactive
jabberwalky Paia do an easy to build linear-to-exponential converter in the shape of the 9756K module. Maybe two of those will take care of upper/lower section hz/v requirement.

EDIT Correction:

Apologies! I believe that's the wrong direction of conversion in this case, though the 9756K could still be worth knowing about for CV traffic in the other direction.
Jruss993
Hey!

Do you have any pcbs left?

I'd love to mod the maxikorg once I get it
andrewF
Pretty sure there are some, will check today
Cymatics
andrewF wrote:
Pretty sure there are some, will check today


I’d be interested in one too if you have another spare, thanks!
andrewF
andrewF wrote:
Pretty sure there are some, will check today


got heaps w00t
MrTea_SF
I need one for my newly acquired DV800!

I just sold my CS5 to a friend, would this work on that as well?

Will DM you.
andrewF
afaik it only works with the dv800
MrTea_SF
What are recommendations for component sellers in the US?

Also, what mods have you guys done besides CV/Gate?
andrewF
In the US best is Mouser but very difficult to navigate if you are new to purchasing components.
Far easier and much cheaper is Tayda
MrTea_SF
I have all but 3 of the components in my Tayda cart, I can't find

10μF electro (at least 35V rating)
78L15 regulator
100nF capacitor (ceramic ok) (2.5mm spacing)

Are there alternatives I can use from that site?

This is my first circuit building project so I am pretty clueless.
andrewF
MrTea_SF wrote:
I have all but 3 of the components in my Tayda cart, I can't find

10μF electro (at least 35V rating)
78L15 regulator
100nF capacitor (ceramic ok) (2.5mm spacing)

Are there alternatives I can use from that site?

This is my first circuit building project so I am pretty clueless.


You can use the 7815, its a bit chunky tho. Also be aware its pinout is opposite the 78L15, so install it backwards - Tayda 7815 Prob best to get a 78L15, ebay will have them cheap.

Tayda 10uF cap

Tayda 100nF cap
MrTea_SF
Thanks for your help again.

Related question...

When do you know to recap old synths?

I recently got the 800DV, Octave Cat and a rare Soviet RMIF Opus. I don't think any of them have been serviced in a while.
elmegil
MrTea_SF wrote:
When do you know to recap old synths?


There's a can of worms.... :-)


Check that the PSU is putting out rated voltages. If not, the PSU alone may be in need of re-capping.

Across the rest of the synth, *MY* watch word is, if it is working to specification, don't mess with it. The main exception being if you see physical changes to caps (usually electros bulging) or leakage, those and ones like them ought to be replaced.

Blindly replacing all the caps in a synth because it's old touches so much of the synth that you're almost as likely to cause a new problem as solve any impending ones.

But there are a lot of more seasoned techs than I am who will disagree. Hence "can of worms".


Edit: IMO more important than how long since servicing is how they were used. If they were in steady use? Probably just fine. If they were mothballed for years, then that's a different matter, there are types of caps that don't like to go without current for extended periods.
MrTea_SF
I see. The guy who sold me the Opus said it would need recapping, some of the rotary knobs need replacing etc too.

I read that you can tell sometimes by noises gear makes when the caps are bad.

The 800 sounds fantastic though love


FYI this is the OPUS.

elmegil
MrTea_SF wrote:
I see. The guy who sold me the Opus said it would need recapping, some of the rotary knobs need replacing etc too.

I read that you can tell sometimes by noises gear makes when the caps are bad.



That Opus is gorgeous.

I have replaced caps that were in the signal path and caused static and noise -- that's *not* performing to spec though.

There's a lot of mythology about recapping or not out there. Like I say, there are experienced techs who would likely agree with the seller, so just take my opinion for what it is -- my opinion smile.
MrTea_SF
elmegil
Thanks!

Back to topic, what was your final mod for the Korg? You mentioned using various switches. Also did you add the filter mod?

The original parts list was missing a few things like the header and the thing that holds the IC's, what should I get?

Also does anyone have an Octave Cat SRM here?
elmegil
Quite honestly the Korg was so long ago, and for someone else, that I don't recall the entire job.
MrTea_SF
I am nearly done building the little mod.

Is there anyway to test it before I install it in the Korg?
MrTea_SF
Another question, I am looking at the "From Accessory" inputs on the back, I am a little confused as they don't seem to be connected to anything.

Do I need to add my own external inputs?
andrewF
On mine, I rewired and relabelled the accessory jacks as I did not use them for anything otherwise.

It is up to you.

Re:Testing
if you put a signal into CV in you should see it at CV out, with a bit of gain added.
Putting in a gate, you should see it at Repeat out. EG/vibe/bender is usally held high so willdrop to 0V when the gate coming in is on.

The SH gate is a bit harder as it pulls down to -V. You could use a LED to check. Connect the Anode (long lead) to Ground and the cathode to the output. It should turn on when the incoming gate is on. Use an super or ultra bright LED as it has a 10k resistor limiting the current.
MrTea_SF
Thanks, I will do the same with the external inputs.

Should I connect the power to the output side of the transformer board is there a better location to do that?
andrewF
MrTea_SF wrote:
Thanks, I will do the same with the external inputs.

Should I connect the power to the output side of the transformer board is there a better location to do that?

Can't remember on mine, but wherever is easy to access will do
MrTea_SF
I read back through this post and trying to figure out the switching, you said you have a switch for everything and elmegil was using 3 switches.

I have 2 x 4DPT switches, can I do it with just those?

1. CV in
2. to switch
3. EG/vib/ben
4. S&H

I was thinking one switch for CV Gate for each voice but elmegil suggested needing another to switch between the gate (master gate?)

Also did you use the foot controller for filter control?
MUFF WIGGLER Forum Index -> General Gear  
Page 1 of 5
Powered by phpBB © phpBB Group