[sdiy] [AH] KORG 700S CV Hz/V / gate retrofit

[cheater cheater]

The 700S has epoxied ICs?
Woah, didn't know that.

D.

On Mon, Jul 26, 2010 at 15:00, Tony Kalomiris <ic1 at bell.net> wrote:
> I'm currently working on a MiniKorg that's in for repair and I've also been looking at some mods for it.
> The keyboard is an exponentially weighted design like in the MS20, but unlike the MS I don't think there is an exponential converter in the 700.
> I'll need to have another look at the schematic, if there is one you can feed in a 1 V/OCT input properly scaled and tuned - you can do this to the MS if you fine tune the scaling at the CV input summer - add a trimmer of 100 ohms in parallel with expo base IIRC to go from 21 mV/oct to the required 18 mV/oct for a 1 v input change.
>
> Of course I'm only working with one sheet from the service manual. Does anybody have the manual or a link to one...I should buy these darn things to have in stock already !
>
> Btw, I'm tempted to pop open those Keio (epoxied ?) modules, and see what's lurking in there..;-)
>
> Tony
>
> On 2010-07-25, at 4:58 PM, cheater cheater wrote:
>
>> On Sun, Jul 25, 2010 at 21:15, David Bulog <d2ba at xtra.co.nz> wrote:
>>> Korg 700S was used entirely for this classic track
>>> http://www.youtube.com/watch?v=S5QErPDNcj4
>>
>> This demo... is not especially encouraging the purchase of a Korg 700S.
>>
>>> Hi there has anyone done CV Hz/V / gate retrofit to e Korg 700S
>>> I have two ways to go--Kenton which would ensure a good match for any of
>>> there midi -cv interfaces
>>> http://www.kentonuk.com/products/items/sockets/korg/700s.shtml
>>>
>>> or DIY
>>> full mod diag
>>> http://www.cykong.com/Synths/Korg%20700S/Images/Korg700-CVGateInModFull-Schmo.gif
>>
>> What you're looking for is an exponential converter. Those can be had
>> in many forms and most VCOs with linear FM input have an exponential
>> converter. You might want to look at a 2164 based one, they're
>> extremely stable. I think David Dixon had some boards for his VCO, but
>> not sure. You'd take the VCO and stuff just the exponential converter,
>> basically, and maybe or maybe not you'd need to add a current->voltage
>> converter with gain but that's not a big thing if it's needed at all.
>>
>> The DIY one you have posted doesn't seem to have any temperature
>> compensation and does not use precision voltage references, so it'll
>> be quite crap I think. That doesn't mean the Kenton's much better,
>> it's probably just as bad. SSM 2164 based exponential converters are
>> currently the best ones you can get, and the chips aren't expensive at
>> all.
>>
>> Cheers,
>> D.
>>
>>
>>> part 1
>>> http://www.cykong.com/Synths/Korg%20700S/Korg700S-Mods1..htm#Proper%20External%20CV/Gate%20In
>>> part 2
>>> http://www.cykong.com/Synths/Korg%20700S/ElabJapan/ElabKorg700CVGateMod.htm
>>>
>>> thanks in advance
>>> David
>>> To: analogue at hyperreal.org,
>>> From: Zane Whitaker zanewh2000 at yahoo.com,
>>> cc:
>>> Subject: [AH] MiniKorg Mod Woes
>>> Date: Tue, 2 Dec 2008 17:38:38 -0800 (PST)
>>>
>>> ________________________________
>>> Hello AH'ers.
>>>
>>> Long time archives lurker here. I have posted once or twice since around
>>> 2002, usually when one of my synths breaks, and this is no exception.
>>>
>>> A little background first:
>>> This site:
>>> "http://www.cykong.com/Synths/Korg%20700S/Korg700S.htm"rg700S.htm" is the
>>> most common source of information for Minikorg mods. I previously did the
>>> 'basic' CV/Gate and Audio Filter-In mods with no problems. By basic, I mean
>>> I didn't need to build the buffer/tuner circuit, as you get everything but
>>> the repeat function without it, and you don't even need to hold down a key
>>> to use the external Gate, at least not on mine.
>>> is the most common source of information for Minikorg mods. I previously did
>>> the 'basic' CV/Gate and Audio Filter-In mods with no problems. By basic, I
>>> mean I didn't need to build the buffer/tuner circuit, as you get everything
>>> but the repeat function without it, and you don't even need to hold down a
>>> key to use the external Gate, at least not on mine.
>>>
>>>
>>> BTW
>>>
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