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

[David Bulog]

thanks for all the info but is the Kenton socket upgrade kit generally  
just a bunch of wires and three sockets and you pay for the  
instructions on how to do it and there would not be really be a  
benefit over DIY with the detailed info at cykong



>>
>> 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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>>>
>>>
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>> --
>> Harry Bissell & Nora Abdullah 4eva
>>