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

[Harry Bissell]

Of course we know (now) they were not potted, but had a plastic cover like the ARP
submodules. From the photo they ~might~ have been potted.  I don't see the potting as much
as technological innovation, but as a deterrent to reverse engineering. Which of course only
slows the competition down, not stops them...  :^)

H^) harry


----- Original Message -----
From: cheater cheater <cheater00 at gmail.com>
To: Harry Bissell <harrybissell at wowway.com>
Cc: : Heaven <analogue at hyperreal.org>, Synth DIY <synth-diy at dropmix.xs4all.nl>
Sent: Mon, 26 Jul 2010 12:49:46 -0400 (EDT)
Subject: Re: [sdiy] [AH] KORG 700S CV Hz/V / gate retrofit

You mean like a potted IC?
http://en.wikipedia.org/wiki/Operational_amplifier#1961:_First_discrete_IC_op-amps
:^)

notice the first IC pictured under the "First IC op amp" heading there
isn't even potted. Potting was an improvement in the technological
process! Harry I know you know, but you know I know some don't know
;-)

Cheers,
D.


On Mon, Jul 26, 2010 at 16:19, Harry Bissell <harrybissell at wowway.com> wrote:
> They look a lot like the ARP modules... more of a potted subcircuit than an "IC"
>
> H^) harry
>
>
> ----- Original Message -----
> From: cheater cheater <cheater00 at gmail.com>
> To: Tony Kalomiris <ic1 at bell.net>
> Cc: : Heaven <analogue at hyperreal.org>, Synth DIY <synth-diy at dropmix.xs4all.nl>
> Sent: Mon, 26 Jul 2010 10:10:55 -0400 (EDT)
> Subject: Re: [sdiy] [AH] KORG 700S CV Hz/V / gate retrofit
>
> 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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>>>
>>
>>
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> --
> Harry Bissell & Nora Abdullah 4eva
>

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Harry Bissell & Nora Abdullah 4eva