[sdiy] Fairchild uA726

[Mike Gorman]

Gergo,

As if I haven't got enough projects on the go already (60U of an MOTM style
synth, of which 3U has been completed so far and an E&MM Spectrum synth
build), you go and find me another one.

Marc Bareille's Polivoks filter does look nice though.

Regards

Mike Gorman

-----Original Message-----
From: Gergo Palatinszky [mailto:Gergo_Palatinszky at epam.com] 
Sent: 24 September 2009 12:33
To: Mike Gorman; 'synth-diy'
Subject: RE: [sdiy] Fairchild uA726

Hi,

So let's build Polivoks filter(s) from uA776s :O)

Br,
	Pala

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Mike Gorman
Sent: 2009. szeptember 24. 13:26
To: 'synth-diy'
Subject: RE: [sdiy] Fairchild uA726

Graham,

I've just spotted a minor cock-up by me. It appears that I ordered uA776's
rather than the uA726's I intended, a good typo methinks. It sort of gave
the game away when I spotted that they were only 8 pin devices rather than
10 pin. That would pretty much explain the date code issue as well.

Ah well, back to the drawing board. I've requested a quote from utsource for
uA726's anyway, to see what sort of price they come back with.

Regards

Mike Gorman

-----Original Message-----
From: Graham Atkins [mailto:gatkins at blueyonder.co.uk] 
Sent: 24 September 2009 12:04
To: Mike Gorman
Cc: 'synth-diy'
Subject: Re: [sdiy] Fairchild uA726

In the "Datasheet Archive" the most recent Fairchild catalogue with them
listed is dated 1977. I've just checked the 3 I bought around 2001 as  
NOS
and they are dated between 1976 and 1978. I would be suspicious of any
device much more recent than the 80's although I do not know when
production ended.

Graham

On 24 Sep 2009, at 09:59, Mike Gorman wrote:

> Geoff,
>
> The three that I received from utsource have a date code of 9850, so
> hopefully they aren't parts from the eBay scam.
>
> It will be a while before I can test them, but I've just had a look  
> at the
> Formant circuit and it should be possible to breadboard part of the  
> Formant
> Oscillator to see if these chips are working. I might give them a  
> try next
> week sometime.
>
> Regards
>
> Magman
>
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of geoff james
> Sent: 24 September 2009 08:49
> To: synth-diy
> Subject: Fw: [sdiy] Fairchild uA726
>
> Hi all , are these possibly the knock offs that were for sale on ebay.
> The image they show seems to indicate they were manufactured in 2005.
> Maybe not the real deal. Go look--www.utsource.net
> Regards
> Geoff
> ----- Original Message -----
> From: "Carsten Tönsmann" <carsten at analog-monster.de>
> To: "David G. Dixon" <dixon at interchange.ubc.ca>;
> <synth-diy at dropmix.xs4all.nl>
> Sent: Thursday, September 24, 2009 2:09 PM
> Subject: Re: [sdiy] Fairchild uA726
>
>
>>
>> The old Formant VCOs did.
>>
>> Carsten
>>
>> ----- Original Message -----
>> From: "David G. Dixon" <dixon at interchange.ubc.ca>
>> To: <synth-diy at dropmix.xs4all.nl>
>> Sent: Wednesday, September 23, 2009 7:50 PM
>> Subject: [sdiy] Fairchild uA726
>>
>>
>>> I was flipping through a fantastic (albeit very old: 1976) book I  
>>> found
>>> languishing in the stacks of the UBC library, the "Handbook of
>>> Operational
>>> Amplifier Circuit Design" by Stout and Kaufman.  I was studying the
>>> schematic for "a differential-input logarithmic amplifier with  
>>> adjustable
>>> gain and logarithm base" in Fig. 17.1 on page 17-2, when I came  
>>> upon this
>>> passage:
>>>
>>> "Several other design tricks will keep this circuit from drifting  
>>> with
>>> temperature.  Transistors Q1 and Q2 should be a matched pair of  
>>> devices
>>> on
>>> one chip.  Ideally they should be gain-regulated such as the uA726
>>> temperature-controlled differential pair (Fairchild).  This device  
>>> has
>>> active temperature-regulating circuitry on the same chip as the  
>>> matched
>>> pair
>>> so that external temperature sources have no effect on transistor
>>> parameters."
>>>
>>> This sounds like the ideal device for building expo converters.   
>>> However,
>>> I
>>> could find no reference to it on Google, and no datasheet in the
>>> datasheetcatalog.com database.  Does anyone here know of this  
>>> chip?  Is
>>> anything similar still being manufactured?  Did any vintage synths  
>>> use
>>> it?
>>>
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at dropmix.xs4all.nl
>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
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