Dual Offest Sub-audio Test Signal

"David Eather"
>> Phil Allison
>>
  ( big snip)

> ** Harrison ( editor of ETI magazine in the 1980s) was a ham radio 
> ru   - so knew little about electronics ....
>
> He was obliged to trust contributors and staff alike, having no way nor 
> much interest in seeing through the smoke and mirrors game that was going 
> on.
> There were a number of front page projects that simply did not work, but 
> he was not interested in hearing about any of them nor the scam "TIC" 
> brand,
> fake MJ15003/4 power transistors that DSE had imported thousands of.
>
>
> I remember them. I had a job at DSE and they sent around memos (and a 
> weekly video) claiming they were all kosher but a lot of people knew the 
> truth.

** Just in case any of the regulars think  "TIC" = Texas Instrument 
Corporation  -  in this case, it does not.

The initials stood for the "Transistor Instrument Co."  of Florida.  A 100% 
scam business whose only expertise was screen printing new numbers and logos 
on reject and discarded TO3 devices.

FYI:  when tested, most of the devices marked " TIC" and  "MJ15003/4 " 
turned out to be high voltage switches or power Darlingtons.



....  Phil

On Sunday, May 25, 2014 5:37:18 PM UTC-4, jgil...@netscan.com wrote:
> On Sun, 25 May 2014 03:23:49 -0500, John Fields
> 
> <jfields@austininstruments.com> wrote:
> 
> 
> 
> 
> 
> >I'm late into the fray.
> 
> >
> 
> >Is your supply's output: +6V 0V -6V or is it lacking a common?
> 
> >
> 
> 
> 
> Hello John. To achieve the waveforms shown below, I believe the coils
> 
> cannot be ground referenced. Maybe I am wrong, but so far I do not see
> 
> any other suggestion that would do this.
> 
> 
> 
> http://www.4shared.com/download/Z_6zeE2yce/dual_dc_offset.jpg?lgfp=3000
> 
> 
> 
> I know this is not a conventional design, however some viewers have
> 
> kindly sent in circuits that appear to address the problem, and
> 
> correct my own flawed attempts.
> 
> 
> 
> https://dl.dropboxusercontent.com/u/16764432/SED_JG_MAY14_a1.pdf
> 
> 
> 
> http://www.digikey.com/schemeit/#u7g
> 
> 
> 
> I know you are one of the long-time "experts" here, so if you have any
> 
> comments they would be most appreciated.
> 
> 
> 
> John Gallimore

Hi John G,  
So have you got this working yet?

I might try something like this.  (I'm an opamp type of guy.)
https://www.dropbox.com/s/u8684izdbylf68a/DSCF0019.JPG

The TCA0372's should be fine at your required ~100mA.  

You'd make the +/- 4 volts from resistor dividers or reference's
 depending on how stable you wanted them.  

Can you tell us what this is for?

George h.