TGSL EDU Mod

[morganton]

I'm building the TGSL - EDU kit from silverdog and I wanted to incorporate the mod described here before testing:

http://www.geotech1.com/forums/showthread.php?21579-TGSL-EDU-Mod&highlight=mod

"Remove D8, D9, C20, C23, R33 and put diodes at C20 and C23 reversed from D10 and D11
and change R29 and R31 to 1 meg."

I have attached a photo of my board with the changed/removed components outlined in white. Is this correct regarding components to change?

It seems that silverdog's PCB kit already had changed R29 and R31 to 1M from 470K, so I just used those kit components. Correct?

If anyone has any other mods I missed in reading thought the forum that I should consider before moving on to the next step, I'd appreciate that info too.

Thanks.

[paku]

can i ask! why you mod the tgsl component ?

[satdaveuk]

it ups the gain (more sensitive)

[dfbowers]

The mods are a two edged sword. It makes it more sensitive but you loose stability to some degree. I went with 470k for R29 and R31. Depth is quite adequate without the mods. Plus the shining feature with the TGSL is discrimination, not depth.

[paku]

but TGSL is still not stability without mod

[dfbowers]

but TGSL is still not stability without mod

R29 and R31 are feedback resistors for the OP AMPS. 1M OHM resistors more than double the gain.

[morganton]

R29 and R31 are feedback resistors for the OP AMPS. 1M OHM resistors more than double the gain.

Would you recommend keeping the other changes of the "Mod" while using 470K's for R29 and R31?

[dfbowers]

Would you recommend keeping the other changes of the "Mod" while using 470K's for R29 and R31?

I kept everything else. Other improvements were the audio and slower filters.

[morganton]

I kept everything else. Other improvements were the audio and slower filters.

Thanks.

[Prospekteur]

"Would you recommend keeping the other changes of the "Mod" while using 470K's for R29 and R31"
"I kept everything else. Other improvements were the audio and slower filters."

I have tested the mod without cganging 470K's (r29,r31). Performance is better (snappier sound and better hearing of depth). But the readings of Arduino-VDI is bad:-(. It doesnt read all around zero....you cant read "foil" with the mod. Without that mod my Vdi has perfect accuracy, with the mod the reading are very jumpy. I use the twotone mod too. I think this two things didnt work very good together.

I will change my Tgsl back to the "original" layout;-).

[bernte_one]

possible to change the two Feedback ressitors, with one Stereo pot, or a simple Switch normal mode and boost mode, or?
so you have clear disc if you need it, and better depth if disc is not important

[Prospekteur]

a switch or stereopot as "Boostmode" is a good option and a good idea;-) i test it and will attach it to my device........one feature more;-)

[morganton]

"possible to change the two Feedback ressitors, with one Stereo pot, or a simple Switch normal mode and boost mode, or?
so you have clear disc if you need it, and better depth if disc is not important"


Yes, that's a good idea about the dual pot.

[ashefr10]

I read in a forum that was better than the NJM2068 LF353 when in fact it is not better and more we are readjusted obbligé of the GEB but in terms of detection depth that does not change anything.

[Davor]

You'd experience a quieter operation if resistors R13-16 are reduced proportionally by ~1/3. NJM2068 is better not only because of lower noise (which you can't obtain with the current values of R13-16) but more so because of better distortion.