Surf two stage preamp

[dbanner]

Adding a two stage preamp(2xNE5534), first stage non inverting, second stage non inverting, or first stage inverting second stage inverting, which is better way to do this. I noticed surf stock preamp is non inverting.

[dbanner]

Has anyone tried modding surf PI with a two stage preamp. Any advice would be welcome.

[kt315]

DB

they recall it front end. http://www.geotech1.com/forums/searc...earchid=467262

[dbanner]

Yes, the front end, was just asking if anyone actually DID add two stage preamp to surf PI. Instead of theorizing on different simulations.

[dbanner]

KT, seems you had the same idea some time ago to modify bara. I don't want to radically change the front end, just wanted to add two stage preamp and inductively balanced tx an rx coils. Just wanted to know if anyone has actually done these mods to their surf Pi. And if the results are worth the effort. Theoretically yes but there are many other variables, only one way to find out. Re

[6666]

DB

they recall it front end. http://www.geotech1.com/forums/searc...earchid=467262

that link does not work for me

[dbanner]

That's his way of saying do a search

[kt315]

that link does not work for me

that? http://www.geotech1.com/forums/showt...dual-front-end

[dbanner]

that? http://www.geotech1.com/forums/showt...dual-front-end

Yes, that exactly is what I want to try. Something that plugs into socket on PCB.

[dbanner]

Here is two stage preamp. The first stage is inverting. Not so in surf. Pin 2 and 3 have to be swapped and 1k resistor added to pin 2 as in surf, the second stage remains the same. Is this correct?

[kt315]

http://www.geotech1.com/forums/showt...he-Surf-PI-kit

[6666]

that? http://www.geotech1.com/forums/showt...dual-front-end

that works thanks

[6666]

http://www.geotech1.com/forums/showt...he-Surf-PI-kit

there is a very good quote from that thread

With all this in place you will end up with detector having 10+ times more "system" gain compared to original. Then, every imperfection, mechanical, electronics, shield, ground, interference etc, being below threshold level before, now will be clearly audible. At the end, you may have more trouble whit all this instead of any real benefits. Goes just like this: unproportional increase in gain is needed for just modest performance increase. For small gold, fast coil and fast sampling is most important, concentrate your effort on this, modify latter. Best mod for Surf is probably 100% redesigning it from ground

t

[6666]

I seem to recall that some time ago, I think it was davor who said that a two stage pre amp is quicker useing the ++ inputs , the -- was slower.
I hope I got that right.
It would be interesting in using Eric's values from his GS5 dual front end and test this theory out

[dbanner]

Yes, two stage preamp is the way to go, at least for going on to beginner's intermediate level as I am student in metal detectors. The surf PI is beginner's device, adding two stage preamp and inductively balanced coils is next step up. If care is taken in doing modifications properly, then device will perform better. Of course there are other mods which go in tandem with these. The objective should be obvious in that along the way you will gain great deal of knowledge and experience. So it's not just about modifying the device, rather it's about mastering the fundamentals.