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**Reg** · 09-01-2006, 01:28 PM

Hi Gef,

Right now, there are no obvious improvements available for the HH amp that I know of.

You might check to see if your battery voltage is drooping when the audio comes on. This could cause what you are experiencing. If so, you might want to reduce the signal by adjusting R 41. If setting this resistor at a higher resistance value helps dramatically, then the problem is most likely a voltage droop problem.

My guess, this is what is happening, since it is a common problem.

You could reduce the pulse current some and this would help. However, the best fix is to use a regulator on the power supply to the HH.

By this I mean, you could use a couple more batteries and the regulate the voltage back to 12V. DO NOT SIMPLY ADD A COUPLE OF BATTERIES WITHOUT THE REGULATOR CIRCUITRY. THE VOLTAGE WILL BE TOO HIGH AND WILL CAUSE DAMAGE.

I personally use 4 Li Ion batteries which has an output of about 14 to 15V and the this feeds to a -12V regulator circuit so the voltage to the HH circuity is back to the required 12V. The regulator circuit stabilizes and minimizes this current/voltage drop problem. Also, the use of heavier current capability batteries also minimizes the problem, such as using the Li Ion types.

One could build a simple separately powered amplifier to power the headphones or speaker and then capacitively couple the signal to this amp. This would reduce the problem dramatically since there would not be the interaction between the speaker current and the pulse current. This amplifier could be as simple as a single transistor circuit.

The mini Radio Shack amp works but is a little touchy and works best when using the speaker on the RS amp.

If you decide to go this route of using an external amp, you should set R 41 for maximum resistance and add a 500 ohm across the speaker terminals on the HH board. and the add a 100 uf bi-polar cap to the junction of the R 41 and the 500 ohm resistor. The other leg of this cap will connect to something like a 5K which has its other leg connected to ground. The junction of the cap and the 5K is then fed to the external amp.

Now, adjusting R 41 will will adjust the volume somewhat. Also, you might have to adjust values of resistors or even the cap value depending upon the amplifier used.

Reg

**gef12** · 09-02-2006, 09:57 AM

Hi Reg

THanks for you assistance
Yes have already made a separate amp and is powered independently via 9v battery .. works really good .. i have coupled it via transformer so as to not affect other circuit workings. .. also have tried to power it from the HH but am having some problems .. so did away with that and went back to the original idea of separate amp and power supply.
Also picked up a second hand small coiltek coil 10in oval shape.. and is picking up my .9 gram nugget at about 4inch .. of which i am happy with.
Thanks again Reg

Gef

**gef12** · 09-02-2006, 10:03 AM

Reg

Sorry forgot my other piece
The idea of shooting 14 - 15 volts into the circuit is good too .. might well try that also
Thanks for the info ..
Tell me how many controls have you made accessable on the panel ..
I have all .. but wish to cut back on some .. just curious mate

thanks again
gef

**Reg** · 09-24-2006, 09:30 PM

Hi Gef,

I have several controls brought out on my PI. I have the on/off/threshold, the main delay, the pulse width, the pulse rate, a sensitivity control, and the autotune.

Of those, about the only one I might consider removing would be the pulse width.

Reg

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