CS 700 External Sp/Mic low audio fix

Spoke to :  Connect Systems Inc Chris Edwards - 10/26/2015
Contact :  Chris Edwards
The only way to adjust the volume, is HARDWARE mod., or upgrade to Newer Model CS750.
To adjust the volume of CS700 = upgrade to CS750 = $60.00 send unit to Connect Systems
- Only FIX is an upgrade to the new model CS750 !!!

CS 700 External Sp/Mic microphone low audio fix

1) Remove the 5 screws holding the external mic. together. Remove back cover.

2) Gently but firmly take out the Mic. (by pulling it from the wires), located in upper right corner above the PTT. Clean and enlarge the 2 small holes in the plastic housing if needed.

3) Take out the small circuit board holding the PTT switch.With a soldering iron, remove the little 0402 resistor located on the back of the board. (You can solder it on a side if you don't want to lose it, if you ever want to put it back. You just need sharp tweezers.).

4) Put everything back. It is OK if you don't push the mic completely into the slot, so that it has about 1/16 inch gap to the bottom of location.

I can talk into that mic in normal voice now, and nobody will say it is to low. Before, I had to shout waking up all neighbors, and it was still to low. So i stopped using external mic. until now.

Here is a photo of the removed resistor soldered on a side. See inside the red circle, that is where the resistor was:

Let us know how the mod works for you, in the comments below.

But here are a few things to consider:

1) Not all CS700 radios have the "low level" problem. I have spoken with several CS700 owners on DMR, and most of them sound just fine on their radios, comparable to the way more expensive HTs. Similar, when I am in a group QSO, the others don't notice significant difference between my CS700 (with modded external mic.) and the more expensive radios.

2) If your radio has very low audio, they will replace it under warranty.

3) There is a new firmware coming out soon, that is likely to solve the problem. CSI are aware of the issue.

4) In the worst case, if the new firmware will not address the problem, it is possible to increase the mic. gain (for both the internal and the external one) by opening the radio and replacing 1 resistor. (change the gain of the microphone amplifier by 3-6 dB). This method may void your warranty since you have to open the radio.
I will post this method on this forum if anybody is interested.

Conclusion: For $180 you can not beat this DMR/Analog radio. Some reported that it is solid built and that it can take some significant level of abuse (like dropping it and banging it against hard surfaces).

The service manual is quite well done too. So if you are not afraid to open a radio, you have nothing to lose with CS700. And even if you don't feel comfortable doing it, CSI are very supportive and very HAM friendly.


  1. Anonymous10/26/2015

    I find no samll resistir on the back of the board.
    Do you mean that the little metal block that the switch is mounted in needs to have the 4 pads unsoldered and the little metal block needs to be lifted off the board in order to see the resistor?

    I do see a component mounted between the 2 solder terminals coming out of the back if the Mic which could be cut out with a set of cutters. Thought it might be a cap to prevent any hum.

  2. Anonymous10/26/2015

    Tonight 7 Dec checked out the photo after it being mentioned by you on DMR. Opened up the Orig Mic again and would you believe there is no resistor on the board at the location you show. Evidently your Mic was an early run and then CSI in order to try to resolve problem on future runs did not install the resistor.
    Here we are back to square 1.
    John W6FE

  3. Spoke to : Connect Systems Inc - Chris Edwards - 10/26/2015
    Contact : Chris Edwards
    The only way to adjust the volume, is HARDWARE mod., or upgrade to Newer Model CS750.
    Cost to adjust the volume of CS700 = upgrade to CS750 = $60.00
    - Only FIX is an upgrade model CS750 !!!


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