CS700 audio improvement

[Mars]

Does anyone have:

- A hardware modification/fix for the shit low TX audio of the CS700; or
- A service manual/schematic for the CS700

Since Connect Systems refuses to fix the CS700 low audio issue, it's time for us to do it ourselves. The issue is hardware related; likely a resistor changeout affecting audio gain on the analog input going to the DSP.

For those whom are unfamiliar, this radio does not have a AGC software/firmware setting, nor does it support adjustment of the TX audio gain/amplitude. The radio is notorious for LOW TX audio. It's one of the main reasons CS came out with the CS750.

I know we're more than capable of fixing this issue. Let's identify the cause and correct the circuit. The amateur DMR community would be grateful for the fix, even if it involves hams shipping their radios' to those of us who are qualified/competent to work on surface mount circuits. The vendor is useless and hasn't done anything whatsoever. If it was Motorola, they'd have a SRN/FSB out and this would be a thing of the past.

 

[Alpha]

If it's fixed in the CS750, then getting a hold of and comparing schematics for both would be the first approach, if they are obtainable. If there is an op-amp in the mic line then a simple resistor change might be sufficient.

 

[Bill_G]

Haven't seen the product. Is this the correct manual for CS700 series portables? A block diagram describes IC601 amp and IC609 codec, but no discrete schematic. A little reverse engineering probably required.

 

[N4KVE]

If it's fixed in the CS750, then getting a hold of and comparing schematics for both would be the first approach, if they are obtainable. If there is an op-amp in the mic line then a simple resistor change might be sufficient.

It's fixed because a different group is writing different CPS for the 750, & the mike gain is now adjustable on the 750, but was not on the 700. Some people actually send in their 700 to be upgraded to a 750. A chip is replaced to use the new CPS, & hold the 65,000 contact list, but no mike gain mod is done by CS. I'm sure somewhere a fix can be implemented. I briefly had a 700 which I brought to a friend on my yearly Montreal visit. I knew where to hold the radio when I spoke, & no one ever complained about my audio, but my friend Steve, VE2FSQ does not hold the radio correctly, & people do complain about his weak audio. GARY

 

[twojaygee]

The service manual in the files section of the Yahoo csidmr board has schematics. There are also schematics and circuit descriptions in the FCC documents zip file in the same location.

https://groups.yahoo.com/neo/groups/csidmr/files/Radio Manual and Related Documents/


jeff

 

[PSEhub]

Slightly related, some of the best audio I have heard from the CS700 was using Moto commercial series RSMs. The audio performance in the CS700s is really not bad, definitely just poor gain/level optimization.

Heating up the internal gain levels is something that would help lots of users.