I know not a lot of the tube type Regency Range Gain CBs are around. However, if you own one the transmit audio is less than great. The Regency has a wonderful 6AQ5 push pull modulator. Most modulators are single-ended, that is either a single tube 6AQ5 or 6BQ5 tube. Not many CBs have superior push pull audio modulators. The expensive Sonar FS-2340 has 6BQ5 push pull audio. The following mods will increase the bass and clean up the audio overall. The transmit audio response is around 400 Hz. This is not great sounding. The schematic is on line to view the capacitor numbers for replacement. Replace the old electrolytic power supply capacitors. I used JJ 32-32uf & 50-50uf dual section capacitors. These are rated at 500 volts DC. The smaller can cap on the chassis is not available, but room exists for the standard 1-3/8" can. Simply bend the capacitor + leads closer together and insulate the terminals button fasteners with a piece of electrical tape to fit the small chassis hole. The old capacitors are three section. So, add a 10uF @ 450 volt capacitor and a 47uF @ 50 volt audio grade capacitor such as an ELNA Silmic II for C2 (was 20uF). Remember the Silmic and other capacitors are electrolytic type that have a polarity. That is + and - leads. Wire these in the same polarity that is in the radio. All audio chain capacitors are ceramic type. These do not sound near as good as polypropylene type capacitors, but do last forever. So, do not change all the ceramic capacitors in the radio. I refer the capacitors listed below as 'poly type'. All poly type capacitors below are rated at 400 volts or higher. C64 & C65 must stay the same capacitance so use poly type .0047uF. The 6AQ5 audio tubes have limited feedback, thus higher capacitance will cause 'motor boating'. .0047 will play to 150Hz. C67 is .005uf, change to poly type .047uF C63 is .001uF, change to poly type .047uF C80 is .0015uF, change to .047uF C60 is .2uF @ 100 volts, change to ELNA Silmic II at 4.7uF @ 50 volts. You do not have to remove the old .2uF cap & it is extremely difficult to access. So, just add the 4.7uF capacitor. This capacitor makes the most difference in the audio. Now you will have a transmit audio to about 100Hz and same 4000-5000Hz on the high end. The audio is now very high quality like the best CB sets. My radio dead keys 3 watts and swings to 15 watts. That is a lot of forward swing for a tube CB set. Before the mods, I only got 10 watts forward swing. The receiver is most sensitive I ever heard from a tube CB set. The receiver is as good as any solid-state radios and has clearer audio that only a tube can produce. It way out receives the tube type Japanize chassis that many manufactures used. They are known as Robyn T-123 & Robyn T-240, Colt, Kris, Lafayette & Gemtronix. It also outperforms the Courier & Cobra Cam 88 series. Note- The Olson Side Bander II is a Regency Range Gain CB chassis.