Am radio to drive DX-500?

[338_MtRushmore]

I am going to get a new am radio to pair with my dx500. Is a cobra 29 or 148 enough to drive it? I'm not looking for 600+ out of it, heck I'd be good with 300. Would I be better off with something like a connex 3300? Also, is it a problem that my truck runs at 15 to 15.2 volts? I would assume that if I keep it under 400 watts it shouldn't make much difference? Thanks

 

[222DBFL]

Not sure the DEI transistors will handle the voltage. Have to check the spec sheet for the max voltage they can take. As far as a radio, yes the cobra 29 or 148 would make about 300 watts output depending on how it's setup power wise. I get about 250-300 watts from my TNT 600hd with a uniden 980 set at about 2 watts dead key and swinging to about 8 watts pep. But my amp has Toshiba 2879's. Here is a quick overview. Looks like 14vdc max is what they will take. Don't know if I'd risk 15 or more volts.
Hope this helps.
2SC2879-DEI Transistor
2SC2879-DEI SILICON NPN TRANSISTOR

2-30MHz SSB LINEAR POWER AMPLIFIER APPLICATIONS.
(LOW SUPPLY VOLTAGE USE)

• Specified 12.5V, 28MHz Characteristics
• Output Power : Po= UP TO 100WPEP MAX

NOTE: Please follow these guidelines when using this part:

• MAX VOLTAGE 14v.
• Typical power is 90% of original Toshiba part.
• Cannot mix this part with original Toshiba. If replacing parts in circuit, you must replace all the parts with same manufacturer.

 

[543_Dallas]

I'd use the Cobra 29. You will probably be ok at 15 volts but the issue with higher voltage is that the Texas Star is biased. The bias circuit being unregulated will make matters worse. As voltage increases the transistors will draw more bias current. Proceed with caution

 

[338_MtRushmore]

I'd use the Cobra 29. You will probably be ok at 15 volts but the issue with higher voltage is that the Texas Star is biased. The bias circuit being unregulated will make matters worse. As voltage increases the transistors will draw more bias current. Proceed with caution

I knew the these amps didn't like over voltage, but I didn't know what the actual reason was. I think it is wired with about 12 feet of 4 Guage so I'd probably lose a fair amount of voltage on key up. Would that make a difference, or is 15 volts unkeyed just as bad? Then there is the issue of finding someone to checkout the amp since it made a little smoke on my last attempt.

 

[543_Dallas]

I knew the these amps didn't like over voltage, but I didn't know what the actual reason was. I think it is wired with about 12 feet of 4 Guage so I'd probably lose a fair amount of voltage on key up. Would that make a difference, or is 15 volts unkeyed just as bad? Then there is the issue of finding someone to checkout the amp since it made a little smoke on my last attempt.

With that wire you should have very little voltage drop.The bias circuit is off when the amplifier is not keyed so it's not a big deal if the voltage floats up a bit. As long as you are running it conservatively and it stays cool I don't think you'll have an issue because of voltage. Something else underlying may cause a failure at any voltage.

I have ran amplifiers like that on 15 to 16 volts just so they would draw more bias current and loafed them along. Most people that volt an amp are looking for maximum output and it fails. If it's released some smoke in the past who knows what could be wrong with it. If it has those DEI transistors in it I'm not sure how it will hold up.