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Thunderbolt 305

snippits75

Sr. Member
Nov 11, 2019
508
773
103
Have a very good condition Thunderbolt 305 that has been converted from 6LQ6 to 24LQ6. It's one driving three. I saw it doing 600 PEP watts on a Paradynamic PEP meter. My Daiwa CN-501H does not have true PEP, but does have an average and PEP switch. On the PEP measurement setting, the Thunderbolt does just a tick over 400.

Now to the problem I am having. I can do line recordings from my RCI-2980 20 watt radio to my computer. While using stock dynamic microphones with the amp on, the transmitted sounds like there is a blanket over the mic. Amp off it's crystal clear.

Using an amplified Astatic mic with amp on, the transmitted sound does not sound like a blanket is covering the mic. It does lower the tone on the mic transmit sound just a tad, but it still sounds good.

I have tried three different stock microphones including Ranger SRA-158, Stryker stock mic, and a SuperStar. All of them sound good with the amp off. Turn the amp on, and they sound like they are covered with a blanket...slightly muffled. Have verified this problem over the air while talking to a friend.

I have lowered dead key on my RCI-2980 all the way to one watt, and it's still the same. Amp on carrier watts of 70 to 125 does not change a thing with the stock mics.
 
Last edited:

No don't use it on SSB just AM.

I did not do any work to the Thunderbolt. When I bought it, it was already converted to 24LQ6. I took the top cover off, and it was immaculate on the inside and the outside, so I bought it for a reasonable price.

I am not a tech, so it's hard for me to follow along in the linked thread. For the time being, I will just keep on using the amplified microphone which still sounds good on AM with the amp on. Various stock microphones with amp on sound like crap.

Thanks for the reply!
 
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Place an RF choke (ferrite bead) on the audio cable feeding the recorded audio to the computer. It should be most effective at the computer end of the cable.
 
Amp has been doing good with the 2980. Stock power that does around 7 to 8 watts average.

I just did some more testing, and I do think Shockwave is right. I think the line in from radio to computer is picking up RF with amp on.

Some times a stock mic will sound fine doing a line recording with the amp on, but most of the time not. I called a friend of mine to get on the radio, and he said he could not tell a difference with amp on or off with a stock SuperStar mic.

What was throwing me off was the fact that with an amplified mic doing line recordings they sounded good all the time, but had a slight change to a lower tone. I will get hands on some ferrite, and see what happens.
 
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