I'll buy this. You can key a transistor radio right through a tube box, or you can key it all up at once. I'd also be aware of "pitting" on the relay contactors, but there is no other "detriment", or catastrophic failure that I'm aware of.
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tube box drive pill box or vice versa
- Thread starter fatboy
- Start date
I'll buy this. You can key a transistor radio right through a tube box, or you can key it all up at once. I'd also be aware of "pitting" on the relay contactors, but there is no other "detriment", or catastrophic failure that I'm aware of.
While "shit in = shit out", the last amp in-line dictates the class of operation.
If the tube box had it's RF input connector at any DC voltage other then zero, it means the DC blocking cap on the input is shorted or missing. This would allow bias voltage to arrive at the input. If you drive that amp with something that appears as an open to DC it would work fine. Most equipment has the output at DC ground and this would short the negative bias on that tube amp without the blocking cap.
One thing I would like to add for those situations where you use a transistor driver on a tube amp. One bag of garbage in is 20 bags of garbage out. If you choose a transistor driver make sure it's of good quality, don't overdrive it, and consider a low pass filter between it and the final amp. When designed and operated correctly there is no difference in sound quality between the tube driver and the transistor one. The main advantage the tube has is high power in a single device.
Nope, I didn't say that at all. A class C driver will always be class C. If you run that class C driver into a class AB-1 tube amp for example, your final class of operation will be AB-1. But again, shit in = shit out regardless of class of operation.
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Quote:
You key the mic and then put the pedal down, when done talking you have to get off the pedal and then un-key the mic. With tube on tube if your timing is off no big deal. With a transistor radio if your foot stays down when you un-key the radio bad things happen.
Just to make sure I understand, are you saying it is bad for the radio, or the Amp?
I have ran several Tube Amps with Transistor radios, and never had a problem as far as the radio is concerned. If you are driving a lot of input into the amp, I would close the relay first...a lot of the old tube amps do not use vacuum relays and I would not want a load on the contacts when they close, and I would UN-key the radio/driver before I open the foot switch, this increases the chance of pitting the contacts. "
I'm just going by what I can remember an old timer told me maybe 10 years ago. The guy has passed away but he used to build tube amplifiers and service tube radio's. Most of his big tubers had a foot pedal. I thought it could damage the transistor radio if you had the pedal down and un-keyed the radio. He preferred tube driving tube with a foot pedal.
Quote:
You key the mic and then put the pedal down, when done talking you have to get off the pedal and then un-key the mic. With tube on tube if your timing is off no big deal. With a transistor radio if your foot stays down when you un-key the radio bad things happen.
Just to make sure I understand, are you saying it is bad for the radio, or the Amp?
I have ran several Tube Amps with Transistor radios, and never had a problem as far as the radio is concerned. If you are driving a lot of input into the amp, I would close the relay first...a lot of the old tube amps do not use vacuum relays and I would not want a load on the contacts when they close, and I would UN-key the radio/driver before I open the foot switch, this increases the chance of pitting the contacts. "
I'm just going by what I can remember an old timer told me maybe 10 years ago. The guy has passed away but he used to build tube amplifiers and service tube radio's. Most of his big tubers had a foot pedal. I thought it could damage the transistor radio if you had the pedal down and un-keyed the radio. He preferred tube driving tube with a foot pedal.
I have to Dis-agree...
If the Class C driver is CREATING distortion, the Class AB final amp will simply take that distorted signal and increase it.....the "class of operation" of the final amp will not change.. (Distortion is "created by using" a class c amp as a driver)..I think this is what 359 meant when he said..
"Donkey Poo in = Donkey Poo out"
Agreed?
73
Jeff
Good Input......So if the Amp is poorly built/damaged ( missing/shorted DC blocking cap) it "could cause damage to the transceiver"
On a properly built/operating amp, It should be no problem?
I have a tube amp that I run regularly that is switched manually and i always close the relay before keying the radio, never had a problem.
I used to have a old "Sky Hook" Amp that the relay was actually closed by contacts in the Mic......kind of crude, but it worked.
73
Jeff
Agreed.
If you take a SBB transistor radio, drive it into a class C transistor driver amplifier and then into class AB-1 tube final amplifier, none of the classes of operation will change. Your final class of operation will still be AB-1 and your driver stage will still be C (and the radio probably B, I dunno). You can't change that.
HOWEVER, distortion created by the class C driver will then be amplified by the AB-1 final. You can most certainly have a "dirty" AB-1 signal, and this is one way to do it, but that doesn't mean that the class of operation has changed. You'll just have a cleaner, dirty signal, lol.
Understand now?
It has already been said RF is RF.
If your theory was true driving a tube amplifier with a solid state radio would cause issues and the same goes for driving a tube radio into a solid state amplifier. Just another CB myth.
So I would be txing Doo,dOO in class ab-1, lol, good point so why do it is the next ?
LoL....Why to do it?
One should not....but often it happens.
Class C Amps are very available on the internet, and the price is almost always lower than a better built class ab amp.....a lot of guys can not tell the difference,and some just do not care.
It is good that we debate this topic, over time it helps to dispense with a lot of BS that gets posted on the interneck.
73
Jeff
- No one is chatting at the moment.
...runna pile-up on 6m SSB
W4AXW in the air