Carl Built 400HDHG Amplifier / 2SC2879 Wattage Help

[Capt Crunch]

First may I say I love my 400HDHG Amp and Carl is good people. That being said, I have read on spec sheets 1 2SC2879 transistor max in says 10 watts PEP each. Carl says on his website about the amp "400 4 hg 2879, Class C bias, fan cooled. Max amp draw 110a, install recommended with 4ga wire and 125a fuse. Max input carrier of 10 w or 175w max carrier from amp. Max peak input 150w". I also asked him again later on and he replied "Key amp around 180 max and keep peak in amp around 100 watts". Also there are review videos of the 400hd with an "FCC" radio and then usually hook up a Stryker 955 doing 80+watts pep. When they hook the 955 up they say that it was about half the power this amp likes. One pushed 2X2290s @ 160 watts pep into it and it did 675 watts PEP. If true, how is that possible. I understand how high people have had these transistors but is it possible to talk for periods of time with no issues that high? Is there something they do and/or the amps class that makes that possible, or should I just follow the transistors specs when using mine? Right now I am using a stock Galaxy DX979 doing about 30 watts PEP. Trying to decide if I should get a 1x or 2x 2290 driver for the 400hd. Thanks in advance. Here is my amp at Carl's bench.

 

[freecell]

anything is possible when the transistors are operating in their saturation region.

 

[Rick Miller]

May just be me, but I tend to look at parts specifications. I know I've had good luck using a single 2290 as a driver for 4 2879's. Specs would indicate @ 40W of drive, although a 2290 does a little more than that, it's well matched. Beyond that you're really pushing it into saturation. It may show more on a watt meter, but what does a spectrum analyzer show?

 

[groundwire]

Take the 500w-600w you get out of it and be happy. Thats what it is meant to do and it will last you a lifetime. Everyone always wants to push their amps to the limit and beyond. "Im gonna get a 1×2 to drive my 4pill, then i can get the 1200w they say it can do", If you want bigger watts, buy a bigger amp.

 

[freecell]

Capt Crunch posted:
"One pushed 2X2290s @ 160 watts pep into it and it did 675 watts PEP."

let's look at the gain of the 4X2SC2879. the minimum gain of a 2SC2879 is 13 db. with a power multiplier factor of 20X. in a transistor rated for 100W PEP output at 13 db. the required drive input for full modulated power output is 5W PEP., i.e., 20X 5W PEP = 100W PEP X 4X2SC2879 = 400W PEP. with 20W PEP input. now let's get crazy and increase the drive input to 40W PEP input and use your input and output figures of 160 and 675. the power multiplier factor is now reduced to 4.28175X. this ratio translates to a reduction in gain of all four transistors from 13 db. to 6.25 dB., a whopping 6.75 dB. below the 2879's minimum rated gain. at a reduction of only 1 dB. the transistors are already 1dB. into the compression curve/region and we still have an additional 5.75 dB. loss in gain to account for. the devices have moved out of and beyond the active region and are in deep saturation. if you drive them like this then with regard to saturation, that ship has already sailed. now the question is not if she's gonna blow, but when.

in addition, the other bad thing with regard to running them like this is that if you should have any kind of an antenna or feedline problem between the amplifier and the antenna (an open or short) then you have completely lost the ability of the 4X2879 transistors to shrug off any swr conditions that might result in destruction of the transistors from a 15, 20 or even a 30:1 swr.. that safety factor is gone.

and all of this is for what? for an extra 2.2 dB. of gain over operating them at 400W PEP which is sad because under real time conditions no one is ever going to notice the difference in signal strength.

dB. gain = 10log (power output divided by power input)
dB. loss = 10log (power input divided by power output)

 

[Capt Crunch]

Capt Crunch posted:
"One pushed 2X2290s @ 160 watts pep into it and it did 675 watts PEP."

let's look at the gain of the 4X2SC2879. the minimum gain of a 2SC2879 is 13 db. with a power multiplier factor of 20X. in a transistor rated for 100W PEP output at 13 db. the required drive input for full modulated power output is 5W PEP., i.e., 20X 5W PEP = 100W PEP X 4X2SC2879 = 400W PEP. with 20W PEP input. now let's get crazy and increase the drive input to 40W PEP input and use your input and output figures of 160 and 675. the power multiplier factor is now reduced to 4.28175X. this ratio translates to a reduction in gain of all four transistors from 13 db. to 6.25 dB., a whopping 6.75 dB. below the 2879's minimum rated gain. at a reduction of only 1 dB. the transistors are already 1dB. into the compression curve/region and we still have an additional 5.75 dB. loss in gain to account for. the devices have moved out of and beyond the active region and are in deep saturation. if you drive them like this then with regard to saturation, that ship has already sailed. now the question is not if she's gonna blow, but when.

in addition, the other bad thing with regard to running them like this is that if you should have any kind of an antenna or feedline problem between the amplifier and the antenna (an open or short) then you have completely lost the ability of the 4X2879 transistors to shrug off any swr conditions that might result in destruction of the transistors from a 15, 20 or even a 30:1 swr.. that safety factor is gone.

and all of this is for what? for an extra 2.2 dB. of gain over operating them at 400W PEP which is sad because under real time conditions no one is ever going to notice the difference in signal strength.

dB. gain = 10log (power output divided by power input)
dB. loss = 10log (power input divided by power output)

Here is the video. Also I added my amplifiers video at Carl's bench in my original post, if interested .

 

[Capt Crunch]

Take the 500w-600w you get out of it and be happy. Thats what it is meant to do and it will last you a lifetime. Everyone always wants to push their amps to the limit and beyond. "Im gonna get a 1×2 to drive my 4pill, then i can get the 1200w they say it can do", pshh ridiculous. If you want bigger watts, buy a bigger amp.

I am happy with it but the Builder and other people are saying it can be run higher. I am not everyone and I am by no means any kind of tech, hence the question I posted. I know what the transistor specs are but I don't know how they build amps. Nice attitude by the way.

 

[freecell]

i can't promise anything but if things slow down here a bit i'll take a look.
thanks CC !

 

[Capt Crunch]

May just be me, but I tend to look at parts specifications. I know I've had good luck using a single 2290 as a driver for 4 2879's. Specs would indicate @ 40W of drive, although a 2290 does a little more than that, it's well matched. Beyond that you're really pushing it into saturation. It may show more on a watt meter, but what does a spectrum analyzer show?

Yes same here that's why I'm running a Galaxy Dx979 with it right now. I read in a couple places that class C amps were built differently and I don't know how so I was just curious to find out if it's just really running the 2879s incorrectly or the way they actually build the amp.

 

[Capt Crunch]

i can't promise anything but if things slow down here a bit i'll take a look.
thanks CC !

Thank you for the information.

 

[freecell]

you're welcome.

 

[Mikey1966]

I am happy with it but the Builder and other people are saying it can be run higher. I am not everyone and I am by no means any kind of tech, hence the question I posted. I know what the transistor specs are but I don't know how they build amps. Nice attitude by the way.

They want you to run it higher so when it blows they have a chance of selling you other stuff. I never punish my equipment, 650 watts to 1000 watts isn’t a s unit difference so why blow your shit up? This hobby is to have conversations with others local or distance on ssb. I’ve talked to people overseas on my icom with 100 pep no amp. Just the other day I turned it down to only 1 watt now & talked to Florida on 27.385.00 LSB. That’s the shit I like. I use a Texas star dx350 HDV behind my icom & others think I’m using a tube linear it’s so clean. @15 volts even & 6 gauge power wire with no fuse that affects it too drawing amperage through that small lead in that fuse. It’s not needed as long as you don’t hook it up in reverse. It peaks 400 pep with 20pep input on ssb.

 

[linearone]

I'm not even really sure I understand the question in this thread. That's 2 years old. Was the original poster asking if he should drive it harder to get more watts? If so, the answer is yes if you want more watts.
If you want less watts, drive it with whatever you want.
I'm just not sure I understand the actual question/ problem.

That being said, it always amazes me the problems that people have with small amplifiers. I know you don't really have a problem per se, but in general i see countless questions about drive for two pills and four pills and constant issues getting the watts they're supposed to have.
I was over at my shop today on the garage side, I was with my buddy, another radio guy, and I was swapping axles and hub bearings on my daily driver suburban. We were talking about amplifiers and during a coffee break we walked into my shop area, I flicked on two switches, key the microphone and showed him four kilowatts out of a three tube. Z. And then I shut it off and I went back to work. I can generate 4000 watts easily without any hangup and everything works every time and I see countless questions on forums about people worried about their Texas stars... I just don't get it.
None of this is that hard. Not to rain on anybody's parade or insult anybody, but quoting a data sheet for CB amplifiers is a worthless endeavor. I mean it's just CB and they're just amplifiers. It's like when people like to correct me when I say the word pills, and they say the word transistors back. Those usually the same guys that can't run anything bigger than a four pill.

 

[Capt Crunch]

I'm not even really sure I understand the question in this thread. That's 2 years old. Was the original poster asking if he should drive it harder to get more watts? If so, the answer is yes if you want more watts.
If you want less watts, drive it with whatever you want.
I'm just not sure I understand the actual question/ problem.

That being said, it always amazes me the problems that people have with small amplifiers. I know you don't really have a problem per se, but in general i see countless questions about drive for two pills and four pills and constant issues getting the watts they're supposed to have.
I was over at my shop today on the garage side, I was with my buddy, another radio guy, and I was swapping axles and hub bearings on my daily driver suburban. We were talking about amplifiers and during a coffee break we walked into my shop area, I flicked on two switches, key the microphone and showed him four kilowatts out of a three tube. Z. And then I shut it off and I went back to work. I can generate 4000 watts easily without any hangup and everything works every time and I see countless questions on forums about people worried about their Texas stars... I just don't get it.
None of this is that hard. Not to rain on anybody's parade or insult anybody, but quoting a data sheet for CB amplifiers is a worthless endeavor. I mean it's just CB and they're just amplifiers. It's like when people like to correct me when I say the word pills, and they say the word transistors back. Those usually the same guys that can't run anything bigger than a four pill.

You seem to be the only one with a problem here.

 

[linearone]

You seem to be the only one with a problem here.

You're not the first person to tell me that