KL-503 & KL-500?

[hammer0630]

What is the difference between KL500 & KL503 it seems they are very similar in appearance and wattage out put except for the difference of about $125.00

 

[Diesel2650]

I know the kl-503 uses mosfets, the 500 is still pills. Am the 503 swings 200-250, the 500 I read 300+

 

[mr_fx]

I have owned both and let me tell you the kl-500 uses transistors, BUT it is a class C box, where the KL-503 uses mosfets and is a class AB box

the big issue I see with the 503 is the driver, it has a driver that is about the same as an irf520... I have heard people do bypass it, but other than that the drive into the amp has to be low

you should see a solid 250-325 out on the kl-503

the kl-503 generally speaking runs ice cold, while the kl-500 is a barn burner

 

[Onthecoast]

Are all the rm Italy amps that end with a 3 MOSFET amps?

 

[basstracker1970]

I run the KL-503 amp and love it. I am getting about 325 out of it from a dead key of 2 watts on radio. I added a 120mm cooling fan on top of it as it gets a bit warm if you talk alot on it. With the cooling fan it stays cold all day long. I am told by everyone that I am very loud and clear with this amp. Been my favorite so far. Blows away the palomar amps....

 

[bob85]

fx,
the kl500 is a class ab amp, they use a bc547 to switch a bd179 bias pass transistor or bd241 on later revisions ,
originally they used 4x1446 but later revisions are a bit of a lottery, some have mrf455's and some have another sd transistor that struggles to make over 200w.

kl160 kl200 kl300 = class C

kl351p kl400 kl500 kl550 kl800 = class AB

the kl203 is the only 100w amp rm make that is biased to sound ok on ssb.

 

[dd18]

KL500

I believe that RM is now using the MS1051 transistor in their KL500 amplifiers.
How does this compare with the 1446 they were using in the past?
any opinions /observations?
thanks,
Dave

 

[bob85]

on paper/datasheet the ms1051 looks like a higher rated device than anything i have found in new rm amps, i have not had the 1051 version here to see how they perform vs sd1446.

 

[liquidh8]

I have the version with the newer transistors, my antenna coax got messed up and took out all four transistors immediately. But it had about 350 watt ssb on the bird, with 20 watt pep drive from my 2510

 

[dd18]

RM advise that max drive for the new 1051 transistors should be 7w.
Pity they don't put that in the box or on the amp so a lot getting over driven and sounding like shit.
Who has a 7w radio these days.?
Asking for trouble...hard to keep a dual final radio down to 7w on ssb

 

[mr_fx]

RM advise that max drive for the new 1051 transistors should be 7w.
Pity they don't put that in the box or on the amp so a lot getting over driven and sounding like shit.
Who has a 7w radio these days.?
Asking for trouble...hard to keep a dual final radio down to 7w on ssb

yes but you are missing something, the kl-500 has 4 ms1051... so now can, in theory, hit it with 28

 

[dd18]

kl500 input

yes agreed. But this is what RM responded when I told them I was reccomending 12w max input!! it looks like these amps need a lot of head room.
it is not making much sense to me either.