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Heatherlite Hunter

Posted: Mon Nov 10, 2008 10:30 am
by Yamanx
Its a linear amplifier, fairly rare uses a 3-500z valve. Good for slightly under 500w FM/AM

Is it possible, or even likely, to be able to uprate this amp? Source a different valve which uses similar voltage etc.?

I have found through internet searching that some have used a 4400 valve, but what is that? cant find any info on it at all :)

Posted: Mon Nov 10, 2008 11:23 am
by Voodoo Guru
It's hard to beat the 3-500Z both in durability and performance.
If you were going to upgrade, the best thing would be to save up your coins and get an amplifier using a Ceramic Tube.
If your going to play audio on the air, you really need an amplifier with allot of 'Headroom'.
The Ceramic Tube amps have a very low drive input and a very high amplification factor to give this 'Headroom'.
That is lets say 25 to 50 watts in for 1500+ watts out as compared to a Glass Tube amp which requires about 100 watts in for 1000 to 1500 watts out.
Using the Ceramic tube amps lets you run your rig with NO ALC action showing on the Transmit ALC meter which makes for a very, very clean signal.
I order to drive the 100 watt input amps, you usually have to increase the Mic Gain to drive full ALC for Full 100 watt output, this makes for a dirty signal when using full range audio.

Now pops up another problem...Cut-Off Biasing.
With most of the currently produced Ceramic Tube Amplifiers, they are using the Tetrode.
We like the Triode like the 3CX800A7. It's easy to tune, and a workhorse.

The Tetrode tube runs pretty hot, so to compensate the manufacturers started to use a biasing scheme to cut-off the Tube in-between syllables of speech.
This creates a unique distortion when using Full Range Audio, it is most prevalent on the upper frequencies.
There is no fix for this on some amps, like the Alpha 99.
But the manufacturers have heard the Cries of the Audiophiles and will now give you a mod, or build your amp without this biasing if you are going to use it for ESSB.
So you have to research the amps to make sure there is a way to bypass this biasing.
We just got a bias mod for the ACOM from a friend of ours that hounded the ACOM factory until they came up with one.
Go ahead Jeff!!!!
Take Care,

Posted: Mon Nov 10, 2008 3:12 pm
by Yamanx
Thanks, It appears from some internet research that Penta may do a direct Ceramic replacement for the glass 3-500z.

I found an old newspapaer artical online suggesting that Penta had developed a direct replacement for the 4-400 and the 3-500ZG called the 4CX400C, but this valve (Tube) doesnt exist. A bit of investigation found this was only a prototype. However penta did develope the 4-400CM. Which by all accounts (Well no accounts at all really :) ) could be the production version of that prototype.

I have asked Penta the question, I'll let you know the answer.