I would say that the fidelity was pretty good compared to a BC-610, mostly because the audio amplifier was of exceptional quality and so lightly loaded.

The power at carrier was pretty low, only about 80 watts, and when we were done tweeking, we were getting about a 340 watt PEP signal out of it.

Running the power low, with low voltage and current allowed the rare tube to stay cool.

As for power, I imagine the BC-610's carrier is much more powerful.

The modulator amplifier is rated at 175 watts and is an Altec 1570B, using two 811A's in class B push pull with the grids driven directly from cathodes of some beam power tubes, the schematic of this unit is here:

http://www.soundpractices.com/altec.html

It has 10 tubes, and operates with 930VDC on the 811A's.

I use two of these amps in my stereo.

best regards,
Patrick


From: "Brian Carling" <[EMAIL PROTECTED]>
Subject: Re: [AMRadio] Home brew AM

How does that compare to the performance of say the 250TH final
stage in a BC-610?
It sounds like you are running at lower power.
Also how many tubes do you use in the cathode modulator?

On 2 Oct 2004 at 20:12, Patrick Jankowiak wrote:
>> Cathode mod works very well on a 250TH. We are getting 80-90
>> watts carrier no problem at 2200V. For the details:
>>
>> http://www.montagar.com/~patj/cathmod01.htm
>>
>>
>> Patrick

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