But is there any advantage over the 8 ohm to grid setup? The disadvantage is a lot of complexity, additional power supplies, transistors that can fail, heat sinks, etc....
A lump of iron is a lot simpler... Brett N2DTS > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Geoff/W5OMR > Sent: Monday, July 30, 2007 10:19 AM > To: Discussion of AM Radio in the Amateur Service > Subject: Re: [AMRadio] Subj change - HB designs > > Brett gazdzinski wrote: > > Think that circuit is better then a hifi transformer > > (say 2500 ohms center tapped) to 8 ohms? > > 8 ohm side goes to the hifi amp, the 2500 ohm > > side goes to the grids. > > Swamping resistors go across the 2500 ohm side > > (1250 ohms to center tap) > > > >> > >> http://www.qsl.net/wa5bxo/driver1.html > > In this case, there's nothing connected to the low-Z side of the > transformer. I only acts as a center-taped High-Z choke. The audio > then goes to the bases of a pair of vertical output transistors in > emitter-follower configuration. The emitter outputs of the > transistors > then directly drive the grids of the Class B modulator tubes. > > The only variation from that circuit, to what I'm using now, > is the 6k > Ohm 1:1 isolation transformer. > > Before, the audio was pulled from the plates, through some > .6uF @ 1000v > capacitors, for DC blocking. > Now, the 1:1 transformer isolates the DC from the secondary, > which then > still acts as a high-Z choke. > > Transformerless audio-driving a Class B modulator. This way, you can > impose whatever audio you can get from your speech-amp > (source) onto the > grids of the modulator... and, with ~600v peak-to-peak, you > could drive > even a pair of 450TL's with this setup. It's certainly over-kill for > pentodes, tetrodes, or smaller triodes like 811's, or 812's. > > -- > 73 > W5OMR > > ______________________________________________________________ > AMRadio mailing list > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > To unsubscribe, send an email to [EMAIL PROTECTED] with > the word unsubscribe in the message body. > ______________________________________________________________ AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected] To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
