XPost: sci.electronics.design   
   From: tauno.voipio@notused.fi.invalid   
      
   On 29.12.18 01:32, Chris wrote:   
   > On 12/28/18 03:11, tubeguy@myshop.com wrote:   
   >> I found a schematic of a stereo amplifier containing TWELVE 6L6 audio   
   >> output tubes. But aside from sharing the power supply, it's two   
   >> mono-blocks with each having SIX 6L6 output tubes. Unfortunately, I was   
   >> not able to get any real detailed information on this.   
   >>   
   >> I compared it to several guitar amp schematics which use FOUR 6L6 tubes   
   >> in push-pull parallel, and this is very similar. It just has 3 tubes on   
   >> each side of the phase, rather than two. The plates are all wired   
   >> together and cathode / grid components are duplicates to each tube.   
   >>   
   >> They did use as bias adjust potentiometer on each tube, which I have not   
   >> seen on the guitar amps.   
   >>   
   >> Obviously the purpose is to increase wattage output.   
   >>   
   >> I'm not intending on building this, but it's interesting and makes me   
   >> wonder if someone could use EIGHT 6L6 tubes, or TEN?   
   >> (Of course adding more tubes mean bigger audio output transformers and   
   >> heftier power supplies.   
   >>   
   >> Another question that comes to mind is the impedience of the primary on   
   >> the audio output transformer. Assuming I could find a transformer that   
   >> would handle the wattage, would the impedence be the same as those used   
   >> with FOUR 6L6 tubes, or would that change since there are two more tube   
   >> plates connected in series.   
   >>   
   >> Anyhow, looking at this schematic makes me think that any PPP amp with   
   >> FOUR tubes could have more output tubes added, as long as power supply   
   >> current is available and a suitable audio output transformer is   
   >> obtainable.   
   >>   
   >>   
   >   
   >   
   > If you want to see an interesting audio amp, look up the Editors and   
   > Engineers Radio Handbook from the mid 60's. There's a design that   
   > which uses 6 or 8 6080 double triodes to build a direct coupled   
   > amplifier, no output transformer and dual power rails, positive and   
   > negative. Never built built it here, but a very original design. Could   
   > probably update that to use power mosfets...   
      
   I found it in my copy, 16th edition, 1963.   
      
   The amplifier is not direct coupled, there are several stages   
   with coupling capacitors. The final is series-connected with   
   3 series pairs of 6082 triodes in parallel and direct feed to   
   a 16 ohm speaker. The power supplies are + and - 140 V.   
      
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