On one schematic, the cathode resistor/capacitor goes to a 47 K Ohm resistor, and on another schematic for the same tube, a 220 K Ohm resistor is connected. Could someone please tell me why there are such vastly different resistances on the different schematics?. https://diyaudioprojects.com/Schematics/DIY-Push-Pull-PP-6V6-Tube-Amplifier/
Where do you see the cathode resistor/capacitor returned to 47K? In the schematics you posted it is the grid of the second triode going to pick up the attenuated signal of the input one. That's a paraphase splitter. If you meant the output tubes, there is clear ground between the RC and the 47K.
Where is the other schematics? Are you sure it's the same topology and same tubes?
Where is the other schematics? Are you sure it's the same topology and same tubes?
http://www.r-type.org/articles/art-272.htm Here we have another schematic that has almost the same circuit as I posted last time. With a 220K Ohms resistance where the second circuit had a 47K Ohms resistance
Have you looked at the improved “Boffin” schematic I referenced in post #38. Notice R22=150k, but R20 and R21 are different in that schematic. My understanding is that the different values for R20 &21 improve the balance of the phase splitting operation. Also separate cathode resistors and bypass capacitors.
https://www.diyaudio.com/community/attachments/exboffin-png.880093/
Not necessarily true that 10-12% difference for the anode resistor of the 2 triodes in the paraphase improve the balance. It could but it depends on the actual tubes in hand. First thing to check is the actual gain of each triode. They are generally not exactly the same. This is one circuit where 2 unbalanced halves of a double triode can be put into good use without using different the load resistors. If one has more than 2e double triodes, just swapping tubes could fix it! The different anode resistor must assume that the 2 halves are the same.
In my PCL82 amp I use the same plate resistors and distortion is very low right up to the clipping.
In my PCL82 amp I use the same plate resistors and distortion is very low right up to the clipping.
Stumbled across this thread and have this sudden desire to build the EL84 Dynaco A-410 circuit from 1955, just to see what an amp might sound like from nearly 70 years ago. I am guessing the 16 ohm tap on the OPT would be mandatory, which negates using an OPT with only 4 and 8 ohm taps, am I right?
The feedback components can be adjusted for a lower tap connection to maintain the same amount of feedback but you'd have to do some tuning with a scope to get the compensation working well. And the transformer quality of a newer unit would be a variable that could affect whether it can be made to work as well as the original. It's very possible as there are some good currently made transformers.
