I'm wanting to build an EL84 PSET project this year and been going through my schematics. Can anyone suggest a schematic maybe they've had success with? I seem to remember a PSET RH-84, not sure. Or maybe a good SET EL84 and I can get some help here with the changes to add the parallel tube. Thanks!
Being the EL84 very easy to drive in UL (20-25V of swing, small capacities), if tou want to use two paralleled EL84 in the RH you can keep all prameters the same except:
- Power transformer must have twice the current (same voltage) for heater and B+;
- Output transformer must have half the primary impedance and twice the power;
- Output stage cathode resistor must be half in resistance and twice in wattage;
- Output stage cathode capacitor must be twice in capacitance and same voltage.
Look for Audio NoteUk there are some simple circuit and maybe a kit
They have a good iron
But maybe a pp will be more interesting to build
Walter
They have a good iron
But maybe a pp will be more interesting to build
Walter
I know it's out of fashion, but a push-pull amplifier has several advantages, if you're already committing to two output valves per channel. They have lower distortion, minimal interaction with the power supply, better output transformers (by a lot), so better bandwidth and lower distortion at lower and higher frequencies, much lower noise induced by the power supply, and a simpler and less expensive power supply.
Folk will compulse about the "sound" of various almost perfect coupling capacitors (which operate with essentially zero signal voltage across themselves), but will ignore the effects of the power supply capacitor (which operates with significant signal voltage across itself) which is in the direct signal path for SE designs but largely cancelled in the class A region of push-pull amplifiers. Same for signal "ground" paths.
SE amplifiers look "simple" because we believe schematics, and pretend that power supplies and signal "grounds" are perfect. We're fashion victims about that.
All good fortune,
Chris
Folk will compulse about the "sound" of various almost perfect coupling capacitors (which operate with essentially zero signal voltage across themselves), but will ignore the effects of the power supply capacitor (which operates with significant signal voltage across itself) which is in the direct signal path for SE designs but largely cancelled in the class A region of push-pull amplifiers. Same for signal "ground" paths.
SE amplifiers look "simple" because we believe schematics, and pretend that power supplies and signal "grounds" are perfect. We're fashion victims about that.
All good fortune,
Chris
Thanks Chris,
I have had my mind on building the John Broskie 6BQ6 amp below for some time, considering your points I will plan on a "xBQ5" PP amp instead of jumping into a PSET. But I do have several 6, 8 and 10 volt NOS tubes in my stash for 6BQ5, so I'd like to devise a way to use that 25 watt dropping resistor trick and AC over-voltage to allow all-of-the-same-voltage to simply be plugged in and arrive at the correct heater voltage.
Here is the original Broskie triode strapped article and a DIY'er modification of the same article for ultralinear and CCS: This will be point to point so I can do my own mods easily. The third schematic is a similar circuit by Morgan Jones using a regulated supply for the input tube, which is something I'd like to add probably after it's all working on the same unregulated B+ and I know what voltages are there.