A Beovis Valley.
I was hoping to swap between PCL86 and EL84, so the output transformers are 10k a-a and I can drop a GZ34 in place of the 1st smoothing cap to drop the HT. The voltage was still too high for a PCL86 though so I've had to go for the EL84s. The HT transformer is just a 1:1 isolation transformer. LM317's as ccs set to 40mA in place of the cathode resistor. Toroidy output transformers mounted upside-down.
I was hoping to swap between PCL86 and EL84, so the output transformers are 10k a-a and I can drop a GZ34 in place of the 1st smoothing cap to drop the HT. The voltage was still too high for a PCL86 though so I've had to go for the EL84s. The HT transformer is just a 1:1 isolation transformer. LM317's as ccs set to 40mA in place of the cathode resistor. Toroidy output transformers mounted upside-down.
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Pardon the cluttered countertop used for testing...
6SN7 push pull flea amplifier.
The amp sounds absolutely fantastic!
Build/discussion thread here-
6SN7 push pull flea amplifier project
Speakers are DIY (score and fold) Karlsonators made of foamcore board with Vifa/Tymphany TC9FD, discussion here-
Mini Karlsonator (0.53X) with Dual TC9FD's
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Mullard Edcor EL34
This is the improved Push-Pull Mullard EL34 tube amplifier circuit. The original uses the Dynaco A420 audio output transformers which have a primary impedance of 6600 ohms. The schematic is from the Dynaco Super Fidelity Output Transformers catalog. Obviously I didn't use Dynacos, and I used bigger caps in the power supply. My first tube amp, and I am very happy with it. Time to build another amp, now I have the confidence to do it.
This is the improved Push-Pull Mullard EL34 tube amplifier circuit. The original uses the Dynaco A420 audio output transformers which have a primary impedance of 6600 ohms. The schematic is from the Dynaco Super Fidelity Output Transformers catalog. Obviously I didn't use Dynacos, and I used bigger caps in the power supply. My first tube amp, and I am very happy with it. Time to build another amp, now I have the confidence to do it.
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Wow, I almost forgot I had those labels made because I wanted the "Made in USA" more predominant. They are Edcor stock items however.
The toroidy’s? Well the cables tend to exit the toroidy's straight up, so I was expecting to have to cover them with some kind of shroud until I realised If I flipped them upside-down and cut a couple of holes in the panel where the cables exit the trannies then I can route the cables neatly into the chassis.
I’ve used rubber grommets and had to cut a grommet-sized hole in the transformers rubber mount to keep it neat. It works quite well.
This is an older pic with the pcl86’s still in place. This has a 50V toroidal transformer with a two transistor regulator providing 67.2V for the series heater chain (4xPCL86 & 2xPCC88). Since swapping to EL84’s I’ve switched to AC heating.
It's a great sounding amp. I was running an SE 45 but this EL84 amp has a much flatter response with my BC Acoustique Niger loudspeakers. Horses for courses I guesss?
I’ve used rubber grommets and had to cut a grommet-sized hole in the transformers rubber mount to keep it neat. It works quite well.
This is an older pic with the pcl86’s still in place. This has a 50V toroidal transformer with a two transistor regulator providing 67.2V for the series heater chain (4xPCL86 & 2xPCC88). Since swapping to EL84’s I’ve switched to AC heating.
It's a great sounding amp. I was running an SE 45 but this EL84 amp has a much flatter response with my BC Acoustique Niger loudspeakers. Horses for courses I guesss?
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Uuuuhhh, that's some nice glow.
My tubes are already hitting ~240c (~440F) and heating the room; it's summer here... how hot do they need to go?
