valve amplifiers and high efficiency speakers

Single Ended power amplifier with type '45 triode (1)

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lots of ideas... at least I have. Most of the time they pass, not in this case.. What idea? Well, the latest modifications regarding Super E-cap indelible impressed me, both mentally and fiscally (referring to the price...!). When using BlackGate N/NH/NX in super E-cap, the sound is unbelievable clean and colorful, almost like there's no capacitor... What if a complete amplifier is built using solely super E-cap, instead of "only" as cathode-bypass? My current preamp "Mystique" is already equipped with super E-cap, both cathode-bypass as power supply, with VERY good results. In my power amplifier is this not feasible due to a power supply voltage of 425 Volts. The BlackGate NH can coop with 350 Volts max, so putting them in series can be an option, expensive though and not guaranteed (never tried it, too expensive...).

The idea.
A power amplifier with the '45 or 2A3 as power tube will not exceed 350 Volts B+, and because of the '45 being one of my all-time favorite tubes, this would be the choice. The '45 can deliver a full 2000 milliWatts of output power, not much... Low-end response is not impressive but mids and highs are almost undefeatable. When used with super E-cap this maybe could be solved as "energy" and "power" are some of the benefits of super E-cap. When also power chokes with 0,05mm silicium steel-core are used, low-end response might be very good. So the idea is basically a SE-amplifier with super E-cap and 0,05mm sil.steel power chokes...

The design.
A power tube is driven by a driver (?). I prefer "iron" as plate load, so an interstage seemed a good option here: no coupling capacitor is used and a grid resistor for the power tube can be omitted. The power tube needs an amplification of about 6 for full power when using Mystique as preamp. Also the plate resistance should not exceed 5 KiloOhms regarding the design of the interstage. At the internet I ran across the Philips 4606, an "Post" tube used in telephone repeater amplifiers back in the '60's. With a Rp of 5K5 and a amplification of 5.5 and a powerful 4.5Volts/1Ampere cathode, the choice was not difficult. The filament of the '45/2A3 will be AC-heated and the 4606 DC-heated. Cees Pel, a fellow tube-enthusiastic, advised me in also using super E-cap at the filament power supply. The filament power supply is carrying signal since the filament is also the cathode in DHT designs... Cees has tried it and never took the super E-cap from the filament supply since... what more to add? The power tube will have a hum-pot as will the DC-heated 4606! Why? well, when using Schottky diodes and 2 x 2x2200mF/16V and not willing to dissipate an awful lot of power on a resistor in a pi-filter, a residual hum is obvious...AC-heated power tubes at 2,5 Volts are remarkably quiet, even at high efficiency speaker systems (101dB, in my case). The chassis will be made of wood, no metal used(!), this because of the benefits as experienced with Mystique. Click here to see the schematic.

As in every tube amplifier, a reasonable amount of transformers are part of the design. Silicium steel cores with 0,05mm laminations are very good sounding, so all transformers should be made using these cores. AE-Europe from Schagen also uses these cores and when spoken to, they agreed in making the transformers for these mono blocks. Each mono block will carry 8 transformers: 3 power supply chokes, an OPT and an interstage on 0.05mm sil.steel and 3 power transformers, 1 power supply and 2 filament, on EI-core. All "on top" mounted transformers are potted and have a powder-coated finish.


The chassis.
Also available from AE-Europe were 2 chassis frames: nice round curved 18mm, at front and rear even 36mm thick white oak. These are the chassis TriodeDick uses for his "Little Ceasar". Top side is intended for inserting a copper/aluminum plate, this will be replaced by oak as well...