Thanks for the kind words. This is my first push-pull "hi-fi" build. The amp sounds...fun. I just have a smidge of NFB (-1.3dB, seriously, why bother), that I tuned by ear with a 10k pot. I'm sure the THD is through the roof, but it sounds nice and warm. It has a lot nicer bottom end than I thought possible with the dinky Edcor output transformers. My audio snob buddy was shocked by the sound stage, but he poo-pooed the top end clarity. I though it was pretty good. Then again, he's the dude who sprang for an "audiophile power cable".
The amp is dead quiet at idle, but there's a very slight mechanical buzz from the output transformer. I think I need to tighten the bolts on the bell housing.
The damper diode is there to drop some volts and to provide a slow startup. Plus it increased the tube count. More tubes=more better, right? I also got 2 of them for 99 cents, so that may have something to do with it.
Oh yeah, schematic:
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Great, thanks for the info and schematic. Kudos for the build. Looks great and if it's silent and you like it, then all the better. Even more so if it's your first PP amp. I find the low end to be tighter and more solid with PP amps, but still love SETs.
Egads, that's some extreme kit. BIG amp, BIG speakers (OK, big as in tall...) Always wanted to try a line array - one day! Nice gear.
how did you construct the speakers?
Hello, wonderful setup! I have built a 2x 6C33 Circlotron driving horn speakers (over low-impedance output transformers, so its not OTL), but I'm sympathizing since years with constructing such a speaker column, too. How did you build it? Would you share some more details with me?
Do you drive them in OTL mode?
all the best
Uli
Hello, wonderful setup! I have built a 2x 6C33 Circlotron driving horn speakers (over low-impedance output transformers, so its not OTL), but I'm sympathizing since years with constructing such a speaker column, too. How did you build it? Would you share some more details with me?
Do you drive them in OTL mode?
all the best
Uli
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I drive them in OTL mode. No iron in sight. Only a LOT of iron in the PS 
Here is a link where you can see how I made my Line Arrays.
Stupid Cheap Line Array
And here a guy that partly got inspired form my build:
The making of: The Two Towers (a 25 driver Full Range line array)
Here is a link where you can see how I made my Line Arrays.
Stupid Cheap Line Array
And here a guy that partly got inspired form my build:
The making of: The Two Towers (a 25 driver Full Range line array)
Nice amp koldby. I am also using 4x6C33 OTL monos. Love the sound. Mine is Transcendent design. No doubt similar.
Thanks lot, Koldby, so your speakers also have an impedance around 8 Ohms? I use 150:4/8 Ohms transformers in my Circlotron outputs (built by experience-electronics.de), otherwise performance was not acceptable.
Heating is by a 24V 12A switchmode-PS, operating voltages are 4x 220V plates and -240V for the negative rail, all mosfet stabilised.
Thanks for the links, I also looked already at the "Two Towers" thread... amazing....
best, Uli
Heating is by a 24V 12A switchmode-PS, operating voltages are 4x 220V plates and -240V for the negative rail, all mosfet stabilised.
Thanks for the links, I also looked already at the "Two Towers" thread... amazing....
best, Uli
Hello Gideon,
I buy them from a factory in Germany (Glasbläserei Stauber, Passau, Bavaria), they offer a broad range of these glass cylinders. Sadly, the site is in German only:
Glasblaserei Armin Stauber - Glaszylinder klar aus hitzebestandigem Borosilikatglas 3.3
My amp has an active cooling using a slow running fan (120mm 12V fan running at about 8V) in the bottom plate of the main chassis, and the air is blown out over the power tubes - their sockets sit about 5mm below the chassis, with a ring of additional holes around each tube. The boron silicate glass of the cooling chimneys absorbs very well the immense infrared radiation of the tubes, so the heat stays within the chimney, is almost completely carried away by the airflow and does not heat up the surroundings. So the amp remains very cool at all times. To fix the cylinders, I drilled small holes into them (diamond head) and fixed them with small wire hooks at the chassis.
best, Uli
Absolute no problems driving 6/8 Ohms. No need for a x-former at all. This is a close clone of the Atmasphere Novacron.
