Finished one of my 200WPC SET Monoblocks

[Maxamillion]

Sounds EXCELLENT. Clean and clear with very powerful bass! Like a 300B with twin superchargers! Two stage design with Russian 6E5P driving the 833C DHT.

The filament alone is 100W (10A, 10V). Plate voltage on the 833 is 2300VDC. Total of 425W dissipation in the 833.







Currently working on the other channel. When that's done, we can have a Rave!

[BobM]

Those monsters might actually be able to drive my 83db inefficient Apogees. I can't help thinking of this picture when I see them.

[topround]

Bob,
looks awesome..can't wait to hear it

those should be featured in an audio show


Mike

[StereoNut]

Way cool looking. I especially like the name on the faceplate!

[Maxamillion]

Those monsters might actually be able to drive my 83db inefficient Apogees. I can't help thinking of this picture when I see them.

How did you get a picture of me firing them up???!!! Are you in the NSA?

[Triode Pete]

Rob,
Cool, very cool! I'm surprised you don't get a lot of hummmmmmmmmmmm with the 10V filament.

How many watts output have you measured???

Boy, that high voltage on the plate really scares me, though!

Be careful, my friend! Drink wisely!

Cheers,
Pete

[Emil]

Those monsters might actually be able to drive my 83db inefficient Apogees. I can't help thinking of this picture when I see them.

Exactly. Looks like something out of Dr Frankenstein's lab.

Its ALIVE!!!! ALIVE!!!!

[Maxamillion]

Rob,
Cool, very cool! I'm surprised you don't get a lot of hummmmmmmmmmmm with the 10V filament.

How many watts output have you measured???

Boy, that high voltage on the plate really scares me, though!

Be careful, my friend! Drink wisely!

Cheers,
Pete

No Hum. Filaments are DC, using an LCLC supply feeding two of Rod Coleman's DHT filament regulators in parallel (CCS and gyrator combination).

Haven't measured the power yet, but LTSpice simulations show 197W at 2.5V input.

I have a pyrex cylinder that fits over the 833 to protect us all from the high voltage, but I don't put it on while adjusting/tweaking on the bench. Picture below:

[Maxamillion]

Here's a look at the insides:

[DaveC]

Wow! Nice Amp!  

[richidoo]

Wow, that is awesome.

[GT Audio Works]

BEAUTIFUL   
I WOULD LOVE TO HEAR THEM !!!
Will they handle 4 ohm loads ??
May I suggest creating an air gap between the chassis and the bottom of the Pyrex glass tube to help induce proper cooling air flow through convection...looks like those babies will get HOT !!  Greg

[Maxamillion]

BEAUTIFUL    
I WOULD LOVE TO HEAR THEM !!!
Will they handle 4 ohm loads ??
May I suggest creating an air gap between the chassis and the bottom of the Pyrex glass tube to help induce proper cooling air flow through convection...looks like those babies will get HOT !!  Greg

There is a 3" fan (31 CFM Noctua - whisper quiet!) under the 833 tube which draws warm air out of the chassis and blows it up around the 833 to cool the tube. The chassis is fairly well sealed, with two 3" filtered air intakes in the back to let cool, clean air in. So far it seems to work; in a three hour test run the chassis temp reached a max of 59C and the tube didn't melt, but I'm continually checking things with an IR thermometer to make sure.

PS: I also built a circuit to detect a fan failure using the fan tachometer output. When the tach reading falls too low (signaling a fan failure) the circuit sends a 12VDC signal to a SPST NC relay which then cuts off the 833 B+. A little bit of extra protection, at least...

The OPT is a 12K:4 unit, and the output impedance should be ~1.5ohm with zero negative feedback. I'm going to try it as is on my Infinity RSIIb speakers (4 ohm nominal), and see how it sounds. If it need better damping, I can add up to 4dB of local negative feedback to the circuit which should get me down to about 1ohm or so. Or, since the amps have quite a bit of power I could also invest in a pair of Speltz Zero autoformers to make the speakers look like an 8 ohm load - or maybe I can talk Dave Slagle into making me something better....

[topround]

are those tesla rings on top of the tubes

[shadowlight]

Wow.   Good looking build.  Would love to hear it someday