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In the Forum: Melquiades Amplifier
In the Thread: A different breed of 6C33C amplifier.

Post Subject: 6C33C amp.Posted by KOTriode on: 9/8/2011

Without regulation, this amp would not work correctly due to its design: DC coupled and fixed bias. The high transconductance will make the bias current varied as much as 50-100ma due power line fluctuation without the regulators. It might work if the amp used cathode bias, but I chose fixed bias for various reason. The input stage (with or without the Cathode follower stage) bias the output tube from the plate voltage, fluctuation in unregulated B+ will cause the grid voltage to swing which in turn change the output tube bias current. Transformer with high current output, choke and capacitor would not help much with this design with line voltage fluctuation.Also since this is a setreo amp, good regulator definitely help crosstalk.All my systems are multi-amp and put a heavy load on the power line on the average of 1000W and more, so regulator in this amp is necessary, not an option.

Why the adjustable voltage? this tube to me is an experiment, the regulator for me is very convenient to understand the bias of this tube with different plate and grid voltage in the amplifier, and how the sound will be affected with different operating point. I am not too crazy building a high voltage amp (the voltage is as high as 520V on this amp) with multiple power supply and wire hanging.

This amp is never intended to work in A2, so does my other DHT amp. The amp can be played with or without the Cathode follower, my aim to get the driver as linear and wide bandwidth as possible, hence feedback will be unnecessary.

I will try the amp with few different speakers as full range and later in tri-amp system, among them are mini monitor, Stacked Quad ESL, Horn system.... It would be very interesting to compare with the big DHT tube. Into the 10 hrs of break-in with a monitor, I am very happy with the sound so far.

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