6C33C SE Amp - Ideas on refinement?

[GlidingDutchman]

Here is the updated schemes

Audio Section

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PSU Section

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[Jeb-D.]

It's coming along well. Are you happy with the sound? Do you know how much power it's putting out?

I only have a few suggestions

1) Move R4 to between R17 and the input tubes grid.
2) Change R10 to 100k
3) Change C14 to 1uF - 4.7uF range.
4) Change C5 of the power supply to 1uF - 4.7uF range.

 

[GlidingDutchman]

It's coming along well. Are you happy with the sound? Do you know how much power it's putting out?

I only have a few suggestions

1) Move R4 to between R17 and the input tubes grid.
2) Change R10 to 100k
3) Change C14 to 1uF - 4.7uF range.
4) Change C5 of the power supply to 1uF - 4.7uF range.

I am now very much happy with the sound. All that I need to figure out is how to get the last bit of mains buzz away...

I did attempt to measure the power output with a 6 ohm dummy load and it comes to 11.5 watts per channel. Thats alright I would say... but many other non-diyers would go: "11.5 watts per channel from a 23 kilogram beast of an amplifier!? Thats crazy...!"

I will note the alterations as suggested.

May I also ask. The bias network seems to be a tad sensitive in the following way: When I adjust the one tube to 200mA the other tube's biasing drops a tad. The one seems to influence the other. How can I isolate them?

And a last crazy question: Would it be advisable to put the two halves of the 6H30Pi tubes in parallel to drive each 6C33C and then use a single 6H30Pi to feed the paralleled second 6H30Pi tubes? Hopes this makes sense...?

An externally hosted image should be here but it was not working when we last tested it.

 

[Jeb-D.]

I did attempt to measure the power output with a 6 ohm dummy load and it comes to 11.5 watts per channel. Thats alright I would say... but many other non-diyers would go: "11.5 watts per channel from a 23 kilogram beast of an amplifier!? Thats crazy...!"

I know what you mean. It makes me want to do a class AB Pentode amplifier.

May I also ask. The bias network seems to be a tad sensitive in the following way: When I adjust the one tube to 200mA the other tube's biasing drops a tad. The one seems to influence the other. How can I isolate them?

Check the plate voltage of one output tube when varying the bias of the other. I suspect that when you are increasing the current of one, the DC resistance of the power transformer is dropping more voltage, which will cause the current of that tube to decrease.

Also, as check the voltage across C8 when varying the bias of one channel. It should remain constant.

Let me know what you find.

And a last crazy question: Would it be advisable to put the two halves of the 6H30Pi tubes in parallel to drive each 6C33C and then use a single 6H30Pi to feed the paralleled second 6H30Pi tubes? Hopes this makes sense...?

I don't think it is necessary. Half of a 6h30pi should be more than capable of driving the 6c33c from a current and output impedance aspect. If you need more voltage swing, you can change the second stage to cap coupled. I haven't checked your operating point for the first stage, but I hope your running it at a low plate voltage. Otherwise your really going to limit the headroom of the second stage.

 

[GlidingDutchman]

I don't think it is necessary. Half of a 6h30pi should be more than capable of driving the 6c33c from a current and output impedance aspect. If you need more voltage swing, you can change the second stage to cap coupled. I haven't checked your operating point for the first stage, but I hope your running it at a low plate voltage. Otherwise your really going to limit the headroom of the second stage. [/B]

Using paralleled 6H30Pi's will merely be an attempt to be different and to 'add' one more tube on the chassis. It looks sparse at the moment with just 4 tubes... he-he!