75 Watt/Channel Monoblock Custom Amp

[bigwill]

To concur with many posts in this thread, despite being "polar opposite" to Class-A triodes in audiophile terms, there's nothing wrong with Class-AB pentode/UL output stages. There are good technical reasons why all the classic amps were designed like this, which have been articulately explained by others in the thread. Despite what many people say, and much to the detriment of beginners who end up believing (through no fault of their own) they must build expensive, hot and dangerous amplifiers, there are no sonic compromise with using conventional AB, penotde/UL output stages.

 

[Johan Potgieter]

I can not agree with the idea that adding feedback is the way to getting response flat to 20kHz. In general, my view is that this is a bad design idea.

I cannot find anybody saying that. It is obvious that maximum power handling cannot be extended by NFB, and one does design the OPT for whatever maximum output one wants to achieve at whatever lowest frequency and distortion.

In case my own post has created a misconception, one must differentiate between frequency response at maximum power, and that at low power. If the former is say 30Hz to 15kHz, the latter might well be some <10 Hz to >80 kHz, depending on the design. That is what is not aimed for; it comes automatically.

 

[Johan Potgieter]

for a response down to 20hz at 75watt, you need an opt that can do at least 150watts at 1khz.....and that is huge...

AJT, yes ......

Depending on what one considers huge. I currently work on a 100W unit, 20 Hz - >20 kHz, and my OPT measures some 13 x 12 x 11 cm, weighing 5 kg. The core is a C-core double loop 500VA at 50 Hz type.

But I digress.

 

[chrish]

Why does it have to be point to point and not a circuit board? Is it to give you the kudos that you 'built it all yourself'? To me, if you built it point to point knowing how and why you did stuff, it would give you kudos. If all you did was copy someone else's layout with zero knowledge of why it was laid out that way, there is no kudos.

I think that if you want to take the intellectual short cut of completely following a step by step process with no intention of learning about the 'why', then a circuit board or a kit is the best answer.

There is obviously some psychological aspect to your listed requirements for this project. With an understanding of those aspects you might be able to work out which of the mutually incompatible ones you are happy to rule out.

 

[TonyTecson]

$1000 for tubes may buy you these....

https://www.facebook.com/tony.tecso...09418564029.1073741846.100000349293477&type=1