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Old 19th September 2005, 08:51 PM   #1
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Default An amplifier project Im looking for...


This is my first post on these forums, and this project will be my first DIY amplifier.

I have a pretty good general knowledge of how electricity/circuits work, and know how to observe decent safety practices.

What I'm looking for is a good starter project for a pair of tube monoblock amplifiers.

Currently, I use a pair of dahlquist dq-20's driven by an old HK PM665.

What I would like to do is replace my HK with the homebrew tube amps, but I am concerned about power requirements.

I have spent hours googling different amplifier designs, and just can't make a choice as to what I want to put my money in to.

The 300b diagrams i've looked at seemed to be the best way to go, but with only around 8-12W of output, I'm wondering if this will be enough to drive the dahlquists. Additionally, 300b's can be quite expensive, and for a first time around I don't know if I trust myself to do a smoke test with $500+ parts =)

My listening space is a rectangular 20'x15' room and the optimum listening seat in the room is stationed roughly 10' from the speakers (governed in part by the way my wife wants the livingroom set up =) )

The speaks are 3-way, 4 ohm minimum, with a minimum stated input power of 50W and a max of 250W.

Given these parameters, can anyone suggest a good amp to start off with that will drive these speakers to decent listening levels and won't cost an arm and a leg if I happen to fry the electronics?

Thanks in advance,

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Old 19th September 2005, 09:11 PM   #2
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Here's the good news. Welcome to the forum.

Now the bad news. There's no way that a 300B SET is going to be able to drive your loudspeakers in that listening room to any sort of a level. The poor little things will be running at full power all the time and sound terrible. I'm afraid that for a loudspeaker like that you really are going to have to go push-pull (alright, I know that 833 SET designs exist, but they're not exactly a "first project").

As you point out, 300B are expensive. For a first project (which might not work first time), you'd be better off going for something push-pull based on 6550 in UL configuration (should be good for 50W+).
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
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Old 19th September 2005, 11:07 PM   #3
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Ok, I really appreciate the quick response. I'm headed off to work for now, but when I get home, I'll do some searching for 6550 PP designs.

In the meantime, if you happen to have any links to some good diagrams that I could look over, that would be great.

Thanks again,

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