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hugobross 24th November 2001 04:01 PM

Hi, I was just searching for new schematics to build and suddenly I came on this site, this designer doesn't think about some hundred watts but more about THOUSANDS of watts

just check this out:

http://homepages.picknowl.com.au/glenk/default.htm




HB

djk 25th November 2001 12:54 AM

A design exercise, so what.The Carver M1.5T ran on higher rail voltages and was bridgeble too.Just take the Carver design and add however many outputs you need to drive whatever impedance you need.Other than a shaker table I have no idea what you could drive with this thing.

Hedlund 25th November 2001 07:21 AM

As far as I can see, the designer is serious about this amp.
But with these gain stages sound quality won't be very good.
Like a midprized integrated Yamaha or so.

For PA use, it's a killer, even if 20KW is a little optimistic.

This amp is not for you if you want goose bumps.

Janne

walker 25th November 2001 10:09 AM

Is he going to rewire his house with superconductors?
I fail to see any high fidelity or PA, (not smart to have so many eggs in one basket) applications and damn lethal to boot.
Thatís not to say that it isnít an interesting project.
Regards WALKER

djk 25th November 2001 10:47 AM

"even if 20KW is a little optimistic" It is a brdge amp that runs on regulated +/- 115V DC. If the CE voltage drop at full power was 15V (an excessive value for the 100 output transistors) it would be putting out 141.4V RMS, which would be 20KW at a 1 ohm load. I use such an amplifier daily to shake things at 10+Gs. My amp is also watercooled and is built into a six foot tall 19" rack."Is he going to rewire his house with superconductors? " Mine runs on 480V three phase. "But with these gain stages sound quality won't be very good. " With cascoded cross coupled dual differential inputs loaded with current sources driving a cascoded complementary second voltage amp this would be a very high fidelity amp. The Leach 'Double Barreled' amp, GAS Ampzilla II, and the Crest 8001 have virtually the same front end. The Crest uses a tiered power supply too, although with a different means of swiching between rails. The rail switching scheme presented here is similar to what QSC and AB International use. Since this is a bridge amp the designer could simplify his rail switching design considerably by using the same method used by Crown in their VZ 5000 and VZ 3600 amps. It is just a bit large for the average hi-fi.

Hedlund 25th November 2001 12:18 PM

Djk,

I don't agree with you.
I have designed more than 80 different amplifiers and KNOW that differential gain stages is the worst thing you can have when the signal is single-ended.
Only odd-order distortion and with NFB even worse.
And things get worse the more differential stages you add.

I have built both Leach amps and can only say that I have past thier sound quality by quite a margin.
Had GAS The Nine which was considered better than Ampzilla and must say that it sounded bad.

Janne

djk 26th November 2001 07:24 AM

"Hedlund Djk,

I don't agree with you.
I have designed more than 80 different amplifiers and KNOW that differential gain stages is the worst thing you can have when the signal is single-ended.
Only odd-order distortion and with NFB even worse.
And things get worse the more differential stages you add. " That is all fine and good.But what do you listen to? All recordings are made with the signal going through many differential stages.Any mic pre-amp with a balanced input would fail your criteria, including a single ended class A triode running open loop because the mic input transformer is differential.Any push-pull output stage even if it was a pair of triodes running class A with no feedback would also not meet your criteria because of the differential action of the output transformer.And what about the interstage transformer? A very common technique is to reverse the phase between single ended stages, this is a differential distortion reducion technique too. Do you make wax cylinder recordings exclusively or have you progressed to cutting your own laquers? Do they let you take your record lathe to the concert hall? I'll grant you the 20KW amp that was the subject of this discussion had way too much open loop gain, but I know how to fix that. I've heard amps with and without feedback that sounded good. I've heard both single ended and push-pull amps that sounded good too. I've heard single ended amps that didn't sound good. I've heard amps with no feedback that didn't sound good. I can't in good faith agree with the generalization that you have made. In parting I must say that I find great potential in the push-pull tiered power supply design embodied in the Nelson Pass patent http://www.passlabs.com/images/misc/pat_5343.jpg with the amp running class A on the lower voltage tier and transitioning to a cascoded high bias class AB off the high voltage tier. This patent can be easily rerofitted into any amp with series connected outputs, ie: SAE 2400, Dynaco 400/410/416, Ampzilla, Heathkit AA 1800, Leach 'Double Barreled', etc. If you look at the LC Millenium, a very highly acclaimed no feedback class B amplifier, you will see that it is basically a Leach with the feedback input removed, more emitter degeneration for less loop gain, and a DC servo so that it can be direct coupled. I would like to try the Nelson Pass Patent on this to increase the bias to class A and still keep the high power without the heat. Not all of us are satisfied with a 2A3 running class A single ended open loop with a whole whopping 3.25W!

Hedlund 26th November 2001 08:55 AM

Djk,

you better start reading my statements better, so here is a little update.

If you have a single-ended signal that is feed into a differential stage you better use both halfs outputs, not just one of them.

If you only use one of them you better have the signal into the differential stage balanced.

I have nothing against balanced signal or differential stages, but you have to use the correctly.
And in the case of 20KW amp, Leach amps and also LC audio's amplifiers they will sound much worse with single-ended signal input than with a balanced.

Janne

Hedlund 26th November 2001 09:01 AM

Djk,

regarding LC Audio's Millenium.
It already is a class A design, not class B.

Janne

djk 26th November 2001 11:08 AM

http://www.lcaudio.com/forst.htm
The ZAPsolute Mk4 is a kit form (or handbuilt ready to play) high end Pure Class A amplifier, configurable in 50, 78 or 118 Watts in 8 Ohms Class A. Capable of driving down to 1 Ohm with 6 times higher power. (Shown on picture).

The End Millennium, a 100 - 300 Watt Class A/B amplifier in kit form, with short circuit protection, DC servo, easy to build, but with sound quality comparable to the best available factory made amplifiers in the world. Built with high grade capacitors, high quality cabling and a huge power supply, with The End Millennium You'll have the amplifier to knock out Your freinds' 10 times higher priced factory built amps.

Like I say, I'd like to try an efficient class A design of the Millenium using the Nelson Pass patent.As to your remarks about the 'GAS the Nine', the Sumo Nine was designed by GAS founder James Bongiorno. And it did have differential inputs. And it also had horrible capacitors. Unbypassed polarized electrolytics in the signal path, ceramics everywhere, and no power supply bypassing. It's a wonder it sounded as good as it did. But I believe the topology was sound. I just picked up one to play with. I'm sure I will be able to make it sound vastly better with a little bit of effort. Have you seen the schematic on one of these? It's two single ended output stages bridged and driven differentially from a common diff pair. A Wiggins Circlotron.


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