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Old 18th October 2007, 10:07 AM   #1
Shaun is offline Shaun  South Africa
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Default The last Hurrah

I'm looking for the amp to end all amps (what's new?). Recommendations requested, please. But before you brush me off, please listen to my story.

I've built a few power amplifiers, from the ETI 5000 to Elektor Mini Crescendo to some chip amps and finally, being EE educated, I successfully developed my own amplifier with the guidance of Douglas Self's EWW articles & books.

Link to Luc Henderieckxs' web page. He helped me develop the amp.

I have to thank DS for demystifying the design of power amplifiers for me (I had so bought into the 70's/80's audio industry hype that I truly did not believe it was within my capabilities to produce anything that could compare to the illustrious audiophilia of the day).

But now, aged 41, I have to draw the line and get rid of all those spare parts that I have collected over the years. I finally realise that I'm never going to develop that class D amp, and I'm not going to start my own audio line. Besides, the main factor that motivated me to Do It Myself all those years ago is no longer (fully) applicable to me- poverty! (Know any rich students)?

I still can't afford to splash out on the latest Krell or even vintage Yamaha, so I have to do what I know best: build it myself. My Blameless/Load Invariant amplifiers are good medium-powered amplifiers, but I now want to build something with the pretensions of those Nakamichi's and Thresholds in the other discussion thread. You know? Go out in a Blaze of Glory!

But perhaps the specification for this amp will be different:

Negative Feedback: Global
Configuration: Lin-based, single-ended, solid state, bipolar
Slew-rate: similar to Stochino amp
Class: AB and/or class H (not class A!)
Output Power: 200W/8R, 400W/4R, 800W/2R continuous (accepted that these figures will be different in practice)
Protection: Short-circuit, overload, VI, DC
Power bandwidth: 5Hz-100kHz (for the helluvit)
Sensitivity: 1V gives 100W/8R

I already have some transformers, bridge rectifiers, reservoir caps, heatsinks, Motorola driver transistors & output devices.

In summary, I want to build a higher-powered Stochino power amp with "the works" electronic protection.

So: know any amplifiers that fulfill these requirements (perhaps they already exist in these pages)?

Alternatively, do you have suggestions for the right ingredients (beyond Douglas Self) for a super-fi amplifier?
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Old 18th October 2007, 10:37 AM   #2
Nordic is offline Nordic  South Africa
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Hey Shaun, nice to get you over here at last, those tweeters sound pretty good hey. shame my drivers in those boxes are so tired... I'm thinking of useing them in biamp config, with another HRII amp.
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Old 18th October 2007, 11:20 AM   #3
Gordy is offline Gordy  United Kingdom
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1. Perhaps by 'single ended' you mean 'not bridged'?

2. Presumably you would like to design with some form of push / pull output stage, as single-ended output would require Class A, and be difficult at your desired power levels.

3. Take a look at some of the suggestions in this thread: Reference DIY amplifiers

4. Perhaps a tweaked and re-biased Krell KSA clone, as noted elsewhere on this site, might be a possible direction for you.



( Moderator : the following links to the Krell projects given in the thread 'Reference DIY amplifiers' do not work. Please update...
http://www.diyaudio.com/forums/show...t=&pagenumber=1
http://www.diyaudio.com/forums/show...t=&pagenumber=1 )
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Old 18th October 2007, 11:32 AM   #4
Shaun is offline Shaun  South Africa
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Quote:
Originally posted by Gordy
1. Perhaps by 'single ended' you mean 'not bridged'?

2. Presumably you would like to design with some form of push / pull output stage, as single-ended output would require Class A, and be difficult at your desired power levels.
Hi Gordy

Yes, that's exactly what I meant. Sorry about the incorrect terminology.

Aren't those Krells class A? If so, they would require a revised biasing scheme.

I'll check out that link.
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Old 18th October 2007, 11:46 AM   #5
Gordy is offline Gordy  United Kingdom
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Quote:
Originally posted by Shaun


Aren't those Krells class A? If so, they would require a revised biasing scheme.


Yes they are, and yes they would.


I think help may be available from ACD on this forum. His commercial site : http://www.delta-audio.com/Krell-Clone.htm

Also check out the schematics section on his personal site for inspiration: http://www.audio-circuit.dk/
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Old 18th October 2007, 12:28 PM   #6
Shaun is offline Shaun  South Africa
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Wow! ACD's site is a treasure trove! I rather like the Lynx 3 design. Will have to analyse that.

My intention is to build a "laboratory grade" amplifier; esentially, it needs to be neautral.
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Old 18th October 2007, 01:25 PM   #7
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Do yourself a favour and build the Stochino Amp. You will never regret the effort and the results.
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Old 18th October 2007, 02:05 PM   #8
Shaun is offline Shaun  South Africa
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Hi Samuel

I assume you have built this amp? IIRC, it is a 100W amplifier. I like the concept, and do wish to retain the ethos behind the design, but I also want more headroom, thus the power spec. It should not be a problem for me to develop a higher-powered version, but re-engineering it may push the present set of components beyond their capabilities (in terms of their operating conditions). It is this input that I need (design considerations/pitfalls) to make it a success.

For instance, the standing currents around the circuit would change, and extra buffering stages may be required. I'm just speculating right now, but these all need to be considered.
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Old 18th October 2007, 05:21 PM   #9
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Default You are welcome Shaun..... HRII is excelent, and i will bring something even better


in December 23, because of Christmas time.

I am already listening to the Dx Precision.

I will explain how it works...or how i forced it to work.

regards,

Carlos
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Old 18th October 2007, 06:17 PM   #10
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I understand the need for more headroom. However, the Stochino can hardly be pushed into any kind of overdrive in normal domestic environments, even with speakers that have low sensitivity. The 100 watt Stochino sounds like a much more powerful amp that it really is.

If you were to change the input differential pairs to 2SA970 and 2SC2240, as well as the outputs to IRFP240/9240, use +-58 volts for the input stages, the amp will easily do more than 120watts into 8 ohms.

The sound is so resolved and dynamic, it would take something of an equally class act, to even rival its sonics.
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