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Old 18th September 2012, 02:18 PM   #21
ide2003 is offline ide2003  Indonesia
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This is the biggest, the meanest and the heaviest DIY amp box I've ever made for a friend, needless to say that he is a Pass fan, so do I , made only one and that tile is 30x30cm btw..Thank you mr Pass for inspiration, I hope you don't mind
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Old 19th September 2012, 03:02 AM   #22
JZatopa is offline JZatopa  United States
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Originally Posted by Cassiel View Post
An F5. Not that big but for a tube guy pretty big. I'd never build a tube amp like the one in the second picture. That's not big, that's huge and crazy and awesome....and kinda stupid too. Dr Frankenstein was mad, you know....
What the hell is that second amp, something from an old movie theater? That thing looks awesome.
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Old 19th September 2012, 11:48 AM   #23
Cassiel is offline Cassiel  Libya
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It's a tribute to the Fertility Gods by Chinese worshipers.

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Old 19th September 2012, 02:10 PM   #24
Krisfr is offline Krisfr  United States
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Originally Posted by jacco vermeulen View Post
If not the most Stupendous, my vote's for the most stupid power amp ever.
The amp driving a MagnaPlaner was listened to by several people and they said that they never heard anything so easy to listen to before. I never got to build a second channel, so the stereo effect never got listened to. It slewed in excess of 400 volts a second, I did not have the greatest of test equipment back then.

But Jacco why did you use the word stupid, that amp had a lot of peoples attention back then, including Fredrick Barrett, the person behind the Sequerra tuner. You seem petty to use such a pejorative term. I do not see your point, SORRY but I just feel it was un-called for.

The originator of this thread did not ask for anything but "what was the biggest"
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Old 19th September 2012, 08:30 PM   #25
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Originally Posted by Krisfr View Post
why use the word
Easy, read the MJ15024/25 datasheet ;
- Not meant to be used with rails way over 110Vdc.
- At 120Vdc rails, second thermal breakdown at anything over ~0.6A

Even attempting to reach the 746W level would terminate the output stage, all 20 of them.
Otherwise a fast transient would take care of it.
120Vdc rails are very dangerous, 250Vdc cans very exotic, and all that for an output stage that self-destructs.

Even a quarter century ago, the ticket for very high power was to go bridged/balanced.
750W from a pair of 250/300W amps is a stroll in the park, much safer rail voltage levels, cheaper parts, and a peak output current number that's more in line with continuous power level.

This forum is crowded with folks from India and Pakistan, who just crave to build amps of bizarre power levels.
Advocating the use of 120Vdc rails is not smart, in particular with devices such as TO3 Motorolas. (and anything other BJT than MJL4281/4302)
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Last edited by jacco vermeulen; 19th September 2012 at 08:35 PM.
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Old 20th September 2012, 03:52 AM   #26
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Originally Posted by CharlieLaub View Post
Looks like Dr. Frankenstein should have invested in some non-marking wheels for his super tube amp thingy...
- - - - > SNIP PHOTO < - - - -
I'm surprised that nobody has picked up a pair of AM radio transmitters from the last generation of tube gear and re-worked them as audio amps. From what I recall of the Collins 820D-1 I think it could be done as a DIY project. Conceptually, I speculate the biggest technical challenge would be rewinding a modulation transformer as an output transformer. Non-technical challenges would include floor space and the WAF.

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Old 20th September 2012, 03:59 AM   #27
iko is offline iko  Canada
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Originally Posted by jacco vermeulen View Post
This forum is crowded with folks from India and Pakistan
You might want to check your facts again on this one. Way off...
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Old 20th September 2012, 04:42 AM   #28
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Originally Posted by Itsmee View Post
Does anyone know if there is a taller domestic amplifier than these?

Not speakers - My Photo Gallery

I remember speaking to the designer Colin Wonfor, the largest was 500 Watts single ended class A, the output stage was unusual in that it was a mixture of bipolar and FET, if I remember correctly, the bipolar was used for the CCS, while the FETs did the driving.

It was 300W mono, used 80 FETs,, two HT rails with 1.5 Farads on each, 2 1KVA transformer, 180Kgs, 1.8M Tall and ate 1800W just in idle.
It was not based on Nelsons design but on a large dynamic load I designed once.
The largest I had to design (Class B) was 10KW, in Class D 1.5MW, toys now days.

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Old 20th September 2012, 08:34 AM   #29
Itsmee is offline Itsmee  England
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Hi Colin, thank you for the correction, my memory is not what it use to be.

Those amps did leave a lasting impression on me, I have always been curious about what was inside them, is the schematic for the 300W available to the DIY community - not that I need that kind of power.

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Old 20th September 2012, 03:07 PM   #30
Krisfr is offline Krisfr  United States
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Jacco just to being doing something in my spare time, and just because I have dealt with much more dangerous circuits than High Current plus and minus 120 rails and caps, I will attempt to learn something with the MJL4281/4302 you recommend.... How about a 1000 watter for our good friends from the sub-continent. Maybe you could kibitz on the design in a helpful way and make my day.

I wish Mr. Barrett was alive today and would give the world another Superbly Excellent State of the art, audio product such as the Sequerra Tuner, he would show you for sure. But at least I will try.
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Last edited by Krisfr; 20th September 2012 at 03:09 PM.
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