John Curl's Blowtorch preamplifier part II

[Zaphod Beeblebrox]

You probably are not totally used to Max's take on Vogon poetry.

Ah, that explains everything.

The answer, in that case, is 42.

 

[Tournesol]

Back EMF does not occur...

????

 

[Jim the Oldbie]

Ah, that explains everything.

The answer, in that case, is 42.

Damn, now I wanna watch the movie again.

Wish I could figure out what's wrong with my projector...

 

[Zaphod Beeblebrox]

Do the right thing and listen/watch/read The Hitchhiker's Guide to the Galaxy in the order that they were unleashed on the world.

First came the radio play.
Second was the book.
Then came the 1981 BBC TV series.

All three are far superior to anything released subsequently. IMO.

 

[scott wurcer]

First came the radio play.
Second was the book.
Then came the 1981 BBC TV series.

I have the radio play on 6 cassettes, and the original 1981 series on DVD. There is an old LP series (?) but I have only one and don't know if they did the whole thing.

It even invented bitcoin. The last instalment is pure genius only "The Prisoner" had as many insights into the future. "It's not me it's the committee".

 

[Jim the Oldbie]

...First came the radio play.
Second was the book.
Then came the 1981 BBC TV series.

All three are far superior to anything released subsequently. IMO.

Yeah, I know... I still like the movie too.

Plus, I miss my crappy old 720p projector, and can't afford to upgrade right now...

 

[dadod]

This is an interesting PA design. I hope it gets written up in Linear Audio or better.

Here is 2 Ohm data some one asked about.... limited by the bench supply ->

The distortion hardly changes with load Z and output level and freq. (!)


View attachment 651072



THx-RNMarsh

If someone interested in this amp I am selling two tested boards, look here.
http://www.diyaudio.com/forums/solid-state/243481-200w-mosfet-cfa-amp-111.html#post5275554
Damir

 

[gpauk]

I still have the original HHGTG LPs... Must get them out again...
"Starship Titanic" was a good game, as was the original text based DOS game, if anyone remembers that!!

 

[billshurv]

He did get one thing wrong. We are not heading for the shoe event horizon, rather the starbucks event horizon!

 

[FdW]

..."Starship Titanic" was a good game, as was the original text based DOS game, if anyone remembers that!!

Should be floating around here... somewhere

 

[stinius]

This is an interesting PA design. I hope it gets written up in Linear Audio or better.

Here is 2 Ohm data some one asked about.... limited by the bench supply ->

The distortion hardly changes with load Z and output level and freq. (!)


View attachment 651072



THx-RNMarsh

Hi
You don't say anything about what the test frequency is, I guess it is 1K.
If it is 1K those numbers are not anything to write home about.
Maybe you could do the same test at 20K?
I would also like to see the clipping behaviour.
Please run it in to clipping and show us if it is oscillating.

Yours
Reodor

 

[john curl]

I think they are VERY GOOD NUMBERS Richard. '-)

 

[scottjoplin]

Damn, now I wanna watch the movie again.

No,no,no, listen to the original Radio 4 series
Oh. I see he's already been told good and proper.......

 

[gpauk]

Now what about repair? I don't know how to make my amps easier to fix.

Does that mean that you have designed them to be as easy to fix as possible?

 

[john curl]

I have very little control on the 'fixability' of my designs. I make schematics and prototypes. The final assembly is done by others, none of whom I have ever met.

 

[hitsware]

If your prototype layout were straightforward and open enough,
one would assume fixability (in that whoever did the final layout
couldn't resist following your example)

 

[Zaphod Beeblebrox]

I have very little control on the 'fixability' of my designs. I make schematics and prototypes. The final assembly is done by others, none of whom I have ever met.

Thank goodness for that. I had to repair a JC1 awhile back. It was not much fun at all. Clearly, an amplifier designed to be assembled inexpensively. That said, it does sound quite decent.

 

[billshurv]

Can't be as bad as the double-DIN stereo in my car where the power amplifier ICs are buried under everything else and you have to take it apart from the top down!

 

[simon7000]

And I just had a Crest P9200 come across my bench. A bit of bother to get the main PC Card out. You have to remove the power cord, the input terminals, the output terminals and the power switch/circuit breaker. Once all that is out you can with a bit more trouble jiggle out the card.

This one once out showed the switching power supply failed and not just burned a hole through the fish paper insulation but deep into the case top.

Ordinarily when I get a product like this it goes to eBay as a dead unit. Folks buy it that way. Looking at the damage and lack of safety this one goes to the recycle bin.

As to eBaying bad stuff it seems to be an excellent way to economically handle some gear. One particular amplifier sells for a bit more than $200 DEAD! A new unit costs $325 wholesale. Just not worth fixing them if it is anything other than stupid simple.

 

[john curl]

I don't repair them, because they are so hard to fix. I have a JC-1 under my workbench that needs fixing. I just converted it to a high voltage power supply by pulling the fuses from the B+. Still, we make a pretty good amp for the cost of the unit.