SEWA - Seven Watt Amplifier

[Geek]

Hi Mad_K,

It reads 0,5'C/W.

OK, that's the problem. My eyes are old!

What rating are your HS?

Dunno, it was scavenged from Planet10's basement.

What is your rail voltage? You need 0,25'C/W (@100W) for 2 channels if assembled as per that schematic.

About 21V with SS power filter or 22V direct to the caps.

Sounds to me like thermal runaway. To test this, try to use just one 1,5ohm resistor (R12, leave R13-16 Not Mounted)
You should now get a stable 0,4A bias. If still unstable, it might also be that the current sink is unstable, try adding a 100-1000pF cap across Q3 Base and Collector.

It's fine and dandy long as she's cool. I gave that CCS a real workout on the breadboard before assembling it (had it sinking about 8 amps for 20 minutes with the MOSFET submerged in a water bath 'cause I didn't have the heatsink yet)

Thanks for pointing out my error. As a glassfet dude, I don't normally concern myself with heat

Cheers!

 

[lineup]

Here is the prototype of SEWA, my latest power amplifier creation:
Inspired by Nelson/First Watt, this is my take on a simple-as-possible power "amplifier".
----
It requires a preamp that can swing +/-10-12V and has low output impedance.

So, here you have it: A couple of resistor and caps and a mosfet.

What a great idea, Mad_K
Why didnt I think of this one first
Regards
Lineup

 

[Tyimo]

Hi my friend Lineup!

Don't you think that you are a bit late with this comment?

BTW, I would like to ask some offtopic from you about your Widowmaker amp. Where can I reach you with private mail?

Greets:

Tyimo

 

[lineup]

As always, you can reach me via PM / Posts
in my own audio forum
if this is not good, then nothing is good

In what way is my comment late - you must be jokin', Tyimo
Cause, I have even still today read comments of the Trojan War in Hellas
and about some fellow Jesus Christ (2000 years)

 

[lineup]

Hello! Mads_K

I post the Rev. 1 schematic of SEWA.
I hope it is the latest version, but I am not sure.
I just did not have the time to search all pages ...

It is one sweet project
It is as close to Nelson Pass early philosophy we can get.
Keep it simple AND good, boys.

Here are some osci pics.
Preamp with 0.2V and 1.5V input.

It has a lot of power! Wit the ZV9 and A5 has incredible good sound!
Tyimo

Awesome stuff Tyimo!
Glad the followers worked out

Sweet.
.

 

[lineup]

Here is what is Rev. B
and probably is Mad's latest variant. Bill of material needed + Circuit.
From post #233 and following:
http://www.diyaudio.com/forums/showthread.php?postid=926979#post926979

THE SCHEMATIC .. uses 2 x IRFP150N
http://www.diyaudio.com/forums/attachment.php?s=&postid=926979&stamp=1148818676


Regars - lineup

 

[lineup]

Thanks for the nice words!
Here is the schematic.
I think it is as simple as possible!

I forgot some parameters:
Case weight: 15Kg
Temp: only around 40C. (!)

Greets:
Tyimo

P.S.: No CCS, No resistor! Choke Load is RULEZ!!

Sweet.

Wooow!

Even our father (papa) thinks it is sweeet!
Now your fortune is made, Tyimo.
How good for me to be one of your friends.

I could create a diy website .. just based on that amplifier of yours!


Line 'linie' Lineup - greets

 

[Tyimo]

Thanks Lineup!


Tyimo

 

[Tyimo]

I could create a diy website .. just based on that amplifier of yours!

Wait a little bit please!
Something new will be born in some weeks....

Tyimo

 

[lineup]

I wait
No problem.
you make me very curious .. like a child or one monkey .

 

[Gyuri]

Hey, Tyimo, we could keep a seance once.


Gyuri

 

[Tyimo]

Hey, Tyimo, we could keep a seance once.

Yes, just give me some more time to finish my next projects....

Tyimo

 

[zlati84]

Here is my design of SEWA

Inside

 

[planet10]

Have you got bigger picture?

dave

 

[zlati84]

yes, sorry for my mistake
[img=http://s2.postimage.org/oqzY9.jpg]
[img=http://s2.postimage.org/oqYUA.jpg]
[img=http://s4.postimage.org/KAZ8S.jpg]
[img=http://s4.postimage.org/KB5Di.jpg]
My amp works on 32V supply, 2.5 amps bias, temperature of the heatsinks is about 62 degrees C. ( Power is in a separate box)
The preamp is BOZ
Next week I will made rear panel with speaker and signal connectors, i hope

 

[zlati84]

I finally made it with pictures, sorry for my double post

 

[zlati84]

My SEWA become to a little hybrid amp with big sound
The tube preamp is E88CC SRPP, made by this schematics

This is the final design

 

[Roscoe Primrose]

Tyimo - When you did it, your choke loaded design was about as simple as possible. But, if you use the now available IXTH6N50D2, you can eliminate the bias circuit and input cap if you use a choke with the correct DCR to properly bias the FET, 0.54ohms ought to be a pretty good number ;-)

Even simpler!

 

[Tyimo]

Hi Roscoe!

Thanks! I know it, but it is hard to find this Mosfet here in Europe.
Do you know any source?

Greets:
Tyimo

 

[djk]

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