SEWA - Seven Watt Amplifier

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you know steenoe, those small perky single ended class a amps are just too simple not to give a try, made myself a headphone amp with those smtp mosfets you gave me btw, it hums like mad, but the music it makes is nothing to sneeze at. (if you can ignore the HHUUUMMM)

i have to at least try some different paths to audio nirvana.

-Marius:)
 
frugal-phile™
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steenoe said:
with your interest in fullrange speakers, some kind of Zen amp ought to be just the thing;)

:)

Got one of those coming together. Boards swapped for postage. Power supply surlus from a DEW line installation (ie military grade CLC 48V 10A) $5, Board populated to collect a debt i wouldn't otherwize have collected. Heat sinks for helping a guy move. Just need a bit of chassis, and some assembly.

dave
 
steenoe said:
How is your grounding done? Did you make a starground?
Hum is absolutely not funny, especially into headphones.

Steen:cool:


huumm(phun), i made a starground yes, even used a big phat choke on the power rail. oh well i have not the time to be playing to much with it now anyways, i'm building the critical q subwoofer, two of them to be precise.

oh, i'm looking forward to hearing them sing. :D
making my own amps though, offcource.
 
The attached file includes the djk sugestions and why not "let there be light"... as maybe Mr. Pass would say. At least one can save heatsinks.

Nice project, BTW. Looks more linear than Follower99, published years ago in an Italian site.

Regards
Asen
 

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I was kind of hoping someone would suggest some illumination :D

No need for a 10uF input cap with 470K input R 0,47-1uF will be plenty. It is also important to add a similar cap in paralelll with the 10000uF outputcap.

After listening to the amp for some weeks, I am stunned over the performance. Especially the pitch black silence (it is absolutely quiet) followed by firm and controlled bass attacks!

edit: There is also no turn on thump, because the bias network starts the amp up slowly. It takes a little minute to fire it up, and another hour to warm up.


I didn't specifiy a powersupply, but I use a 600VA toroid (~32VAC secondaries would be nice) rectified by ISL9R3060G2 30A 600V Stealth diodes and a pi filter with 22000uF-0,22 Ohm-22000uF Evox-Rifa PEH200 caps. One secondary/rectifier/filter per channel.
 
Neat little amp! I seem to have missed it the first time around.

By the way, you don't necessarily need to run everything through the output cap. If you're running two or more way speakers, particularly those which are set up for bi-wiring, you can split the high and low pass sections and drive the high pass section straight off the amp's output provided there's no DC path to ground ahead of the series cap in the high pass section.

I've been experimenting with some similar ultra simple followers and even using the big Black Gate 4,700uF N type cap, it sounds significantly better when driving the high pass section straight off the output.

se
 
Hello Mad_K,
This is a nice little project which I would like to try. Thanks for posting it. Since I am a noobie..... I have a question about the schematic. There is a V+ symbol in the top right of the schematic close to +40V. What should be connected to this point?
Thanks:angel:
 
if I understand correctly output power of SE MOSFET amp depends on used PSU. In your design 40 Volts gives 7 Watts. I would like to use this amp to work with DIY single-drive voight pipes. Used drivers are 8 Ohms with no X-over. I think, those speakers are rather efficient. I do not listen to music at high levels. Would it be possible to lower the amplifier 's output power to maybe 3 Watts by using lower PSU voltage? The reason I ask this question are two R-core transformers which I bought long time ago. Those are 19 Volts @ 2 ampers units. Output voltage after rectification would be 27 volts at 2 amps. Is it enough for lower poweramp?
Thanks again for your help.
 
It is very easy to scale the amplifier down. My prototype runs on 22,5V and gives about 3W. I'm using a 600VA 2*18V transformer (2*18V@17A). You could get by with a 250VA 2*18V (2*18V@7A). I'm afraid your existing transformer are just not heavy enough.

To make a 3,5W (Let's call it SEWA-3,5) simply use a 24VDC supply and reduce the 10 Ohm power resistor to 6,8 Ohm. Current draw will be approximately 2,15A. ;)
 
SEWA Rev.1

janneman said:



Hmmm. Yes, you're right. On to a CS, then...

Jan Didden

Here is the revised version of The Seven Watt Amplifier.
I've been listening to this design for about 3 months now, and I can honestly say that it really lets me "Live The Music". This new version features an active CCS, higher input impedance (250K), lower power dissipation (45W per channel) and generally better performance.
 

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