SEWA - Seven Watt Amplifier

[seagull]

Hey all, I've built this design a couple of times now and the pictures below are of my latest build. I used an Elektor op-amp design with "high-end" caps and the set-up is magical. I typically drive the SEWA with valves (Class A or SRPP), but oddly enough this op-amp design is the best I've heard.

Chris

 

[Bigun]

Chris - I really like what you've done there. The pre-amp looks great, nice high quality parts, very clean construction. It's one of those secrets that many won't admit - a good opamp is a great solution.

I like the construction method for your SEWA too; a little off-the-wall but I can see your 'valves' heritage in there.

 

[res07njc]

Love the terminal strips too. bravo!

 

[Bare]

Ok.. seems like a LOT of bits.
No longer a very simple construct .. is it?

 

[johnego]

I typically drive the SEWA with valves (Class A or SRPP), but oddly enough this op-amp design is the best I've heard.

Class-A or tube lovers prefer opamp with second order distortion, monotonic distortion spectrum or simply opamp with very good mid. OP27 is known for its vocal superiority, and OP227 is an improved version of OP27. The only issue is probably the 2.8 V/us slew rate which is low but probably not too critical for most music.



Other opamps that might be preferred by tube lovers are AD795 (slew rate below 2 V/us), AD823 and LT13xx (LT1358 for low current, LT1364 for high current drive).

 

[seagull]

Hi again all,

I recently upgraded my OTA (2.5-Watts) to SEWA (3.3-Watts). This has a valve based Class A pre as the driver. Attached you'll see I dispensed with half of the heatsinks and fan - runs only warm. Very pleased with my upgrade.

Chris

 

[volker1887]

Sewa boards

I am new to this forum. A friend of mine has built the SEWA7 and uses these two power amplifiers. My question: If I want to build this amp, how can I get the schematics, etc.? Is there someone who wants to sell his SEWA? Unfortunately, I myself can not build this part because I have no idea about electronics. Thanks for the information!

 

[Dennis Hui]

There is a schematics attached to the first post:

https://www.diyaudio.com/forums/pass-labs/66822-sewa-seven-watt-amplifier.html#post753744

I don't know if there has been any revisions since then.

If you are interested in an amp with no voltage gain (like the SEWA), one
that is really easy to build is the Mofo:

Build This MoFo!

https://6moons.com/audioreviews2/mofo/mofo.pdf

 

[volker1887]

There is a schematics attached to the first post:

https://www.diyaudio.com/forums/pass-labs/66822-sewa-seven-watt-amplifier.html#post753744

I don't know if there has been any revisions since then.

If you are interested in an amp with no voltage gain (like the SEWA), one
that is really easy to build is the Mofo:

Build This MoFo!

https://6moons.com/audioreviews2/mofo/mofo.pdf

Hi Dennis, thanks for the tip! Can you build me some? ;-) Unfortunately I have absolutely no experience with the construction of such components! Or do you have some for sale? I would like to operate the two amplifiers with the Altec Santana I. Greets, Volker