SEWA - Seven Watt Amplifier

[Tyimo]

Hi!

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. (!)

I'm no good at webdesign, so I need help to do it properly.

I think I could...... if you want.

Greets:

Tyimo

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

 

[Mad_K]

Nice Do you really need the 8R2 between GND and 0V?

 

[Tyimo]

Thanks Mads!

Do you really need the 8R2 between GND and 0V?

Yes. I think it is very good for keep the amp noiseless. I used to built my JLH1969 the same way.
What do you think what could be better: to use two 100R gate resistor like i did or only one 220R?

I forgot to tell: I drive my amp with Geek's Tub Preamp for SEWA E88CC mu follower. Maybe I am a perverse, but I atracted to the "followers"......

Greets:

Tyimo

 

[Mad_K]

Try to short them and listen if you can tell the difference. It will give you test of your grounding arrangement; you shouldn't need it

The two 100R's perform two different tasks. The first one is to shield the source (preamp) from looking directly onto the zener (also, it slows down the charge/discharge of its capacitance), the second to keep the mosfet from parasitic oscillation

If you want, you could place the first 100R directly in line with the zener, to have only 100R in series with the mosfet gate

 

[Tyimo]

Try to short them and listen if you can tell the difference.

Good idea!

It will give you test of your grounding arrangement; you shouldn't need it

In this time I tryed a "new" way of grounding and it is working perfect. I connected only the case to the mains safety earth. Nothing more.

As you remember last time I had very serious noise truble with my Tubpre and SEWA connection. I didn't tell you how solved I the problem:
-Tubepre's input RCA's shield is connected to the case and to the mains safety earth.
-SEWA PSU grund and the (isolated) input RCA's shield connected together into one starpoint, then via 10R/5W+220nF to the case and to the mains safety earth. Only this variation worked good. So I can hear some very little idle noise from 30cm.

Until now all of my DIY amps has a very-very little idle noise. Sure You know this very little hissss sound. With my new amp ther is absolutely 0 noise! I think my groundig is perfect.

The two 100R's perform two different tasks.

Thanks. So I will leave as it is.

Greets:

Tyimo

 

[Mad_K]

The SEWA has ground isolation via the two 10R thermistors in the psu, I take it you didn't use them?

 

[Tyimo]

I used diode bridge instead of the 10R thermistors.
I also tryed 10R resistors without succes.
The solution was that I had to connect the input RCA's shild to gether. I got even better result with the PSU ground and the input ground together etc. as I wrote. I don't know why I need have to do this. It is strange..... Woodoo.... The most important was the 2 RCA need to connect together!?! Why?!? I don't understand......

Tyimo

 

[Geek]

Awesome stuff Tyimo!

Glad the followers worked out

 

[Nelson Pass]

Here is the schematic.
I think it is as simple as possible!

Sweet.

 

[Tyimo]

Hi!

Thanks Geek!

Thank you very much Mr. Pass!

Greets:

Tyimo

 

[cumbb]

Hai.
Do not take channel-separate power supplies. Please try it.
C.

 

[marc brown]

I would love to build a sewa like Mads & Tyimo but I'm not an electrical engineer -- just a programmer that enjoys listening to music and woodworking.

Is there any way for someone to assemble a kit that could be built by a novice? I have no idea how to read schematics (my college EE courses were many years ago) or order a PCB.

many regards,
Dave

A bit about myself: during college and afterwards I was an audio geek. In college I had a pair of Magnepan 2.5R's and an Aragon 8008BB. After college I bought some Cary SE amps and a sonic frontiers pre-amp driving some Soliloquy speakers.

After selling off my system to pay for bills & three kids, etc I'm really missing audio.

PS Thanks for hours of great reading and whetting my appetite to get back into critical listening.

 

[Mad_K]

Hello Dave, I'm sorry, but I really feel like it would be better for you to start with a comercially available kit with ready made pcb and full instructions. Like the ones from Lars Claussen (www.newclassd.com and www.lcaudio.com)

 

[tinitus]

Nah, I would take a look at this Burson, and money well spent - but they do have more expencive stuff

http://www.enjoythemusic.com/magazine/equipment/0807/bursonaudio_pi_100_buffer.htm

Instead you should use your woodworking skills and make some really nice speakers - the Burson will drive any speaker you like


OR this cheap little Trends amp may be interesting with an effektive SPAWN family speaker - there is some devellopment going on at the moment, so its hard to say which Spawn design to prefer, that is if you like fullrange sound at all

http://www.tnt-audio.com/ampli/trends_ta10_e.html

http://www.frugal-horn.com/spawn.html

Or maybe one of these GM BIBs

http://www.zillaspeak.com/BIB-Supravox.asp

 

[flg]

Dave or "marc brown", where in Maryland??? I'm a little further north but my brother "a programer" lives down there... I've seen a few members from NJ, NY, Md, Penn area. Or are you on the south side?
You can't get to much simpler but there is a handfull of other similar simplistic ideas. You just need a little help getting started

 

[Tyimo]

Hi Dave!

I think I could help you to build the SEWA.
Please send me an e-mail!

Greets:

Tyimo

 

[Tyimo]

Hi C!

Do not take channel-separate power supplies. Please try it.

What do you mean????

Greets:

Tyimo

 

[meanman1964]

Finaly,start building my choke loaded sewa.
This is the layout that I've in mind.

 

[meanman1964]

another picture

 

[marc brown]

Hi Guys,

Thanks for the responses. I'm in Germantown, MD -- about 20 miles north of D.C.

I'm sure the SEWA is pretty simple -- I just need some hand holding .

I'm a programmer myself, in bethesda. I took a bunch of EE courses in college for my engineering degree but they never seemed as easy as the differential equations or thermodynamics.