SEWA - Seven Watt Amplifier

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#201
Looks OK at first glance, except for the 0V connection (PSU return ground) should be on the opposite side of the boards near the source resistor array 😉 edit: Remove the ground loop that runs around the board edges too..
 
#203
Because all of the return current (2A) to the PSU runs through the 0V pad. You don't want to have this current running through your signal ground and mixing with the speaker return etc. In short, you will get higher distortion and noise. 😉
 
#206
Proto PCBs arrived today ;-)

I'm going to try te get them assembled and tested during the weekend. If everything is OK, I can ship them next week 😉
 

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#210
Mad_K said:
Assembly completed. I think I'll take a break now and test them tomorrow 😉
Click to expand...


WOAH! looks nice.. I love smd stuff. I should post a pic of what i just completed 🙂

When are we able to buy them from you ? When i purchase mine would you mind including the smd resistors and the smd transistors for a few extra $$

I just did a order for 20 resistors ( smd from mouser ) and well the resistors were 1$ us and the shipping was 12$ 🙁
 
#211
JFet SEWA

Hi Mad!

If you could find a JFET that can take as much heat as a MOSFET, you can simply pop it in the SEWA circuit with a minor adjustment of the bias voltage divider to account for the different VGS. However, since such a device is not yet avaliable, you'd have to get smart and utilize some tricks like cascode operation to get the dissipation down.
Click to expand...

Would it be possible to use paralleled JFets? I mean just to use 3 or 4 Lovoltech's Jfets instead of the one IRFP150.

Greets:

Tyimo
 
#214
Thanks Lars, good suggestion. Unfortunately I don't have much time for developing new stuff novadays.

Now I'm drilling and tapping holes in my heatsinks 😉

(While listening to my brand new Gamma Ray - Majestic picture disc vinyl record) 😎

-Live The Music-
 
#218
DC test: passed ;-)

The SEWA proto boards have passed the initial DC test.
There was a small change in idle current, because the BC850C only has a little over 0,5V BE drop in this circuit. Bias current dropped to 1,7A. This is a little on the low side for 4 ohm speakers, but might be beneficial for people with 8 ohm speakers and marginal heatsinks as the amp now only dissipats 38W pr channel. What do you think, should I change the idle current back up to 2A or alter the design to 1,7A idle current? (This is what I'll be using). I will be taking the AC signal and critical listening test tonight or tomorrow 😉
 
#219
Re: DC test: passed ;-)

Mad_K said:
The SEWA proto boards have passed the initial DC test.
There was a small change in idle current, because the BC850C only has a little over 0,5V BE drop in this circuit. Bias current dropped to 1,7A. This is a little on the low side for 4 ohm speakers, but might be beneficial for people with 8 ohm speakers and marginal heatsinks as the amp now only dissipats 38W pr channel. What do you think, should I change the idle current back up to 2A or alter the design to 1,7A idle current? (This is what I'll be using). I will be taking the AC signal and critical listening test tonight or tomorrow 😉
Click to expand...


When should we pay for these Boards ? I guess ill have to build a buffer now to run this OR use the Bosoz Pre-Amp.
 
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