SEWA - Seven Watt Amplifier

[Tyimo]

30Vx3,5A=105W/ch. Hmm.. 0,25'C/W heatsink per channel, IRFP250, 600VA trafo, 47Kuf caps. BOZ with VDrain@25V in front. Oh, mama

Ohhh! It is too much for me.....

What about on +24Vdc or even lower?

How sensitive will they be?

Double 92dB drivers = 95dB

Tyimo

[Mad_K]

95dB = You can run a stock SEWA

24V would be ideal (18VAC trafo, loads down to 22,5V) for 4 ohm. With 2A bias it can do 8W. I would probably adjust the bias up a notch (as much as the heatsinks can take) 2,5-3A would be nice 3A will give you about 13W.

22,5V, 3A=67,5W => 0,4C'W heatsink.
With the IRFP250 you could get away with a 0,5'C/W (actual) heatsink, but it will be hot; 60'C But the mosfet will stay happy @ 67,5/2 x (0,65+0,35 (al-oxide washer+grease)) +60=34+60=94'C junction temp.

[MIKET]

EDCOR’s XSM transformers are not gapped.
I just redieved confirmation from the factory, OK to parafeed however.

[Ryssen]

EDCOR’s XSM transformers are not gapped.

Just out of curiosity,do you have a schema how to do?Never done such a thing before.

[Tyimo]

Thanks Mads!

These are good news. I will try!

Tyimo

[MIKET]

Originally posted by Ryssen


Just out of curiosity,do you have a schema how to do?Never done such a thing before.

This post is an example of parafeed, http://www.diyaudio.com/forums/showt...565#post986565

Parafeed is feeding a transformer through a capacitor and loading the plate with an inductor, not allowing the DC current through the transformer

Here is a little light reading on the subject from Steve Bench
http://members.aol.com/sbench/outstru.html

[tinitus]

My long term plan is to build a bi- or tri-amped system

So here is the deal

To be able to use SEWA I could build BOZ as pre, and have multiple outputs - one with fixed full gain fore SEWA, and others with adjustable gain

Main attennuator on input could be a seperate TVC or simply a build in att

PROBLEM ? I recall to have read that PASS pre need main attennuator on output, with regards to stability ?

Comment on this, please

[Mad_K]

tinitus, shure you can do that. I would probably just insert fixed attenuators on the inputs of the power amps with gain. Drive them in paralell from BOZ. Use a 10K stepped att or pot on input of BOZ. There is no stability issues without att on output.

[DIGORA]

Originally posted by Mad_K
The main difference is the mounting of the board/mosfets. The board also acceps a little larger filtering caps. The reason for the difference in price is the pcb size. I have 4 Rev.B boards and 9 Rev.C boards left.
Rev.C schematic attached

8W



http://perso.orange.fr/jm.plantefeve/sche.html

[Tyimo]

Hi DIGORA!

8W

And? What should we do with this schematic?
Did you buid or listen it?
You should translate the text:

Un seul transistor traite le signal: le BUZ900DP, la contre réaction disparaît. Très proche d'un pur générateur de courant, l'impédance du HP qui servait de convertisseur U/I "s'efface" pour une force appliquée à la menbrane directement image du courant généré. Ce principe est adapté aux transducteurs "large bande" à faible Qts et voies médium aigu en filtrage actif. Le gain est de 24 dB (x16). Ce schéma a une entrée référencée au "-" et non au "0". Du coup, le condonsateur de liaison se charge à la mise sous tension et la sortie haut-parleur doit être temporisée.

Greets:

Tyimo