Explendid amplifier designed by Michael Bittner, our MikeB - Page 61

jarkaa · 15th October 2005, 05:01 PM

And after etching...

The result wasn´t that good but these are prototypes only... maybe...

I have to go shopping on moday because I could not find suitable resistors from my stash

Jarno

MikeB · 15th October 2005, 06:21 PM

Hi Jarno !

I don't see any flaws in the etching, looks well done !
Obviously you have more than enough devices... Going to build a 5 channel ?
For resistors i use normal metalfilm 250mw resistors, except the
4.7/1.2/10 in outputstage, there i use 2watt version (also metalfilm). And the 0.22ohms are 5watts.
The trimpot is a normal Piher.

Happy drilling !

Mike

jarkaa · 15th October 2005, 06:42 PM

Hello Mike

Drilling is tomorrows business... Now it´s time for a couple of biers.

You should have a few too!

This is way OT but I am beginning to be worried about myself. I got few friends over on the other room and I am here browsing throuhgt the forums

I´ll be back after drilling and assembly is done

Jarno

MikeB · 15th October 2005, 10:52 PM

Hello !

I started to collect important informations about symasym into a webpage...

http://www.lf-pro.net/mbittner/Sym5_.../symasym5.html

Suggestions/critics welcome !

Mike

anatech · 16th October 2005, 01:38 AM

Hi Mike,
Your site is very clear, and loads fast. I like it.

-Chris

mod_evil · 16th October 2005, 03:37 AM

Hi, mr MikeB.

Can I use this amplifier with 1ohm? How I can use it on 1ohm? Addiding more pair of output transistors?

Thanks a lot.

PMA · 16th October 2005, 07:43 AM

Mike,

thanks for creating the webpage. This will greatly help diyers interested in the project.

Regards,
Pavel

sajti · 16th October 2005, 09:38 AM

Quote:

Originally posted by mod_evil
Hi, mr MikeB.

Can I use this amplifier with 1ohm? How I can use it on 1ohm? Addiding more pair of output transistors?

Thanks a lot.

More output devices are not enough. To drive 1ohm load, You need to use predrivers between the VAS, and the MJEs.

sajti

MikeB · 16th October 2005, 10:06 AM

Quote:

Originally posted by mod_evil
Can I use this amplifier with 1ohm? How I can use it on 1ohm? Addiding more pair of output transistors?

Hi mod_evil !

Symasym was not designed to deliver THAT much current, it does easily drive a 4ohm speaker, but not 1 ohm...
To do that, it would need a complete redesign. The VAS does not supply enough current, and changing it to triple darlington like sajti suggested will make it oscillate without further modification.
One possibility would be changing the outputstage to mosfets, and put enough of them in paralell.

Mike

PMA · 16th October 2005, 10:23 AM

Do not forget their high input capacitance.

16th October 2005, 03:37 AM	#606
mod_evil diyAudio Member Join Date: Dec 2004 Location: Rio	Hi, mr MikeB. Can I use this amplifier with 1ohm? How I can use it on 1ohm? Addiding more pair of output transistors? Thanks a lot. __________________ Brazilian Tube Amp Builder.

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15th October 2005, 06:21 PM	#602
MikeB diyAudio Member Join Date: Apr 2004 Location: Gütersloh	Hi Jarno ! I don't see any flaws in the etching, looks well done ! Obviously you have more than enough devices... Going to build a 5 channel ? For resistors i use normal metalfilm 250mw resistors, except the 4.7/1.2/10 in outputstage, there i use 2watt version (also metalfilm). And the 0.22ohms are 5watts. The trimpot is a normal Piher. Happy drilling ! Mike

15th October 2005, 06:42 PM	#603
jarkaa diyAudio Member Join Date: Feb 2004 Location: Tampere	Hello Mike Drilling is tomorrows business... Now it´s time for a couple of biers. You should have a few too! This is way OT but I am beginning to be worried about myself. I got few friends over on the other room and I am here browsing throuhgt the forums I´ll be back after drilling and assembly is done Jarno

15th October 2005, 10:52 PM	#604
MikeB diyAudio Member Join Date: Apr 2004 Location: Gütersloh	Hello ! I started to collect important informations about symasym into a webpage... http://www.lf-pro.net/mbittner/Sym5_.../symasym5.html Suggestions/critics welcome ! Mike

16th October 2005, 01:38 AM	#605
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Mike, Your site is very clear, and loads fast. I like it. -Chris

16th October 2005, 07:43 AM	#607
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	Mike, thanks for creating the webpage. This will greatly help diyers interested in the project. Regards, Pavel

16th October 2005, 10:23 AM	#610
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	Do not forget their high input capacitance.

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