Explendid amplifier designed by Michael Bittner, our MikeB - Page 49

anatech · 6th October 2005, 07:58 PM

Hi Mike,
Those are the transistors I had in mind. Pro-electron parts are harder for me to get.

I have to make the PCB by hand, so the most current artwork will help me out. I'll just size it, drill the holes and connect the dots. That much I can do.

-Chris

destroyer X · 6th October 2005, 08:36 PM

organizing to start.

I am more happy than other days.

I will have a wine for that.

all of you!

Cheers

Carlos

thanh · 7th October 2005, 12:43 AM

Hi ! symasym5 has a low distortion because
-beta of mpsa18 is so high ,>900
-no use degeneration reisistor
If input trsansistors is replaced by 2n5551 ,or a low beta transistor such as c1815 , symasym5 will be defeated by Blameless .
Iq for VAs is only 1.5mA .This is a normal thing . Because VAs use current mirror load . Output impedance of current mirror is high extremely ->gain of VAS is also high teriblely ---> 1.5mA is high enough to fed output satge

destroyer X · 7th October 2005, 03:08 AM

Where's my pils!
Call the Doctor!.....no!.... this doctor will kill me more fast!
Air!!..... water!...oxigen to me!!!
Blood pressure increasing now..... 33 by 29!!!

Flamebless is too much for me..... good by evil world!

ahahahahaha!

regards,

Carlos

destroyer X · 7th October 2005, 03:20 AM

That was very strong to me.... really excessive impact to my 54 years off existence.

The day the Gamestress win Symassym, i will be in paradise!

Hô Hô Hô..... wanna know?...... really wanna know?.... i will tell ya!!!.... your avatar is not pretty anymore, will not give you more Ice cream and will not borrow you my Bike anymore!

regards,

Carlos

PMA · 7th October 2005, 06:26 AM

Michael,

this 10 Ohm resistor really helps to reduce hum/buzz in some instruments arrangement, as it inserts impedance into groundloop and allows input pair to work in CMV rejecting manner.

The background of my concern is this: the same aid was used in another amplifier, produced in hundreds of pieces. The 10 Ohm resistor worked and reduced groundloop hum/buzz problems. In case that 0V power GND was connected to mains protective earth, and this was the case, and second instrument like preamp, CD ar another one somewhere in the arrangement had also ANA GND connected to PE, and mains cord in several meters distant wall outlet, even a potential difference between the 2 PE pins of the wall outlet plugs - or a simple mistake - created current high enough to burn the 10 Ohm resistor. This had really happened in several cases, resulting in 10 Ohm resistor burned and unfortunatelly together with output protection relay not working well, the disater was here - burned speakers. That's why I am always a bit concerned when I see this solution. 1N4148 is not enough, I would guess 1N5408 at least.

I have already added the resistor into Eagle layout, just for my personal evaluation or for DIY purposes, but would be careful if it was industrial product to be sold. You might consider output DC protection?

Regards,
Pavel

PMA · 7th October 2005, 06:46 AM

Here we go with 10 Ohm resistors, I will produce 4 PCBs, with non-solder mask, 2 of them for me for evaluation, 2 pcs will remain, if someone interested ....

amplifierguru · 7th October 2005, 06:48 AM

Hi PMA,

10 Ohm with parallel back to back 1N4004's has worked for 1,000's of PA amplifiers I produced in the '70's. Never broke.
Amps to 500W. Road conditions.

Cheers,
Greg

PMA · 7th October 2005, 06:56 AM

Greg,

Thanks for valuable comment.

Pavel

PMA · 7th October 2005, 09:08 AM

Michael, how does the amp behave in limitation? Especially collector currents of Q1 and Q2 ......, consequently the whole circuit ...

6th October 2005, 08:36 PM	#482
destroyer X diyAudio Member Join Date: Feb 2004 Location: Recife - Brasil Northeast	Today, a special day to me, watching Sheldon commenting, PMA starting, Anatech also organizing to start. I am more happy than other days. I will have a wine for that. all of you! Cheers Carlos __________________ Try to build an amplifier folks ... it is pure adrenaline!.. when not work first time, then becomes a nice challenge...and we usually overcome the trouble... and we feel very well to be mastering the machine.

7th October 2005, 12:43 AM	#483
thanh diyAudio Member Join Date: Jan 2004 Location: ho chi minh city	Hi ! symasym5 has a low distortion because -beta of mpsa18 is so high ,>900 -no use degeneration reisistor If input trsansistors is replaced by 2n5551 ,or a low beta transistor such as c1815 , symasym5 will be defeated by Blameless . Iq for VAs is only 1.5mA .This is a normal thing . Because VAs use current mirror load . Output impedance of current mirror is high extremely ->gain of VAS is also high teriblely ---> 1.5mA is high enough to fed output satge __________________ Justice for Victims of Agent Orange http://www.petitiononline.com/AOVN/Thank all of you!

7th October 2005, 06:26 AM	#486
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	Regarding the 10 Ohm resistor Michael, this 10 Ohm resistor really helps to reduce hum/buzz in some instruments arrangement, as it inserts impedance into groundloop and allows input pair to work in CMV rejecting manner. The background of my concern is this: the same aid was used in another amplifier, produced in hundreds of pieces. The 10 Ohm resistor worked and reduced groundloop hum/buzz problems. In case that 0V power GND was connected to mains protective earth, and this was the case, and second instrument like preamp, CD ar another one somewhere in the arrangement had also ANA GND connected to PE, and mains cord in several meters distant wall outlet, even a potential difference between the 2 PE pins of the wall outlet plugs - or a simple mistake - created current high enough to burn the 10 Ohm resistor. This had really happened in several cases, resulting in 10 Ohm resistor burned and unfortunatelly together with output protection relay not working well, the disater was here - burned speakers. That's why I am always a bit concerned when I see this solution. 1N4148 is not enough, I would guess 1N5408 at least. I have already added the resistor into Eagle layout, just for my personal evaluation or for DIY purposes, but would be careful if it was industrial product to be sold. You might consider output DC protection? Regards, Pavel

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6th October 2005, 07:58 PM	#481
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Mike, Those are the transistors I had in mind. Pro-electron parts are harder for me to get. I have to make the PCB by hand, so the most current artwork will help me out. I'll just size it, drill the holes and connect the dots. That much I can do. -Chris

7th October 2005, 06:48 AM	#488
amplifierguru Account Disabled Join Date: Aug 2004 Location: Earth	Hi PMA, 10 Ohm with parallel back to back 1N4004's has worked for 1,000's of PA amplifiers I produced in the '70's. Never broke. Amps to 500W. Road conditions. Cheers, Greg

7th October 2005, 06:56 AM	#489
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	Greg, Thanks for valuable comment. Pavel

7th October 2005, 09:08 AM	#490
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	Michael, how does the amp behave in limitation? Especially collector currents of Q1 and Q2 ......, consequently the whole circuit ...

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