Amp design

tiltedhalo · 5th January 2006, 08:30 PM

Could anybody give me a hand and take a look at this circuit and give a little creative critisism?? I would greatly apreciate it!

moamps · 5th January 2006, 09:00 PM

The Q7 should be NPN type.

Regards,
Milan

mastertech · 5th January 2006, 09:00 PM

Q7 should be npn

edit=sorry came in secomd

moamps · 5th January 2006, 09:11 PM

What's the purpose of the Q8?
Why 4k7 for the R15, 19?
C2, C3 may have a higher value.

Regards,
Milan

darkfenriz · 5th January 2006, 09:36 PM

Same question about q8.
and why lead circuit from output when from vas too?
Beside this it looks nice.

tiltedhalo · 5th January 2006, 09:43 PM

The original image post should now reflect changes, sometimes I start plopping in components faster then my brain works

yes Q7 should be NPN, R15,R19 are 4.7 ohm current limiters, also I made a mistake on R5 it should also be 4.7 ohm it provides the ground path for VR1 to set the offset.
Q8, VR2, R16,R17, D1 and R22 make up the bias cicuit, Q6 provides thermal tracking.
The amp will be biased into class A for a roll off into AB at about 20watts. Thanks and keep the observations coming........

hughmon · 5th January 2006, 10:10 PM

Looks like the old Mark V TA1000 design with a few tweaks.

Onra · 5th January 2006, 11:11 PM

Hi,
Is there a real connection between the base of Q7 and ground below C4 or is it a misdrawing due to your amendments?
Onra

tiltedhalo · 5th January 2006, 11:31 PM

To tell you the truth I dont know where it originated from, it was in one of my old books from my school days about 15 years ago, I drew it, but dont remember why, but it looks pretty decent. So I thought I might throw it together just been working out semiconductor choices.
Yes there is a connection from R3 to the juntion of R12 and C4. looks to provide a error correction for DC offset.

Onra · 5th January 2006, 11:52 PM

Hi,
if this is an intented connection, it makes R9 absolutely useless and will serve a current of about 450mA through the base of Q7 and R14 to the negative rail.
This would in addition clamp the collector of Q7 near ground and the amp won´t work. The collector of Q7 must be able to swing close to the negative rail.
It has to be a misdrawing ( or the amp is designed for communication by smoke ).
Onra

5th January 2006, 08:30 PM	#1
tiltedhalo diyAudio Member Join Date: Sep 2005 Location: Melbourne Florida	Amp design Could anybody give me a hand and take a look at this circuit and give a little creative critisism?? I would greatly apreciate it!

5th January 2006, 09:43 PM	#6
tiltedhalo diyAudio Member Join Date: Sep 2005 Location: Melbourne Florida	corrections The original image post should now reflect changes, sometimes I start plopping in components faster then my brain works yes Q7 should be NPN, R15,R19 are 4.7 ohm current limiters, also I made a mistake on R5 it should also be 4.7 ohm it provides the ground path for VR1 to set the offset. Q8, VR2, R16,R17, D1 and R22 make up the bias cicuit, Q6 provides thermal tracking. The amp will be biased into class A for a roll off into AB at about 20watts. Thanks and keep the observations coming........

5th January 2006, 11:31 PM	#9
tiltedhalo diyAudio Member Join Date: Sep 2005 Location: Melbourne Florida	amp design To tell you the truth I dont know where it originated from, it was in one of my old books from my school days about 15 years ago, I drew it, but dont remember why, but it looks pretty decent. So I thought I might throw it together just been working out semiconductor choices. Yes there is a connection from R3 to the juntion of R12 and C4. looks to provide a error correction for DC offset.

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5th January 2006, 09:00 PM	#2
moamps diyAudio Member Join Date: Oct 2002 Location: Croatia	The Q7 should be NPN type. Regards, Milan

5th January 2006, 09:00 PM	#3
mastertech Banned Join Date: Mar 2005 Location: Australia	Q7 should be npn edit=sorry came in secomd

5th January 2006, 09:11 PM	#4
moamps diyAudio Member Join Date: Oct 2002 Location: Croatia	What's the purpose of the Q8? Why 4k7 for the R15, 19? C2, C3 may have a higher value. Regards, Milan

5th January 2006, 09:36 PM	#5
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	Same question about q8. and why lead circuit from output when from vas too? Beside this it looks nice.

5th January 2006, 10:10 PM	#7
hughmon diyAudio Member Join Date: Jun 2004 Location: Los Angeles	Looks like the old Mark V TA1000 design with a few tweaks.

5th January 2006, 11:11 PM	#8
Onra diyAudio Member Join Date: Jul 2005 Location: near Frankfurt/M	Hi, Is there a real connection between the base of Q7 and ground below C4 or is it a misdrawing due to your amendments? Onra

5th January 2006, 11:52 PM	#10
Onra diyAudio Member Join Date: Jul 2005 Location: near Frankfurt/M	Hi, if this is an intented connection, it makes R9 absolutely useless and will serve a current of about 450mA through the base of Q7 and R14 to the negative rail. This would in addition clamp the collector of Q7 near ground and the amp won´t work. The collector of Q7 must be able to swing close to the negative rail. It has to be a misdrawing ( or the amp is designed for communication by smoke ). Onra

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