The "Freebird" ultra clean ultra simple preamp design - Page 9

kmj · 31st October 2006, 07:30 PM

by the way, the wires heat up quite a bit when i connect the batteries in series.

kmj · 31st October 2006, 07:47 PM

I got the batterypower to work and the buzzing sound was still there. So the PSU seems to be working OK.

kmj · 1st November 2006, 09:41 AM

I changed potentiometer for the volyme, shielded the wires and tried a jumper istead of resistor between signal and commonground. Still the buzz is there.

kmj · 1st November 2006, 09:54 AM

I'll be... There must be higher powers at work here. I tried opa627 and buzz, opa604 and buzz. In the back of my mind I seem to remember reading something about buzzing and if you couldn't get a preamp or similar stable then you should try opa134. And what do you know? No Buzz! Dead quiet.

Wasim · 11th August 2008, 05:51 AM

Hi Russ

I am very much interested in freebird. But one thing I can not understand I have seen the DataSheets of OPA627 and OPA228. The PIN configurations of these two OPamps look different I think but you said that you have OPA228 with the same PCB . Can you explain that to me.
I am new and plz do not mind my stupid questions

I am also attaching its image

abid_rehan · 11th August 2008, 05:58 AM

Dear Wasim:
when working with an Op-Amp one needs to be more concerned with Invereted and non-inverted inputs and outputs along power supply pins, in pinout picture that you attached it is clearly evident that OPA627/228 share the same pinouts for inverted and non-inverted inputs both at pin 2 and 3, outputs at pin 6, postive power supply at pin 7 and a negative rail at pin 4, as for offset trim pins, not many preamps use offset pins.
rehan

AndrewT · 11th August 2008, 08:30 AM

Hi Was,
look at the PCB again.
Pins 1, 5 & 8 are all unused.
The pinouts of the other 5 pins are identical.

Wasim · 11th August 2008, 09:28 AM

Hi Thanks for the reply

I was wrong. I got it. The pin points are same. I was actually looking at it from other side. Thanks anyways.

Wasim

31st October 2006, 07:30 PM	#81
kmj diyAudio Member Join Date: Feb 2004 Location: Falkenberg	by the way, the wires heat up quite a bit when i connect the batteries in series. __________________ .....Where the music comes to die.

31st October 2006, 07:47 PM	#82
kmj diyAudio Member Join Date: Feb 2004 Location: Falkenberg	I got the batterypower to work and the buzzing sound was still there. So the PSU seems to be working OK. __________________ .....Where the music comes to die.

1st November 2006, 09:41 AM	#83
kmj diyAudio Member Join Date: Feb 2004 Location: Falkenberg	I changed potentiometer for the volyme, shielded the wires and tried a jumper istead of resistor between signal and commonground. Still the buzz is there. __________________ .....Where the music comes to die.

1st November 2006, 09:54 AM	#84
kmj diyAudio Member Join Date: Feb 2004 Location: Falkenberg	I'll be... There must be higher powers at work here. I tried opa627 and buzz, opa604 and buzz. In the back of my mind I seem to remember reading something about buzzing and if you couldn't get a preamp or similar stable then you should try opa134. And what do you know? No Buzz! Dead quiet. __________________ .....Where the music comes to die.

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11th August 2008, 05:58 AM	#86
abid_rehan diyAudio Member Join Date: Mar 2007	Dear Wasim: when working with an Op-Amp one needs to be more concerned with Invereted and non-inverted inputs and outputs along power supply pins, in pinout picture that you attached it is clearly evident that OPA627/228 share the same pinouts for inverted and non-inverted inputs both at pin 2 and 3, outputs at pin 6, postive power supply at pin 7 and a negative rail at pin 4, as for offset trim pins, not many preamps use offset pins. rehan

11th August 2008, 08:30 AM	#87
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi Was, look at the PCB again. Pins 1, 5 & 8 are all unused. The pinouts of the other 5 pins are identical.

11th August 2008, 09:28 AM	#88
Wasim diyAudio Member Join Date: Aug 2007 Location: Lahore	Hi Thanks for the reply I was wrong. I got it. The pin points are same. I was actually looking at it from other side. Thanks anyways. Wasim

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