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Old 31st October 2006, 07:30 PM   #81
kmj is offline kmj  Sweden
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by the way, the wires heat up quite a bit when i connect the batteries in series.
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Old 31st October 2006, 07:47 PM   #82
kmj is offline kmj  Sweden
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I got the batterypower to work and the buzzing sound was still there. So the PSU seems to be working OK.
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Old 1st November 2006, 09:41 AM   #83
kmj is offline kmj  Sweden
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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.
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Old 1st November 2006, 09:54 AM   #84
kmj is offline kmj  Sweden
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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.
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Old 11th August 2008, 05:51 AM   #85
Wasim is offline Wasim  Pakistan
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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
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Old 11th August 2008, 05:58 AM   #86
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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
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Old 11th August 2008, 08:30 AM   #87
AndrewT is offline AndrewT  Scotland
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Hi Was,
look at the PCB again.
Pins 1, 5 & 8 are all unused.
The pinouts of the other 5 pins are identical.
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Old 11th August 2008, 09:28 AM   #88
Wasim is offline Wasim  Pakistan
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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.

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