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Hello, i need a help to identify a diagram attached ,

What is the RED arrow pointing to?


What is the GREEN arrow pointing to?


i will appreciate if anyone can help out. thanks
 

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The dots mean the wires connect.

The "humps" mean there is no connection between the crossing wires.
 

Pommie

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That is an old way to draw schematics. On modern diagrams "humps" aren't used and crossing wires aren't connected unless a dot is present.

Mike.
 

gophert

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Most Helpful Member
That is an old way to draw schematics. On modern diagrams "humps" aren't used and crossing wires aren't connected unless a dot is present.

Mike.
so now the OP will know how to read old schematics. Text books don't change - if he pages forward, he'll probably get to read about an LM741.
 

JimB

Super Moderator
Most Helpful Member
That is an old way to draw schematics. On modern diagrams "humps" aren't used and crossing wires aren't connected unless a dot is present.
When hand sketching a circuit I still draw in the humps, just so that there is no confusion in my own mind.*

JimB


* That's not to say that there will not be lots of confusion about other things! :D
 

Pommie

Well-Known Member
Most Helpful Member
When hand sketching a circuit I still draw in the humps, just so that there is no confusion in my own mind.*

JimB
Not sure if I do or don't, been a long time since I drew a schematic on paper. :D

Mike.
 

unclejed613

Well-Known Member
Most Helpful Member
if he pages forward, he'll probably get to read about an LM741.
LM741... an 8-pin noise source :woot:

when i was in a band and we were trying to record a demo tape, we had an 8 channel mixer, and the drummer was trying to figure out why there was a noticeable background hiss. taking the cover off the mixer revealed the output was driven by a socketed 741. popping a TL071 into the socket instead cured the hiss...
 

Nigel Goodwin

Super Moderator
Most Helpful Member
LM741... an 8-pin noise source :woot:

when i was in a band and we were trying to record a demo tape, we had an 8 channel mixer, and the drummer was trying to figure out why there was a noticeable background hiss. taking the cover off the mixer revealed the output was driven by a socketed 741. popping a TL071 into the socket instead cured the hiss...
Shouldn't be a problem on the output, and if properly designed pretty well throughout the entire mixer. I imagine the 741 was probably faulty?.

People here, and AG in particular, slag off 741's - but they will all have many albums recorded using mixers full of them - in a properly designed circuit they perform quite respectably.

Obviously though, now isn't the time to be using a 741 (and hasn't been for decades), as there are thousands of much superior pin compatible replacements (I'm currently used TL072's for various purposes).

I was having the same discussion with AG a fair few years back (probably about 15 or 16 years?), and at the time I was setting up a cheap PA system for a small gig my daughters band had got. As it happened, I'd been given a small amplifier, which had four input channels, and I built a pair of 1x12's with piezo tweeters, and bought some cheap Behringer mikes. Ih, I also replaced the mains transformer in the amp to a lower voltage one (and did a few minor changes), as it was designed to feed 8 ohms, and I wanted it to feed 4 ohms.

The amp used 741's in the mixer, so as an experiment I removed the 741's from one channel, and fitted 8 pin sockets - then tried a variety of different opamps, and compared that channel with the others. Not a smidgen of audible difference, and you couldn't tell which channel you were using.

Obviously it could easily be a FAR different story for other uses, such as a preamp to record bird song out in the woods.
 

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