Transformer Help

[peter5355]

How can you tell the differance between a Driver transformer
and an output transformer.

And how can you a identify one from another is there any markings on them that tell you.


Peter

 

[Nigel Goodwin]

The number of windings might give you a clue?, but you don't even mention what they might be transformers for?.

 

[stevez]

Some thoughts based on stuff I've seen (this is a hobby, I am not a pro). All comments assume this is audio stuff.

1. Sometimes an output transformer will have COM, 8, 16 near one set of windings - usually means 8 or 16 ohms and my experience is related to vacuum tube/valve amp. It tells you nothing about the primary but you can work backward and apply small AC voltage to the secondary -then measure the primary to get a turns ratio.

2. Usually the driver transformer will be smaller and neither the primary nor the secondary will be low impedances (like 8 ohms or 16 ohms).

3. For a time, solid state audio amps made use of transformers between stages and at the output. I've wondered if this wasn't a carryover from vacuum tube days - then designers eventually found a way to live without them. Typically the drivers were smaller - though for solid state stuff I've only seen transformers on relatively low power amps - a watt or two at most.

 

[Nigel Goodwin]

I've wondered if this wasn't a carryover from vacuum tube days - then designers eventually found a way to live without them.

Same reasons as valve amps used them, you couldn't get NPN/PNP versions of either output transistors or valves back then

They were useful though, because if an output transistor died, it didn't cause lot's more damage as well, as the driver transformer isolated the rest of the amp from the output.

 

[peter5355]

Some thoughts based on stuff I've seen (this is a hobby, I am not a pro). All comments assume this is audio stuff.

1. Sometimes an output transformer will have COM, 8, 16 near one set of windings - usually means 8 or 16 ohms and my experience is related to vacuum tube/valve amp. It tells you nothing about the primary but you can work backward and apply small AC voltage to the secondary -then measure the primary to get a turns ratio.

2. Usually the driver transformer will be smaller and neither the primary nor the secondary will be low impedances (like 8 ohms or 16 ohms).

3. For a time, solid state audio amps made use of transformers between stages and at the output. I've wondered if this wasn't a carryover from vacuum tube days - then designers eventually found a way to live without them. Typically the drivers were smaller - though for solid state stuff I've only seen transformers on relatively low power amps - a watt or two at most.

Yes it is an audio transformer thanks for all your replys it has been very helpful

 

[Hero999]

They are still used today in large PA systems which use 100V to distribute the audio and small transformers at each speaker to lower the voltage to work an 8hm: speaker.

 

[peter5355]

Thank you all for your reply's that is all folks!!! great forum ask a lot of question and got great answers