Drive an audio transformer from an AOP. Good or bad idea?

[Matt Syson]

Operational Amplifier of course referring to the initial premise of a block of circuitry (amplifier) that had inverting and non inverting inputs and a single 'output' that given certain characteristics could be used to do linear computation functions such as integration, differentiation, summing and others which were useful to the arms industry (gun aiming) where the overall function relied on external components and for convenience simple plug in active parts (the amplifier itself) so that exchange in the field was a simple afair.
Fun to implement with valves because they are unipolar devices but when transistors became a thing of both NPN and PNP flavours many new possibilities were dreamed up. Many things were understood and theorised WAY back but it was often near impossible using the technology of the day.

 

[Newmarket]

Yes, I thought about legacy being a possible explanation. Apparently in ignition applications, the rationale was to simplify wiring, since both windings ended up grounded at a side.
This cut-out, taken from Wiki, shows that the construction is not an autoformer at all. Pri and sec are clearly distinct.
View attachment 139374

The only thing that makes it an autoformer is the connection. Saves one terminal.
View attachment 139376
Sorry for the OT.

Yes. Terminology can be a bit "loose" here. But nowhere near as loose as "Tremelo Arm" in elec guitar world

 

[abbey road d enfer]

Yes. Terminology can be a bit "loose" here. But nowhere near as loose as "Tremelo Arm" in elec guitar world

Direct consequence of the fact that Leo was not a musician.
Did not prevent him to create 3 miraculous instruments, Tele, Strat and PBass.

 

[Newmarket]

Direct consequence of the fact that Leo was not a musician.
Did not prevent him to create 3 miraculous instruments, Tele, Strat and PBass.

Yeah - although if I had to choose I'd take a Jazz Bass. Or a Musicman bass. Maybe a G&L...

 

[erintse]

It is not recommended to use an operational amplifier (AOP) to directly drive an audio transformer because AOPs are designed for voltage amplification and have limited current drive capability, while transformers often require higher current.

 

[abbey road d enfer]

It is not recommended to use an operational amplifier (AOP) to directly drive an audio transformer because AOPs are designed for voltage amplification and have limited current drive capability, while transformers often require higher current.

Typical old wives tale.
Many opamps have enough current drive to drive a transformer, as long as the transformer is designed for the specific task.
I have 10's of thousand products in the field that use a 5532 ot 5534 with a transformer.
Most of the current required to drive a transformer comes from the reflected impedance at the primary, except at low frequencies.
A 1:1 xfmr reflects a 600 ohms load as about 600 for most of the frequency range.
Problems may happen if the nominal inductance is too low, which increases the current demand at low frequencies.
A good 600:600 ohms transformer should run with a magnetizing current about 1/10th of nominal current.
Many designers use cheaper transformer, with low nominal inductance, resulting in large magnetizing current at low frequencies. That is why they have to resort to output stages capable of much more current drive than necessary.

 

[abbey road d enfer]

Yeah - although if I had to choose I'd take a Jazz Bass. Or a Musicman bass. Maybe a G&L...

I love my '51 reissue PB. Totally utilitarian, like the Telecaster.
I must say I'm not a dedicated bass player. I play bass occasionally in jams and for my own demos.

 

[dai h.]

Direct consequence of the fact that Leo was not a musician.
Did not prevent him to create 3 miraculous instruments, Tele, Strat and PBass.

that was my understanding also, but apparently he did have some experience playing (according to Fender, so the info looks legit) :

https://www.fender.com/articles/beh...n music,radio and electronics took precedence.

(kind of mind-blowing to me that (besides the PBass) he also designed the Jazz and Stingray--all hugely popular standards in the world of electric bass--plus loads of other stuff)