Amber / AP1 output transformer?

[GK]

I’m putting together a revised low distortion spot frequency generator for distortion measurements. I want a balanced output but haven’t decided on a transformer or active output yet.
The AP system 1 and Amber audio analyser used an output transformer I believe, with nfb taken from a special winding to cancel the transformers inherent distortion to <0.001%.
Does anyone know if this transformer can be readily bought as a spare or off-the-shelf part?

Cheers,
Glen

[syn08]

Originally posted by G.Kleinschmidt
I’m putting together a revised low distortion spot frequency generator for distortion measurements. I want a balanced output but haven’t decided on a transformer or active output yet.
The AP system 1 and Amber audio analyser used an output transformer I believe, with nfb taken from a special winding to cancel the transformers inherent distortion to <0.001%.
Does anyone know if this transformer can be readily bought as a spare or off-the-shelf part?

Cheers,
Glen

Don't know about AP, but Amber does not use such an animal. A Hammond transformer is used only to provide a floating output (employing a active stages). Hammond is still manufacturing such: http://www.hammondmfg.com/560.htm

[GK]

Originally posted by syn08


Don't know about AP, but Amber does not use such an animal. A Hammond transformer is used only to provide a floating output (employing a active stages). Hammond is still manufacturing such: http://www.hammondmfg.com/560.htm

Sorry, badly worded in haste - what you describe is what I mean. Thanks for the Hammond link. If you don't mind me nagging, which part # is used in the Amber and have you got an output amplifier schematic showing the implementation of that clever feedback scheme using that extra winding ?

Cheers,
Glen

[syn08]

Originally posted by G.Kleinschmidt



Sorry, badly worded in haste - what you describe is what I mean. Thanks for the Hammond link. If you don't mind me nagging, which part # is used in the Amber and have you got an output amplifier schematic showing the implementation of that clever feedback scheme using that extra winding ?

Cheers,
Glen

Glen,

I have the Amber schematics. Unfortunately I'm on the road now, tonight I may scan and post the schematic.

But I don't recall any clever feedback loop involving the transformer. The output stage is simply a class A power amp having the input fed by the transformer (to provide ground isolation). The output is feeding a second identical power stage set to G=-1.

[GK]

Originally posted by syn08


Glen,

I have the Amber schematics. Unfortunately I'm on the road now, tonight I may scan and post the schematic.

But I don't recall any clever feedback loop involving the transformer. The output stage is simply a class A power amp having the input fed by the transformer (to provide ground isolation). The output is feeding a second identical power stage set to G=-1.

OK, thanks. That would be great.

Cheers,
Glen

[syn08]

Originally posted by G.Kleinschmidt

OK, thanks. That would be great.

A memory flash brought up this reference for an AP US patent 4,614,914

http://www.freepatentsonline.com/4614914.html

It is certainly not the same in the Amber.

[GK]

Originally posted by syn08


A memory flash brought up this reference for an AP US patent 4,614,914

http://www.freepatentsonline.com/4614914.html

It is certainly not the same in the Amber.

OK, thanks - that rings a bell. I Though I wasn't imagining things
I was under the impression that the Amber unit was basically the same as the early AP.

Cheers,
Glen

[orjan]

Hi,

from Lundahl:

http://lundahl.se/pdfs/papers/feedbck.pdf

örjan

[Corvus corax]

I would appreciate seeing the Amber schematics as well. I was able to repair my 5500 recently without them, but I think I need to recalibrate the internal frequency generator- It isn't outputting the entered frequencies accurately. Kind of a problem when you are trying to check RIAA curves.

[jwb]

Sorry to barge in on this thread, but I wanted to email Corvus corax to reply to a private message but unfortunately his private email doesn't work. I hope this reaches him. Please reply with a working email.