Transformer I/V stage, pros&cons.

[Brian Guralnick]

I've been looking into transformer based I/V stage. I really like the idea that the gain is not derived from any active silicon components, and the isolation & ease of choosing balanced & unbalanced is also a really helpful.

What are the main cons in using a transfomer for the I/V conversion?

[ThorstenL]

Konnichiwa,

Originally posted by Brian Guralnick
I've been looking into transformer based I/V stage. I really like the idea that the gain is not derived from any active silicon components, and the isolation & ease of choosing balanced & unbalanced is also a really helpful.

First an essential key point here. There is no such thing as Transformer I/V nor can there be, certain patent claims nonwithstanding. A transformer is by definition an I/I and V/V converter, meaning there is a certain relaitionship between input and output current or input and output voltage.

Even if a transformer is used, it acts as simple impedance matching device, the actual I/V conversion is still carried out by resistors....

Sayonara

[Brian Guralnick]

Originally posted by Kuei Yang Wang
Konnichiwa,



First an essential key point here. There is no such thing as Transformer I/V nor can there be, certain patent claims nonwithstanding. A transformer is by definition an I/I and V/V converter, meaning there is a certain relaitionship between input and output current or input and output voltage.

Even if a transformer is used, it acts as simple impedance matching device, the actual I/V conversion is still carried out by resistors....

Sayonara

Ok, well understood. It's still 1 resistor + 1 (low turn:high turn) transformer + 1 other resistor, + optional follower buffer.

Here is an example of some transformers which may be configured to 'act' like they are converting I/V.

http://www.sowter.co.uk./dacs.htm

[mdlover]

Hello Brian,

You mean the tansformer for the Crystal DACs? Their outputs are voltage and not current, there is no such need to perform the I/V conversion.

Cheers

[Brian Guralnick]

Originally posted by mdlover
Hello Brian,

You mean the tansformer for the Crystal DACs? Their outputs are voltage and not current, there is no such need to perform the I/V conversion.

Cheers

Not the Crystal voltage out DACs, take a look at transformer #9055, or 8347.

http://www.sowter.co.uk./specs/8347.htm

[Bricolo]

Originally posted by Kuei Yang Wang
Konnichiwa,



First an essential key point here. There is no such thing as Transformer I/V nor can there be, certain patent claims nonwithstanding. A transformer is by definition an I/I and V/V converter, meaning there is a certain relaitionship between input and output current or input and output voltage.

Even if a transformer is used, it acts as simple impedance matching device, the actual I/V conversion is still carried out by resistors....

Sayonara

A very skilled DIYer wrote this:

The use of a Transformer as Current Voltage Converter is a patented technology owned by Audio Note UK and is used here with kind permission by Audio Note and Peter Qvortrup.

do you know who?

[agent.5]

Don't mean to hijack the thread, but does anyone use Stowter 9395 (attenuator 48db in 2db steps 0/+6db/+12db gain taps) directly with Crystal DAC output? I am thinking of using this 1 transformer to replace the output stage of the DAC, balanced to unbalanced converter, and volume control of gainclone.

[ThorstenL]

Konnichiwa,

Originally posted by Bricolo

A very skilled DIYer wrote this:

The same DIY'er also wrote within this thread:

"There is no such thing as Transformer I/V nor can there be, certain patent claims nonwithstanding."

The note on my DAC Project was included after AUdio Note asked for it and threatened legal action. I did not feel like having a court battle over this at the time although I must note that I am certain that a court review of AN's patent would see it dismissed for reason of obviousness.

Sayonara

[Peter K]

Originally posted by Brian Guralnick

What are the main cons in using a transfomer for the I/V conversion?

Maybe this discussion can be focussed on Brian's question. I am (and I am sure others are) also interested in a technical explanation.

best regards,

Peter K

[bequerel]

Interesting topic! I cannot contribute much, but Andrea Ciuffoli has been doing some work regarding this. Have a look at:

http://www.audiodesignguide.com/cdplayer/dac3.html