Differential follower?

[abzug]

Re: Re: Differential follower?

It's been a month now. Are you still adamant about that?

Yes. It's been a month because I've pulled 13 hour shifts at my day job and haven't had time for this.

I'm not putting cored inductors in the signal path.

 

[abzug]

Erno Borbely has a new DAC board coming out which allows triming of with an added input stage voltage reference to allow direct coupling of single supply DAC chips.

Borbely's I/Vs are discrete opamps. They don't have low impedance inputs, so it's not a proper solution for a current-output DAC chip, which behaves best with a virtual ground on its output (virtual since it has DC offset; low impedance in AC terms).

 

[Tim__x]

The whole point of a differential receiver is to reject common-mode signals, including common-mode dc offset. My suggested differential opamp topology will work to remove that offset, so long as the differential offset at the output of the I/V stages is low.

 

[abzug]

The whole point of a differential receiver is to reject common-mode signals, including common-mode dc offset. My suggested differential opamp topology will work to remove that offset, so long as the differential offset at the output of the I/V stages is low.

It's 2.8 V -- the same as the DAC output offset is. Does that count as 'low'?

 

[Steve Eddy]

Re: Re: Re: Differential follower?

Yes. It's been a month because I've pulled 13 hour shifts at my day job and haven't had time for this.

Ah.

I'm not putting cored inductors in the signal path.

But you'll put transistors in the signal path?

se

 

[abzug]

Re: Re: Re: Re: Differential follower?

But you'll put transistors in the signal path?

They don't have hysteresis.

 

[Steve Eddy]

Re: Re: Re: Re: Re: Differential follower?

They don't have hysteresis.

Not according to Lavardin's Gerard Perrot.

se

 

[abzug]

If you're referring to thermal memory, there are ways to deal with that with transistors, such as described on peufeu's page.

Anyhow, I've made up my mind regarding transformers. If I were to build a tube power amp, I'd still not use a regular transformer but something like Berning's ZOTL, or high impedance speakers like plasma or electrostatic.

 

[Tim__x]

The 2.8v is common-mode, common-mode is what a differential circuit rejects, it won't show up on the output.

What I meant when I said "as long as the differential offset is low" is that the DC offset on the output will not depend on the common-mode offset (remember it's rejected) but will depend on the differential offset of the DAC. As long as both DAC outputs sit at the same voltage (2.8v) the single ended output offset will be low, any differential offset from the DAC will be indistinguishable from desired signal and WILL show up on the output.

 

[abzug]

Sorry Tim, I misread, didn't notice you said differential offset as I was thinking common mode.