Influence of the delay amplifiers for listening characteristics

[Federmann]

The result is not very good. It is good to 50V, there is Vdif 2x24mV. When the output voltage of 86V is Vdif 83mV and it is very much.

[Federmann]

Originally Posted by Upupa Epops

That's nice, Federmann...and with output mosfets ?

"And with output MOS-FETs" No worries, the result is very similar.

[janneman]

Originally Posted by Federmann

The result is not very good. It is good to 50V, there is Vdif 2x24mV. When the output voltage of 86V is Vdif 83mV and it is very much.

Federmann,

Vdif is the effective input signal. Of course, if you increase the output voltage, Vdif MUST rise in proportion (within the linear range of the amp).

So if your Vdif is 46mV with 50V output, that shows an open loop gain of just above 1000. (Actually 1087 exactly). With 86V out, and the same open loop gain, I would expect a Vdif of 86/1087 = 80mV. That's close enough to your measured 83mV I would think.

jd

[Federmann]

Amplification stages are not linear. Greater Vdif represents a decrease gain.

2 x 24mV = -10%
83mV = approx -20%

48mV, the third harmonic output voltage 10%, 1% output power.
83mV, the third harmonic output voltage 20%, 4% of output power.

[Federmann]

Open loop, gain decreases the frequency but also decreases the size of the output voltage, accurately the size of Vdif.

[janneman]

Originally Posted by Federmann

Open loop, gain decreases the frequency but also decreases the size of the output voltage, accurately the size of Vdif.

Correct. The gain decreases slowly with increasing output voltage. I just didn't want to bring that secondary effect into it yet. It's called gain compression.
Since the OL gain also rolls off with frequency, you will also see the Vdif increasing in ratio with frequency. ALL amplifiers will show this to varying degrees, as I'm sure you know.


jd

[Federmann]

The precise setting Vdif without a signal, using P - I controller, everything is much better.

[janneman]

Originally Posted by Federmann

The precise setting Vdif without a signal, using P - I controller, everything is much better.

Not sure I follow you. The only Vdif without signal is the DC offset.

jd

[BV]

Not sure I follow you. The only Vdif without signal is the DC offset.

"P - I controller"
Yes, he means DC servo, to hold conditions in the midlle of linear region, and he is believing this should improve also hf linearity..

[janneman]

Originally Posted by BV

"P - I controller"
Yes, he means DC servo, to hold conditions in the midlle of linear region, and he is believing this should improve also hf linearity..

Ahh yes, thanks!

jd