Stetsom oscillations duty cycle

[imraneesa]

Hi all
Stetsom with 2 irs2092 Ic. Two channel input with one speaker terminal output.
One ic has 42% duty cycle and the other has 47% duty cycle. Will that make any problem for the amp to go into protect after playing a minute or less?

 

[Perry Babin]

That would likely mean that the DC offset on the output of the amp would cause the amp to go into protect.

What model amp?

 

[imraneesa]

That would likely mean that the DC offset on the output of the amp would cause the amp to go into protect.

What model amp?

Stetsom Ex3000 black edition.

 

[imraneesa]

The high pass has two different value pots is that correct? Will that be the problem?

 

[Perry Babin]

That's normal.

I'm trying to get some more definitive information on this amp but it may take a few days.

 

[Perry Babin]

Does switching 'flat' on/off make a difference?

 

[imraneesa]

Does switching 'flat' on/off make a difference?

Both sides makes no difference. I have 3.4v dc on speaker terminals.

 

[Perry Babin]

Where was your black probe when you measured 3.4v?

 

[imraneesa]

Where was your black probe when you measured 3.4v?

Across two terminals. Black on negative speaker and red on positive speaker terminal.

 

[Perry Babin]

If you monitor the offset across the speaker terminals from the time the amp powers up (output goes to about 75v (referenced to ground), does the offset increase just before the amp goes into protect?

Using the primary ground as the reference, is the DC voltage on pins 1-6 of the two driver ICs essentially identical?

If not, which pins are different?

 

[imraneesa]

If you monitor the offset across the speaker terminals from the time the amp powers up (output goes to about 75v (referenced to ground), does the offset increase just before the amp goes into protect?

Using the primary ground as the reference, is the DC voltage on pins 1-6 of the two driver ICs essentially identical?

If not, which pins are different?

Voltages on Pins 1 and pin 6 are very identical.
What i notice is Amp only goes into protect when the flat switch is off. When the flat switch is off gain is very sensitive as I turn very very little amp goes into clip and then protect. I still have 3.2v across speaker terminals. Speaker offset is 45v on one terminal and other terminal has 49v referenced to primary ground.

 

[Perry Babin]

With the flat switch is on, does the amp produce clean audio on both output terminals?

Are you driving it into a load?

 

[imraneesa]

With the flat switch is on, does the amp produce clean audio on both output terminals?

Are you driving it into a load?

Yes when flat switch is on it produce clean audio. I did not give any load.

 

[Perry Babin]

Do you have a dummy load that you can connect to the amp to see if the offset changes?

 

[imraneesa]

Do you have a dummy load that you can connect to the amp to see if the offset changes?

I used 2.5ohms dummy load and it still have 3.4v across speaker terminals.

 

[Perry Babin]

Does the amp drive clean audio on both output terminals with the dummy load?

 

[imraneesa]

Does the amp drive clean audio on both output terminals with the dummy load?

Yes it have clean sine wave on both terminals. Even though it has 3.2v across it.

 

[Perry Babin]

What's the DC voltage on R4, R5, R36 and R37?

Test with the flat switch in both positions.

 

[imraneesa]

What's the DC voltage on R4, R5, R36 and R37?

Test with the flat switch in both positions.

Switch on
R4=5.18v
R5=5.18v
R36 = 2.53v
R37 = 2.53v

Switch off
R4 = 5.18v
R5 = 5.18v
R36 = 2.53v
R37 = 2.53v

 

[Perry Babin]

Can you zero the offset with P10?