Tripath amp - passing by input stage ?

[theAnonymous1]

It needs 2 times the voltage to go 3db up on the electrical power side. That doesn't mean necessarily that the SPL goes up also 3db. There should be a slightly audible difference though. I guess it'll be hard to distinguish without measuring it.

I centered my head exactly between the two 3" test drivers and closed my eyes while adjusting the trim pot until the sound was balanced.

You don't think it's strange that what sounded perfectly balanced just happened to be almost exactly twice the voltage?

Did you try to feed the signal right into the RF output to avoid the opamp totally?

And do what with the inverting input; leave it floating?

Before I forget. How is the sound up to 1.9VRMS? Still distorted?

I just hooked it up to one of my main speakers and it sounds OK until it starts clipping. Doesn't play very loud though.

Anyway, hope this helps you in some way. I need to dismantle this mess and put it away for good this time. Too many other projects and piles of mess strewn about right now.

 

[soundcheck]

>> And do what with the inverting input; leave it floating?

Yep.

 

[theAnonymous1]

>> And do what with the inverting input; leave it floating?

Yep.

Ohhhh...... that's not a good sound. I don't recommend you try this.

 

[soundcheck]

Looks like we're done, aren't we.

1,9VRMS max on the output won't be sufficiant.

Though we're not sure why it clips at 1.9V. Probably another impedance mismatch somewhere.

Anyhow, I had this subject on my mind since quite while. Great that it is kind of solved now. Except somebody else comes up with a better/new idea.

THX a lot again.

Cheers

 

[Eric_R]

The opamp have a single 5 Volt supply, so the AC signal input is biased to 2.5 volt by
the opamp. 1.9V rms is more than 5V peak to peak so can not pass the opamp.
If you try to input your signal at Rf the opamp will still try to drive its output
with low impedance and short out your signal. So its not possible.

 

[soundcheck]

THX. That finally explains what we figured out.

 

[soundcheck]

One more question (I am thinking loud).

What would be the lowest limit of RF to have the amp working under stabil conditions?

 

[soundcheck]

Let me guess, I'll try to answer my question by myself:

It'll depend on the current delivery capability (actually V/I graph) of the opamp - which we don't know!

RF sits in parallel to Rload, right? If RF draws too much current Uload of the modulator will have a problem. We have seen that.

We have also seen that Rload should be in the range of 395R.

My guess ( I don't have any experience with these kind of guesses ) would be that a Rload/RF=1/10 should be a save bet to avoid burning too much power on RF.


Can somebody confirm above? Otherwise let me know if and why my guesses are nonsense.

THX