I am getting DC offset on the output of Ventus EZ - both left and right. Currently only one channel's Ventus has connected input but both of them are showing large output offset. The one that is connected to Ivy 3 balanced out shows about 240mV while the other with nothing at input shows about 110mV. The input offset between + and - of the connected amp is around 1mV or less, and each of the inputs (+ and -) has their own individual offset to ground of about 4mV. That looks like pretty good offset to me.

I can't see why would this be happening as the output buffer is within the feedback loop and the gain is 1. The schematics is textbook balanced amp with equal impedance visible on both inputs. Both of my Ventuses are showing offset, whether connected to input or not, so it doesn't seem like I made a soldering error (there are barely any parts anyway).

Any ideas?

(I saw the 4 month old thread but there was no solution offered in there).

Ventus is definitely oscillating, I pulled one out of the box and connected it to my lab power supply. It is oscillating at around 69MHz producing about 120mV peak to peak pure sine at the output.

Yes, CC1 cap is not intended for every config, and in some cases it can (and should) be ommited - it is there for those who wish to experiment.

It is there to form another pole for compensation. Remember that the kit can be configured a number of ways and with a number of different op-amps. That cap is required in some cases - but as you see, not in all. :)

I will make to mention it in the manual. That should be sufficient.

Hi all,

I'm still coping with a Left Right channel problem trough my Headphones.
Left is louder than Right.
If I mute the Left channel only the right channel can be heard trought the right speaker. So far so good.
If I mute the Right channel I can hear from what I believe is a mono signal but trough both speakers (left louder than right speaker though).

I have a Dual Mono BIII IVYIII setup.
Do you think this can occur due to the CC1?

Thx,

Jordo

Hi Brian,

I have checked it over and over again.
I draw the signal lines for the Ventus directly from the same output as for the balance XLR outputs.

Here I have a Hookup Sceme.
The black grounding wires on the Jack should be on terminal 'T' i.s.o. 'S'

Edited by user Wednesday, April 3, 2013 3:42:38 PM(UTC)  | Reason: Not specified

It's a Neutrik.
It's the NJ5FD-V 2x switching normalling stereo to be exact.
I removed Poles Tn and Rn while troubleshooring this problem so it can be considered as a NJ3FD-V Non switching Stereo model.

http://www.neutrik.com/e...4-vertical-jacks/nj3fd-v

Thx!

Jordo

Yes you are correct.
I remembered there was a fault in the scematic but I already seem to corrected it.
The picture asside is contra. That was confusing me earlier too.

S is the Sleeve. That is how it's wired up.

So if everything is correct in theory and CC1 does not have to be removed for my setup... Wat is going wrong here than?
I must mention that if I connect the LH channel without the RH, all is good. (LH channel trough the LH channel and dimmable)
If I do the same with the RH channel all the same for the RH channel.
But together seems to be a problem.

The only thing the two channels share is the ground at 'S'....

Thx,

Jordo

I would omit CC1

Russ, Brian,

I think I might have found wat was causing this behaviour.
Somehow I misinterpreted the connections on the Jack.

Last night when I was taking a good (fresh) look again at the contacts of the Jack I noticed that S and R must have been cross connected. So The RH channel was connected with the ground of th headphone.
I cannot see why I missed this over and over again.
This also might explain the 38 ohm between the channels. The resistance between the both channels should be 75 ohm and that is equals approximately two times 38 ;)

I do have CC1,2 and 3 omited from the boards. Still ok?

For now I do not have my amplifier in operation due to the Teleporter modification.
As soon it will be ready to test (with good results I hope) you will be informed.

Thx,

Jordo