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Re: SuSy dynahi v2

PostPosted: July 8th, 2015, 1:23 am
by DEFL
mloutfie wrote:We should be aiming 750mV of bias voltage actually not 75mV. I read in some post that says 75mV which is wrong and led me to a wrong path when I started building mine.

Yes, 750mV of course. Typo.

Re: SuSy dynahi v2

PostPosted: July 8th, 2015, 4:27 pm
by mloutfie
not sure if I've posted this before but this looks good as a quad stepped attenuator for the Dynahi http://www.ebay.com/itm/Balance-XLR-23- ... 4197c5f6bf

Re: SuSy dynahi v2

PostPosted: July 8th, 2015, 5:39 pm
by amb
That's the same one we used in the "group build β22". It's good for the price. I wished for more steps and a better feel.

Re: SuSy dynahi v2

PostPosted: July 9th, 2015, 3:37 pm
by mloutfie
hows the sound quality? I've used the valab stereo stepped attenuator for by bottlehead crack and it's pretty good but looks like the design is different to the balanced one. I think I need to change the khozmo stepped attenuator because it's 50k. I head slight floor noise on the right channel. THis mostly caused by the attenuator mismatch right?

Re: SuSy dynahi v2

PostPosted: July 9th, 2015, 5:28 pm
by amb
It "sounded" fine.

I don't know what's causing noise only one one channel without knowing more information.

Re: SuSy dynahi v2

PostPosted: July 10th, 2015, 2:10 am
by mloutfie
I'll try to borrow a cro to trace where the noise starts but when I start building this the cro shows that the noise shows up on the attenuator output point

Re: SuSy dynahi v2

PostPosted: July 11th, 2015, 4:28 am
by mloutfie
Still having problem with ground noise. Quick question. Is the signal ground supposed to be connected to both power ground and chassis ground? That's what I have now.

Re: SuSy dynahi v2

PostPosted: July 11th, 2015, 6:02 am
by amb
There are different grounding schemes. How well it works depends on actual implementation, and what other equipment is used in the audio chain. I prefer the grounding schemes shown at the β22 website, in the "Wiring & ground" section.

Re: SuSy dynahi v2

PostPosted: July 11th, 2015, 6:39 am
by mloutfie
Thanks for that. That write up for b22 is great. I think I found the issue as per the note in that page. My headphone jack is not isolated from the chassis ground. I will replace it with an isolated headphone jack. The xlr shouldn't matter right? Since there is no ground connection there. Or will I get better noise performance if I use a plastic isolated xlr plug there too?

Re: SuSy dynahi v2

PostPosted: July 11th, 2015, 6:45 am
by amb
You don't need to use a plastic XLR connector. As balanced headphone jacks, the XLR connector's outer shell isn't used for anything.