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SuSy dynahi v2

Kevin Gilmore's higher-powered version of the dynalo

Re: SuSy dynahi v2

Postby mloutfie » July 12th, 2015, 12:56 am

I've removed the trs jack from the case to try the isolation issue before replacing the jack. Sadly the noise is still there. So I've done more trouble shooting.

My setup is power supply and amp in one case and transformer in another case figure 2 of the b22 guide. The transformer case is made of abs so there is no chasis ground. The iec ground is not wired to anything. The power plug itself is isolated. The rca plug is also isolated. The attenuator is not isolated and since I put the trs jack outside of the case it is now isolated.

So based on that the only difference seems to be the rca ground should not be isolated. Is that correct? I thought rca should always be isolated.

Also while troubleshooting I tried to wire the trs sleeve to a couple ground point. The hum is loudest when the sleve is wired to the sigma22 output ground. It hums on lower volume when I connect to amp board out put. Interestingly the hum is only in one channel. I then wire the sleve to output ground of both amp board. The hum gets less but it appear in both side now. I've wired the rca ground to both ground and negative input of the amp board
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Re: SuSy dynahi v2

Postby amb » July 12th, 2015, 10:23 am

The single chassis solution I prefer uses a ground loop breaker, so the signal ground does not connect to the chassis directly.
Maybe the hum is caused by another cause, such as power transformer magnetic interference?


Sorry, I misread your post.

In the two chassis configuration, I recommend tying the signal ground at the input jacks directly to the chassis.
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Re: SuSy dynahi v2

Postby mloutfie » July 12th, 2015, 2:04 pm

Tried signal input ground to chassis still doesn't work. The volume pot signal ground is not connected to anything. Should that be connected to anything? The volume pot has chasis ground point and it is connected to the chassis
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Re: SuSy dynahi v2

Postby amb » July 12th, 2015, 2:14 pm

The pot is a voltage divider, and therefore its ground must be connected to signal ground, or else it wouldn't work properly.
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Re: SuSy dynahi v2

Postby mloutfie » July 13th, 2015, 1:19 am

Since the pot body is connected to the case like the rca ground is. If I want to connect to a ground wouldn't it make a loop? If that's the correct way so I just connect the pot ground to the rca ground?
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Re: SuSy dynahi v2

Postby amb » July 13th, 2015, 2:10 am

Connecting the pot's body to the chassis is for shielding. There is nothing in the pot that is electrically connected to its body, so you still need to connect its ground pins to signal ground in order for the voltage divider to work properly. My preferred wiring scheme is run the pair of wires (signal and ground) from the input jack to the pot, and then another pair from the pot to the amp board. Do the same for each channel.
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Re: SuSy dynahi v2

Postby mloutfie » July 13th, 2015, 2:25 am

I've connected the pot to one of the rca ground. Since the rca is not isolated the ground of them are connected so don't need to join them. Still have the hum. What about making a star ground before the power supply and connect all signal ground, trs ground, trs ground and transformer ground to it?
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Re: SuSy dynahi v2

Postby mloutfie » July 13th, 2015, 4:13 am

Is there a chance the khozmo attenuator is not compatible with the rest of the circuit?
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Re: SuSy dynahi v2

Postby amb » July 13th, 2015, 6:44 am

I don't know, I've seen the pretty photos of Khozmo attenuators but never used one.
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Re: SuSy dynahi v2

Postby mloutfie » July 13th, 2015, 12:48 pm

So there is specific type of attenuator for the the dynahi? Any other grounding way I should try?
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