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 Post subject: Re: MCA - Son of ZCA
PostPosted: 05 Nov 2014, 12:19 
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Joined: 26 Jan 2011, 08:57
Posts: 50
i have audio but with very low volume


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 05 Nov 2014, 15:04 
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Joined: 26 Jan 2011, 08:57
Posts: 50
ok here is what happened next.
I took a look at the underside of the pcb I put together and noticed i did not connect the drain of the 170 to anything.
Is this why I was getting low volume audio?

So I connected it to the collector and now get no audio and hot 15ohm resistors.
So I will unsolder the drain from the collector and have another look.


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 05 Nov 2014, 15:26 
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Joined: 06 Jun 2008, 18:23
Posts: 5301
Location: Australia
Did you check Vcc at the collector?

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Projects: "Carbon” - MM phono preamp | 180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 05 Nov 2014, 15:32 
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Joined: 26 Jan 2011, 08:57
Posts: 50
O.K. i have audio and volume.
I am tempoarily using gator clips to the star ground off the audio in.
The audio is a bit noisy seems like I could clean up the ground wiring some.
Maybe that will do it.
But IT DOES WORK!
Will continue to test and improve in the next hour or so.


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 05 Nov 2014, 15:34 
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Joined: 26 Jan 2011, 08:57
Posts: 50
When you say check the Vcc at the collector are you saying check voltage from ground to the collector?
I get 4.6 volts there


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 05 Nov 2014, 15:54 
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Joined: 06 Jun 2008, 18:23
Posts: 5301
Location: Australia
gyrene wrote:
When you say check the Vcc at the collector are you saying check voltage from ground to the collector?
I get 4.6 volts there

Yes from ground to collector. Should be half the PS voltage e.g. 12V. Adjust bias until you get this.

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Projects: "Carbon” - MM phono preamp | 180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 05 Nov 2014, 15:58 
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Joined: 26 Jan 2011, 08:57
Posts: 50
ok p.s.is putting out 24.6 volts
adjusted till I had 12.4 per collector.
This should make the 15 ohm resistors cool down some?
Still need to kill that buzz I can hear.


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 05 Nov 2014, 16:01 
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Joined: 06 Jun 2008, 18:23
Posts: 5301
Location: Australia
Try it. It's how I run mine.

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Projects: "Carbon” - MM phono preamp | 180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 05 Nov 2014, 16:03 
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Joined: 26 Jan 2011, 08:57
Posts: 50
o.k.


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 12 Nov 2014, 10:26 
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Joined: 26 Jan 2011, 08:57
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I am going to change the input capacitor to a .1 polypropylene by Wima and see the difference.
Then change the input resistor to a 220 ohm like Kramme did .
Right now I have a 100k in there
One at a time and see the difference


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