Dual Class-A Line and Headphone Output Board Documents

Construction information for DIY projects, including the MS Mid Side Matrix, Elliptic Equalizer, Mastering Console, Phono Transfer System, Insert Switcher and the Dual Class-A Amplifier. You can post your baby pictures here.
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mediatechnology
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Re: Dual Class-A Line and Headphone Output Board

Post by mediatechnology » Tue May 22, 2012 9:53 am

I would hope that the PEQ DIY planning and zoning committe don't swoop in because you're having too much fun. All hell would break loose if you sold one. :roll:

If there are build-out resistors used with the DCAO driving the Pultec filter network it would be interesting to see the drop across them vs. frequency and EQ settings.

The build-out is a current sense resistor and the point of lowest impedance (greatest shunt voltage) might be interesting to measure. You could use a 1240 across that resistor and look at the 1240 output or the 'scope in differential mode.
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Re: Dual Class-A Line and Headphone Output Board

Post by mediatechnology » Tue May 22, 2012 1:44 pm

Figuring out how low the impedance actually goes might help us dial in Iq for that application.

I just noticed something in the PC board photo: There are only three resistors (per DCAO channel) that are actually in the signal path.

The MS Matrix only has two.
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Re: Dual Class-A Line and Headphone Output Board

Post by mediatechnology » Wed Jun 06, 2012 3:34 pm

I just posted schematics of the DRV134 build here:

viewtopic.php?f=7&t=509&p=5700
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Re: Dual Class-A Line and Headphone Output Board Documents

Post by Gold » Fri Jun 15, 2012 12:12 pm

Hey Guys,

I haven't checked in for a while. This board looks great. Great job as usual Wayne and Roger. I'll have to dig out the chip data sheets and try to figure out what all that fancyness is doing. I'm sure I can learn a lot by studying it.

Paul

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Re: Dual Class-A Line and Headphone Output Board Documents

Post by mediatechnology » Fri Jun 15, 2012 12:22 pm

Thanks for checking in Paul!
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Re: Dual Class-A Line and Headphone Output Board Documents

Post by Gold » Fri Jun 15, 2012 5:17 pm

This would be really nice as line preamp with gain for my mastering console. It needs to be able to drive multiple loads at once. It looks like there is plenty of room on the board to mount a daughter board with an opamp for gain. I don't mind an impedance balanced output. There wouldn't be enough room in the chassis to mount eight boards. Since I am no designer I would feel safer running the gain opamp in an inverting configuration. Could I flip the output polarity by reversing pins 1 & 8 on the DRV?

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Re: Dual Class-A Line and Headphone Output Board Documents

Post by mediatechnology » Fri Jun 15, 2012 5:45 pm

Could I flip the output polarity by reversing pins 1 & 8 on the DRV?
Thanks Paul.

Actually you could just re-define the inputs at the THAT124X calling "-" "+."

If there was an inverting stage after the 124X producing gain the resulting double-inversion would give you an in-polarity output.
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Re: Dual Class-A Line and Headphone Output Board Documents

Post by Gold » Fri Jun 15, 2012 6:03 pm

mediatechnology wrote:
Could I flip the output polarity by reversing pins 1 & 8 on the DRV?
Actually you could just re-define the inputs at the THAT124X calling "-" "+."
I guess the word 'duh' applies here.

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Re: Dual Class-A Line and Headphone Output Board Documents

Post by mediatechnology » Fri Jun 15, 2012 7:17 pm

I guess the word 'duh' applies here.
I used it, in reference to myself, just yesterday. :D

Proud of it too. I earned it.
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Re: Dual Class-A Line and Headphone Output Board Documents

Post by mediatechnology » Sat Jun 23, 2012 6:53 pm

Thanks Roger!

What are the details e.g. primary impedance, build-out resistance, Cinemag model etc?
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