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-   -   Salas DCG3 preamp (line & headphone) (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone.html)

donhughes111 9th April 2020 10:06 AM

Thanks, Salas

shattered_dream 13th April 2020 12:44 PM

Stupid Question : Upa68h slim Version... Where OS the first pin?

jimk04 13th April 2020 12:46 PM

I dont think you can get it wrong...it goes in either way

DGSSGD

Oracle1 13th April 2020 12:46 PM

look at post 31


Good afternoon

shattered_dream 13th April 2020 01:19 PM

Quote:

Originally Posted by Oracle1 (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post6159878.html#post6159878)
look at post 31


Good afternoon

Thanx... Just realized it doesnt matter.....

orelli 13th April 2020 09:36 PM

1 Attachment(s)
Hi Nick,
I just build a DCG3 for my friend Sound63, and he's very entusiast.
I not hear to it, cause virus, but now I wanna build one for me.
I want a balancede one.
I read the first 240 pages of thread and I liked very much the realisations of Magic Bus and Nashbap, they both made it balanced.

Actually my preamp is a SE balanced JFET by Borbely.
It sounds Amazing, but it get caps in the signal path ( at the end to cancel DC)and it get too much gain, 26 dB.

My speaker system is a 4 ways biamped fullhorn with sensivity of 108 dB/W/m in the bass, and over in the high ways.
The gain of Borbely is overkill!!

Actually I've the electronic crossover inside the preamp.
I've splitted the signal at the output in two ways:

1- low pass filter 12dB oct builded around a k170 / j74 push pull buffer, followed by a 10uF cap to null DC.

2-a voltage divider to attenuate 7 dB the high ways, followed by another
k170 /j74 buffer, followed by one 1uF cap, that make a 6dB high pass filter
at 150 Hz ca ( the amp have 1k1 imput impedance)

I would make the same thing with DCG3 with somedifferent things:

1-the same low pass without the 10uF cap at the end

2-a voltage divider followed by the 1 uF cap, without buffer. See schematic.

I think that the brute force of DCG3 can drive the volt divider and cap without the buffer.
I'm correct?

What the best values for Rs and Rp to attenuate about 7 dB?

Thank you for another GREAT design!

Salas 13th April 2020 09:53 PM

Hi

Rs=10k Rp=8.2k

orelli 13th April 2020 10:09 PM

Actually in the borbely preamp , they are Rs=10k and Rp 7,8k (5k6 +2k2).
I ask to you to know if the ohmic value is too low or too high, wich values are best to load the DCG3 optimally.

orelli 13th April 2020 10:18 PM

Thanks.
No need to buffering, I suggest.

Salas 14th April 2020 12:24 AM

With Rs=10k and Rp=7.8k attenuation is -7.17dB. When Rp=8.2k its -6.91dB. It needs 8k (5k6+2k4) for -7dB spot on.

The preamp is going to see both filters in parallel which is easy to DCG3 and you still have a low noise enough divider impedance for your purposes.


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