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Bruno Putzeys Balanced Preamp - Group Buy Part 3

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#22
AndrewT said:
It's not unity gain.

The gain is set by the vol pot.
The residual resistances at the vol pot extremes effectively sets the limits of the attenuation and gain.
Typically expect >>+40dB of gain at the top end and <-50dB of attenuation at the bottom end.
But the steepness of the rate of change towards the ends of the vol pot track make the last ten to twenty degrees of rotation nearly useless. Expect only the middle 200degrees of rotation be be an effective control and half of that will be gain (i.e. >+0dB)
I found all my range of volume adjustment was squeezed into less than 90 degrees of rotation. I changed to a stepped vol pot, to set the attenuations of the inverting opamp stage. Much better.
Click to expand...

Thank you, this is important to me. Unity gain would not really serve me well.

And, I assume the tech discussion is moving to "the main thread", meaning the one linked in the second line of the top post of this thread. cheers
 
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#33
fredlock said:
Can you guys post the latest BOM? I will start buying parts.

Thanks,

Fred
Click to expand...

A parts-list is given in the paper which explain the design http://www.hypex.nl/docs/papers/The%20G%20Word.pdf


The link to a BOM in the original GB is not available anymore.
Google gives this discussion Bruno Putzeys Balanced Preamp Group Buy - pink fish media in which a link to the following dropbox is given: http://redirect.viglink.com/?format=go&jsonp=vglnk_147999518823613&key=7e51c1edcf74d4431ed8286703ccf9c1&libId=ivwew8pi010009pj000DAp7ikrahx&loc=http%3A%2F%2Fwww.pinkfishmedia.net%2Fforum%2Fshowthread.php%3Ft%3D178449&v=1&out=https%3A%2F%2Fdl.dropboxusercontent.com%2Fu%2F63020789%2FBrunos%2520Balanced%2520BOM.xlsx&ref=https%3A%2F%2Fwww.google.nl&title=Bruno%20Putzeys%20Balanced%20Preamp%20Group%20Buy%20-%20pink%20fish%20media&txt=BOM

I have not checked this BOM but i saw that the quantity of a lot of resistors is higher than the actual number needed
 
#34
The BoM is at the end of this published article. It came in four parts/articles and has been combined into one .pdf

Be careful with the resistors. It is not easy to differentiate between ordinary (thick film), metal film (thin film) and matched (high precision thin film).
Compare to the sch and work out which is which before you order.
And order the eight extras that let you change the gain (using 2k2 instead of 1k (R2, 30, 13, 40) and 22k instead of 10k (8, 35, 17, 44)).

There is a further improvement in interference rejection by matching the precision resistors and the capacitors that set the HF input impedance.
 

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#40
Just a quick question like that and I know there shouldn't be any advantages but let's say all the audio chain is balanced but one of the sources added is unbalanced, can it still be connected through this preamplifier and if yes, do we connect it as usual by shorting anti-phase (Pin 3) with shield (Pin 1) for RCA gnd and phase (Pin 2) with RCA positive?

I'm asking since I have a DAC which is unbalanced and would like to still use it.

Thanks
Do
 
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