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Gain stage and output buffer in Tube DACs

Please help me understand what the gain stage in a tube dac does. (for eg. the Jolida Glass FX DAC)

I understand  the gain stage helps control volume level and in in such DACs it is implemented using tubes. But I am not clear if it is attenuating or amplifying (voltage/current/both) the signal ?

Also, wondering about the related term "output buffer". From what i gather is merely something that helps match impedance... but not sure if it has anything to do with "volume control".
roxito
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jjss49's avatar
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jjss49
6,612 posts
 
https://www.effectrode.com/knowledge-base/steampunk-technology-the-inner-workings-of-vacuum-tube-buffers/

http://www.moxtone.com/Tube_buffer_en.html

unleash the power of the internet young skywalker -- it is called google search!!!!
cal3713's avatar
cal3713
1,421 posts
 
This article is a little more targeted: https://www.psaudio.com/pauls-posts/duties-output-stage/9298/

"Most of the work designers do to make sure their output stages are good sounding and well serving of their products were developed in preamplifier designs they’ve produced."

cal3713's avatar
cal3713
1,421 posts
 
And here's some real discussion about the process. If you want to learn more look up I/V (current to voltage) conversion stage...

https://www.whatsbestforum.com/threads/dac-design-the-i-v-stage.21636/
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