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Old 8th December 2009, 11:52 AM   #21
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The idle current is not much right around ~30ma. So you will mostly just need to figure for. Your load.
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Old 22nd December 2009, 03:07 AM   #22
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Russ/ Brian; Just ordered Ventus Kit---any suggestions for a volume control at the input?

Pete
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Old 22nd December 2009, 03:38 AM   #23
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Quote:
Russ/ Brian; Just ordered Ventus Kit---any suggestions for a volume control at the input?
What is your source?
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Old 22nd December 2009, 01:31 PM   #24
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Super Pro Dac
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Old 23rd December 2009, 01:00 PM   #25
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On a budget, a 10K pot would be fine. Single-ended Joshua Tree would also work very well.
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Old 23rd December 2009, 07:10 PM   #26
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Thanks Brian; JT is a bit beyond my reach--will go with the pot for now!

Merry Christmas to the "Pear People",

Pete
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Old 23rd December 2009, 08:23 PM   #27
glt is offline glt  United States
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Default Transistor matching

Elsewhere it is indicated that specification can be improved by matching the transistors. Since these are very inexpensive, one can buy a bunch, and match them by measuring hfe with a capable Multimeter.

Although I find no claims of audible differences, matching the transistors is part of the fun of diy. Which of the transistors would benefit from hfe matching?

Thanks and Merry Christmas to all...
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Old 23rd December 2009, 09:55 PM   #28
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Hi glt,

If you feel like matching the best way to do it would be to create matched pairs for each pair in the schematic.

For example QN2/3, QP1/2, QP3/4, QN5/6, QN7/8, QN1 and QN4 do not need to be matched at all. All pairs need only be matched to their mate. You do not need to match "all" the transistors.

One other change that people might want to play with is adjusting R6/7. The value of those resistors sets the current through the front end. They should be 1% or better.

Cheers!
Russ
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Old 26th December 2009, 05:42 PM   #29
n_maher is offline n_maher  United States
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Russ/Brian,

A few questions that I figured I'd ask here so that they could be used by others.

1. If I want to run both SE and Bal inputs is that easily possible? From my reading here it sounds like there are some adjustments that need to be made to the amp boards to run SE inputs.

2. Is there any risk (oscillation) running the amp at unity gain? I'd like to set this up to use with sensitive headphones like IEMs to start. Any issues with running a switch that would jumper R3 when enabled?

3. Could you list the complete set of recommendations if one is planning to power the Ventus with the Placid BP? As a start do I need to remove the 1000uF caps that I already installed on the ventus boards? Second, what's the recommended initial setting for the shunt current? I saw mentioned somewhere that the expected draw is ~30mA so I'm thinking 35mA through the shunt would fit your normal +10% recommendation that I've seen elsewhere.

Thanks in advance, this looks like a really cool project. Well, for a headphone geek anyway.

Happy Holidays!

Nate
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Old 26th December 2009, 08:19 PM   #30
glt is offline glt  United States
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Some answers: Introducing Ventus

Yes. cool project...
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