In article , Mike Rivers wrote:
On 11/5/2016 6:26 PM, wrote:
What are your thoughts on this?
http://sound.whsites.net/project66.h.../project66.htm
They want $22 for the circuit board. Not sure what the components
cost.
Since Phil is around here, you might ask him about whether it's even
available currently. I notice that the date on the linked web page is 2008
The circuit is pretty common, very much like a Mackie, maybe even
exactly like a Mackie. I didn't compare the schematic for component values.
This circuit is pretty much what you will find in any transformerless mike
preamp with a couple exceptions.. everything from Millennia to Mackie. It is
as good as the front end is allowed to be.
The 2N4403 is not exactly a low noise transistor but if you're careful about
where you get them and cull out the occasional outlier, they can work pretty
well in this circuit. The thing about the 2N4403 is that it's sold as a
swithing transistor with very relaxed specifications on the datasheet, and it
only has to meet the specifications. Most of the time it does much better,
but not always. This is the difference between spending three cents for a
transistor and three dollars.
Now... this said... if you build this, you're still in for building a
power supply and the power supply is going to be more expensive than the
circuit itself. Add a nice machined case and the cost goes up even more.
But, if you build it well with good parts it will outlast any of the consumer
stuff you'll find at that price range.
I disagree strongly about there being no problem with DC bias on modern
electrolytics, but there ought to be a couple volts across C2 and C3 if
I read this right. If there aren't, mylars might be a good plan. I might
also dramatically increase the values of C2 and C3 well beyond the values
needed to get good response.
You're going to need to add some input capacitors on this as well if you add
a phantom supply, so put that into your price equation.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."