Search found 169 matches

by carlmart
Thu May 22, 2014 1:24 pm
Forum: Pro Audio Design
Topic: Portable mic preamp project
Replies: 47
Views: 91992

Re: Portable mic preamp project

With a gain switch, you can switch the pole frequency with the Rs. It is an old trick to let the LF response fall off at highest gain to make the preamp appear quieter than it is. This way the preamp makes less noise Please elaborate on how to do this. The 1.1 uF/4400 Ohm cutoff (2.2uF/2 and 2K2x2)...
by carlmart
Thu May 22, 2014 8:24 am
Forum: Pro Audio Design
Topic: Portable mic preamp project
Replies: 47
Views: 91992

Re: Portable mic preamp project

The suggestion to switch off the phantom to V/2 came from THAT themselves. But I do have to prevent anyone might plug a ribbon into it. So what should I do? Don't worry that I got your point on the protection diodes, and I will not use the zeners. Will also add the 1N4148s as you suggest. The reason...
by carlmart
Wed May 21, 2014 1:32 pm
Forum: Pro Audio Design
Topic: Portable mic preamp project
Replies: 47
Views: 91992

Re: Portable mic preamp project

About the battery. The reason for working with 12v as my standard voltage, is because this project is to have several powering option, meaning the battery types you will be able to choose from should be different types. But it should designed for film & video applications, where there's not just...
by carlmart
Wed May 21, 2014 11:11 am
Forum: Pro Audio Design
Topic: Portable mic preamp project
Replies: 47
Views: 91992

Re: Portable mic preamp project

Well, I re-designed my schematic more or less following the alerts and recommendations, and I think it might work well. As I think I explained, what I will be doing is modifying some pre-assembled boards I already had and see what happens. This time I added the filter I had before the input caps (wh...
by carlmart
Wed May 21, 2014 5:37 am
Forum: Pro Audio Design
Topic: Portable mic preamp project
Replies: 47
Views: 91992

Re: Portable mic preamp project

OK, yours are very interesting comments. Thanks. One detail I should have corrected was the voltage for the zener diodes, which should be lower for my supply. Zeners were (and still are) the recommended types for the protection. But I think I'll switch to the diodes bridge. Your also bought me on us...
by carlmart
Tue May 20, 2014 5:43 pm
Forum: Pro Audio Design
Topic: Portable mic preamp project
Replies: 47
Views: 91992

Re: Portable mic preamp project

I have three suggestions for implementing an analog supply on several chips: SSM2019, INA217 and THAT 1510.

What I wonder is they will work on all those chips with the mods suggested, particularly the one I called SSM2019_single2
by carlmart
Mon May 19, 2014 10:17 pm
Forum: Pro Audio Design
Topic: Portable mic preamp project
Replies: 47
Views: 91992

Re: Portable mic preamp project

What exactly would it mean to make a solid V/2? Just one well filtered divider to take care of all V/2? Buffered or unbuffered? I think the only way to keep repeatable values is using a regulator. Other than that there will be small variations. Maybe on a passive VU-meter, with diodes and needles, t...
by carlmart
Mon May 19, 2014 7:29 pm
Forum: Pro Audio Design
Topic: Portable mic preamp project
Replies: 47
Views: 91992

Re: Portable mic preamp project

Here's the DC-DC switcher. It works quite well. Presently I'm modifying my old SSM2017 design, which was fed by +9/-9v batteries into one using just one single 11 to 14.4v battery, depending on what you plug into it. I still don't know how the different voltage will affect the output, as the 0db VU ...
by carlmart
Mon May 19, 2014 2:23 pm
Forum: Pro Audio Design
Topic: Portable mic preamp project
Replies: 47
Views: 91992

Portable mic preamp project

Hi, Have just joined the club (thanks, Wayne!) and I am open to tips and suggestions. I am involved in designing a 2-mic small sized, affordable, balanced mic preamp, with 48v phantom power, single-supply (12 to 14.4v), 12-segment or more LED metering and, did I mention affordable? Even if I should ...