9k power supply

Keith anyone

I just got done building two channels of the green. I built it with parts I had. I used a 18 0 18 transformer. It works fine for the +- 16V I am using for the preamps. The problem is it is not enought voltage for the 48V phantom I am getting 47.8 before the regulator.

I have a 10Vac tap on the transformer could I use this in the centertap of 18 0 18 to bring up the voltage. I could just order a 20 0 20 but I like building with what I have sometimes

Well, the 10V isn't going to be 10V DC, so it'll just add 10V AC to the phantom without trickery...

If you have 47-point-something, you could just skip the 317 and put a 2-stage trick as follows:

"100Ω series/100µF-to-ground/100Ω series/100µF-to-ground" which will give you alost 48V at the end of it, and so little as to be unmentionable...

...of course I wouldn't push it by trying to drive 8 mics with it or anything...

The lack of absolute regulation should be fine, since the phantom spec requires that most mics accept a window from fifty-something volts to thirty-something volts anyhow...

If you need to use a 16-0-16, then you could try economising further using the described method, then report back to us and let us know how you get on!

Keith

economising is not the issue its that I got all this stuff from decades of collecting and I would like to find a use for it.

I was going to try adding the 10vac winding to the center tap. I thought I would ask first to see if anyone knows of a problem with that. I will try it and post .

I thought a 36 VAC CT would work but like your schematic shows you need a 40VAC CT for the phantom to reg right.

I do think you need heatsinks on the ICs in the power supply with this circuit the IC without the heatsink have the temp of devices that always seem to fail without heatsinks it takes sometime, like over a year for failure.

Gus,
I would incorporate a voltage clamping circuit on the +18V side like the one Rane uses on their MS 1b preamp ( http://www.rane.com/pdf/ms1bsch.pdf ) to make the B+ voltage.

I just was testing my green build. I added the 10vac to the center tap of the 18 0 18 every thing measures and sounds good now.

That is a nice clean preamp. I built two on the first PCB design. I changed some stuff 3 caps on each channel were changed to two back to back with a forming voltage. I used Pan FC, HF,HFS and standard, some Nichicon LOW Z ones and rudycons at the phantom part. The higher voltage rubycons seem to measure better than some other caps with ESR. mica 22pfs, 1000 and 100pf polystryenes and some older RC5532 1982 datecode I had. I also used CF resistors that I matched between channels and in each channel. I used matched 2n4401s. The phantom is wired always on.

SSLtech's PS is used to power both channels. I used an EI transformer that I had

Like may have said here before the Green seems to be a very good early build for new builders