Well, there were different versions of the PSU...
Assuming you have the version with the bugfix summarized here, the transformer should be the limiting part, i.e. ~400mA for the 15VA version, ~700mA for the 25VA version. Be careful as there are no secondary fuses on the PCB, afaik.
Looking at power dissipation of the output transistors: The rectifiers will output +-18V*1.4=+-25V DC. If you use +-15V at the outputs of the supply, there will be a dissipation of (25V-15V)*output current, i.e. 4W for 400mA. Shouldn't be a problem, I guess, depending on your heat sink.
Sorry I did not precise it at first, that's definitely this one I'm using.
Wow! Many thanks for the insights, definitely what I was looking for.
Best to all.
The sound of silence
It works! Thanks to everyone on this thread, especially Carl and Doug, I have arrived at the point in my build where this thing actually plays music.
First impression is that this is one quiet preamp. And does it sound good! My first listening test was far from ideal, but I did prove that, a. It works, and b. It didn’t blowup or burn down the house - two good signs in any build.
The images show the boards completed and connected to each other; the preamp connected to a test setup on my bench; lastly, I thought I would show off the Douglas Self/Signal Transfer Co. phono preamp I built at the same time. I used one of Carl’s PSUs to power it.
Next step is to box it up. I’m debating 1U or 2U, deciding knob choices, and planning how I want my silkscreens laid out front and back.
It works! Thanks to everyone on this thread, especially Carl and Doug, I have arrived at the point in my build where this thing actually plays music.
First impression is that this is one quiet preamp. And does it sound good! My first listening test was far from ideal, but I did prove that, a. It works, and b. It didn’t blowup or burn down the house - two good signs in any build.
The images show the boards completed and connected to each other; the preamp connected to a test setup on my bench; lastly, I thought I would show off the Douglas Self/Signal Transfer Co. phono preamp I built at the same time. I used one of Carl’s PSUs to power it.
Next step is to box it up. I’m debating 1U or 2U, deciding knob choices, and planning how I want my silkscreens laid out front and back.
Attachments
Hm, when using XLR inputs, 4 relays need to be driven simulaneously, i.e. 4*12mA=48mA. Current through the 1st BC550 is limited by the 47k resistor, i.e. 14V/47k=0.3mA. This means that the 2nd BC550 needs an hFE of at least 160@50mA. Looking at Fig.3 in the datasheet of the BC337-40, it *should* work, but it's close...
https://www.onsemi.com/pdf/datasheet/bc337-d.pdf
2SC2240 should work.
2SC1845 is limited by maximum collector current of 50mA and hFE (s. Fig.3 in https://cdn-reichelt.de/documents/datenblatt/A100/SC1845-FSC.pdf).
Both have different pinouts.
Noise doesn't matter for the relay drivers.
I would recommend a Darlington, too. Or use the two BC550 as a Darlington
I was just checking them out. Any appreciable difference between the “CTA” end suffix and the “B” versions?
I believe the CTA is the SOT package, whereas the B is a TO-92. This build uses the TO-92 package.
Rear Panel FPD file
glenv6,
Here is a rear panel layout for a 1U case. I cannot remember who sent it to me, so thank you whoever you are.
Dropbox - REAR_PANEL_1U.fpd - Simplify your life
glenv6,
Here is a rear panel layout for a 1U case. I cannot remember who sent it to me, so thank you whoever you are.
Dropbox - REAR_PANEL_1U.fpd - Simplify your life
Here is the one I drew.
https://www.diyaudio.com/forums/att...g-self-preamp-linear-audio-5-a-rear-panel-pdf
https://www.diyaudio.com/forums/att...g-self-preamp-linear-audio-5-a-rear-panel-pdf