Recomendations for phantom blocking caps?

[babyhead]

I have some circa 1979 transformerless channel strips I am planning on recapping. All of the psu and phantom blocking caps are axial so my choices are limited. I'm willing to stick almost any 220uf/40v above a Xicon in there as I have 70 of these to replace, but I would think the phantom blocking caps should deserve special attention.

Does anyone have any experience with different caps here?

Can I just jumper them if I never use phantom on the strips? The design calls for it to always be on...

I also have to make a psu that will cover +/- 32v and +/- 28v. I have a Power One that can handle the 12v logic but it's kind of hard to find any stock psu to handle those voltages. I'm looking at the 51x psu for my solution. Any thoughts?

Mark

 

[pucho812]

for 28V check this out

2 amps 28V it's single ended so you would need 2 to give you your +/-



here is a 5.5 amp 28V supply

and you should be able to adjust this down to 32V

http://www.mpja.com/prodinfo.asp?number=16034+PS

again would need two of them for the +/- 32V


as for phantom just do not connect it and it's not an issue. But make sure your  blocking cap voltage rated for over 48V so they don't pop

 

[babyhead]

Shouldn't the supply be linear?

I'm probably going to stick Atoms into that position.

For the whole system, there are ~35 gain blocks and I know of a comparable system that uses 28 and operates under 1 amp. Each strip has 2 regulated supplies, but the +/- 28v had 'some design flaws' according to the designer,  so I am looking for an option. If I run all 7 strips from the same rails, am I looking at introducing crosstalk? The LM350 is capable of 32v @3A+ so the 51x psu looks appealing, maybe even 4 of them with the last rails handling the 32v. The +/- 32v is used for the peak indicators and is regulated down to +/- 18v for servos and EQ fun. 

 

[pucho812]

fwiw digi/avid uses switching supplies in their 192 i/O units as well as other units in their line. You can pick up the switching in your audio lines but the frequency is so high you do not hear it. I see no real problem using switch mode supplies for audio especially if your PSU is external but I am sure some of the experts will chime in...

 

[pucho812]

fwiw the ssl 9000 uses switch mode supplies

 

[gemini86]

those supplies are extremely well designed specifically for audio, also heavily filtered. you may be able to MAKE those cheap ones work, but it would end up costing more time than building linear supplies. Unless you're willing to be a pioneer in cheap chinese SMPS modding.

 

[ruairioflaherty]

You can pick up the switching in your audio lines but the frequency is so high you do not hear it...

That is until it hits an opamp stage and demodulates into the audio band, which is why RF filtering before your first stage is important.

I see no real problem using switch mode supplies for audio especially if your PSU is external but I am sure some of the experts will chime in...

For DIY I'd definitely be sticking with linear. SMPS are used buy several manufacturers and can work well, I have two of Roger Foote's P3 compressors powered by external switchers and they are excellent, I know from talking to Roger that these are not cheap supplies.  As Gemini says using a switcher well demands serious design chops.

 

[babyhead]

Thanks for the input on linear vs. switching. As I am holding on by the skin of my teeth in putting my little sidecar together, I will go with the 51x psu.

When putting together multiple circuits on a single rail, whats the best method for distribution of the current? In the 500 stuff, I see the protection diodes functioning like that and in other designs a resistor. The best solution being independent rails per channel, which would be better, build out resistors or diodes?

I have no real idea of the current consumption of the unit @ 3 28v DOAs plus a 28v mic pre module per channel. A popular eq uses 14 of these and 2 can be powered with a 1 amp supply, which would make for a 36ma draw per DOA, but that just doesn't feel safe.

The 15v regulator section knocks the 32v down for only 10 ICs and is based on a NE5554V, which the designer was happy with. The 32v to 28v is handled by a UA79NG regulator which I cant find any data on. I'm sure the LM350 is better design.

Thanks!

 

[pucho812]

most doa's I have seem draw around 15 miliamps

 

[[silent:arts]]

When putting together multiple circuits on a single rail, whats the best method for distribution of the current? In the 500 stuff, I see the protection diodes functioning like that and in other designs a resistor. The best solution being independent rails per channel, which would be better, build out resistors or diodes?

Look at old german broadcast modules:

there are other variations.
it even slowly starts your module, reducing inrush current problems.