Low Phantom power from 500 rack?

[DrummerMan]

So, I think my API 500 10 space rack may not be providing enough phantom power. Is that a thing?

Basically, I've got 4 pres in the rack. When I have a dynamic or ribbon, everything sounds fine. When I plug in a condenser it gets a little quieter (to different levels, depending on the mic, some barely give me anything).

Now, to double check, I tried the same thing on one of my pres that's not in the rack, and the same condensers get noticeably louder than the dynamic with Phantom engaged.

Obviously some power is getting through otherwise the condensers wouldn't be making the sound that they do. The little 48v led on the rack is lit. I tried switching it off and on on the power supply. No difference.

I don't generally use condensers with these pres so I don't know if its a new or old problem, though I definitely HAVE used condensers with them at some point. Just can't remember when. In case anyone's curious, the rack pres are a pair of AEA RPQ500's and a pair of CAPI VP28's.

So does anyone know an easy way to check if the rack is actually supplying the full 48v of power? Or does this seem like it could be another issue?

[FNM]

Grab yourself an auto-ranging digital multimeter (a must have tool for life in general). Set it for DCV (DC voltage), touch the black lead to pin 1 of the XLR from the pre (or the case if it's metal and that's easier), that's ground. Now touch the red lead to either pin 2 or 3, while still holding black to ground. I believe BOTH should have +48VDC.

[DrummerMan]

Grab yourself an auto-ranging digital multimeter (a must have tool for life in general). Set it for DCV (DC voltage), touch the black lead to pin 1 of the XLR from the pre (or the case if it's metal and that's easier), that's ground. Now touch the red lead to either pin 2 or 3, while still holding black to ground. I believe BOTH should have +48VDC.

Was just doing that as you responded!

I'm getting 10.83v DC and 1.2mA between pins 1&2, and 1&3. And 0vDC between pins 2&3. That's the case for both the AEA and CAPI pres.

Soooo, not enough power. I'm surprised I was getting anything from any of those mics.

Also, just for shits n giggles, I sprayed some deoxit on the plug from the power supply to see if there was some bad connection there. No difference.

Just to make sure I wasn't using the multimeter wrong, I tried it out on my rack mounted LA-610 and that gave me a solid 49.7vDC.

I guess I'll give API a ring tomorrow. I've had this for at least 5 years. Probably more.

If I have to buy a new power supply, do people use some other brand that is more reliable? I've definitely heard of power issues with the API branded racks but I can't seem to find the threads specifying what those were right now.

[FNM]

Can you take stuff out easily? You could pull each unit one by one and re-test, there may be a chance one of them is faulty and effecting the rest. Disclosure: I've never owned a 500 series anything.

I wouldn't worry about, or F with reading amps that much since that's when stuff tends to get toasted.

[DrummerMan]

Can you take stuff out easily? You could pull each unit one by one and re-test, there may be a chance one of them is faulty and effecting the rest. Disclosure: I've never owned a 500 series anything.

I wouldn't worry about, or F with reading amps that much since that's when stuff tends to get toasted.

I'll try that. It'll have to be later though. I wonder if I pulled all the units and tested inside the chassis. Just need to figure out what points inside to are the 48v...

[losthighway]

I'm super curious because I was just thinking this will be the year for me to graduate to a 10 spacer, and I have a local shop that sells API which was what was going to help me make up my mind.

[DrummerMan]

Can you take stuff out easily? You could pull each unit one by one and re-test, there may be a chance one of them is faulty and effecting the rest. Disclosure: I've never owned a 500 series anything.

I wouldn't worry about, or F with reading amps that much since that's when stuff tends to get toasted.

So...

With everything out of the chassis, I tested pin 15 (the bottom pin), which is the 48v as far as my research has revealed. That gave me 13v DC

Then I did each pre one at a time:
Each AEA pre gave me between 11.03-11.05v DC
Each CAPI pre gave me between 13-13.03v DC

Interesting that the AEA pres don't supply as much. Wonder if that's normal. Also interesting that there's a either small or slightly larger drop down to a collective 10.83v DC when they're all plugged in at the same time.

Either way, if it was a problem with one of the pres, I should have gotten a solid 48v from the pinout in the chassis, right?

[FNM]

Either way, if it was a problem with one of the pres, I should have gotten a solid 48v from the pinout in the chassis, right?

Yeah, sounds like a problem with the chassis.

[alexdingley]

Not mentioned above:

Is this problem new, or has it always been this way in this rack & w/ these preamps?

Also, which preamps are they? And which rack unit?

Additionally (from FNMs suggestion to pull units out and keep testing, I was reminded) I believe I read somewhere that the Retro 500pre draws a lot of power, and so, some racks cant host 8 of them, for instance. So, if that can be true for one preamp... is it possible that there are other 500-series preamps that draw so much DC for their essential functions, that not enough juice remains to properly fulfill the phantom power needs? Just a wild guess based on something I only read a little bit about. Disclosure: I too am a non-500-series user. I will eventually, it haven’t gotten one yet.

[digitaldrummer]

Which 500 rack to you have? I have an API 8 slot and a 10-slot. no problems with the power supplies. The 10-slot has the big external brick (linear power supply) and the 8-slot has an external switching supply. I did previously own one of the 6-slots - that one has the power supply built into the chassis.

sounds like you have a bad power supply (or maybe a bad connector or cable but most likely the supply itself).

Mike

[DrummerMan]

Not mentioned above:

Is this problem new, or has it always been this way in this rack & w/ these preamps?

Also, which preamps are they? And which rack unit?

Additionally (from FNMs suggestion to pull units out and keep testing, I was reminded) I believe I read somewhere that the Retro 500pre draws a lot of power, and so, some racks cant host 8 of them, for instance. So, if that can be true for one preamp... is it possible that there are other 500-series preamps that draw so much DC for their essential functions, that not enough juice remains to properly fulfill the phantom power needs? Just a wild guess based on something I only read a little bit about. Disclosure: I too am a non-500-series user. I will eventually, it haven’t gotten one yet.

I think I mentioned this all in the first post, but I *think* this is a relatively new problem. I usually use only dynamics and ribbons with these pres. I definitely HAVE used condensers before but I don't remember when the last time was. I think I would have noticed this issue, but who knows.

The chassis is a 10 space API rack unit, with the big external brick, though I've only ever had 4 pres in it: 2 AEA RPQ500's and 2 CAPI VP28's.

I would be surprised if it was one of the pres at this point because I just tested the chassis completely empty and was still only getting 13v.. Also, it would be a pretty bad look for API if their 10 slot chassis couldn't power 4 preamps.

[digitaldrummer]

I don't ever recall hearing bad things about the AEA pres taking too much power. And I have a couple of Capi VP312's in mine. in fact my rack is full (10 modules) and they all work fine.

so yeah, if you are only getting 13v then something is wrong. you might check the pinout on that supply to see if you can read it there too. Just to rule out something in the chassis itself is reducing the voltage.

[DrummerMan]

I don't ever recall hearing bad things about the AEA pres taking too much power. And I have a couple of Capi VP312's in mine. in fact my rack is full (10 modules) and they all work fine.

so yeah, if you are only getting 13v then something is wrong. you might check the pinout on that supply to see if you can read it there too. Just to rule out something in the chassis itself is reducing the voltage.

Do you happen to know what pin is 48v on the cable? I can't find that info anywhere.

API isn't picking up the phone right now. I sent their technical support an email. We'll see if/when they get back to me..

[Scodiddly]

Sounds like a bad PSU. Probably you should start worrying that the other outputs are nearing the end of their lives as well.

[DrummerMan]

Sounds like a bad PSU. Probably you should start worrying that the other outputs are nearing the end of their lives as well.

What do you mean by the other outputs?