Should I Build 500 or 51X?

[amarten]

I posted this earlier today in the Brewery section. Didn't have a complete understanding of where to post it. I suppose this is a better location. Tried to delete the initial post, got an error message telling me that I couldn't delete the post. This is a time-sensitive question, so I'm reposting it here. Sorry about the repost, I realize that's probably frowned upon.

A) I'm a student building a 500 or 51X series rack for a class project, and I'm trying to get the most long term use out of the money I'm about to spend. I plan to have these racks for a long long time. The ~$1200 that I'm spending for the rack/PSU/my first two modules is pretty much all the available spending money I have, so I want to be absolutely sure I do this right.

B) So, from this moment in time, which format would I get the most use out of for the future? 500 series or 51X?
I see a bunch of DIY modules that I want to build, and many of them are for either 500/51X. I'm going to be building one of the racks from classicapi.com. According to him, I can't put more than 11 VPR modules and 11 51X modules on the PSU he specs for his racks. So, I would be stuck at 11 modules of 500 series, and 11 modules of 51X. I'm fearing that I won't find enough 51X modules running off of 24V to fill the 11 spaces, and will end up with empty useless spaces, as I can't have more than 11 VPR modules.

This confuses me though. Wouldn't the only determining factor for how many modules I can have in a rack be the current consumption of each module?
If that's true, then why am I only able to have 11 VPR modules? Would it not make sense that I could have more than 11 VPR modules running so long as they ran well below the 130mA per module spec, allowing the 24V modules to eat up whatever they needed?

I get myself turned around. Any direction at all would be great.

 

[ruairioflaherty]

Unless I'm reading you wrong you are mistaken.  The rack kit you are looking at can take 11 x 500 series OR 11 x 51X (+/- 24 volt) modules, not 11 of each.

 

[Winetree]

The 51X Power Supply can power 11- 16 volt modules and 11-24 volt modules.
(one 11 space rack of 16 volts and one 11 space rack of 24 volts)
You can get the other offered transformer and power 22-16 volt modules
(2 - 11 space racks of 16 volts).

'For example using the VPR spec of 130mA per main voltage rail, 11 modules drawing the maximum allowed current would be 11 * 130mA or 1.43A. Now, keep in mind that all 500 series modules differ. My VP26 mic preamp draws from between 23.3mA to 28.1mA on each of the 16V rails with a gar2520. When driving a 600 ohm load, the VP26 will draw nearly 51mA per each 16V rail. Well within the VPR specs. So, in theory, the 51x Power Supply PCB can easily drive 25 plus VP26 mic preamps on the 16V rails, and still have some headroom. Keep in mind, this example still leaves the 24V rails unused! Many possibilities can be handled with a beefy PSU design like this!'

Does that answer your question.

 

[AErige]

if you go for a 51X rack, you'll be able to put a mix of VPR and 51X modules on the same rack as long as your PSU can provide +-16V and +-24V....although it can sometimes be mechanically delicate to put a VPR card in the 51X slot.

the 51X rack from capi is a 11 slots rack and the PSU he sells can supply DC up to 11*51X modules and 11*500 modules according to his webpage.
Here are the spec I found : http://classicapi.com/catalog/product_info.php?products_id=351
1.5A @ +16VDC
1.5A @ -16VDC
1.5A @ +24VDC
1.5A @ -24VDC
179mA @ +48VDC

Remember current draw really depends on the type of the modules...for instance lots of modules using +24V pin are based on old neve class A designs and need more current than original classAB api modules.

 

[amarten]

So if I have the 51X PSU, in theory wouldn't there be no problems at all with running, for example:
6 modules @ 24V and 16 modules @ 16V.
So long as they don't eat up a collective 1.5A per rack I should be alright?

From what I can tell browsing through the available DIY modules (and most modules in general), it seems like most use MUCH less than 130mA. That would mean that having a module eat up more than 130mA would be fine, assuming the rest of the rack was using modules eating up much less than 130mA.

Also this is of course assuming that I have 2 11-space racks.

 

[[silent:arts]]

Your understanding is right.
It does not depend on the number of modules, it depends on the total current draw.

The initial PSU design was 1 PSU for 1 Rack.
People started to use it for one Rack @ 16V and one Rack @ 24V, which is totally fine and the reason Jeff is offering the "two DC cable" option.

With this option many customers without electrical skills started to put in module after module, without thinking of current draw, ending up having blown 16V fuses from the 20+ unknown VPR modules they installed. For sure this is the fault of the bad designed PSU and the seller not telling you ;-)

This is the reason why Jeff now clearly says: 11 VPR specced modules, and 11 51X specced modules!

 

[amarten]

Your understanding is right.
It does not depend on the number of modules, it depends on the total current draw.

Okay, thanks everyone for the clarification!
Looks like the 51X route is indeed the direction I'm heading. Huzzah!  ;D

 

[Bassniac]

Hi Folker
How can I measure the cureent draw of one of my modules.
Seems like 6 NV73 modules and 2 Laz EQN are the limit on the 24V+ rail. As the voltage supplied starts decrasing with every module stuffed in. (Now starting to stuff in 16V modules).

Cheers, Mathias

 

[Bassniac]

Found it out by myself... dont bother.