Preamp spacing

[NoFear13X]

I understand that for wire management and heat issues, everyone recommends spacing the ADA8000's a 1/3rd rack space apart. Does this apply to the TubeOpto8's as well? I mean, with all rear-mounted I/O the wire management reason is out the window, which leave heat. Is that problematic for other preamps or is it mostly just the Behringers?

[Cary B. Cornett]

I understand that for wire management and heat issues, everyone recommends spacing the ADA8000's a 1/3rd rack space apart. Does this apply to the TubeOpto8's as well? I mean, with all rear-mounted I/O the wire management reason is out the window, which leave heat. Is that problematic for other preamps or is it mostly just the Behringers?

Every converter device I've had or checked out produces a certain amount of heat. I think the ADA8000 may be a little worse in that regard, but I find the Digimax FS can get a bit warm as well, so no matter what converters you use you want to be careful about heat management. I try to avoid putting any two converter boxes directly against each other in a rack. I will either leave some air space, or I will try to put things that don't heat up much between converter boxes. For example, those Furman power "filter" units (like the PL-8 Series II in my rack) don't generate any heat to speak of, so in my road rack I put it between my MOTU 2408 and a Digimax FS.

As for the TubeOpto units, remember the word "tube" is in there, and I'm pretty sure there are 4 tubes in that box. Tubes have to get warm because they have to heat up the cathode element or they won't work... so you've got 4 little heaters in there. Probably just over 7 watts of total power consumption goes just to the heaters, to say nothing of all the other heat sources in the box.

Whatever unit you use, put one in a rack with an open space above it and let it cook for a while, then put your hand on top of it and see how warm it gets. If any part of the surface gets uncomfortably warm, you know you should be careful about heat management. If you can't leave much air space, then at least put "cool" things between "warm" things to even out the heat.

[Richard Rupert]

Every converter device I've had or checked out produces a certain amount of heat. I think the ADA8000 may be a little worse in that regard, but I find the Digimax FS can get a bit warm as well, so no matter what converters you use you want to be careful about heat management. I try to avoid putting any two converter boxes directly against each other in a rack. I will either leave some air space, or I will try to put things that don't heat up much between converter boxes. For example, those Furman power "filter" units (like the PL-8 Series II in my rack) don't generate any heat to speak of, so in my road rack I put it between my MOTU 2408 and a Digimax FS.

As for the TubeOpto units, remember the word "tube" is in there, and I'm pretty sure there are 4 tubes in that box. Tubes have to get warm because they have to heat up the cathode element or they won't work... so you've got 4 little heaters in there. Probably just over 7 watts of total power consumption goes just to the heaters, to say nothing of all the other heat sources in the box.

Whatever unit you use, put one in a rack with an open space above it and let it cook for a while, then put your hand on top of it and see how warm it gets. If any part of the surface gets uncomfortably warm, you know you should be careful about heat management. If you can't leave much air space, then at least put "cool" things between "warm" things to even out the heat.

Cary,
In no way am I arguing with your statement because I know very little about electronics. But I have noticed that my two channel Aphex tube preamp runs very cool. And my Frontier Designs converters run very warm. So, I guess I would (or could at least) conclude that tubes do not necessarily generate much heat. Or am I missing something? I do agree that "whatever you use" as a converter, put space between the units. It certainly can't hurt.

[Cary B. Cornett]

Cary,
In no way am I arguing with your statement because I know very little about electronics. But I have noticed that my two channel Aphex tube preamp runs very cool.

There is nothing wrong at all with you asking for the logic behind my conclusions, and I am glad to answer.

I had one of those Aphex "Tubessence" 2-channel mic preamps for a while. It had one 12AX7 tube in it. "Essence" indeed. I agree that I found no significant heat issues with that unit. It did not require any special consideration to keep it cool.

And my Frontier Designs converters run very warm.

Yes, I had one of those also, and it did indeed run rather warm.

So, I guess I would (or could at least) conclude that tubes do not necessarily generate much heat. Or am I missing something?

For any given function, a tube circuit will generate significantly more heat than a solid state circuit doing the same job. The Aphex mic preamp you mentioned has relatively little going on for the size box it occupies. Only 2 channels, and no A/D/A converters. Plenty of space for the modest amount of heat generated to dissipate. Now look at your Tango converter. 8 channels of A/D and 8 channels of D/A in the same height box means more work being done per unit of space and thus more heat generated/concentrated. Now add 8 channels of mic preamps, including 4 tubes, and there is that much more heat to dissipate in a relatively small space. Sure, you can generate plenty of heat without using any tubes, but tube circuits are always less efficient, thus producing more waste heat for whatever function they perform.

I do agree that "whatever you use" as a converter, put space between the units. It certainly can't hurt.

For anything that you can just put on casters and roll around, there is no reason to crowd stuff together if you don't have to. My situation requires some of my equipment to go up a flight of stairs every time it goes out for a gig. This includes my converter rack, which is limited to 6 units so that it can be conveniently lifted by an ordinary mortal. By the time my rig gets up to 24 inputs, I won't be able to leave blank space in the rack, so I will then have to get a bit more "creative" about thermal management. My guess is there are not a few other users with similar constraints on rack size. I don't know whether the OP has to worry about that.

[NoFear13X]

By the time my rig gets up to 24 inputs, I won't be able to leave blank space in the rack, so I will then have to get a bit more "creative" about thermal management. My guess is there are not a few other users with similar constraints on rack size. I don't know whether the OP has to worry about that.

Currently, the rack is stationary, and oversized now that all of my analog gear is out of it. My 14U rack has a 1U UPS, 1U Power, 4U computer, 2U amp and 3 ADA's, which are more than adequately spaced apart. All of my other heat generating gear (amp and cpu) are not adjacent, and all ventilate front to back, so I don't really have heat issues. My thought was to drop to a 12U rack with locking doors, and eventually possibly add a second amp, so that was part of my concern.

Also, eventually the idea is to set up a travel system. For size reasons, having preamps with rear I/O only would hypothetically allow me to eliminate the gaps and the need to remove the front door during use (protect controls, power switches, etc), but I was still aware of potential heat issues. Spacing 1/3rd unit apart for 3 or 4 preamps would only require one extra rackspace anyway, but, just thinking in advance...

[Cary B. Cornett]

Also, eventually the idea is to set up a travel system. For size reasons, having preamps with rear I/O only would hypothetically allow me to eliminate the gaps and the need to remove the front door during use (protect controls, power switches, etc), but I was still aware of potential heat issues. Spacing 1/3rd unit apart for 3 or 4 preamps would only require one extra rackspace anyway, but, just thinking in advance...

I would not do the "1/3 space" trick with a travel system. If you are going to move a rack around, you want both the upper and lower screws on every piece of gear, because of unpredictable shocks of failure to always keep "this side up". Fractional spacing will cause you to lose the ability to screw down all 4 corners on at least some of the units thus spaced.

[905shmick]

You can purchase 2U and 3U exhaust fan kits which you can mount on the back of the rack.

[NoFear13X]

Given the weight of the preamps, I'd say it's less critical, but I could understand your point. I personally move all my own gear, so I typically have no incidents during travel events.

My biggest problem so far is a missing mic stand that has a clip to hold an overhead mic, and the mic has been gaffing-taped on to the stand ever since

[Cary B. Cornett]

You can purchase 2U and 3U exhaust fan kits which you can mount on the back of the rack.

Yeah, but how much noise do they make? Most of what I have been working with is, well, a lot quieter than a rock concert. It's normal for me to have the rig out in the audience, and with something like a traditional choir concert you don't want people distracted by fan noise during the quieter passages.

[brianklock]

I would not do the "1/3 space" trick with a travel system. If you are going to move a rack around, you want both the upper and lower screws on every piece of gear, because of unpredictable shocks of failure to always keep "this side up". Fractional spacing will cause you to lose the ability to screw down all 4 corners on at least some of the units thus spaced.

I agree. Hopefully we will have our new ADA8K ears finished in the next week. We are machining some new ears which will hold 3 units in 4 rack spaces. This will be a single pair of ears mounted to all 3 units (we are calling this a 'preamp package') The time involved in machining the ears will be well worth it. There are several distinct advantages to our ears:

1. The longer ears will allow us to recess the units an additional 1.5" allowing cables to be full recessed into the front of the case.
2. The ears will allow the units to be fully mounted and allow for spacing between each unit. The ears will allow for .44 inches above and below each unit. This will minimize wasted space in the rack as these ears space the bottom unit up and the top unit down in the configuration allowing the 'package' to have units mounted directly above and below and still allow ventilation space around all units.
3. I am going to add a side exit cable hole onto the ears allowing permanent cables to be routed around the side of the rack, exiting through the ear... neatly cable tied, and not occupying any of the ventilation space between the units.
4. Theoretically, the larger ears will provide more heatsink capacity However, with the added ventilation space plus the reduced heat generation (as specifi3ed below), I think that additional heat dissapation capacity will be of little significance.

Being the kind of guy to maximize any advantage possible... I do have a voltage reduction transformer setup built based upon the schematic provided in the following post:
http://www.sawstudiouser.com/forums/showthread.php?t=11596

I didn't mount the transformer in a rack unit like the original post shows. I put the transformer in a 4" electrical box which is mounted on the side of the rack. I cut IEC cables which are cut to length, hardwired to the transformer, exiting the box to feed the ADA8K's. I liked how nice and neat the rack unit in the original post looked, but my concern was that somehow somebody would accidentally plug something else into a reduced voltage outlet... I know it isn't likely to happen, but I try and keep things as 'error-free' as possible. The good thing is that when the IEC cables come out of the electrical box, they are cut such that they are unlikely to reach any other units if unplugged. I will say that the heat on the units is reduced and will hopefully prevent ADA failure.

I'll try and get some pictures up of the whole rig in the next week. We are just finishing everything up. We were planning on using it this weekend, but an illness resulted in a gig cancellation. Good news is more time to get things finished.

OT: Thanks to everybody on the forums! The discussions, experiences and expertise shared here are indispensable in helping someone get up to speed quickly. Of course I can't thank Bob enough! First the software is just awesome... and I appreciate him jumping in the forum almost daily.