Okay, this thread is far from definitive, but hopefully by the time it's finished it'll be comprehensive.

I recently purchased a SD 302 mixer (hasn't arrived yet) and I'm trying to work out all the logistics of how I will be connected the two devices.

My understanding (and do correct me if I'm wrong) is that I have the following options, given the necessary cords/adapters:

SD302 XLR Out to Zoom H4n XLR In
SD302 XLR Out to Zoom H4n 1/4" In
SD302 XLR Out to Zoom H4n 3.5mm mic in
SD302 Tape out/Mixer Out* to Zoom H4n XLR in
SD302 Tape out/Mixer Out* to Zoom H4n 1/4" in
SD302 Tape out/Mixer Out* to Zoom H4n 3.5mm mic in

*Tape out is unbalanced stereo on TA3 type connect and level is fixed at -15dBu according to the manual. Tape out requires the Sound Devices 3.5 mm to TA3-F link cable ($26).

Dan McComb has a tutorial about connecting the MixPre to the Zoom H4n here: Zoom H4N with Sound Devices Mixpre: how to properly connect the two for pristine audio | Dan McComb (http://www.danmccomb.com/posts/880/zoom-h4n-with-sound-devices-mixpre-how-to-properly-connect-the-two-for-pristine-audio/) and Connecting Zoom H4N to Sound Devices MixPre – Part II | Dan McComb (http://www.danmccomb.com/posts/987/connecting-zoom-h4n-to-sound-devices-mixpre-part-ii/)

However, the MixPre has line level output only whereas the SD302 has line level or mic level or somewhere in between. According to the manual, attenuation can be set from 0-16dbu and from and 40-56 as well as -10, -40, and -56.

The problem appears to be that going from XLR on the SD302 to XLR on the H4n still activates the H4n's preamps and defeats the purpose. So the options left are to go into the 1/4" inputs or the 3.5mm mic input.

Dan points out in regards to the MixPre:

If you do connect the MixPre to the Zoom as described above using the xlr-to-phono [1/4"] option, you will need to add 15-20 db of attenuation to get the correct level into the Zoom. To achieve this, you need to buy an inline attenuator, preferably a selectable attenuator, that lets you dial in how much attenuation to apply. And, you would need to by two of them if you want to send signal to both channels independently, which you almost certainly will want to do. So, lots of stuff to buy with this option, and it’s not cheap at $45 a pop for each attenuator. And why would you want to add all that extra weight and awkwardness to your lean, mean sound bag anyway? No, you want to use the following option instead.

Is this need for attenuation still in play for the SD302 as well? If I'm understanding correctly, the 1/4" inputs of the Zoom H4n do not engage the preamps and that is why they're preferable. The solution that Dan ended up going with for his MixPre was a PINKNOISE -25db 3.5mm DSLR cable (see: DSLR, PINKNOISE AUDIO CABLE, CANON 5d mk11, CANON AUDIO CABLE, -25DB AUDIO CABLE (http://www.pinknoise-systems.co.uk/pinknoise-25db-35mm-dslr-cable-p-459.html) ) but I would prefer to use the XLR to 1/4" route if that's viable on the 302.

But then I find it stated by Jon Goodman that:

Hi Eric. I run a zoom H4N in my bar with a SD 302 as a back up recorder. I found that the line in is not a +4 dbu level and needs padding. I found some variable pads that work well for me made by Rapco. cvpblox variable pad blox. Here's a link. http://www.rapcohorizon.com/products/devices/blox/Default.aspx
Hope this helps.

I found this quote by Tim Joy:

You can't bypass them, but get yourself an XLR to 1/4" TRS or TS cable. (doesn't matter) The 1/4" inputs are the line level ins.

Also, you'll need to go into the setup menu of the 302 to attenuate the outputs. (hold the brightness button while powering up, if I remember correctly, and it's the first adjustment) It takes a little trial and error to get the sweet spot. When sending tone from the 302 I set it up to read -12 on the H4n with it's input level set to @ 25.

I also lowered the spot where the 302's limiters kick in to about +11. That will keep it from clipping the H4, although you don't want to be hitting that too hard.

Jon Goodman writes:

I've been using the tape out from the 302 to 2 variable pads for the inputs to the H4N. I found I had to pad it down well down past -10 -db. This leaves me my main outs to the camera at line level. I haven't found the Zoom to be especially noisy. So far I've been pretty happy with the set up.
Jon

Tim's solution seems to be the simplest. But there are a lot of variables here.

I was hoping you all could help me find the simplest solution (buying a 702 doesn't count).

dvinfo threads of relevance:

http://www.dvinfo.net/forum/all-things-audio/469177-small-recorder-use-sd-302-a-2.html
http://www.dvinfo.net/forum/all-things-audio/119241-adjusting-sound-devices-302-line-out-mic.html

So what did you discover?

I want to use my 302 mixer tape out to send audio to my mic level input on my Tascam DR-05, so I can use the xlr line outs for my camera line level input.

So I assume I will need about a 15 db attenuator on the left and right channels.

How can I build them with what value resistors? Or does someone sell one that works with the TA3F to stereo miniplug adapter?

You can reduce the output of the 302 to mic level in the menus, avoiding the pad altogether.

You can reduce the output of the 302 to mic level in the menus, avoiding the pad altogether.

As long as the Zoom truly has real line level inputs and that is what you are using. Else it defeats most of the reason for even using the 302.

As someone who has made their own cables, adapters, pads, iso transformers, etc. for several decades, I have sympathy for those who must pay $45 for a store-bought pad with maybe $1 worth of resistors inside.

SD has an attenuation diagram on their website for using the unbalanced 'tape out' at mic level.
Adding a Mono Mic or Tape Level Output to the 302|Sound Notes|Sound Devices, LLC (http://www.sounddevices.com/notes/mixers/302/302-tech-note-adding-a-mono-mic-level-output/)
But why use mic level ? The 'Tape out' line level connection is an option with the 302> Zoom.

double post, deleted

See the manual for the 302 on page 21, describing how to lower the mixer's main output level to properly match a mic level input using the mixer's menus settings. No pad needed between the devices.

Larry mentioned the Tape out output so he could send line out out from the mains. Does the SD 302 let you adjust the Tape out level?

No, the SD 302 does not have an internal 'Tape out' level adjust .

My previous post was directed to Larry, who stated "I want to use my 302 mixer tape out to send audio to my mic level input on my Tascam DR-05, so I can use the XLR line outs for my camera line level input." Furthermore, I don't know if the DR-05 could handle the 302s tape-out level w/o attenuation. And to elaborate, I don't see that much of an advantage to recording to the DR-05 in addition to the camera, (except for back-up or transcription purposes) since the input would go though an additional 'less than stellar' unbalanced preamp.
Otherwise I would concur with using the 302's internal main out attenuation facility.

As long as the Zoom truly has real line level inputs and that is what you are using. Else it defeats most of the reason for even using the 302.

As someone who has made their own cables, adapters, pads, iso transformers, etc. for several decades, I have sympathy for those who must pay $45 for a store-bought pad with maybe $1 worth of resistors inside.

it's my understanding that the zoom h4n doesn't have line level inputs as we know them, but line levels designed to accept signal from instruments... meaning it's actually somewhere between mic level and line level (from a mixer), which is why many people still need to pad it down... but some don't. depends on your signal out i suppose.