If what you have is the TC Electronic RH450, then the chassis-mounted XLR plug on the rear is an AES/EBU digital interface. This can be connected to your Saphire 56's RCA S/PDIF input via a suitable adaptor (either a home-made kludge or something pricier like the Hosa CDL-313).

As for getting the re-amping to work, you have two problems. The first is returning a signal out of your DAW and interface. Without knowing what DAW you are using, it's difficult to give specific advice, but you have to set the DAW up for tracking, i.e. replaying a track while recording another, and the routing so that your replayed track is sent to one of the higher-numbered outputs on the interface.

The second problem is what to do about the signal amplitude. The Saffire's output is around +16dBu balanced and the RH450 main amp (not the pre-amp) expects a balanced input of around +8dBu. So on paper you have to lose around 8dB in order not to overload the main amp, and it's not possible to tell from the TC data sheet whether the input will cope with higher than that with the Master volume control dealing with the level difference. My guess is that you should use something like a 12dB balanced attenuator to avoid distortion due to overloading of the main amp input.

Tell us a bit more about your set-up and we can probably help further.

Thanks,

I'm using cubase 5, I routed the bass DI out of a few different outputs instead of the stereo bus, both out of the Focusrite and an ART tube/opto 8 channel via ADAT. The sale rep suggest putting the active DI between the output of the Saphire and the bass amp to "step down" the signal. This is the unit (no volume control) [="http://www.hollywooddj.com/275acdibox.html"]275 Active Direct Box[/]="http://www.hollywoo…"]275 Active Direct Box[/]

As for the digital out on the RH450, (not that concerned about it, the bass player and I just wanted to see what it did) I took the XLR out of the RH450 into my POD HD 500 to convert it to spdif and then into the saphire, but I am preeeettttty sure the POD HD didn't recognize the digital signal, analog only I think. I have used the POD HD to convert to spdif with my LA 610 [[url=http://="http://www.uaudio.c…"]LA-610 MkII Classic Tube Recording Channel | Universal Audio[/]="http://www.uaudio.c…"]LA-610 MkII Classic Tube Recording Channel | Universal Audio[/] and it sounded great, clear and clean with all the warmth from the 610, just have to pay attention to the input gain (tiny little "knob") on the POD HD .....

So I think the next question is, can I use the active DI "backwards" or do I need to pick up one of these? [[url=http://[/URL]="http://www.funky-ju…"]Radial X-AMP Active Re-amplifier[/]="http://www.funky-ju…"]Radial X-AMP Active Re-amplifier[/]

thanks...

No, you can't use an active DI box backwards - an active DI box has internal electronics that has inputs and outputs and these don't reverse. I also would not spend money at the moment on the Radiall X-Amp box. Although these are great boxes, you don't actually need something like that since your RH450 already has a balanced high-level input at its main amp.

Before laying out any cash, what I would do is record a few more bass tracks, but this time under two conditions. Firstly, try recording via the TC amplifier's DI output into a line input on your Saffire rather than through an external DI box. Secondly, keep the record level as seen in Cubase lower than normal so the peaks never exceed (say) -12dBFS. In this way, you will have recorded tracks that will replay directly from a Saffire line output through a length of balanced cable into the TC main amp without overload without having to use an attenuator or any other electronics.

Once you have got this route working, you can take the time to evaluate your options and decide whether you need to spend money, and, if so, on what.

The POD does not take an AES/EBU signal in, so that digital route will not work.

hmmm

"Firstly, try recording via the TC amplifier's DI output into a line input on your Saffire rather than through an external DI box." I think I may encounter the same issue as the POD.. but I have only had the saphire for 3 weeks so I am still finding out what it can do. Unless it has 2 DI outs (not my amp so I dont' know it well)

"Secondly, keep the record level as seen in Cubase lower than normal so the peaks never exceed (say) -12dBFS." now I am wondering if I can simply use the gain function to reduce the level?

-12dbfs ... what does the FS stand for.. I haven't seen this unit before?

thanks

FS stands for "full scale", so -12dBFS simply means 12dB below the maximum level.