Ampeg SVT-CL and thru speaker DI question

[jmon]

I have a Radial DI. The one pictured below. I am thinking of going speaker out of my Ampeg SVT-CL into this DI (speaker button engaged) output to my 4ohm CL 115 cab. Then DI out to the board. This is to capture the full power section to send to FOA.

I love this head and I don't want to risk damaging the tubes ect. These heads are very clear about having the correct load on them before even powering them up.
Has anyone done this setup before? Seems pretty straight forward but I wanna be 100% sure this will in no way put more strain on the head/tubes ect. If it does it's not worth it to me.
Thanks for help
@JimmyM adding you Jimmy since you have always put up such great info.

 

[rodl2005]

I don't THINK that is the correct DI to do that with. I could be wrong, and hopefully others with more experience will chime in to help.

 

[coreyfyfe]

It will work but I believe the speaker setting on the radial boxes adds a cabinet simulation filter. There are other DIs which can be used in line with the speaker load which don't have this feature like the country man type 85 and I think maybe the neve RNDI.

Here is the JDI manual which describes this

http://www.radialeng.com/wp-content/uploads/2017/12/JDI-mk3-Manual-web.pdf

 

[JimmyM]

It'll work and it won't put strain on the tubes whatsoever. Always remember to have a cab hooked up, though. And Corey does make a point about the speaker sim. You may like it and you may not. I never tried it. From the description it sounds like it's made for guitar to me, though, so it may cut too much low end. If I were you, I'd get the Whirlwind Director instead. Pretty much a JDI but without the speaker sim.

 

[rodl2005]

It will work but I believe the speaker setting on the radial boxes adds a cabinet simulation filter. There are other DIs which can be used in line with the speaker load which don't have this feature like the country man type 85 and I think maybe the neve RNDI.

Here is the JDI manual which describes this

http://www.radialeng.com/wp-content/uploads/2017/12/JDI-mk3-Manual-web.pdf

So, the Radial JDI IS. ok to use between amp and cab on a tube amp? Ok! Super news to me, as I'm sure our regular sound engineer has a few JDI's in his arsenal.
I WAS onto him about getting one that would be able to do this and thought it was only....... a different Radial DI that allowed it to be done.

 

[Wasnex]

I have a Radial DI. The one pictured below. I am thinking of going speaker out of my Ampeg SVT-CL into this DI (speaker button engaged) output to my 4ohm CL 115 cab. Then DI out to the board. This is to capture the full power section to send to FOA.

The input impedance of the JDI is listed as 140K Ohms typical. When properly hooked up, the 140k will be in parallel with the load provided by your speakers...essentially 140k is so high that it won't make any difference.

For example if you are running a 4 ohm cab, the math would be: 1/(1/140K+1/4)=3.9998 ohms

The max input of the JDI is only 21dBu per the manual, but I believe this is without the speaker emulator engaged. The important thing here is be careful. If you forget to engage the speaker emulator and hit the JDI with big power, you may damage the JDI. 21dBu works out to about 8.7V RMS. 8.7 volts at 4 ohms translates to 18.9W....(8.7^2)/4=18.9W

Per the SmartSheet, "PARALLEL SPEAKER interface option introduces a second -30dB pad with band-pass filter to emulate a 12" guitar speaker."

Perhaps this is not the ideal speaker level DI.

 

[jmon]

Thanks so much guys for the info!
Sounds like I may need a different DI. I've carried that Radial in my gig case as a backup of sorts in case my amp died and I needed to go direct with a monitor. It saved me one time too. So it will stay that way. I'll look at some different DIs.

 

[rodl2005]

The input impedance of the JDI is listed as 140K Ohms typical. When properly hooked up, the 140k will be in parallel with the load provided by your speakers...essentially 140k is so high that it won't make any difference.

For example if you are running a 4 ohm cab, the math would be: 1/(1/140K+1/4)=3.9998 ohms

The max input of the JDI is only 21dBu per the manual, but I believe this is without the speaker emulator engaged. The important thing here is be careful. If you forget to engage the speaker emulator and hit the JDI with big power, you may damage the JDI. 21dBu works out to about 8.7V RMS. 8.7 volts at 4 ohms translates to 18.9W....(8.7^2)/4=18.9W

Per the SmartSheet, "PARALLEL SPEAKER interface option introduces a second -30dB pad with band-pass filter to emulate a 12" guitar speaker."

Perhaps this is not the ideal speaker level DI.

So, if I only had this JDI to use, I should make sure the speaker emulation is OFF?

 

[jmon]

Neve Designs RNDI DI looks about as straight forward as I can get. The reviews are outstanding as well. We have a killer PA and I'm just trying to get my tone into that board as close and as clean as I can.
Thanks again for the help. I didn't know a speaker level DI was even an option till a week ago.

 

[Wasnex]

So, if I only had this JDI to use, I should make sure the speaker emulation is OFF?

It depends on how you use the JDI. If you're using it at speaker level with a big amp, I believe you have to engage the speaker emulation or you will overload the JDI. The speaker emulation might sound fine if you like playing bass through 12" guitar speakers. I personally think JBL E120s sound awesome

.

 

[Wasnex]

View attachment 3250167

Neve Designs RNDI DI looks about as straight forward as I can get. The reviews are outstanding as well. We have a killer PA and I'm just trying to get my tone into that board as close and as clean as I can.
Thanks again for the help. I didn't know a speaker level DI was even an option till a week ago.

A word of caution. A speaker level DI works fine with tube amps, but not with amps that are run in bridge mode. Some class D amps are run in bridge mode, so be careful.



When you are running a speaker level DI, you can run the signal through the DI **, or any other way that creates a parallel connection. For example if your amp has a set of parallel outputs, run one to a speaker and one to the DI. Or if your speaker has a thru plug. Connect the amp to the speaker, then take the thru from the speaker and run it to the DI. All three examples create parallel connection between the speaker and DI, so the amp sees the exact some load.

** Note. The JDI FAQ says it does not support running speaker level signals thru the DI...see post #30 this thread....or read the FAQ at Invalid Link Removed

 

[JimmyM]

View attachment 3250167

Neve Designs RNDI DI looks about as straight forward as I can get. The reviews are outstanding as well. We have a killer PA and I'm just trying to get my tone into that board as close and as clean as I can.
Thanks again for the help. I didn't know a speaker level DI was even an option till a week ago.

I would think the RNDI would be overkill for this purpose. Honestly, your JDI will probably be good, too. I was just thinking about it, and I don't think you have to push in the speaker button to make it work at speaker level. I missed that you already had one first time I read this thread, and you should at least try it. Don't know how I missed it since it was the first thing you typed, but I'll blame it on old age

 

[Wasnex]

I was just thinking about it, and I don't think you have to push in the speaker button to make it work at speaker level.

EDIT: See page 9 of the attached manual. Review the diagram at the bottom of the left column and note this specific text, "-15dB PAD and SPEAKER pad must be activated."

At the very minimum, I suggest engaging the 15dB pad.

The speaker emulation button engages a 30dB pad. So I believe the 21dBu max input level listed in the product manual become 51dBu which equates to ~275V RMS. At 4 ohms that 275V works out to ~18,900W...so the JDI should be able to handle an SVT just fine with the speaker emulation engage.

The JDI also has a 15dB pad. 36dBu would work out to ~600W at 4 ohms. I would think this is also sufficient for an SVT.

Without the 15dB pad or speaker emulation engaged, max input of 21dBu works out to ~18.9W. Not sufficient.


Probably best to contact Radial if you have any concerns, since I am not an expert.

 

[Roland GR 88]

Run a speaker cable from the second input of the cab to the JDI with both the pad and speaker switch engaged.
I haven't found that the 12" speaker emulation affects the tone much at all. YRMV...

 

[bhoff5150]

I use the Palmer PDI-03 for your exact application. It's not cheap, but the sound to FOH is awesome. If you use in ear monitors you will easily hear the difference. The Palmer is a load box, but can also be used in conjuction with a cabinet. In that case, it uses the cabinet for the load instead of it's internal load. For me, the sound is a bit "sterile" using the internal load and no cabinet, and just full of life and goodness when used with a cabinet. It's almost like the dynamics of the speakers add something electronically to the signal. Don't know what's going on from an electrical standpoint, but from a tone standpoint it's killer. I have used this setup with both a V4B in the past and now currently with a PF-50T.

 

[Kriegs]

@jmon From the JDI Manual, you can do this, but you put the JDI AFTER the speaker, not before it:

 

[TheBassPreacher]

I actually use a Radial JDX, but again it isn't a load box.

From the Radial site showing it hooked up for bass:

 

[beans-on-toast]

On the JDI, press the 15dB pad and the speaker button.

Connect the XLR to the mixing desk.

Connect a speaker cable from the input of the JDI to the ¼" speaker out on the SVT-CL.

Connect the speaker cab to the SVT-CL, either to the other ¼" jack or the speakon. The speaker cab must always be connected when using the JDI.



——————-


The JDI does have a speaker emulator built in. It is basically a bandpass filter. The Neve RNDI does not.

The Neve box requires phantom power from the mixer in order to work because it's an active DI and has a built in preamp. All active DI's require either a battery or phantom power.

 

[Mushroo]

Radial's recommendation is to hook up your rig as usual, and then connect the JDI to the parallel 1/4" on the back of your cabinet (as though you were "daisy chaining" a second cabinet).

Personally I like the cab sim, but if you like bone-crushing sub-low-end, it's probably not for you.

 

[Jim C]

One of the best bass sounds I ever got with a Fender bass in the studio was the preamp out to a passive DI (Jensen transformer) with a 300 watt dummy load (giant resistor) with a V4B. In one studio this was necessary in order to cut live tracks with no islolation booth for a bass speaker cabinet.
While this only gives you the pre amp side of the amp, I don't think any of these boxes (that can take a power amp load) offers a non-linear load (as you speaker cabinet would).