Ampeg SVT-CL DI/Balanced Out

[beans-on-toast]

Note that the Radial JDI (which I have) has an EQ that emulates a guitar speaker. Other DI’s such as the Countryman and Neve do not have this “feature”.

Check out the DI literature carefully because they are not all alike, it isn’t just about the transformer used.

JDI bandpasses the amp’s output signal to limit the energy when connected to the speaker output, this helps their product handle more watts when connected to the speaker out.

Some DI’s require 48v phantom power from the desk for power, others use a 9v battery or phantom for power. Passive DI’s do not require power but as a result, put out a lower level signal than an active DI.

They recommend a passive DI when used with active pickups and an active DI with passive pickups. I do the opposite, I use the JDI with a Fender PBass. The insertion loss is not an issue for me. But something to keep in mind.

Always complications. Ask your sound guy for a recommendation.

 

[Kriegs]

OK, so here's why this sound tech suggested a DI between amp and cab...because it gives you the sound of the entire SVT, including the power section. The built in DI does give you the preamp and it sounds great, but the power amp really ups the tubey quotient to another level.

Another amazing, knowledge filled "Today I Learned..." sponsored by the letters J, M and the number 1

Seriously @JimmyM, those kinds of tidbits and details that I learn from you and the others here are why I keep coming back to TB! I add those nuggets to by personal knowledge base (pun intended) and when we're trying something new in the studio or live, I think back to things exactly like this example and get that 'wow!' reaction from folks. I always do my best to give credit to those that I've learned from because I want folks to understand that it's not about what I know... it's what we all know and can use to make the band/ set/ song sound the best it can.

 

[andykeating]

They recommend a passive DI when used with active pickups and an active DI with passive pickups. I do the opposite, I use the JDI with a Fender PBass. The insertion loss is not an issue for me. But something to keep in mind.

Funny you should mention that. You and our sound guy are two of the only people I’ve heard say passive boxes with passive basses is a decent route to go down.

On the subject of boxes, albeit this is an active box, the Radial JDX-48 seems like it could be a good bet. Has an extra switch to handle bass and up to 300W, when this is engaged it apparently simulates the sound of an 810. Unfortunately I have no experience with that box and personally don’t know anyone who has.

 

[beans-on-toast]

Radial is a very good company in terms of quality and engineering. The JDX-48 was designed with an amp like the SVT in mind. Sometimes you just have to take a leap of faith, make a decision, and move forward.

You might find a local backline or studio supply shop that rents DI’s. That would allow you to try before you buy.

A lot of people use the JDI with passive pickups. Maybe because it is a bit less expensive. But I like the performance of the Jensen transformer that they use in it.

 

[Kriegs]

On the subject of boxes, albeit this is an active box, the Radial JDX-48 seems like it could be a good bet. Has an extra switch to handle bass and up to 300W, when this is engaged it apparently simulates the sound of an 810. Unfortunately I have no experience with that box and personally don’t know anyone who has.

I could be wrong but I don't think that feature on the JDX-48 is a cab simulator. I believe it just allows the DI to handle a larger number of watts from the amplifier head (up to 300W according to the manual http://www.radialeng.com/wp-content/uploads/2018/04/jdx-48-manual.pdf). Again, if I'm reading correctly, the JDX-48 requires an amplifier head on end and a speaker cabinet on the other end and the DI just sends that signal to the FOH/ mixer/ etc.

 

[two fingers]

I always gotta come in and straighten out these threads...geez, you kids...

OK, so here's why this sound tech suggested a DI between amp and cab...because it gives you the sound of the entire SVT, including the power section. The built in DI does give you the preamp and it sounds great, but the power amp really ups the tubey quotient to another level. One difference between the two is that you can make volume adjustments using the master knob when you use the built in DI, whereas it all gets sent to the board with the speaker DI. Not the way to go if you do a lot of knob adjusting, but usually works great. I would at least try it before going with a lesser sounding DI.

As for all this redundancy, I find it redundant. The chances of your amp going down are small as long as you take reasonable care when moving it, and it's just plain not that hard to unplug the speaker DI and use it as a regular DI if the need arises.

Don't you go getting all sensible and logical with ME mister! I won't stand for it!

Wait..... uh......

What were we talking about?

 

[andykeating]

That the JDX-48 was designed with the SVT in mind is very handy to know.

There's a company here in Manchester called STS who are incredible for tour supply and backline hire, just checked their inventory; they have the Countryman 85 and J48 on there but not the JDX-48 unfortunately. Recorded the bass for one of my band's singles purely with a J48 into a Neve 1073 pre and it sounded brilliant.

Think I might take a punt on the JDX-48. Seems like its got a lot going for it; can handle 300W and emulates a cabinet.

 

[Kriegs]

Think I might take a punt on the JDX-48. Seems like its got a lot going for it; can handle 300W and emulates a cabinet.

I don't think you're getting this... the JDX-48 is NOT an emulator you MUST have a cabinet attached.

Again, from the manual:

"THE JDX 48 IS NOT A LOAD BOX
It is mandatory that your amplifier be connected to a loudspeaker or load box at all times. The JDX 48 does not provide a significant resistive load for an amplifier to safely operate. Damage may occur to your amp if the JDX 48 is used without a proper loudspeaker load."

 

[andykeating]

I don't think you're getting this... the JDX-48 is NOT an emulator you MUST have a cabinet attached.

Again, from the manual:

"THE JDX 48 IS NOT A LOAD BOX
It is mandatory that your amplifier be connected to a loudspeaker or load box at all times. The JDX 48 does not provide a significant resistive load for an amplifier to safely operate. Damage may occur to your amp if the JDX 48 is used without a proper loudspeaker load."

Whoah. Calm down. At which point were we ever discussing using this instead of the cabinet?

If you read my original post you'll realise that we're talking about using a DI box BETWEEN amp and cabinet. Not instead of a cabinet.

 

[agedhorse]

As a general note, for those that might be thinking of experimenting, never use a DI between any amp that operates in bridge mode (including many class D amps that use an internally bridged architecture) and the cabinet (or on the amp's speaker output). Because such amps are not ground referenced, the minus terminal carries signal and can be shorted to console ground through pin 1 of the XLR jack. This can damage the amp, the console, or both.

 

[LiquidMidnight]

I love speaker-level DIs (on all tube amps). The SVT has a great sounding preamp, as Jimmy said, but if you have six 6550s, you might as well get them to the front desk. And before anyone starts on with the "...audience doesn't notice/all of your nuance gets lost/etc." stuff: When you have a competent sound engineer and respectable FOH, yes, it does matter and it does get translated to the audience.

 

[andykeating]

I love speaker-level DIs (on all tube amps). The SVT has a great sounding preamp, as Jimmy said, but if you have six 6550s, you might as well get them to the front desk. And before anyone starts on with the "...audience doesn't notice/all of your nuance gets lost/etc." stuff: When you have a competent sound engineer and respectable FOH, yes, it does matter and it does get translated to the audience.

Correct. I'm not so precious that if our sound guy reckoned it was better to take a DI before the amp for a particular show that I'd walk off stage and refuse to play, but it absolutely does matter about getting your sound out there. I don't know if drums are a dirty word round here but our drummer bought a Ludwig Black Beauty before our last tour and the difference that alone made to the overall sound when you listen back to desk recordings and videos etc is phenomenal.

 

[Kriegs]

At which point were we ever discussing using this instead of the cabinet?

You did, maybe unknowingly, with these statements.

On the subject of boxes, albeit this is an active box, the Radial JDX-48 seems like it could be a good bet. Has an extra switch to handle bass and up to 300W, when this is engaged it apparently simulates the sound of an 810

Think I might take a punt on the JDX-48. Seems like its got a lot going for it; can handle 300W and emulates a cabinet.

Those phrases mean something very specific. A cabinet simulator is very different than a DI that sits between your head and cabinet. Either way, the JDK neither simulates nor emulates a cabinet. It requires that a cabinet be attached to it. I wanted to be sure that you got that, because you repeatedly indicated that you might not be getting it. I'm just trying to help prevent damage to your head We've all blown up some piece of equipment because we didn't know everything that we thought we did or that we needed to know ... I know I have!

 

[andykeating]

I was getting it, as such, but maybe there's been a breakdown in communication with regards to terminology/technology.

Basically what my aim is here is to run from a speaker output of the SVT into a suitable DI box, out of that DI box into the speaker cabinet, whilst running the XLR out of the DI box to the FOH so it captures the tubes and not just the pre.

From what I can gather, the JDX-48 seems suitable. And yeah, I blew up an Ashdown 210 several years ago whilst running it with a 410 because I didn't understand ohms.

 

[Kriegs]

Basically what my aim is here is to run from a speaker output of the SVT into a suitable DI box, out of that DI box into the speaker cabinet, whilst running the XLR out of the DI box to the FOH so it captures the tubes and not just the pre.
From what I can gather, the JDX-48 seems suitable.

You definitely picked the right hardware for that!

And yeah, I blew up an Ashdown 210 several years ago whilst running it with a 410 because I didn't understand ohms.

Mine big oops was close to yours... decades ago, in my teenage arrogance, I thought I knew exactly how to wire speakers, I mean how hard could it be, you just connect them with wire right? This scrap electrical lead stuff is wires, so I can use that right? And these leftover speaker wire from my uncle's HiFi installation has to be good because it was expensive!
RIP Ampeg VT-40

 

[andykeating]

You definitely picked the right hardware for that!

Have you had much/any experience with the JDX-48? Consensus around these parts seems to be that the Countryman 85 is the go-to box for what I want to do. I know the Countryman can handle way more input wattage, but the SVT is 300 and the JDX-48 can handle 300, so I'm not concerned about that. I'm drawn to the fact that the JDX-48 apparently sounds like an 810 when sent to the FOH.

RIP Ampeg VT-40

Wow. Ouch. I'll happily mess around with my basses and the electronics in there, but never really get involved in electronics in amps, too afraid. The only thing I've ever done was replace the VU bulb in an Ashdown and replace a speakon socket.

 

[Kriegs]

I only have one personal experience with the JDX-48 and it was when I was doing some studio guitar work for a friend. His guitarist used the JDX-48 and insisted that I do the same for my track. I certainly didn't have a problem with it, I like using/ trying new gear and recording ideas. I used a Bassman 300 head and my Fender Rumble 410 cabinet. I've done plenty of mic/ dry mixing in the past but had never done the DI between the head/ cab route before ... frankly I didn't know it was possible.
One of the things that he really drilled into me was that you MUST have a cab attached or Bad ThingsTM​ will occur... which is why I was trying so hard to make sure that you were understood that too
Anyway, it worked surprisingly well! It provided a nice clear signal with all of the tone and power that was coming out of the speakers. The only thing that I personally didn't like was that it removed the ability to make subtle changes in the voice the mic picks up when you move it to different positions around the cabinet. That said, for the needs of that particular project, the JDX-48 provided the ideal signal for the mix.

 

[andykeating]

Thanks for the detailed info, really appreciate that. Until I started seriously looking into getting an SVT I didn’t know it was possible either. Now I’ve heard the tone of the thing I feel like it’s a necessary thing to do. Would seem like a total waste of all those tubes and tone otherwise.

I first became aware of the need to connect a speaker load years ago when I was a lot younger and thinner, was when I was buying my first head and cab - the guy I bought it from stressed the importance of always having the head connected to a load.

 

[JimmyM]

Should add a couple things about speaker DI's....

1. This:

As a general note, for those that might be thinking of experimenting, never use a DI between any amp that operates in bridge mode (including many class D amps that use an internally bridged architecture) and the cabinet (or on the amp's speaker output). Because such amps are not ground referenced, the minus terminal carries signal and can be shorted to console ground through pin 1 of the XLR jack. This can damage the amp, the console, or both.

2. It's totally useless on most amps with a SS power amp since most of the tonal action takes place in the preamp on them.

3. The DI does NOT take the place of a speaker load, so you must always have a speaker load on your tube amp unless it specifically says you don't need it, and tube amps where you don't need it are very rare and usually limited to 50w or under.

 

[beans-on-toast]

One more point of importance.

When you mic a cab and DI (from the input, preamp out, or diasy chained to the speaker output) there can be phase issues.

This can be fixed in a DAW when recording. There is also a Radial box called a Phazer that can compensate for phase issues in teal time.

Phazer - Radial Engineering

Kind of expensive, street price is around $320US.