Speaker Level D.I.

[NKBassman]

I bet it sounds great!
Next week I'm going to studio for a friend and I'm excited to see what the studio ends up using. I've been to this place before and know what's available.
B-15
Vintage SVT
A bunch of other tube amps
Some great tube pre's
Some great compressors
Radials
P-15's

I know in the past he has used at least two signals, so I'm sure he will do the same. But what two, through what I'm not sure of and that's the best part of it.

It also looks like I'll get to use a Hagstrom 8 string. So that should be interesting.

For studio sessions I usually try really hard to forget any preconceived notions of what should be used, and try to keep an open mind about using whatever sounds best in the context of the session. If that means leaving the t00bs at home and grabbing a Sansamp then I might pout, but the end result is all that matters.

That being said, I once recorded a whole album for one of my old bands where the engineer insisted on using a Sansamp for the dirty tones. I protested but eventually agreed, and the album turned out great. A short time after that I got my Verellen tube head, and the same engineer was doing sound for us at a gig. I convinced him to try using my JDI off the speaker output of the head, and he told me after that it was the best live bass tone he could have asked for, and that all he had to do was pull the volume fader up on the channel. We even briefly discussed reamping all the bass tracks for the album with that amp and a speaker tap DI, but unfortunately never got around to it.

Actually, I think that is the night that my avatar/profile pic was taken... The head is sitting on my guitarist's second cab, and I "borrowed" the opening band's 810 for our set.

Just keep in mind that if using a speaker tap DI with a tube head it still needs to be connected to a cabinet (or other speaker load)! A DI cannot be used on its own for silent studio recording with a tube head.

 

[agedhorse]

Just to verify, when you say a DI should NOT be used with most Class D amps, you are only referring to using a DI with a speaker level output, correct?

and out of curiosity, does any one know if the PF350 is bridged output topology? Because I think I just figured out why mine blew up....

Correct, on the SPEAKER OUTPUT of a class D (or any bridge topology) amp. There's no way to know without testing which amps are BTL topology without testing or understanding class D amp schematics. The safe call is not to try it.

I believe the Ampeg PF 350 and 500 are not a bridged topology, BUT the minus output terminal isn't really at a solid audio ground because of the influence of the common mode chokes on the minus output from ground. I don't know what the ramifications might be tying this back to the safety ground of the console through pin 1 of the snake. It probably wouldn't cause fault currents but might inject RF into the ground, a possible cause for instability in the system, but this is just speculation.

 

[mesaplayer83]

The last recording I did with my Verellen Meatsmoke (tube amp) we used my Countryman out front off the bass, and my JDX off the speaker output. Using the OD channel on the head, and then blending the two signals resulted in a truly great tone on the recording.

I'm sure it did - one of the best live sounds I've ever had was a blend from a Countryman in front of the amp, and a Beta 57 at the cab...

 

[agedhorse]

I am genuinely asking and not arguing. OP is talking about running speaker level DI. So the signal going into the DI has been run through a likely active EQ and a power section before hitting the box. So do the same trends regarding active/passive basses still apply with that huge caveat between the two?

When the DI is used between the bass and the head, you will almost always want to use an active DI with a passive bass, it doesn't matter much with an active bass (other than slightly more noise).

I own three different DIs, all of which are capable of accepting speaker level signals. Two are active and one is passive. One of the two active DIs has some speaker simulation EQ built in, the other is dry. The passive option also has speaker sim baked in when using the Speaker level mode.

• Radial JDI: Passive. Speaker Level option via onboard pad switches. Baked-in EQ when in Speaker Mode only.
• Radial JDX. Active. Speaker Level or Line Level only. Baked-in EQ in all settings.
• Countryman Type 85: Active. Speaker Level option via onboard pad switch. No speaker sim EQ.

Given all these variables, baked-in EQs, and the fact that you are trying to capture coloration (VS wanting clean flat response as typically for DI off a bass), I think that any preconceived notion about using active or passive DIs for this or that reason go out the window.

Not when using a DI between a passive bass and the amp's input, the higher input impedance minimizes the loading artifacts on the pickups.

Sounds like someone owes you for amp repairs or replacement, then...

Maybe, maybe not. I would hesitate to place any blame without knowing a lot more (but I certainly wouldn't recommend placing a DI after the speaker out of any class D amp for the variety of reasons I mentioned.)

 

[NKBassman]

When the DI is used between the bass and the head, you will almost always want to use an active DI with a passive bass, it doesn't matter much with an active bass (other than slightly more noise).

Not when using a DI between a passive bass and the amp's input, the higher input impedance minimizes the loading artifacts on the pickups.

True

 

[baxter_x]

True

Agedhorse can say true things sometimes...

 

[honeyiscool]

Correct, on the SPEAKER OUTPUT of a class D (or any bridge topology) amp. There's no way to know without testing which amps are BTL topology without testing or understanding class D amp schematics. The safe call is not to try it.

I believe the Ampeg PF 350 and 500 are not a bridged topology, BUT the minus output terminal isn't really at a solid audio ground because of the influence of the common mode chokes on the minus output from ground. I don't know what the ramifications might be tying this back to the safety ground of the console through pin 1 of the snake. It probably wouldn't cause fault currents but might inject RF into the ground, a possible cause for instability in the system, but this is just speculation.

I mean, it’s completely understandable if you lack data on this but do you know if it’s possible to use a reactive or resistive load box of sufficient wattage handling with Class D heads? Like the Suhr RL (which I use) or the new UA Ox. I ask because while most Class D amp heads have direct output, they usually have a baked in speaker simulation of some sort and I prefer a completely dry power amp output. And while some people might say that Class D amps don’t act with their speaker like tube amps do, I still wonder whether it’s an important part of tone I don’t want to lose. Thanks.

 

[agedhorse]

I mean, it’s completely understandable if you lack data on this but do you know if it’s possible to use a reactive or resistive load box of sufficient wattage handling with Class D heads? Like the Suhr RL (which I use) or the new UA Ox. I ask because while most Class D amp heads have direct output, they usually have a baked in speaker simulation of some sort and I prefer a completely dry power amp output. And while some people might say that Class D amps don’t act with their speaker like tube amps do, I still wonder whether it’s an important part of tone I don’t want to lose. Thanks.

All DI outputs (that I know of) that are pre-eq are completely flat, there is no speaker simulation of any kind involved. Even post-eq there are very few amps that I know of that use speaker simulation on the DI out. Generally (certainly in the case of the amps I design), the post eq DI output's signal is picked off before the power amp, and represents what the power amp is delivering to the speaker (with the exception of the output tube emulation circuitry that activates when the amp is within 1-2dB of hard clipping, this circuitry is not represented to the DI out)

I wouldn't recommend bothering with a load box of any kind, the risks are likely much higher than any benefits they bring. Because there's no easy way to identify the amplifier's topology, and the level of ground isolation within the load box and associated output, I wouldn't recommend it.

 

[honeyiscool]

All DI outputs (that I know of) that are pre-eq are completely flat, there is no speaker simulation of any kind involved. Even post-eq there are very few amps that I know of that use speaker simulation on the DI out. Generally (certainly in the case of the amps I design), the post eq DI output's signal is picked off before the power amp, and represents what the power amp is delivering to the speaker (with the exception of the output tube emulation circuitry that activates when the amp is within 1-2dB of hard clipping, this circuitry is not represented to the DI out)

I wouldn't recommend bothering with a load box of any kind, the risks are likely much higher than any benefits they bring. Because there's no easy way to identify the amplifier's topology, and the level of ground isolation within the load box and associated output, I wouldn't recommend it.

I should have been clearer. I was speaking about guitar amps, which have just begun incorporating Class D technology and usually do have built-in speaker simulation on the DI output. But thanks for the warning!