Broke Down and bought a DI

[JimmyM]

I guess my question is when do you pay more attention to personal technique and your audience instead of a little "tweak" from "better" gear?

I already know how to play, thanks Jon

 

[B-string]

Yeah you know I wasn't talking about you It was a general question.
The DI's on my amps work just fine, as most do.

 

[JimmyM]

BTW, just wanted to point out how much I disagree with the idea that "the audience can't hear the difference" and "nuances are for studio but not for live." I used to buy into that line of thought until I started putting more effort into making my live sound more happening rather than just accepting what the soundman du jour considered good sound. And then I'd hear the difference. And that's why I'm a bit of a fanatic about getting my way...it truly makes a difference. Do the drunks at the back corner of the bar care or the girls on the dance floor falling out of their tops care? No they don't, but if that's the bar you use, why do you even bother to show up?

 

[B-string]

Girls falling out of their tops while dancing doesn't sound like a "bad" gig.
I take that back, our drummer's tempo would be all over the place.

 

[LiquidMidnight]

BTW, just wanted to point out how much I disagree with the idea that "the audience can't hear the difference" and "nuances are for studio but not for live." I used to buy into that line of thought until I started putting more effort into making my live sound more happening rather than just accepting what the soundman du jour considered good sound. And then I'd hear the difference. And that's why I'm a bit of a fanatic about getting my way...it truly makes a difference. Do the drunks at the back corner of the bar care or the girls on the dance floor falling out of their tops care? No they don't, but if that's the bar you use, why do you even bother to show up?

I know I've told this story a bazillion and one times on here, but I'm going to tell it again. It really hit me one night when we were sharing the bill with one of my very good friend's band. He's a very good bass player - very expressive and very progressive with his approach to the instrument. I asked him if he wanted to use my 400+ and he was very excited to play through it for his set. As many of you know, the 400+'s D.I. takes the signal straight off the OT, so you are getting all of the tubes to the desk, not just the preamp. I was treated to hearing what that amp sounded like out front. And while the engineer that night had a great ear, the FOH was nothing special - just some Peavey tops and subs. The bass had an authority, expressiveness, musicality, and colorization that you're just not going to get from taking a DI off of the bass. Granted, I am biased being a bass player and the amp being mine. However, if you were there that night, it would be hard to argue that the amp wasn't producing some sort of special ingredient to the mix that was having an effect on the band's overall sound. I've heard my friend play many times through different rigs, and he always sounds great because he's a great player. However, there was still something special with the 400+ that night.

 

[agedhorse]

About working on technique... I have another "ol guy" story to share specifically about prectice and technique

Probably 25 years ago, I was fortunate to score a gig with band leader Cab Calloway. This was a short tour (he was already into his early 80's so he limited his touring) doing theatres and small arenas (1000-6000 seats). He traveled with piano bass & drums, his daughter Chris, and picked up a local big band to back him up.

Audio was pretty easy actually, music director ran the show, vocal mics for Cab and Chris, mic at the piano for introductions, Emcee mic to introduce the show and sponsoring organizations, mics on the sections, individual mics on reeds, piano, bass (I think this eas DI's with an underwood pickup) and kick/snare/overhead.

Each show, the music director would rehearse with the band, running through the charts for the day. Then Chris would do a vocal check while Cab looked on, then Cab would do a vocal check and then a quick duo.

One show, there was a reed player who kept criticizing the arrangements, the parts, how to improve the sound and such. He was an ok player but not "great" by any means. Quietly, in front of Cab, Chris and the whole band the music director, who was at the top ofthe "A" list told the guy that there were several ways to improve the sound, the first was for HIM to improve his technique, and the second was for him to practice more. Then he said that since there was not time for this to happen, the easiest way to improve the sound for that night was for the reed player to go home. I thought that was the simplest, most effective statement that could have been said at the time. Cab and his guys were focused on the big picture, getting it done in a way that did not distract from what the music was and how it was presented. There were areas that were intentionally a little rough around the edges, to show a little more about what it would have been like in the earlier days. I heard (really old guy) stories about life on the road in the 20-30's through WW2, the struggles of an early transportation system, the railroads and segregation. These stories stuck with me as much as and maybe more than the music.

Shows were wonderful, Cab was a total gentleman, his daughter had some serious vocal chops of her own, and I got to experience a bit of history that was soon to end. Cab died a few years later from the effects of a stroke, and his daughter Chris died in 2008 from cancer. Ironically, I first met Cab when he filled in for a Count Bassie show that I was doing and the Count fell seriously ill. The Count passed away a few weeks later.

 

[beans-on-toast]

So why does the same passive bass that sounds awful with a passive IMP sound great with a passive JDI?

Transformers perform to different specifications based on their design and construction. Specs such as impedance, frequency response, linearity, distortion, phase distortion, common mode rejection all factor in. This will affect how they sound. Higher quality makes a difference.

Invalid Link Removed is the transformer that is in the JDI passive DI. As far as I know, Whirlwind doesn't publish their transformer's specs.

From the spiel on their site:
The Radial JDI is a passive direct box designed to handle extreme signal levels without distortion of any kind. Unlike an active DI that is limited by the buffering amplifier’s rail voltage, the JDI employs a Jensen audio transformer as the engine. Jensen transformers are legendary in their ability to gracefully handle transients while delivering a smooth, warm sounding Bessel curve, reminiscent of the finest vintage gear. Ruler flat from 10Hz to 40kHz and with virtually zero phase deviation, the JDI delivers the natural, pure sound of the instrument without artifact.

[Invalid or Expired Link Removed]​

 

[Pimmsley]

Now that is sexy

 

[agedhorse]

So why does the same passive bass that sounds awful with a passive IMP sound great with a passive JDI?

Good question...

I think you have to look at the input impedance of the two transformers. The input impedance is really kind of a misnomer as there are 2 parts to this. the first part is due to the inductance of the primary and the back-emf that is stored in the transformer's core. The second part is the reflected impedance, which is due to the load on the secondary reflecting back across the core in the magnetic field. These 2 factors make up the majority of the impedance the bass sees. The primary load is mostly fixed (varies by transformer design but not by loading), but the reflected load is highly variable, so on a lower input impedance mixer, there will be more loading than on a higher input impedance. The reflected impedance is pretty proportional to winding ratio but the primary impedance has much more to do with the design of the core itself.

I do have the specific transformer data for the IMP-2 which uses the TRHL transformer. There is lots of information that lies between the lines, but what's important is the transform ratio is about 130, and while the +16dBu maximum input level seems plenty high, that's for >100Hz so apply 3dB reduction for each octave below 100 and at 50Hz you have +13dBu and at 25Hz you will have approx. +10dBu (this agrees pretty closely with their +11.5dBu spec at 20Hz) at which is adequate for all but very high output level basses. The THD will go up considerably below 100Hz as well, but that's not always bad as many ofthe most desireable transformers and "transformer based preamps" do exactly the same thing. What is also materially a problem is the 20k (nominal) input impedance which IMO is pretty low for most passive basses, especially with a heavy reflected load added (though it should be noted that they do not specify if the nominal input impedance is relative to the rated output impedance of 150 ohms or some other number and it does not say what happens below 100Hz. Gut and some past engineering measurements says otherwise, that the impedance falls by about 1/2 per octave). Another thing that can affect audiio performance but improve performance in high RF environments is the inclusion of a Faraday shield. If you need the faraday shield, you really need it regardless of what it does to the audio. Sure beats hearing a radio station or RF hash leaking through. The audio effects can be mitigated, but it makes the trsnsformer more costly.

Looking at the Jensen transformers, there are some differences that stand out that would make this a better choice for passive basses while at the same time minimizing the differences with active basses. The first being that the total input impedance with a 1.5k reflected load is 200k while maintaining about 22dB of voltage transform indicates that the electromagnetic part of the primary has been designed specifically for high impedance sources. The second is that the low frequency corner is specified at a higher maximum input level and lower THD which indicates also that this transformer does not suffer from impedance drop (nearly) as much between 100Hz and 20Hz, which is probably the gorilla in the room. This might not matter much in a typical band/bar PA, but on a PA with extended LF bandwidth AND ESPECIALLY a passive bass, I would expect significant differences. On an active bass with 1k output impedance I would expect the realized performance differences to narrow a lot.

My educated guess is that the primary difference responsible for sound quality with passive basses is the fall of input impedance with frequency below 100Hz. This is nowhere near the same challenge when fed with an active source.

Is there a difference in performance between transformers? Certanly. Would you expect to hear a difference on a passive bass? Almost certanly, especially on a high quality PA or recording. Would you be able hear a difference on a low impedance active bass? Maybe, especially on a high quality PA, but I wouldn't go out on a limb to say that it's always going to be a noticeable improvement.

The other question relating to this is what happens when you buffer the transformer with active electronics? My guess is that this would make as much difference (especially with single coils) as you are now removing more loading variables from the equation.


Whirlwind:
Model: TRHL
Input
Impedance: 20k ohm
Output
Impedance: 150 ohm
Frequency Response: 20-20kHz
THD @1kHz: 0.05%
Max Input*: 16dBu
Max Input@ 20Hz: 11.5dBu
Pri to Sec Loss: 22dB
Faraday Shield: yes

 

[JimmyM]

Boy, does that explain a lot! Makes me want to bust out all my DI's and compare them in recordings. Only passives I have are two Imp 2's, though. Thx for the great tech talk, Andy!

 

[Joe Louvar]

Agedhorse, even if you throw a buffered petal between a passive bass and the passive IMP-2 it still sounds like junk.

 

[howdoyoudo]

I'm surprised at the cost of the Radial JDI. With a look inside, there is no way the components could cost up to 200 buck, could it? Still, I'll be getting one.

 

[JimmyM]

I'm surprised at the cost of the Radial JDI. With a look inside, there is no way the components could cost up to 200 buck, could it? Still, I'll be getting one.

Has a very pretty and professional looking paint job on it. Also, at least one middleman gets his/her hands on it before you do, maybe two if they farm out distribution (don't know if they do or not). And they sell at $200, and prices are always what the market will bear.

 

[B-string]

The Jensen transformers are the major cost component.

 

[howdoyoudo]

Has a very pretty and professional looking paint job on it. Also, at least one middleman gets his/her hands on it before you do, maybe two if they farm out distribution (don't know if they do or not). And they sell at $200, and prices are always what the market will bear.

Thanks chap.

[Invalid or Expired Link Removed]
Around 1/4th of the cost and they've gotta be buying in bulk getting better deals.

 

[Passinwind]

I'm surprised at the cost of the Radial JDI. With a look inside, there is no way the components could cost up to 200 buck, could it? Still, I'll be getting one.

You can just buy one straight from Jensen instead if you don't need a bombproof box with splashy graphics, or build one using the free schematics on the Jensen website if you're the DIY type.

 

[agedhorse]

Agedhorse, even if you throw a buffered petal between a passive bass and the passive IMP-2 it still sounds like junk.

Fair enough, we are all entitled to our own opinions.

 

[Joe Louvar]

There is a newer REDDI available now too, but I'm not sure what the difference is.

 

[B-string]

Thanks chap.

[Invalid or Expired Link Removed]

Yes $73.08 1 to 3 price direct from Jensen. Invalid Link Removed

 

[JimmyM]

There is a newer REDDI available now too, but I'm not sure what the difference is.

Capable of driving a power amp and more dirt capability as you turn it up, vs the old REDDI which sounds the same at any volume.