Tube Works 4001 Direct Box: Anything Special?

[Vermouth]

I had my Tube Works 4001 DI open for a cleaning, recap, and new tube (ECC83s/12AX7). I took pics of the PCB, could anyone tell me how the circuit compares to other DIs?

 

[scubaduba]

No experience with it but it is one I'd like to try sometime.

 

[esa372]

I have one on my "ampless" board; great piece of kit:

...could anyone tell me how the circuit compares to other DIs?

I'm not sure how to answer the question, but this is from the owner's manual (1990s):

This is the first known tube cathode balanced direct box ever designed.

This break-through design results in the elimination of the typical output transformer. The elimination of the distortion-prone and frequency response-limiting output transformer, coupled with the addition of a low-noise comparator-type input amplifier, has resulted in a literal order of magnitude advance in performance
for this studio quality device.

While using the RTD, you will notice the almost total lack of microphonics, along with one of the lowest noise floors in the industry for tube-type studio gear. The noise parameter was very carefully considered in the design phase.

 

[Vermouth]

I have one on my "ampless" board; great piece of kit:

Nice setup, do you prefer it to the Para Driver? I suppose it's a much more direct sound compared to the Sansamp's (excellent) modeling?

 

[littlebun]

I had my Tube Works 4001 DI open for a cleaning, recap, and new tube (ECC83s/12AX7). I took pics of the PCB, could anyone tell me how the circuit compares to other DIs?

View attachment 4645569 View attachment 4645570 View attachment 4645573 View attachment 4645574

The 4001 is as good as any DI box made. I know because I own some of the nicest DI's, and the 4001 hangs with all of them and might be better than most. When I got mine it had a ground buzz with passive basses, so I had to ground the circuit to the case. The design is very simple, not many parts involved, and it sounds fantastic. It's what Sklar uses, and that says a lot. It's transformerless which is different from most DI designs. The other DI box that I've used and compares to the 4001 is the transformerless solid state active Comara Fat Box DI. When I toured in the 80's with Shubert Systems as our sound company, they allowed me to tour with their Fat Box as my house DI. It sounded amazing. The Tube Works 4001 and the Fat Box are the best direct boxes that I've used. I also own and use DI's that are made from Neve and Telefunken circuits, but I consider them DI preamps so they are in another category. Another fave is the passive JDI into a Cloudlifter; which is great on a Jazz Bass.

 

[JKos]

could anyone tell me how the circuit compares to other DIs?

Based solely on the pictures and the power supply spec of 30 VAC, it appears to be a relatively low voltage tube circuit with an op-amp.

The “balanced tube cathode direct output” would seem to imply that the tube is used as two cathode follower outputs for the balanced output. The op-amp could be used for level setting and inversion to feed the tube stages.

 

[esa372]

Nice setup, do you prefer it to the Para Driver?

Thanks!
If I could only keep one, I'd keep the RTDI.

I suppose it's a much more direct sound compared to the Sansamp's (excellent) modeling?

That's a good way to put it.
I only use the Paradriver for overdrive (which is rare), but the RTDI is essential to my preferred sound.

The 4001 is as good as any DI box made ...and might be better than most ...it sounds fantastic.

+1

It's what Sklar uses...

ha! I didn't know that... and I just met the ol' master a few weeks ago, too!

 

[micguy]

Based solely on the pictures and the power supply spec of 30 VAC, it appears to be a relatively low voltage tube circuit with an op-amp.

Yep, it's got one tube and one dual op amp. Not sure why you'd do it that way, but it is what it is.

 

[Vermouth]

Speaking of the op-amp, I saw that TLE2072AC is a direct drop-in replacement for the stock TL072CN when I searched for info on it.

 

[Camarillo]

Is this the DI mentioned by Leland Sklar here?

 

[Skovgaard]

Yep