DI-Box recommendation for firmware 3.0

  • Here is a simple DI schematic for DIY'ers with line/spkr and without spkr simulation. I can make some PCB project if someone will be interesred. The cost of build one will be about 30$


    [Blocked Image: http://www.leo.ne.kr/data//1012/1891247484_b159b705_active+direct+box.gif]

  • If you read back in this thread you will see where someone contacted radial and they do not make a di box that will work in this situation. I think you want passive because the actives to me are like little amps being introduced into the signal chain. I also agree with some of the other comments that it can't be to cheap to do what it is supposed to do. I'm thinking at least $100 perhaps more.

  • No, it cannot be used as a direct box. It also cannot be used to make Direct Profiles.



    The Radial ProRMP converts a Live Level Input signal to a Instrument level Output signal.


    A conventional Direct Box does the opposite. It converts an instrument level input to a line output.


    And, it does not accept Speaker Level signals, so it cannot be used to make Direct Profiles.

  • I have a few home made Di 's based on a Neutrik NTM 1 , wonder if I can modify them to accept a amp output ?


    Or it would be nice of Kemper to put their Schematic of the DI they've built !!!

  • After reading as much as I've been able to find online in this forum, as well as from Kemper's press releases, I think that the following sums up what will be needed in a DI box to do Direct Amp profiling.


    For a DI box to work in creating a Direct Amp profile it must:

    • be able to take speaker level input from a power amp or head
    • have no tonal adjustment to its output (i.e. no speaker compensation)
    • split the signal. One output is a through bus to a guitar speaker cab so that it can still interact with the amp. This interaction is the loading characteristic which will be (hopefully) captured by the Direct Amp profile. The second output is a balanced output which will be connected to the KPA return jack for profiling purposes.

    It is the first and third requirements that seem to have some potential variables associated with them.


    The first requirement involves how much power the DI box can accept at its input. I've seen that some manufacturers sell DI boxes with differing power input ranges. So, for example, the same DI can be ordered with acceptable input levels of 1 to 50 watts, or alternatively 51 to 100 watts.


    The third requirement is splitting the signal. The through to the speaker side requires a specific nominal expected speaker load. I've not seen a DI box made for this application that can vary the load to match that of the connected speaker.


    So, for example, the Mesa CabClone meets the above requirements. It can handle power amps up to 150 watts. That takes care of a wide range of requirement one's variation. However, it comes in three models, 4 , 8, and 16 ohm. So to do Direct Amp profiles of amps with multiple cabs of differing nominal resistances you'd need to buy three of them. That's an extra $900. Ouch!


    Scratch17

  • So, for example, the Mesa CabClone meets the above requirements. It can handle power amps up to 150 watts. That takes care of a wide range of requirement one's variation. However, it comes in three models, 4 , 8, and 16 ohm. So to do Direct Amp profiles of amps with multiple cabs of differing nominal resistances you'd need to buy three of them. That's an extra $900. Ouch!


    Scratch17


    Last page of the Cabclone manual - it's acceptable to use a lesser impedance. eg the 16 ohm version is OK at 16 or 8 ohms, the 8 ohm version at 8 or 4 ohms. Not the other way though!

    Steve

  • I have a Marshall 100 watt SLP Non-Master Reissue Tube Amp Head that has 2 Speaker out 1/4" connections. I use one of the Speaker out connections to connect to my Marshall Power Brake Attenuator so I can be in the same room with the amp without going deaf.
    My Marshall Amp and my Marshall Power Brake do not have line out jacks so I built a line out box as in the attached picture. I built the "Rockstah" line out box to connect the other un-used 1/4" Speaker out jack on my SLP Amp Head to Effects Return input on another Marshall amp for slaving. Anyone know if this "Rockstah" Line Out box will also work as a line out box to connect my Marshall 100 Watt Amp to the Kemper for Firmware 3.0 profiling?


    NOTE: TO ANYONE WHO DECIDES TO BUILD ONE OF THESE ROCKSTAH LINE OUT BOX AND TRY IT, THIS IS NOT A LOAD BOX, YOU WILL STILL NEED TO HAVE A LOAD OF SOME KIND OR SPEAKER CONNECTED TO YOUR TUBE AMP OR YOU WILL FRY YOUR AMP.


    The Rockstah Line Out Box specs and diagram are courtesy of the late Great Mark Abrahamian of Startship. R.I.P. Mark, we miss you brother!

  • Here is a passive DI box that will work:


    I've had an older version of it for years that I used to record bass (I just remembered it has a "Speaker" switch on it, too) :)


    It can accept a pass through Speaker Level input (up to 600W RMS), and can output a flat signal through the XLR.


    [Blocked Image: http://www.procosound.com/images/stories/db1_g.png]


    http://www.procosound.com/db1

  • Pilotltd quoted the Mesa CabClone manual as saying:


    Quote

    it's acceptable to use a lesser impedance. eg the 16 ohm version is OK at 16 or 8 ohms, the 8 ohm version at 8 or 4 ohms. Not the other way though!


    It may be "acceptable" from a "you won't blow anything up" standpoint. It doesn't necessarily mean you will get a good profile if you cut this corner.


    Consider that if it doesn't change the interaction between the amp and cabinet, why not just make one Cabclone with 16 or 8 ohm specs, and a second with 8 or 4 ohm specs. Why bother making a 4 ohm unit? Somehow, it seems that there must be a difference. Or is the end user supposed to expect that using a 16 ohm Cabclone with an 8 ohm cab will give the exact same result as using an 8 ohm Cabclone with an 8 ohm cabinet?


    My Mesa 20/20 amp comes with outputs for all three standard nominal impedance specs. I know that I can plug a 4 ohm cab into an 8 ohm output. It will not sound the same as using the 4 ohm output with the 4 ohm cab.


    If I'm going to the trouble of doing Direct Amp profiling, I don't want to chance altering the result by cutting corners. I'm no expert. This is just my take on the subject of this form of profiling.


    Scratch17


  • http://www.leo.ne.kr/data//101…705_active+direct+box.gif
    look at above picture - you have untouched part of the signal going from the amp to the cab. What is you take is only Ac voltage from the connection of this two(Input to output).
    There is a pot - you can regulate a Ac signal amplitude with this. So basically 22k resistor and 1k Pot is a voltage divider. So it is no matter how many watts you deliver to the cab you can set by this divider desired signal amplitude from the DI output.


    From what you are writing you do not understand that when your cab has lower impedance then the output impedance of the amp you have lower signal in Volts so you can't destroy a DI. But if you connect larger impedance to the low impedance output your signal become larger and can destroy the DI IC's. I think such Di is bad projecting example.
    You can always protect IC from over-voltages by Zener diodes.

  • I haven't read the specs, but I'd be hesitant to use anything calling itself a 'speaker simulator'. It needs to be a clean but attenuated signal going in to the KPA, not a coloured one.


    Cheers,
    Sam


  • The difference is for the no cab power soak. There is a very large internal power resistor, a 4 ohm in the 4 ohm version, 8 in the 8 and 16 in the 16. It's there to give the amps output transformer an acceptable match in a no cab situation. The line out comes straight from the input socket attenuated to 4dB max and I suspect the version makes no difference as a long as a cab is attached and only comes into play in a no cab situation. Probably just Mesa covering their ass for claims against damaged amps.

    Steve

  • I haven't read the specs, but I'd be hesitant to use anything calling itself a 'speaker simulator'. It needs to be a clean but attenuated signal going in to the KPA, not a coloured one.


    Cheers,
    Sam


    The PDI-03 has 4 unsimulated Line-Outs ;)

  • The difference is for the no cab power soak. There is a very large internal power resistor, a 4 ohm in the 4 ohm version, 8 in the 8 and 16 in the 16. It's there to give the amps output transformer an acceptable match in a no cab situation. The line out comes straight from the input socket attenuated to 4dB max and I suspect the version makes no difference as a long as a cab is attached and only comes into play in a no cab situation. Probably just Mesa covering their ass for claims against damaged amps.


    In one of the NAMM videos, CK indicates Resistor-based Direct Boxes will not provide authentic results.