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Avalon U5 questions

Discussion in 'Recording Gear and Equipment [BG]' started by bdeaux, Oct 7, 2002.


  1. bdeaux

    bdeaux Bass, the final frontier! Supporting Member

    Jun 13, 2002
    Salt Lake City based
    Branden Campbell
    The speaker input on the U5 has a 400 watt max. Is the ohm rating on the amp involved in this? My Ashdown has a rating of about 575 @ 4 ohms. Since 8 ohms may be a little over half that will it be safe to run into the Avalon? The Avalon site says the U5 doesn't pull a load from the amp while using this feature, but then why the 400 watt limit?

    Thanks!
     
  2. Chrisbowmusic

    Chrisbowmusic

    Jul 30, 2016
    Did you ever get an answer to this question? I'm considering to connect a Markbass Little Mark Tube speaker output to my U5 speaker input. But, of course, us bass players need to know the ohm specs as this determines the wattage output. I'm still waiting for a response from Avalon. Thanks in advance!
     
  3. tom-g

    tom-g

    Oct 2, 2007
    While not that obvious, it tells you in the specs:

    Input Impedance: 3 ,000,000 ohm unbalanced (single ended)

    If you do the math for a parallel connection to your amp, you will find that this load is negligible. That's why they say it does not put a load on the amp. The 400 Watt limit is for the Avalon. If your amp puts out more that 400 Watts it will/might destroy the Avalon.
     
  4. Chrisbowmusic

    Chrisbowmusic

    Jul 30, 2016
    Thanks. I did more research on this after posting, and learned some things w still more to learn. I've read that an amplifier has to have a load (i.e. speaker cab) connected. So, I would need to have an amp with 1+ outputs. Or, buy a load box thingy. I'm still waiting to hear from both Avalon and Markbass, but I expect they're going to state the same. Actually, I found the Avalon Speaker Input Diagram online and it shows this exact scenario, an amp with multiple speaker outs; one sent to a cab, the other to the Avalon speaker input.

    What I'm still confused about is ... modern amps like Markbass can be used without a speaker with only headphones connected. So, why then would a cabinet or load box be necessary? Is this because the speaker
     
  5. Chrisbowmusic

    Chrisbowmusic

    Jul 30, 2016
    Sorry, didn't finish my post before mistakenly hitting Post Reply button, iphone typing be cursed. Anyways, is this because the amp has to know (or be fooled into thinking) what type of cabinet is connected (4-ohm, 8-ohm, etc.) in order to drive the speaker output?

    I've never had to be bothered with this sort of thing in the past, only being concerned with my amp head and speaker combination. So, this subject is new territory for me.
     
  6. ofajen

    ofajen

    Apr 12, 2007
    92.4W 38.9N
    1) SS amps generally have no problem running without a nominal speaker load. Tube amps, OTOH, generally should not be driven without a proper speaker load or load box.

    2) The U5 has a high input impedance, so it won't draw much power from the amp, so it should not be damaged, even if you send too high an input level in.

    3) it's rated to input level of +24dBU. In this context it tells you the voltage level above which it will start to clip. If you crank a 400W amp into it, you can probably reach that voltage level and get a crappy, distorted sound. That should not result in damage to the U5, however.

    4) if you run a 400W or even a more powerful amp in, but run it at any reasonable level, you should get undistorted sound.

    5) IME, there is little to be gained from running a SS amp stage at high levels except more volume from the speakers.

    Otto
     
  7. Chrisbowmusic

    Chrisbowmusic

    Jul 30, 2016
    Thanks Otto. The Markbass amp I'm interested in just happens to be the Little Mark III Tube 800. So, it has both a SS and Tube pre, just to make things even MORE complicated. I'm just considering all of this to get a amp/cab sound without upsetting my townhouse neighbors (on both sides). I presently go direct from my U5 into a UR824/Cubase with the Overloud Mark Studio 2 VST amp/cab simulator plugin inserted, which works very good. Maybe outside of actually mic'ing a real cab, the VST is the best solution for me right now.
     
  8. ofajen

    ofajen

    Apr 12, 2007
    92.4W 38.9N
    Tube preamp doesn't matter. SS power stage won't have to have a load.

    OTOH, I'd be amazed if there were any benefit to using the speaker out versus a direct out on the amp. A SS power amp stage should be pretty flat.

    Otto
     
  9. Chrisbowmusic

    Chrisbowmusic

    Jul 30, 2016
    Okay, I just received a reply from Avalon. The U5 will be seen as a 8-ohm load by the amp.
     
  10. tom-g

    tom-g

    Oct 2, 2007
    That doesn't make sense. What was the exact answer from them?
     
  11. Chrisbowmusic

    Chrisbowmusic

    Jul 30, 2016
    Here's their email reply below. If it's a bit confusing for you, imagine how confused I am about "zero load" considering my knowledge in this area is probably less than 10% or yours. Anyways, thanks for helping out a noob here. Hopefully, this helps anyone else out there who may have the same questions.

    "Hello Christopher,

    Thank you for contacting Avalon Design. The speaker input will be seen as an 8Ω load and can handle up to 400 watts of power. So you can use any head of your choosing that will do 8Ω’s and provide 400 watts or lower.

    If you have any further questions please feel free to contact us."
     
  12. I think that you are getting an answer from the marketing department and they don't quite understand the question and/or they don't quite understand how the speaker input works. Given that Avalon says you must use the speaker input in conjunction with the speaker input I'd guess that they mean that when used with an 8 Ohm speaker the load seen by the amp will be 8 Ohms because the load presented by the U5 will be some high impedance in parallel with the speaker impedance and won't affect the total impedance much. Which is how all of the other DIs that can accept speaker level signal work.

    I've been inside a U5 or two and there definitely isn't anything inside it that could dissipate anything near 400W so I don't think the load presented by the U5 on the speaker input could possibly be 8 Ohms.
     
  13. ofajen

    ofajen

    Apr 12, 2007
    92.4W 38.9N
    Yes their reply is not accurate. What they literally say (the U5 presents an 8 ohm load) would melt the unit. It's high impedance so it won't melt, and if you are using a cab, the amp will see just the load of the cab.

    You should still be able to use the U5 for recording an amps output. Again I would say I see little benefit in adding a SS power amp stage in the path unless you are going to drive a cab and mike it. Also, I think your power amp should be able to clip the U5 input pretty easily, so pay attention to overload indications to avoid a distorted signal. +24 dBu is about 12.3V RMS. The power amp can probably generate considerably greater voltage output signal when cranked.

    Otto
     
  14. I'd hazard that the speaker level input is well padded compared to the instrument inputs and based on the 400W rating a bit of math indicates that it should be able to handle 56.5V RMS before clipping. This isn't clear on the spec sheet where they quote the maximum input levels, but it doesn't make sense for a speaker level input rated at 400W power handling to only be able to handle +24dBu. Again, that's SOP for all of the other DIs that can handle speaker level signals. I'm pretty certain the speaker input goes to a pair of 1/4W resistors right after the connector so I'd say that's the pad. The biggest resistors in the U5 are 2W or something so it's definitely not an 8 Ohm load. :D

    Oh yeah, the OP (from 2002!!) says that Avalon said the speaker input doesn't pull a load from the amp, which indicates a high impedance input.
     
  15. ofajen

    ofajen

    Apr 12, 2007
    92.4W 38.9N
    No audio gear can deal with 56 V input signals without significant padding. Certainly not something like the U5. +24 dBu is typical these days for IC based gear with 15V internal rails.

    Either the input pads the signal down a bunch or one will need to watch for clipping if the amp is cranked.

    Otto
     
  16. ofajen

    ofajen

    Apr 12, 2007
    92.4W 38.9N
    I read the (brief) manual. The +24 dBu rating will be for the normal high Z input on the front, the rear speaker input probably has about a 15 dB pad built in to tame the speaker input. As you say, it will need to deal with up to 56 V.

    The input impedance of the speaker input isn't specified, but I would have made sure it was at least 5K. The unit says the speaker input must be used with a speaker cab, which would certainly be necessary for all but a handful of tube power amps. Most SS power amps wouldn't care whether there was a cab or not. OTOH, most SS power amp stages aren't worth putting in the signal path unless you are miking the cab.

    Otto
     
  17. This thread started back in 2002? I just wanted to say how impressive that was.