How to modify Zvex Nano for use as pedal? Mysterious supersonic emmission?

Discussion in 'Effects, Pedals, Strings & Things' started by mrCharlie, Oct 13, 2008.

  1. mrCharlie

    mrCharlie Member

    Messages:
    47
    Joined:
    Sep 30, 2008
    Location:
    Philadelphia
    Finally found a great clean sound in a small package - the Zvex Nano. Even though it's designed primarily as a 1-watt distortion amp, the clean sound is IMO, amazing (tight, focused, complex)

    Any suggestions on how to modify it so it can be used to drive a power amp (as a preamp)? Best if I can avoid a physically large power attenuator. The Nano is being planned for a small, atache sized rig, so size is important.

    I got an unclear message from a Zvex employee that there's a "supersonic" emission coming from the Nano, which would make it dangerous to use as a preamp. Anyone know more about this?

    Many thanks!
     
  2. ♫♪♫

    ♫♪♫ Member

    Messages:
    326
    Joined:
    Apr 15, 2008
    Well I think the power amp part of the nano is what makes it special. The fantastic sound you are getting is mainly from power tube distortion if I understand you correctly...even the cleans are largely dependent upon the power tubes/amp man...so...just taking the preamp and using it as a pedal probably won't get you the same tones...

    You could just buy a tube preamp pedal cheaper anyhow...and probably get better sounds than trying to use the nano.
     
  3. mrCharlie

    mrCharlie Member

    Messages:
    47
    Joined:
    Sep 30, 2008
    Location:
    Philadelphia
    I agree with you. I want to keep the nano power amp section. I would actually prefer buying a preamp pedal; but WHO makes a compact tube preamp with a great fender-like clean? I can only find tube preamps that are tweeked for distortion or overdrive. Any suggestions of where to look?

    Thanks!!!
     
  4. decay-o-caster

    decay-o-caster Member

    Messages:
    7,415
    Joined:
    Jan 4, 2002
    Location:
    The Greater San Jose Metroplex
    I'm an ignoramus on this stuff, but it seems to me that the Nano puts out too much signal for another amp to be happy receiving. A 'normal' preamp won't drive a 4-12, for example, so the fact that the Nano will makes it seem like too much for the input section of a power amp. Seems you'd need to attenuate it, then feed a power amp.

    I've always loved the Nano for not-super-distorted more than I like it for big slabs o' noise. Here's a clip I did a couple of years ago using a Nano, it's called "Guess That Amp", and most people guessed an EL84 amp on it.
     
  5. earthtonesaudio

    earthtonesaudio Member

    Messages:
    1,186
    Joined:
    May 16, 2008
    The Nano makes a high voltage for the tubes internally using a high-frequency switching power supply. Based on what the Zvex employee warned you about, I'm guessing the inductance of the guitar speaker helps filter out some of the switching noise. Therefore if you plugged into anything but a guitar cab (such as a PA cab) you'd be prone to frying tweeters.

    If you want to use it as a pedal, I would suggest making an external box with a good sized L/C low-pass filter and always splicing it between the Nano and the rest of your rig. That way you don't have to poke around inside, risking exposure to high voltages and probably voiding the warranty in the process.

    This is just a guess and some assumptions. Without knowing the details of the circuit it's hard to say if that will be sufficient.
     
    Last edited: Oct 14, 2008
  6. mrCharlie

    mrCharlie Member

    Messages:
    47
    Joined:
    Sep 30, 2008
    Location:
    Philadelphia
    Thanks so much for your help! Much appreciated.

    You're observations sound good to me. Copied below is a copy of an email I received from Zvex, which might give you more clues.

    "The output of the Nano has a constant 27KHZ tone at about 1volt peak-to-peak (at max volume setting) as a result of the power supply that I use for the high voltage. This would be highly destructive to a solid-state amp. Brick-wall filtering would have to be used to make it safe.

    You could theoretically create your own attenuator using smaller 2 Watt resistors and make a very simple load/attenuator, but you'd lose the magic of the speaker cabinet's reactive loading which interacts with the tube output and gives the sound so much of its life.

    I don't see a way of accomplishing what you're looking for using the Nano without a very complicated setup to recreate the reactive load. Weber makes some kind of speaker motor that acts like a speaker cab in terms of reactance but I have no idea if it works."

    The Nano uses a wall wart, which says "switching" on it, so I assumed that the power supply was all built into the wall wart. Are you saying that the PS is internal?

    I like your idea of an L/C filter post Nano. Although, when you read the above, you might draw a different conclusion.

    Then other issue is voltage. The Nano puts out 1Watt (approx). The T-Rex Roommate pedal is looking for guitar or line levels. To reach the required sound levels, I only set the Nano to about a 1 or 2 on the volume pot. Do you think that as long as I'm careful to keep the Nano volume low that I can keep the output power/voltage at a level tollerable to the T-Rex Roommate?

    Zvex mentioned that the great sound requires a speaker load. The T-Rex Roommate is an 880K input, although if I use an L/C filter, I would imagine the impedance would change. I tried the Nano with the T-REx Roommate and it sounded great, so I guess I'm happy even without the reactive loading that Zvex mentioned. Any thoughts on this?

    My technical background is limited, so your thoughts are very appreciated. Thanks, again.
     
  7. zachary vex

    zachary vex Member

    Messages:
    767
    Joined:
    Nov 17, 2002
    Location:
    minneapolis, minnesota
    The switching power supply that's external could be a car battery or whatever you want (even 8 D-Cell batteries!) that supplies 12VDC at 1.5A. The internal high-voltage power supply is what I was talking about.

    The Nano is designed to drive a 16 ohm speaker cabinet. It's not designed for DI use. It needs a proper load for safe operation, and the ultrasonic output from the unit's power supply could easily damage a solid-state amp which likely would be able to reproduce it and send it to the tweeters.

    You can't hear the ultrasonic frequency using a guitar speaker cabinet. It's far above the response of a guitar cab. You wouldn't be able to hear it through a solid-state amp either, but it would certainly be hammering on your tweeters!

    Part of the magic of any tube amp is the amazing interaction between the speaker's reactance reflecting through the transformer to the tube's plate and cathode. It's really where the magic is in the sound... if you take a tube amp and drive a non-reactive resisitive load like an attenuator typically uses, your tone will fall much more flat and lifeless. You can hear this happening when you attach an attenuator to a speaker cab and turn it down more than 12dB... the speaker sounds sterile and lifeless. The Nano is very low wattage (1/2 watt peak, much less RMS), so you can achieve the lively tone of the speaker's reactive relationship with the tubes and output transformer at a very moderate volume. THAT's what I designed it for!
     
  8. JimH

    JimH Member

    Messages:
    1,572
    Joined:
    Jun 22, 2006
    Location:
    Manchester, UK
    One safe and relatively small and inexpensive solution for your problem is line out form a $70 weber micromass. Results may not be what you're after though.

    One thing I would be interested in is Slave Outputs are a nominal 1W - so would the nano be OK into a slave input? presuming you could find one of those old tranny amps that had one? - I realise this will also remove the speaker interaction as mentioned above - and would that still be subjecting the amp to the ultrasonic frequency? I'm not sure about damping factors/filters on slave inputs.
     
    Last edited: Oct 15, 2008
  9. soulsonic

    soulsonic Member

    Messages:
    982
    Joined:
    Nov 15, 2007
    Location:
    Port Jefferson Station, NY
    A MicroMass wouldn't necessarily filter out the high frequency noise. It can be used as a DI/Slave/Line out thing, but it won't filter out the junk. A "standard" guitar speaker doesn't have enough of a high frequency response for you to be able to hear this (and you probably can't hear 27kHz anyway...), but it's not actually filtering it out either.

    So here's the solution for making this gimmick toy a useful device:
    - Put a low-pass filter in series with the output. This is what is truly required to filter the junk out. This can be an arrangement as simple as a resistor and capacitor. I would probably choose a corner frequency around 10kHz.
    - Use a resistor for a load. Just stick a little 8 or 16 ohm 5 watt resistor in the box with the filter. This allows the amplifier to put out the same amount of power as if it were plugged into a speaker. You don't have a "reactive" load with a simple resistor, but guess what; "reactive" does NOT mean "interactive"! The frequency response won't be identical to if it were plugged into a real speaker, but it isn't going to anyway and another gimmick like a MASS load wouldn't fix that problem.
    - Have a simple voltage divider (a couple resistors and/or a volume control) to set the proper output for feeding to whatever you want to plug it into.
    - Lastly, you may want to include a speaker filter like a Red Box or whatever to give a proper "mic'd speaker" sound if you're using this for DI.

    Any electronics hobbyist could knock something like this up in an afternoon easily.
     
  10. mrCharlie

    mrCharlie Member

    Messages:
    47
    Joined:
    Sep 30, 2008
    Location:
    Philadelphia
    Thanks so much. You've really helped me. I'm heading out of town for a few days, so I'll get back to you in more detail when I return. Again, much apppreciated.
     
  11. mrCharlie

    mrCharlie Member

    Messages:
    47
    Joined:
    Sep 30, 2008
    Location:
    Philadelphia
    Hi Zack,
    Heading out of town, so can't work of this today. Thanks for your additional insight. I'll think closely about your thoughts. Thanks, again.
     
  12. mrCharlie

    mrCharlie Member

    Messages:
    47
    Joined:
    Sep 30, 2008
    Location:
    Philadelphia
    Hi Zack,
    Thanks for your additional thoughts. I hear you and understand your design purpose. I can understand you not wanting someone to swrew around with your "baby."

    I understand that I will have to abandon reactivity between the output transformer and speaker. Given that all of my rigs use preamps for tone; they plug into ss power amps - so none of my rigs have an output transformer that's "reacting" with the speaker, and I'l okay with that. I still love the sound.

    At this point, I'm going to look around for an alternative to the Nano, but we'll see. There have been a couple of suggestions to use a webber anerd build a simple low pass filter.

    Thanks, Zack!
     
  13. mrCharlie

    mrCharlie Member

    Messages:
    47
    Joined:
    Sep 30, 2008
    Location:
    Philadelphia
    Hi, I'm back. Thanks so much for your excellent and easy suggestions. I really appreciate that you took the time to help me and your thoughts make a lot of sense and worthwhile.
     
  14. mrCharlie

    mrCharlie Member

    Messages:
    47
    Joined:
    Sep 30, 2008
    Location:
    Philadelphia
    Hi, I'm back. Thanks so much for your excellent and easy suggestions. I really appreciate that you took the time to help me and your thoughts make a lot of sense and worthwhile.
     

Share This Page