Ampeg SVT 2 Pro Send Levels ?

Discussion in 'Amps and Cabs [BG]' started by Xandrell, Jul 5, 2017.

  1. Xandrell


    Aug 23, 2014
    Does anyone know the effect send, preamp out and line out levels? -10db, 0db, +4 ? I'm having a bit of a problem connecting balanced line processors and the sends appear to be real low. Will it mess things up to try the balanced line out and returning in the effect return? I guess other alternatives would be to put a Sansamp Bass DI after the send to bring it to 0 db balanced or get something like a Radial J+4 to increase it to a balanced +4 signal. Any help would be appreciated.
  2. BasturdBlaster


    Feb 19, 2012
    Crandon WI
    AFAIK, the preamp outs on my SVT4pro are rated 0.5v, I really don't know if they would be the same for your SVT2, sorryo_O
  3. Xandrell


    Aug 23, 2014
    That would seem to be way to low for a processor looking for a line level @ 1.25V +4 db. I'm thinking the effects loop is instrument level, -20db or lower depending on the gain setting of the amp which I don't want to increase. I'll try the balanced out, effect return tonight. Thanks
    BasturdBlaster likes this.
  4. beans-on-toast


    Aug 7, 2008
    They don't indicate what the useful effect or DI signal levels are in the SVT-2P documentation or schematics. The effect send and return circuit is not balanced, only the DI out is.
    Last edited: Jul 6, 2017
    BasturdBlaster likes this.
  5. Xandrell


    Aug 23, 2014
    The manual says insert an "instrument" cable into the jacks so I'm thinking it's instrument level along with the send level being so low.
  6. BasturdBlaster


    Feb 19, 2012
    Crandon WI
    I was researching the SVP1600 power amp years ago and apparently it has an input sensitivity of 0.5v to match the preamp output of the SVTpro amps. I forget where I got that info:( so I apologize if I'm way off:)
  7. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    Balanced out on my SVT-3PRO is pretty low, I wouldn't be surprised if your 2PRO is similar. I think this is by design, to avoid slamming the board with a line level signal when the sound crew are expecting mic level.

    If you add some gain on the effect send, keep in mind you may have to attenuate the signal into the effect return. My 3PRO makes a really horrible noise when the effect return is overdriven.
  8. Xandrell


    Aug 23, 2014
    The balanced line out doesn't work along with the pre amp out & in. Luckily the effects loop worked better with a sansamp bass DI level all the way up, but I really don't want to incorporate the sansamp into it. The only remedy I see is buying a Radial J+4 2 Channel Level Driver that's clean and quiet but I'm not even sure 14db of gain will be enough. If not, I guess I could try running the J4 out into it's other channel for twice the gain.:woot:
  9. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Why not just run your processors into the input?
  10. ThisBass


    Aug 29, 2012
    The "nominal" levels (if there is any) for both Send and DI output are stated in the preamp schematic drawing.

    However there is no way to predict how much level you'll get in practice.

    The schematic "states" the following numbers:
    Input jack: 11mV
    Send: 0.4V
    DI pre bal: 11mV
    DI post bal: appro 0.4V

    I think these Voltage numbers are of main interest for test procedure just to check if the amplifier is on specs.

    11mV versus 0.4V calculates to a gain potential of +31dB. In different words this means that even very smallish signals can be gained to rather "decent" signal level inside the preamp itself and as well at the Send-jack and as well present at the power amp in to get full power out of the power amp.

    How much level you'll get in practice depends on several variables.

    Lets start with the DI Out.
    Lets assume the input level was 300mV and the signal passes the preamp under respect to the following preamp settings:
    - pre bal
    - Attenuater pad: Off
    - DI Vol. all the way up
    The signal would pass the preamp steadily and was balanced at the DI-Out section to a total signal of 600mV which equals -2.2dBu

    If the signal was attenuated by the -10dB pad the signal at the DI out signal level was -12.2dBu. In addition the signal level present at the DI XLR jack could also be attenuated with DI vol knob.

    - post bal
    Now the signal has to pass through the total preamp section.
    So it all depends on
    - Attenuater pad On/Off
    - Gain adjustment
    - EQ setting
    - Graphic EQ setting
    - DI Vol adjustment
    how much DI level you actually get at the DI XLR jack

    Exactly the same condition is for the level present at the Send jack except there is no additional attenuater (Vol knob) like it is available for the DI out.

    Based on the supplies of +/- 15V for the OP-amps I guess the signal level present at the Send jack might be anything in the range of
    -20dBu .. +23dBu

    You'll get rather weak (poor) levels at both Send and DI jack if you adjust the master all the way up and adjust volume level needs with the gain knob.
    You'll get rather decent (highish) Send and DI levels if you adjust decent level for the preamp section with the gain knob and adjust loudness level needs with the master knob.

    Some time before there was a thread started with the question asked "how do you adjust volume?".
    IIRC at least 1/3 answered the question with "... adjust loudness level with gain".
    It's not surprising that repeatedly players complain weak Send levels with their amplifier.

    As the conceptional design of MI bass amplifiers is nearly all the same for most of all amplifiers just to provide:
    - attenuator
    - gain
    - EQ
    - Send
    - DI pre/post
    - master
    there is no way to predict the actual Send or DI level present on the jack in (real world) practice.
    Amplifiers can't adjust these levels to steady (line level) numbers like 0dBu or +4dBu by themself.
    Amplifiers need help by the player for proper preamp adjustment if any level is either to high or to small.
    Signal levels stated in schematic drawings are only meaningfull for test procedure just to check if the amplifier is on specs.
    Last edited: Jul 6, 2017
  11. Xandrell


    Aug 23, 2014
    And you've explained the problem. You need dirt dialed in (gain up) in order to have a decent send level. Not good for someone who would rather use the amp in the opposite way of low gain and higher master.
  12. Xandrell


    Aug 23, 2014
    I wish. The processors are line level. Although your point is well taken to just use a pedal. :)
  13. beans-on-toast


    Aug 7, 2008
    The problem is, there is instrument and line level and neither are well defined in the industry other than professional line level which is +4dBu. Effect send somewhere hotter than instrument, less than professional line level. Some outboard gear allows you to select a +4dBu or a lower receive and send level.
    ThisBass likes this.
  14. ThisBass


    Aug 29, 2012
    btw, the following signal routing will not work.

    DI-Out (XLR) -> processor -> FX-return

    cause the FX-return then routes the processed signal again to the DI-Out which will cause a "classical" feedback loop.
    agedhorse likes this.
  15. Xandrell


    Aug 23, 2014
    Thanks, I found out the hard way.

    What about DI out and return through the power amp in? I haven't tried that.
  16. ThisBass


    Aug 29, 2012
    As well there is no common definition respectively standard about the way how to adjust an (pre-)amplifier.
    So as both the FX-send and post DI level depend on the gain adjustment it's impossible to define any common standard for these levels. Some players like it to have a rather hot signal within the preamp section while others may like it to have nearly infinite headroom even for the preamp (for ever what reason).
    I think all manufacturers know very well about those "numerous" different adjustments of a preamp which is very personal biased.
    beans-on-toast likes this.
  17. ThisBass


    Aug 29, 2012
    IMO not a good idea cause the power amp in routes the (processed) signal back behind the master.
  18. ThisBass


    Aug 29, 2012
    If I read the schematic correctly,

    independent of drive adjustment the most sensitive stage within the tube preamp section is the drive section which will (always) saturate first.
    If the graphic EQ is OFF then it should be possible to get an undistorted level at the FX-Send of at least around 0dBu .. +4dBu (rough estimation).

    If you want to send more of level to the FX-send you may use the graphic EQ volume slider to add another +8dB to the FX-send which gives you a total level of around +10dBu.
    The level could be furthermore increased by boosting the total graphic EQ bandwidth which would add another +12dB so you could gain the FX-send to a total of around +20dBu.

    However if there is already a considerably boost with tube stage EQ then you may get the graphic EQ clipped if all sliders are all the way up. And then the level at FX-send would try to exceed +23dBu but, Headroom is off.
    At least it should be possible to gain a signal level at the FX-send that is large enough to fit any needs.

    The svp pro preamp is essentially the same preamp like it is for the svt 2 pro. I can't remember I'd ever had any issues with smallish signals. Never used the graphic EQ. I adjust the signal with gain just to get a "smooth" compression by none audible clipping/dirt, no drive, EQ adjustment to fit personal taste, most of the time some bass and treble boost.
    Last edited: Jul 6, 2017
  19. Xandrell


    Aug 23, 2014
    Thanks. great idea. I actually thought of the eq slider thing but forgot to try it. The gain results in audible dirt to get the level up but haven't tried increasing the drive instead. I prefer graphic eq off, gain down, drive off and drive the power tubes with the master. I'll try the eq slider and drive tonight.
  20. ThisBass


    Aug 29, 2012
    I think I'm a little bit misunderstood. Let the drive at 0. I tried to explain that even highish gain will saturate the drive stage first.
    As you connect the processor with a phone-XLR adapter cable to the FX-send you do loose -6dB of level. Even with attenuation of -6dB the level should be still large enough to just fit to any processor device that comes with balanced inputs.

    What kind of processor do you use ?
    Does your processor have an input sensitivity switch/selector or soft menu item to adjust input sensitivety? Make sure the input sensitivity is set to +4dBu
    Last edited: Jul 6, 2017
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