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Ampeg PF-20T to (power) amp

Discussion in 'Amps and Cabs [BG]' started by Zbysek, Nov 21, 2018.


  1. My worry is it is intended for a mic on a DB, fdeck knows what sending a line out into it would do.
     
  2. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    ~ +21.17 dBu, or 8.86v RMS

    And note the 100K input impedance, which is pretty much useless for a piezo equipped upright without an external preamp.
     
    Ric Vice likes this.
  3. Zbysek

    Zbysek

    Mar 23, 2017
    Czech Republic
    I would do it in order to have the Little Mark's EQ available for fine-tuning the sound on stage. I might have forgotten to mention that I plan to send the signal to FOH from the transformer DI on Ampeg...
     
  4. Zbysek

    Zbysek

    Mar 23, 2017
    Czech Republic
    I see. Thanks for the explanation. It's difficult to find out sitting at the table as the Little Mark's manual doesn't contain block diagram...
     
  5. Zbysek

    Zbysek

    Mar 23, 2017
    Czech Republic
    There is no pad on Little Mark III
     
  6. Zbysek

    Zbysek

    Mar 23, 2017
    Czech Republic
    I am not sure it is. I haven't found such a statement on the manufacturer's web pages. What do you derive this assumption from?

    Even if it is correct-what would it do? I plan to start with gain at zero and increase slowly...
     
  7. Zbysek

    Zbysek

    Mar 23, 2017
    Czech Republic
    I plan to use the Transformer Balanced Out for FOH. I will use the preamp out on Ampeg to feed the Little Mark...

    Does it change your take on this?
     
  8. ficelles

    ficelles

    Feb 28, 2010
    Devon, England
    I tried it with an Eden WTDI, worked just fine. Also worked simultaneously with the jack input.
     
    Zbysek likes this.
  9. Wisebass

    Wisebass

    Jan 12, 2017
    Lost in Space
    :oops: Oops! I really shoud do my homework! :sorry: :D

    I am not a Markbass user.

    With the loop sitting pre EQ, the best solution is obviously using the XLR input on the MB (Ampeg balanced out to Markbass balanced input)

    :( see above. The way I do it, won' t work on your amp.

    The amps I use have their fx loop after the EQ. Using the poweramp section and by-passing the preamp gives me the opportunity to have the Ampeg' s sound (just louder), without fiddling on the second amp' s EQ.


    greetings

    Wise(b)ass
     
    Zbysek likes this.
  10. Zbysek

    Zbysek

    Mar 23, 2017
    Czech Republic
    I understand that the issue is superfluous provided that the loop is sitting pre EQ...

    Generally, I just don't understand the preference to use FX return. My take on this is that I can leave the EQ flat if I don't want to fiddle with it...

    I thought there might have been some technical reasons behind it which I am not aware of. Some kind of magic involving ohms, Vpp, dBu, RMS, and the like...:)
     
    instrumentalist likes this.
  11. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    More active stages often equals more noise and distortion - actually, even passive components like resistors can add noise, especially near the input stages. Also, setting the EQ to all knobs at noon often does not equate to flat frequency response. So a lot of people prefer not to have duplicate functions they are not using in their signal chain. But IMO and IME getting gain staging right is job one. In this case, easy enough to just try it both ways and go with whatever sounds better to you.
     
    punchclock, Ric Vice, Kro and 3 others like this.
  12. Zbysek

    Zbysek

    Mar 23, 2017
    Czech Republic
    That makes sense.

    Exactly. That is why I thought it would make sense to insert the signal at XLR input so I can use the gain knob to make sure that the signal entering the circuits is not too hot. If I use FX return, there is no such control so the signal will hit the circuitry head on...
     
  13. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Gain staging can be pretty complicated and non-obvious, really not sure which will work better for you. I have Aux/EFX return level controls on nearly all my amps, it's kind of mandatory for what I do. Yel_wink.
     
    Wisebass, Stumbo and Zbysek like this.
  14. Zbysek

    Zbysek

    Mar 23, 2017
    Czech Republic
    Little Mark doesn't have one, unfortunatelly..
     
  15. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    It's a feature that many people would never use, although at NAMM the last two years a whole lot of people commented on how much they liked it in my amps. Typically those were the guys who wanted to play along to tracks when doing solo bass demos. Seems like very few people use EFX loops for EFX these days.
     
    Last edited: Nov 23, 2018
    Zbysek, Wisebass and BadExample like this.
  16. ficelles

    ficelles

    Feb 28, 2010
    Devon, England
    Ok so I tried it with my PF-50t and Little Mark 250 going back into my PF-115HE cab... it worked fine, not noisy, but I didn't care for the complexity so don't think it's a setup I'd use myself. Note this is the transformer balanced line out with PF-50t gain and volume at around 50%.

    Ps not noticing any colouring of the tone or overloading of the LM input even with the PF-50t master dimed.

    IMG_1279.JPG IMG_1280.JPG
     
    Last edited: Nov 22, 2018
    Zbysek likes this.
  17. Wasnex

    Wasnex

    Dec 25, 2011
    Here's a link to a conversion table that shows it to be between +31 and +32dBm...so I would think that is overload conditions.
    Table: Power vs. dBm and Volts
     
  18. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
  19. Wasnex

    Wasnex

    Dec 25, 2011
    The PFT20T manual describes the Preamp Out and Transformer Bal Out with the exact same words: "This signal may be used to feed an external power amplifier, mixing console, interface or house PA system."

    Choose whichever output gives you the function and sound you want. If necessary you might be able to split the Transformer Bal Out and send it to your Little Mark and FOH. But you will need an isolation transformer or some other device to protect the Little Mark against phantom power coming from the mixer. Also you need to be mindful of how any control changes you make impact FOH sound. This varies with signal path.

    Depending upon how you eventually connect everything, you may be able to route the Transformer Bal Out from the PF20T to the Little Mark, and then use the Little Mark's DI to get the signal to FOH. This may work well or be too noisy. The manuals don't provide enough detail for me to say sure, so time for you to experiment ;).
     
    Zbysek likes this.
  20. Wasnex

    Wasnex

    Dec 25, 2011
    It's fairly common with modern amps for the FX loop to come after the preamp, but before the master volume. The preference in using the FX return is to bypass the preamp so you get a more transparent sound.

    Many assume that the FX loop is always after the preamp...not true The FX loop in some of my all tube amps comes in the middle of the first preamp tube. Basically plugging into the FX return only bypasses the input circuitry and one stage of amplification, so the rest of the preamp is left in the circuit.
     
    Zbysek likes this.

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