Running straight into a power amp?!?

Discussion in 'Amps and Cabs [BG]' started by Yamarc, Jul 28, 2003.

  1. Yamarc

    Yamarc Supporting Member

    Jun 25, 2002
    Rome, GA
    I've heard of a few people doing this, what do you guys think? It seems a little limiting especially if you have a passive bass. Although it would save a ton of money and give the true and genuine unaffected sound of your bass...Tell me what you guys think; Is this smart or stupid? Marc
  2. thumbtrap


    Jun 26, 2003
    Peavey Max Preamp
    Stewart UDP-1
    Yamaha PB-1
    BBE 383

    All great very inexpensive preamps used. All have basic EQ, gain enough to drive a power amp. Some have crossovers, some compressors, and some exciters. Should be $100-$150 used.
  3. you cant do it with a passive bass.
  4. I've done it. Its just really low volume.
  5. Is there a way to bypass the preamp on an integrated amp? Could I plug into the return jack of the effectsloop? My amp is an SWR Bass750 and I have a Stingray5.
  6. shreave


    Jul 12, 2000
    Seattle. WA USA
    yep, plugging into the effects loop return will bypass the pre-amp. I've never done it without using a seperate pre-amp though. I'm thinking it would sound like flat poop.
  7. Well, flat poop is what I'm having tonight :eek: (I have to try it for fun!)
  8. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    You could also run into impedance problems, which would cause lack of highs.

    It's impractical, you need at least something that gives you a line level signal and lower impedance.
  9. I had to run from my bass (passive 5 string) directly into my stewart 1.2 the other night, because my guitarist left his gig bag at home, so I gave him two of my three cords.

    It wasn't as loud as it could've been, but it was adequate for the gig, which was a three piece power rock thing.

    I was surprised it even worked, but it was fine.
  10. Yea, I've tried plugging my SR4 into the effects return on my Peavey TKO 115. Definitely sounded like flat poop :bassist:
  11. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    You'll need a preamp with that.
  12. BillyB_from_LZ


    Sep 7, 2000
    As others have written, the output level of an instrument typically isn't high enough to drive a power amp to full output.

    If you have and active bass with plenty of EQ, Walter Harley has designed a preamp with no EQ. It does have a slight overdrive circuit in it for added warmth.

    You can see the schematic at

    If you get lucky enough, you can get top quality bass preamps for low, low bux...
  13. That was almost funny when I read it the FIRST time on Harmony-Central.... last year :rolleyes:

    Anyway, I know it's a pre/DI but the rig I'm building will be an Avalon U5 into a Crest LT1000 into a Bergantino NV215 or EX112 depending on the room.

    If your bass has smokin' tone, why bother with preamp tone. at least IMHO & YMMV. I can cut/boost @ the bass for a boomy room... plus the FoH guy has the floor anyway. I just need to sound like me on stage and hope he does me justice.
  14. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    I've done this many times, in various different ways. There's kinda two issues, one being the EQ, and the other being the volume.

    For EQ, it's pretty much whatever's coming out of your pickups, subject to the loading issue that JMX mentioned. I haven't had too many problems with pickup loading, most solid state power amps are upwards of 10k input impedance, and tube amps are usually much higher than that. Many passive pickups end up in the 10k to 20k range.

    For volume, I've used a cheap $5 circuit to get a little bit of a boost prior to feeding the power amp. No EQ, just a little gain. That works fine. If you have an active bass, you might not even have to worry about that, for instance my Roscoe puts out almost 6 volts p-p at full volume, which is more than enough to drive a power amp to full output. But many passives only end up in the 100 mV range, which isn't quite enough. But any of the gain-booster outboard pedals will work, like maybe a blue tube or something like that. Some of 'em even have EQ.

    With "most" pickups, the EQ had been a much bigger issue that the volume. The old passive pickups especially sound thin and lifeless without EQ. They're made to be boosted in the lows and upper mids. The same is most definitely not true of Alembic AXY's for instance, which are so rich that the only way to EQ them properly is to subtract out the stuff you don't want. But, some pickups sound just perfect the way they are, completely flat, and those are the ones that'll work best straight-through into a power amp.