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Bridged PA amp - gobs of power

Discussion in 'Amps and Cabs [BG]' started by coyote1, Oct 26, 2019.

  1. coyote1


    Mar 23, 2012
    I’ve been running a Hartke HA2000 into a pair of 4x10s, one an old Peavey and the other an Ashdown 410T. It works wonderfully for 4-string basses, but the low B is less than optimal.

    I have some old Samson S1000 power amps sitting around from back in the day.... I have bridged an S1000, and am using that (1090 watts) to power the Ashdown. The Peavey cab is getting the Hartke’s full 120 watts. I tried it using the S1000’s parallel mode to power both speakers, and it’s great that way too.

    It’s making a difference in the reproduction of the low-B string, as well as everything else. Ideally cabinets that could get down to 30 hz (like the new Ashdown Neo) would make it even better, but for now and the near future this will suffice.

    Btw, I love those old Hartke bass amps. Tube and SS input gain, compression, low and high pass filters, 10-band EQ with the lowest band centered at 30hz.... very flexible.
    Last edited: Oct 26, 2019
  2. BassmanPaul

    BassmanPaul Inactive

    Is there a question in there somewhere? :)

    Edit: Be careful that you don’t roast your Ashdown with all the power you have released. If a cabinet isn’t capable of reproducing low frequencies trying to force it to do so by adding more and more power is not going to end well.
    Bill Whitehurst and S-Bigbottom like this.
  3. Stumbo

    Stumbo Guest

    Feb 11, 2008
    Try running the high pass at around 55-60hz.
  4. coyote1


    Mar 23, 2012
    Fortunately, the Hartke not only has the adjustable highpass contour filter control but also a rear panel switch to knock back the subharmonics. If I feel I’m endangering the cabinet, i’ll go back to parallel mode. That will have just the Samson powering both cabs, at 340 watts per cabinet. They can handle that.

    But different power amps have different characteristics, so I want to run both the Samson and the Hartke.
    (Edit) Also - stupid as this sounds, I feel kinda ‘guilty’ not utilizing the power amp section of the Hartke lol
    Last edited: Oct 26, 2019
  5. BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    What is the Preamp for the power amp?

    Wondering if the pre made the difference.
    Or if the effect send is before the highpass
  6. coyote1


    Mar 23, 2012
    Damn good question, and it forced me to search for the manual with the block diagram.
    The send is before all tone controls. This explains why there’s a significant difference between the sounds from the two amps.

    Looks like I’ll probably be reverting to stereo mode on the power amp, and using just one channel. That’s 340 watts, and the Ashdown can definitely handle that.

    EDIT: The Hartke with its tone-shaping is now running into the Ashdown, which is the top speaker in the stack and has a tweeter. The S1000 power amp is going into the Peavey, which is on the bottom and has no tweeter. The sound is big and loud and solid, and even the low B is not farting out.

    Thanks to BogeyBass for spurring me to think it through a bit better.
    Last edited: Oct 26, 2019
  7. BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    Its alot less stress on the amplifier to not use bridge mode.

    in bridge mode or floating ouput the amplifier only sees half the impedance for each amp on a floating load.

    Meaning a 8 ohm load is like 4 ohms for each amplifier

    and a 4 ohm load would appear to be 2 ohms for each amplifier.

    a 4 ohm load which im guessing 2 4x10s yeild would be 1.6 ohm murder sentence
    depending on the impedance curve, things can dip slightly below nominal, specially a ported cab

    Either way it is alot more stresss and heat.

    ive used a 810 for long long time now. never really needed more than 200/300 watts for very loud bands.

    the extra ooomphhh your hearing most likely yes was not the extra power, it was bypassing the frequency limits of the amplifier.
    Ive seen some Hartke schematics and they appear to use a 18 dB high pass. how high its set im not sure, never calculated it.
    Either way its pretty smart simple and effective how it was done

    ive had even older 200 watt Hartke amps and they were thunder with a 810.
    and with just a stright forward tone control and multi band EQ options. the amps were actually rather nice.

    for the most part thermal may be higher, but typical 4x10 is about 280 to 330 watts before actual fart out.
    definitively have plenty of power
    Last edited: Oct 26, 2019
  8. coyote1


    Mar 23, 2012
    So we just finished our session in my basement studio. Four songs:
    Larks’ Tongues In Aspic 2
    Wichita Lineman
    Minstrel In The Gallery
    Come Together

    I’m playing drums in this group, my bassist and guitarist are fantastic.

    The bass amp configuration sounds incredible. As stated earlier, the Hartke is feeding 120w into the Ashdown (top cab w/ horn) and one channel on the Samson is feeding 340w into the Peavey. EQ on the Hartke is set up with only cuts, no boosts. Both Hartke preamps running, compression around 5. The Samson amp is being fed by the (post-comp, pre-EQ) Hartke effects send.

    The comp and cuts keep down the overall volume, so it’s only slightly louder to the ear than before. But it’s very noticeably more **solid**, with thick clear luscious low end while the mids and highs still shine.

    While I would perhaps someday like to upgrade the bass rig, given how great it (as well as the rest of the studio) sounded tonight I’m not going to be in a hurry. I’ve found my bass rig, and not had to spend an extra dime to do it.
  9. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

    Feb 27, 2021

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