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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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sailor
Fstein
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    Sloppy Bass

    Fstein
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    Fstein


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    • Post n°1

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    Post by Fstein Fri Mar 22, 2013 7:08 pm

    Have a basically stock pr of Mk 3's(mild parts upgrades eg solen caps) into Klipsch Cornwall 2's. Tubes are EH 6550's biased at 120.
    My bass is s-l-o-w and flabby. Heard a 16 watt EL84 Leben CS300 that in terms of grip blew them away.
    Will the VTA board correct this or am I banging my head against a wall of 50 year old design?
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    sailor
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    Post by sailor Fri Mar 22, 2013 7:58 pm

    Can't comment on the board change but it could also be your preamp. Many tube preamps are very tubbee, mellow, and slow.
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    Fstein
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    Post by Fstein Fri Mar 22, 2013 8:22 pm

    SS preamp, noted for its speed
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    sailor
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    Post by sailor Fri Mar 22, 2013 8:35 pm

    Yup, not the preamp. I had a set of Mark III back in the late 70's I didn't remember them being sloppy in the bass. I originally used them on a pair of speakers I designed and built and later a pair of Magnepan MGII not known for tight bass to begin with. I would check the tolerance of the resistor, and if you have a capacitor checker check the paper caps on the board. Sorry I couldn't be more help.
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    Pillo69
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    Post by Pillo69 Fri Mar 22, 2013 8:46 pm

    The problem may be with the speakers, I had a Polk Audio monitors connected and I did not like the bass with my ST70, then connect a pionner HPM and sounds great.
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    Fstein
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    Post by Fstein Fri Mar 22, 2013 8:59 pm

    klipsch cornwall 2's 98 db efficient
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    j beede
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    Post by j beede Fri Mar 22, 2013 10:13 pm

    You might try running a CD player straight into your Mk III to determine what contribution--good or ill--your preamp is making. To do this you need a CD player with variable output or an attenuator to insert between the CD output and Mk III input.

    Are the Mk III new to you or has their sound changed recently? FYI: My Mk III replaced a Threshold 400A and I never looked back.
    ...j
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    peterh
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    Post by peterh Sat Mar 23, 2013 4:55 am

    Fstein wrote:Have a basically stock pr of Mk 3's(mild parts upgrades eg solen caps) into Klipsch Cornwall 2's. Tubes are EH 6550's biased at 120.
    My bass is s-l-o-w and flabby. Heard a 16 watt EL84 Leben CS300 that in terms of grip blew them away.
    Will the VTA board correct this or am I banging my head against a wall of 50 year old design?

    what do you mean with "based at 120"

    How is this measured ? Is it a common cathode resistor ? Is it accurate ?

    If you suspect unsufficient damping, try the 4ohm output. Also make shure speaker cables
    are large enought ( and not too long)
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    Bob Latino
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    • Post n°9

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    Post by Bob Latino Sat Mar 23, 2013 7:35 am

    Fstein wrote:Have a basically stock pr of Mk 3's(mild parts upgrades eg solen caps) into Klipsch Cornwall 2's. Tubes are EH 6550's biased at 120.
    My bass is s-l-o-w and flabby. Heard a 16 watt EL84 Leben CS300 that in terms of grip blew them away.
    Will the VTA board correct this or am I banging my head against a wall of 50 year old design?

    The original Dynaco driver circuit be it the one on the original Dynaco ST-70 or the original Dynaco Mark III is known for "sloppy, wooly or one note bass". This effect is more pronounced when the amp is used with certain speakers. You have to remember that the original Dynaco tube amp driver circuits were designed to save money and not designed for best sound.

    I am sure if you pull and replace both driver boards on your two Mark III's with two of the VTA Mark III driver circuits, low bass response will improve dramatically. The bass will be tighter and more tuneful.

    Bob
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