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Important Question about amp....Johnny where aire ye?

Discussion in 'Shock Brother's DIY Amps' started by garytelecastor, Aug 11, 2009.

  1. garytelecastor

    garytelecastor Poster Extraordinaire

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    I placed a Celestion Vintage 30 in my HRD that I just bought. I have been reading about different mods that can be done on this amp.
    One I read about was replacing the 12AX7 with a 12AT7 in V1.
    Will this do any harm to the amp?
    I know that I will lose some gain but are there any advantages?
    Johnny Crash where aire ye????? :D :D
     
  2. ibobunot

    ibobunot Poster Extraordinaire

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  3. jh45gun

    jh45gun Banned

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    Should be able to put in any 12a_7 variant tube in the amp only thing that should change is the gain.
     
  4. koen

    koen Friend of Leo's

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  5. teleamp

    teleamp Poster Extraordinaire

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    It will not hurt the amp at all, give it a try and see if it how it sounds.
     
  6. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    As mentioned, yes its safe.

    --

    Here's why. 12A*7 types are all dual triodes - two 3 component (ergo the "tri" in triode) tubes in one glass package.

    They all share the same pinouts (pins 1 and 6 are the plates, pins 3 and 8 are the cathodes, pins 2 and 7 are the grids), and they're all built for 12 volt heaters (but we run them with 6 volts since pin 9 is a center tap).

    While they all have different amounts of gain, most of their specs from datasheets are similar. Plate voltages top out at 250 or 300 (sometimes 12AX7 in the phase inverter or tonestack are run to near 250 volts).

    --

    As far as sound, you may, or may not like the tone. Dropping gain on a MV amp in a variety of preamp spots, PI, etc (V1's first half is the pre, second half feeds the tonestack - V3 is the phase inverter) might make for less preamp drive, but it will also change the sound.

    If its got a MV, why bother swapping tubes for gain purposes? Unless you're diming the pre and master and still want more clean.
     
  7. cousinpaul

    cousinpaul Friend of Leo's

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    I read some reviews on Harmony Central of the THD Yellow Jacket output tube converters (6L6 to cathode bias EL84). The HRD users all seemed pretty stoked. Might be something to check out.
     
  8. garytelecastor

    garytelecastor Poster Extraordinaire

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    Thank you all so very much. I truly appreciate it.
    I didn't want to do any damage to the amp, and Johnny thanks for the understanding.
     
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