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    Pre Amp Tubes

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    papa_moz

    Posts : 5
    Join date : 2017-01-17

    Pre Amp Tubes

    Post by papa_moz on Tue Jan 17, 2017 9:20 am

    Recently purchased a GM40 Deluxe. In general, loving the tone and versatility. Looking to swap tubes but can not locate any info/schematic that specifies which Preamp tube is V1, 2, 3. Looking from the front, are they left to right or right to left?

    I've plenty of experience swapping tubes but Ive always been able to locate a schematic, except for this amp.

    Thanks for any help
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    gravydb

    Posts : 193
    Join date : 2014-06-22
    Location : PA

    Re: Pre Amp Tubes

    Post by gravydb on Tue Jan 17, 2017 9:31 am

    Hey papa.
    Looking at the front of the amp, the tubes are ordered from right to left. Meaning, V1 is the one that's closest to the input jack.

    Enjoy, and let us know how it goes with the tube swapping !
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    papa_moz

    Posts : 5
    Join date : 2017-01-17

    Re: Pre Amp Tubes

    Post by papa_moz on Tue Jan 17, 2017 9:34 am

    Thanks. I thought so but I didn't want to assume.

    Replacing with a set of JJ's, Will post as soon as they arrive and have been put through their paces.
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    gravydb

    Posts : 193
    Join date : 2014-06-22
    Location : PA

    Re: Pre Amp Tubes

    Post by gravydb on Tue Jan 17, 2017 9:47 am

    I have JJ's in my GM36, preamp and poweramp tubes.

    Yeah keep us posted!!!
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    papa_moz

    Posts : 5
    Join date : 2017-01-17

    Re: Pre Amp Tubes

    Post by papa_moz on Tue Jan 24, 2017 10:02 pm

    Dropped in the JJ tubes today and put it through its paces. Here are some observations:

    1- The overall gain structure is much clearer. That fizziness is all gone.
    2- I think its actually less noisy at higher gain settings than the stock tubes.
    3- The boost option still doesn't do much for me except on the clean channel or the crunch channel with low gain dialed in. On lead and ultra it just seems to add volume and a some harsh high end. I get much better results with a EHX East River Drive set like a TS and a Soul Food for lead boost.
    4- Did loose some of the headroom on the clean channel but not enough to really matter. Can still get a nice chimey clean - jsut need to keep the gain around 9 and adjust the volume to keep it balanced with the other channels.
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    j200george

    Posts : 84
    Join date : 2016-09-27

    Re: Pre Amp Tubes

    Post by j200george on Wed Jan 25, 2017 5:16 am

    Great news on the fizziness, though I would loathe to lose some headroom. My amplifier is headed back for replacement, on its return I will also look at getting some tubes ordered.
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    papa_moz

    Posts : 5
    Join date : 2017-01-17

    Re: Pre Amp Tubes

    Post by papa_moz on Wed Jan 25, 2017 8:14 am

    I think the headroom lost is a combination of the tubes and the fact that I am running at 5 watts so I can drive the master volume up to noon without waking the entire neighborhood. I suspect at the full 40 watts it wouldn't be an issue.

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