Monoprice 15 watt tube amp

Discussion in 'Glowing Bottle Tube Amp Forum' started by here4thefall, Jan 25, 2016.

  1. Joe M

    Joe M Super Moderator Staff Member

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    Noticed in your comparison that you had the reverb on 5 with the original tank and 7 with the new tank. Wouldn't that alone make some of the difference in sound??
     
  2. joe_cpwe

    joe_cpwe Tele-Holic Silver Supporter

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    As long as were talking along the lines of using USA made 5751 tubes and 12AX7s...I'll offer that I have 2 vintage RCA tubes that I have yet to bond with and will sell if someone wants.

    I do use vintage RCA & Sylvania 12AX7 in my Monoprice and other tube amps but a couple years ago, while rolling tubes, I got an RCA 5751, short black plate and an RCA 7025, short gray plate that I'll let go of.

    PM if interested.
     
  3. MuddyWolf

    MuddyWolf Tele-Meister

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    I tried various low gain 12ax7's and 5751 things in this amp awhile back. I found that i liked the 12ax7b's in all spots and just keep the pregain no higher than 3:00. Next time i have it open im going to cut the wire that is to the cold clipper bypass cap as described somewhere. If i hate it i can put it back.
     
  4. stellarelephant

    stellarelephant TDPRI Member

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    Somebody who has taken this amp apart before, can you advise which screws must be removed to free the chassis from the cab? So far I took out six; four from the top of the cab, and one out each side. Didn't loosen anything from inside the cabinet yet? What am I missing?
     
  5. stellarelephant

    stellarelephant TDPRI Member

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    Oh, I do have the back cover off, of course. Chassis won't budge so far.
     
  6. MuddyWolf

    MuddyWolf Tele-Meister

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    Its loose , its just stuck. You have to loosen the seal from the chassis pressed into the tolex.
     
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  7. stellarelephant

    stellarelephant TDPRI Member

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    Thanks, MuddyWolf. Lol, a mallet and putty knife did the trick. I've been playing it tonight with the bias set higher. I think I hear more clarity, but I will keep toying for a few days before I put it back together.

    Hi, Joe. I mentioned this in the YouTube video description. The MOD reverb tank on 7 gives approximately the same "wetness" as the stock tank on 5. I first recorded them both on 5, and the mismatch was obvious when I compared clips.
     
    Last edited: Oct 6, 2019
  8. Rick330man

    Rick330man Tele-Afflicted

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    Bias adjustment definitely makes a real difference in these amps. From the factory, the stock Shuguangs were running at about 43 and 45%, respectively. Setting them to 55% made a difference in tone for the better. The current set of 6P14P-EVs in there are set at 56 and 60%, respectively. B+ on my main Monoprice 15 is running at around 292 volts. At these values, these tubes should outlive me.
     
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  9. stellarelephant

    stellarelephant TDPRI Member

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    After playing for several hours, I am convinced that the sound is indeed improved by increasing the bias. I think I am happiest with it set far above the factory's 7.5V, and a bit below the Laney schematic value of 12.5V. I am surprised by how much the voltage drifts around as the amp comes on and warms up (in fact I am not sure if it ever settles completely), but mine seems to have found a sweet spot between 11.6V and 11.8V.
     
    Last edited: Oct 6, 2019
  10. backporchmusic

    backporchmusic Friend of Leo's

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    Agreed on bias, brought mine up from 7-8 to 12, sounds much better, warmer. Older version with knobs on top instead of the front.
     
  11. Midnight Rambler

    Midnight Rambler NEW MEMBER!

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  12. Midnight Rambler

    Midnight Rambler NEW MEMBER!

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    I have the 15 wat mono put 70 wat Jen mod 12" spkr new reverb tank , jj12ax jjel84 sounds great gonna put jj6L6 tubes in for more bottom end can't complain I have $400 into it an it does have the fender blues Jr sound an I use squier classic vibe butterscotch blonde tele and Mitchell ms 400 LP style honey burst with Ernie ball 2221 strings , no complaints
     
  13. MuddyWolf

    MuddyWolf Tele-Meister

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    You may know something i dont but i dont think you can put 6l6's in an el84 amp. Different tube base and pinout. I think youd have to rebuild the entire amp.
     
  14. Keefsdad

    Keefsdad Tele-Holic

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    Has the Blues Junior sound? Mine doesn't.
     
  15. MadJack

    MadJack Friend of Leo's

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    A few pages back, someone had the sonic profile (using a tone stack sim) that was similar to the BJ. Basically it's turn the mids down and the lows and highs up.
     
  16. Keefsdad

    Keefsdad Tele-Holic

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    Yeah, I set mine pretty much like that. It's a little more Fenderish, but still sounds more like a Marshall or Vox to my ears.
     
  17. MadJack

    MadJack Friend of Leo's

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    An "American" voiced speaker would probably get you closer to the BJ sound. Something in the Eminence Legend or Patriot line, Jensen Classic Ceramic, Weber Signature Ceramic, or WGS American Series should get the tone a bit closer.
     
  18. MuddyWolf

    MuddyWolf Tele-Meister

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    No offence to blues jrs but mine doesn't sound like one at any setting and I'm glad. These are essentially Marshall 2204's. Add a emi GB128 for a more american sound.
     
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  19. Keefsdad

    Keefsdad Tele-Holic

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    It probably would, but i'm pretty happy with the way it sounds. I might prefer Fender cleans a bit, but it sounds great overall. I was recently struck by how similar it sounds to an AC30 at the rehearsal space we use.
     
  20. TeleTex82

    TeleTex82 Friend of Leo's

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    There's one of these guys for sale locally for $149.00 might hop on it just for shizz and giggs.
     
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