Jet City Picovalve mod thread

Discussion in 'The Squawk Box' started by Dr.Distortion, Aug 27, 2013.

  1. Dr.Distortion

    Dr.Distortion V.I.P. Member

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    You know it's gonna' happen...
    With all of 'em gettin' scooped up in the last week.
    May as well start it early...

    I've heard using a 12AT7 in the pre amp and a 6550 will get you some headroom.

    Also the grid load resistor is missing from V2...

    More to follow.

    BTW I don't have mine yet... :)

    Update 12AU7 in V1 12AT7 in V2
     
  2. parts

    parts Senior Member

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  3. parts

    parts Senior Member

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    His ebay feedback on these kits is great.. I sent him a message to see if he is still offering. Maybe we can get group pricing if several are interested.
    eBay Feedback Profile for thorny64
     
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  4. parts

    parts Senior Member

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  5. Dr.Distortion

    Dr.Distortion V.I.P. Member

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    Hey Docc...

    Any chance of getting a bigger version of the schematic? I can't read the values on that one. I tried to zoom and it pixelated.
     
  6. parts

    parts Senior Member

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  7. slaveunit

    slaveunit Senior Member

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    Ill be watching this one. Thanks.

    Anyone know what the mod in the schemo changes?
     
  8. kfowler8

    kfowler8 Senior Member

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    Yeah that looks promising. Interested to hear what he says. Definitely interested in a group buy.
     
  9. kfowler8

    kfowler8 Senior Member

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    I mentioned this on the other thread. Apparently it's wired to drain the caps every time. That's a nice safety feature if you're going to mod. I'd still double check them.
     
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  10. PSH

    PSH Junior Member

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    I have had a Picovalve for a while now, got it for 150$ new, you guys got a killer deal for $99. A 12AT7 in V2 helps remove some of the mud (due to missing grid load resistor), a 12AU7 in V1 gives lots of clean headroom. I have used several power tubes, 6L6, 6V6, El34, and each offers something interesting tonally. The best drive tones are achieved using moderate preamp gain with a 12AU7, lots of master volume, and a OD pedal set as clean boost. My Metal Muff also sounds great in front of this amp for much heavier sounds. I run mine through the matching Jet City 1x12 Eminence cab.

    I enjoy this amp, it just takes some coaxing to get the best sounds. Preamp tubes are very important.
     
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  11. kfowler8

    kfowler8 Senior Member

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    FYI, I e-mailed Eurotubes about tube recommendations and here's what they said.

    Yes, these amps come stock with cheap Chinese tubes so the JJ’s will be a nice upgrade. The Pico Valves are clones of the THD Univalve and they can use quite an array of tubes:

    Here are the options for the power section:

    The standard EL34 is just like the old European EL34's. These are a bit soft with a shallower low end and a smooth breakup with a nice crunch.

    The JJ E34L's provide a deeper low end and are more aggressive and punchy than an EL34. The E34L is tighter with slightly more headroom and power with a more aggressive crunch.

    The JJ KT77's have even a bit more low end extension than the JJ E34L's and they have a nice sizzle in the top end that is not brittle. The clean tone is very fat and full and the crunch at loud volumes has more of a chunk to it and it's very punchy but not quite as aggressive as the E34L, a great tube for rhythm and solo work if you like the pushed mid and upper mid tone that all EL34 type tubes have.

    The JJ Big Bottle 6CA7 is as close as you can get to mixing a 6L6 with an EL34. The low end is big and round like a 6L6 and the mids are more like an EL34 but not quite as bright. These are great sounding tubes and especially nice if you're trying to tame down the highs and beef up the lows and low mids.

    So for a comparison the JJ 6L6GC's have a little more low end than the KT77's but are a cleaner tube with a later breakup and they are not as mid-range heavy. More of a traditional Fender type tone. The 6L6GC's are a better way to go if you scoop your mids to any degree and these are a great tube for heavy rhythm and or melodic drop tuned Metal. They will also give the fattest and most linear full spectrum sound of all the small bottle octal tubes which also makes them a great tube for anything from Rock to Jazz to Country.

    The JJ 6V6's at higher volumes are a little crunchier in the mid and upper mids but still have a very full tone and will drop the power down about 10 watts from the JJ 6L6GC's which still leaves plenty of volume.

    The JJ KT66’s are like a big 6L6 and very full sounding. They will breakup a little earlier in the mid and high end than a 6L6GC while staying together on the low end for longer. The KT66 is also more harmonically complex in the mid and high end which makes it a very sweet sounding tube.

    The JJ 6550's are a great sounding tube with a warm sparkly clean sound, and when overdriven they have a very raw and gritty breakup. These are great if you're trying to get a classic raunchy grind.

    The JJ KT88's provide more low end thump than the JJ 6550's or JJ 6L6GC's and are a little more like an E34L in the mids and highs. The 88's have a very aggressive and punchy tone that is FAT. It's kind of like a cross between a huge 6L6 on the bottom and a very big E34L in the mids and highs. If maximum power is the mission these are the tubes.



    There are also several options for the preamp section. JJ makes two main 12AX7 variants. The ECC83S (short plate) and the ECC803S (long plate).



    The ECC83S's have a very linear frequency response top to bottom. This gives them a very warm and round tone right out of the gate. They have a very thick tone when pushed into saturation but they still retain a lot of clarity and articulation. We can pick these out high gain as well if you want as much crunch and sustain as possible.



    The ECC803S has a distinct bump/emphasis in the upper mids and a bit more natural presence/chime in the highs. They also have a slightly cleaner overall character with more of a classic crunch.



    If you’re looking to reduce a little gain the JJ 5751’s are a great choice. They are 20-30% lower in gain than a 12AX7/ECC83 but they retain a warm, round tone.



    JJ also does a gold pin version of the aforementioned tubes. Overall the gold pin versions have a smoother tone with a bit less grit and a very creamy overdriven tone.
     
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  12. Who

    Who are you? Who who who who.... Premium Member

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    When mine comes in, I'm going to pop this open, and see if there's anything worth stealing from back there:
    [​IMG] [​IMG]
     
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  13. parts

    parts Senior Member

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    Got the email back from thorny (the mod guy). He put the kits back up on ebay.. I told him about us all grabbing these so they are now available again..
    And..Price dropped to $59

    http://www.ebay.com/itm/Jet-City-Picovalve-amp-mod-by-River-City-Amps/271266726090?ssPageName=WDVW&rd=1&ih=017&category=10171&cmd=ViewItem
    "Now there is no excuse not to improve your Jet Citypicovalve amp.

    You know who you are, youbought the thing because it is a great deal – it just does not sound good stock."


    Don't sell the amp off cheap! You'd be missing out because this isa well-made amp that has a lot of potential. Install River City Amp's mod.

    - It will make it brighter, punchier, much less muddy

    - Improved clean headroom when roll back volume

    - Distorted tone is clearer, you can still hear all the notes

    - Sounds like a 6w “modded British stack!”

    - Reduces some of that nasty POP sound when you throw thestandby switch

    - Operates like it should, all stock controls, no unsightlyadd-on switches or holes in amp. It doesn't look hacked when you are done. I just works a whole lot better! No drilling holes and mounting switches or unsightly externally visible parts.

    - EZ to install, simple instructions, with pictures andparts - don't have to read a schematic

    - if you can install a pickup, you probably can install this– got to have the equipment and know how to solder and follow some safety rules. I have made it as easy as possible.

    - Includes recommendations for tubes to try out as well (soyou start at a good point and don't waste your money).

    - The amp canreally sound good – even with cheap currently made tubes.


    If you want your amp to sound like it should have in thefirst place, buy and install this simple and cheap mod. Lotsof people already installed, lots of great reviews.


     
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  14. kfowler8

    kfowler8 Senior Member

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    Great!!! Looks like a really viable option. Let me know if anyone orders one.
     
  15. slaveunit

    slaveunit Senior Member

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    They are $10 cheaper from him over at the gear page.
     
  16. twilliams

    twilliams Senior Member

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    Can you be more specific, like which forum or what his user name is there?
     
  17. theaxeman

    theaxeman Senior Member

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    Here you go! :cool:
    thorny64
     
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  18. Dr.Distortion

    Dr.Distortion V.I.P. Member

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  19. Dr.Distortion

    Dr.Distortion V.I.P. Member

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    Mine is sitting at UPS about 9 miles from my place. I'll have it tomorrow... :thumb:
     
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  20. parts

    parts Senior Member

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    Scheduled Delivery Updated To:
    Friday, 08/30/2013, By End of Day

    Last Location:
    Salt Lake City, UT, United States, Wednesday, 08/28/2013
     
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