Jet City Picovalve mod thread

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

  1. twilliams

    twilliams Senior Member

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    I followed this thread in the beginning but got tied up with other things, I am at a point where I want to try some of these mods and wondered about components. What type of resistors and caps are you using? I have a ton of 1/4w 10% resistors and a pretty good assortment of plain old ceramic caps but are you guys using 1/2w 1% resistors and higher end caps?
     
  2. Meniketti 5150

    Meniketti 5150 Junior Member

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    Hi all, I bought the Picovalve back in Jan this year for £119, have carried out the River City mod, and have rolled tubes.. Finally ending up with;
    V1- Tung Sol 12ax7
    V2- JJ 12at7
    V3- Gold Lion Kt66 (amazing valve)

    I've got a number of questions for you experts here-
    Firstly, should I carry out the additional grid leak mod on V2 pin 2 with a 1M ohm resistor- if so what benefit will I see?
    Or would wiring in a 680k resistor give me more if that classic hotrodded Marshall tone.

    Next, I have read with interest and ordered the ECC823 dual triode valve to pop into V1... I've understood the basics here- would the grid leak make any difference coupled with this valve swap.

    Ultimately I'm looking to be able to have the gain wound up/ amp volume maxed and use the guitar volume to go from cleanish to crunch without the dialed back signal becoming too boomy or indistinct.

    Lastly, I have two EL34's which been in and out of the Pico' a Ruby 34STR and a Svetlana 34. The Ruby works great, but the Svet sounds as though it's not working properly when the vol. is wound past 7. It's fine on the 2watt setting at full, but 5watts I get this horrible shorting buzzy tone on the note attack. I have 4 other Svet's in my Marshall 6100 head and all do the same in the Pico so I know it's definitely not a faulty Svet.... Any ideas?

    Thanks for your help with the above and in a great thread!
    Barry
     
  3. coldharbor

    coldharbor Junior Member

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    Hello. I have been following this thread from the beginning and finally decided to jump in and mod my Pico valve. I installed the River City mod kit and the V2 resistor mod, just finished today. Turned it on, no smoke. Everything looks good. One problem. I have a hum which increase's as I turn up the preamp, from about 5 up it gets progressively louder. Any suggestions on what I did that caused this and how do I get rid to it? I don't know anything about electrical circuits, I just followed the instructions provided with the kit.Would appreciate any help or suggestions.
    Thanks
     
  4. Who

    Who Who is not here. Please leave a message.... Premium Member

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  5. tol

    tol Junior Member

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    hi! sorry to hear about the humming. Did you have much humming prior to the mod?

    Are you using the same tubes? Maybe swap V1 and V2. Sometimes hum and noise will be less after 5-10 minutes. Once the amp is warmed up.

    The amp was pretty dark in tone stock. The mid scoop can sound quieter(less hum). So what you may be hearing as hum could be the increase in mids.

    a track could have been lifted when removing the old parts.

    sorry these are just guesses. Humming drives me nuts too.
     
  6. shendey

    shendey Junior Member

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    I'm not sure if this is the right place to ask but you guys seem to be more knowledgeable about these than anyone else. Is it possible to plug headphones into these? They are 38 ohms. I prefer to play with headphones on at night to keep the peace and I ordered it before I realized it didn't have a headphone jack. Any help is greatly appreciated.
     
  7. Who

    Who Who is not here. Please leave a message.... Premium Member

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    Don't plug in headphones. It won't go well for them or your ears (and could be a problem for the amp, as well).

    This would help you, but adds $80 to your cost:
    https://taweber.powweb.com/weber/hpa50.htm

    For that kind of $, I'd just get an amp-sim (like a Line 6 pocket pod).


    Alternatively, return the Pico, and get an Orange Micro Terror.
     
  8. drob

    drob Junior Member

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    I picked up one of these recently, and joined the site so I could take advantage of the best thread on these amps. I have played with a few different pre tubes and have a question about V2. What's it for? I know some people were stating an AT7 cleans it up a bit, and can help if you don't have the grid resistor fixed. Why does a the AT7 help? I currently have a 5751 in V1, and a 12AY7 in V2 along with a TAD 6L6WGC. I know a few people have the opposite - AY7 in V1 and 5751 in V2. I personally think anything below a 5751 in a V1 slot makes an amp a little sterile. I also tend to favour AY7's over AT7's. This combo retains it's character, while giving a much broader sweep to the Tone controls. Well that's what I currently think. Happy to hear other opinions on my tube selection.
     
  9. shendey

    shendey Junior Member

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    Thanks! That's exactly what I wanted to know and pretty much what I thought I'd hear.
     
  10. rhythmtech

    rhythmtech Junior Member

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    Here I am using V1: 12AX7 V2:12AX7 and a 6L6
    Picovalve Modded for sale - YouTube

    If you massage the gain stages some you can get it to be more reactive.
     
  11. lunchie

    lunchie Senior Member

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    I don't plan on modding mine however here is the tubes I am using.

    TAD 6L6WCG-STR
    V1 - NOS GE 12AU7
    V2 - NOS Westinghouse 12AT7

    Cab - Fender Hot Rod Deluxe Extension Cab loaded with a WGS G12Q

    Guitar - Squier Vintage Modified Thinline w/ Bill Lawrence Keystones and a 4 way.

    Bright Channel
    Preamp 6
    Treble 8
    Mid 6
    Bass 6
    Volume 8
    Bright Channel

    Very Fenderish setup. Nice bright sparkly treble, a bit of a scooped midrange, smooth and snappy low end. Stays pretty clean with a bit of nice grit when pushed hard.

    With the Vox 112NT cab not too much difference with the treble or bass but a definite mid range boost with the greenback. I prefer the scooped mids of the WGS though with this particular set-up.

    With the dark channel, same outcome however erm darker sounding. I much prefer the bright channel.

    I'm going to play around with this combo for a while, I really wanted to keep this amp fairly clean and I got it where I want it. If I do get bored with it, I may load a 6v6 and a couple 12AX7's and see how it sounds with higher gain.
     
  12. rabinnh

    rabinnh Junior Member

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    Old thread but just wanted to say that I implemented duhvoodooman's resister mod and it was the most simplest, most effective mod possible. I love experimenting with tubes in the Pico, and after the mod I changed out the following:

    EL84 (with adapter)
    EL34
    6550
    6L6
    KT66

    I left it the bright switch in. All sounded better with more clarity. The KT66 actually sounded a bit too harsh, which was interesting. Before the mod I was running the EL84, but after the mod I decided that the 6550 was the best sounding.

    I am away for the weekend with the amp and only one guitar, a Les Paul Special with Gibson P90s. Can't wait to get home and try my 1994 Standard with humbuckers. Even more my favorite; 2011 Les Paul Traditional with BK Mississippi Queens. And just to round things out I'll plug in a 2000 American Standard Strat with a Rio Grande Big Top set.
     
  13. PSH

    PSH Junior Member

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    Tube update for picovalve:

    I found a pair of 1960s or 70s GE 6L6 GC at work in an old power supply, holy sh!t does this power tube wake this amp up. Makes it very bright (which I didn't think was possible) and crisp. Higher gain sounds are very 80s sounding hot rodded tones when pushed with pedals. Current preamp tubes are JJ 5751 in V1 and JJ 12AT7 in V2.
     
  14. Dr.Distortion

    Dr.Distortion V.I.P. Member

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    After a year wait, I finally modified my buddy's amp.
    He bought one the same time I did and never took it outta' the box.

    He works in a electronics lab, (doing IT work) so we went there and used one of the benches.

    We did only 2 things. The grid leak and the V1 bypass cap. We used a .68uf

    I had a chance to hear them side by side. (mine with the mods his not)
    Defiantly all around clearer and not mushy on the bass notes.

    Set it up so there was both clean and grind tones to be had at bedroom levels.

    All tubes were NOS JAN. A 12AU7 in V1 12AT7 in V2 and 6V6GT for the power...

    Total $99 + $1.30 in parts and $23.00 for tubes... $123.30
     
  15. wagdog

    wagdog Member

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    Hi Guys,

    Been a while. I finally dragged this amp out for a make over. Here's a video of it now - MUCH improved. The main change was removing the cathode follower and reconfiguring that stage to be a recovery stage for the tone stack. This involved cutting traces and rerouting things - not recommended unless you know what you're doing.

    https://www.youtube.com/watch?v=YBMu8pwgqM0

    I've updated my site with a description and schematic: http://wagner-usa.net/picovalvemods/
     

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