NAD - Jet City JCA22H

Discussion in 'Other Amps' started by USAPatriot, Jan 31, 2015.

  1. USAPatriot

    USAPatriot New Member

    Joined:
    Mar 22, 2014
    Messages:
    1,876
    Likes Received:
    1,315
    I couldn't pass this up at $279! I keep an eye of the CL ads here in Texas and it's virtually impossible to get even a used tube amp for under $300, so at $120 off, this was a steal, brand new from Musician's Friend as one of their "Stupid Deal of the Day" sales.

    I cracked it open, replaced the chinese tubes in V1 and V2 with Marshall branded 12AX7's then rigged up a speaker cable so I could hook up my loose 70/80 to check the PV and bias. The PV was settled in at 340V after 30 minutes while the bias was a very chilly 16.6mv, which I boosted up to 24.1mv. Jet City changed the vertical variable resistor design so it can only be adjusted from inside the device versus the old style where you could move it with a thumbnail. The tolex is also black, which surprised me. My original JCA22H from late 2011 or early 2012 was blue. I think the black suits it better. Also, in the original version, I could check the bias by putting my probes on the solder joints where the 2 purple wires attach to the PCB (and labeled "bias"). Or I could use the TP (test point) below and between V6 and V7. Neither method works anymore. I had to put my probes on R52 to get a direct reading in mV. According to the Weber Bias Calculator, I'm getting 7W per tube, which are chinese EL84's. I have a spare set of EH's but they won't be much better.

    These amps aren't the bee's knees, but they aren't awful either, in fact, they are quite good. With no reverb on board they can sound a little sterile and the chinese preamp tubes aren't the best choice. Had I thought about it I would have added another Marshall tube in the PI slot, or maybe a JJ or Tungsol. I spaced it and closed it up with the chinese tubes still populating V3, 4 and 5.

    I don't have a cab to run this through so will have to piggyback it on top of my DSL40C and use it's speaker, which is on the agenda for tomorrow.

    Question! Can I simply attach a second set of leads to the terminals on the V-30 in my 40C's cab and just switch back and forth as needed? Or leave them both plugged in? I obviously won't try to run them both at once! -Rod-

    [​IMG]
    Check the bias at the pink resistor!
    [​IMG]
    Porno!
    [​IMG]
     
  2. jcm800gridlock

    jcm800gridlock Well-Known Member

    Joined:
    May 16, 2010
    Messages:
    1,947
    Likes Received:
    2,570
    Location:
    Tampa, Fl. USA
    Congrats, looks like a nice amp for the money.

    ******************************************
    Not sure about your idea.

    I think the better method is just to extend the speaker wire (and the 1/4 speaker plug) from the speaker to about two feet long so that it will reach the head.

    I once did this to one of my combos so that I could run a small head or an attenuator through it. It worked really well and cost was minimal and would be cleaner than a second lead.
     
    USAPatriot likes this.
  3. USAPatriot

    USAPatriot New Member

    Joined:
    Mar 22, 2014
    Messages:
    1,876
    Likes Received:
    1,315
    Thanks. Yeah, I cut one plug off of an old 3' speaker cable and soldered the ends to my 70/80 so I'd have a speaker load. I could buy some blade connectors or just solder them to my V30. It'd be plenty long enough. -Rod-
     
    jcm800gridlock likes this.
  4. Ghostman

    Ghostman Well-Known Member

    Joined:
    Jan 29, 2012
    Messages:
    10,321
    Likes Received:
    10,027
    Location:
    Hopehouse, Selkirk, UK
    I'd love to get one of these and then send it to BFG Amplification out of Oregon. He can turn these guys into beasts!
     
    HOT TUBES 70 likes this.
  5. Rocktane

    Rocktane Well-Known Member

    Joined:
    Apr 15, 2012
    Messages:
    1,534
    Likes Received:
    1,133
    Location:
    Grimmlandia
    I had a BFG modded 22H and it was an ass kicker! I had to sell it for reasons that had nothing to do with the amp. You would not be disappointed if you get one from Brian.
     
  6. USAPatriot

    USAPatriot New Member

    Joined:
    Mar 22, 2014
    Messages:
    1,876
    Likes Received:
    1,315
    I don't think you need to send one. Last I saw he was selling them already modded. As of a few years ago it was about $550 I think. -Rod-
     
  7. Pat6969

    Pat6969 Active Member

    Joined:
    Apr 21, 2014
    Messages:
    274
    Likes Received:
    110
    Location:
    Canada
    Rocktane, USAPatriot and Ghostman like this.
  8. alhayesmusic

    alhayesmusic New Member

    Joined:
    Jan 2, 2013
    Messages:
    1,644
    Likes Received:
    1,009
    Location:
    Houston, TX
    Great find! I'm in Houston, we may have to jam!
     
  9. HOT TUBES 70

    HOT TUBES 70 Well-Known Member

    Joined:
    Oct 13, 2008
    Messages:
    11,285
    Likes Received:
    5,850
    Location:
    The frozen hell called Canada !
    I had contacted the guy who once owned this head you see in the video about it , and was i thinking of buying this very amp as he had it for sale on the Guitars Canada forum , but it was too late , it was already sold a few days before i inquired .
    Sounds pretty good !



    [ame]http://www.youtube.com/watch?v=cWtDDnhsCgI[/ame]
     
  10. USAPatriot

    USAPatriot New Member

    Joined:
    Mar 22, 2014
    Messages:
    1,876
    Likes Received:
    1,315
    I broke down and ordered a single 1x12 JCA2S+ cab for the amp, new, for $139. As I recall I paid $229 apiece for my old pair that did not have the pass thru when I bought my previous head. I don't have a cab to put my 70/80 in, the 70/80 isn't that great and I really didn't want to share the V30 in my DSL40C with this head.
    Contrary to what some people think, a lot can be done with EL-84 based amps, at least when Mike Soldano designs them. You'd not mistake one of these for a small Fender, for sure. -Rod-
     
  11. HOT TUBES 70

    HOT TUBES 70 Well-Known Member

    Joined:
    Oct 13, 2008
    Messages:
    11,285
    Likes Received:
    5,850
    Location:
    The frozen hell called Canada !
    These could run a 2x12 loaded with my fav G12H30's !!!
    I bet it would sound killer ...
     
    USAPatriot likes this.
  12. Pat6969

    Pat6969 Active Member

    Joined:
    Apr 21, 2014
    Messages:
    274
    Likes Received:
    110
    Location:
    Canada

    LOL, I bought it!! Can't wait to try it! That's the link in my post above yours.
     
    USAPatriot and HOT TUBES 70 like this.
  13. stilllifer

    stilllifer Active Member

    Joined:
    Jan 2, 2013
    Messages:
    560
    Likes Received:
    241
    Location:
    Somewhere in Time
    Awesome - I had a JCA20H original and it was great. If these amps still run EL-84's, I would put some vintage Mullards in there...it made mine sound so much better!!! I actually miss mine a lot...:ugh:
     
    USAPatriot likes this.
  14. USAPatriot

    USAPatriot New Member

    Joined:
    Mar 22, 2014
    Messages:
    1,876
    Likes Received:
    1,315
    Well, I AM BAFFLED!

    My new cab arrived today so I was able to try out my new 22H. I found that on the OD channel there was a lot of noise with the preamp pushed past 2. My old one never had this much noise. I contacted Robert Perales and he said it sounded like a preamp problem...possibly, we'll see after I roll some tubes, but he also said that factory specs were to have the bias at 16mv. When I first got the amp I checked the PV and got 340v and doing the math, that works out to 24mV on the bias, which s what I adjusted it to. I just don't see how they come up with 16mV as the bias, though it's worth noting that you can't bias each power tube individually. When you tweak the bias, you are tweaking the pair of EL-84's. I'm not sure how this works and do not know how it figures in as far as the factory spec being 16mV for 340VAC as the PV at each Pin3. Maybe someone can clue me in? Anyhow, tonight I'm going to drop it back to ~16 and see if my noise problem goes away. I know that a gain stage is going to have some noise...it's a fact of life, but there was just too much noise here. On the crunch channel the noise level is about 1/3 of that of the OD channel. Any thoughts? -Rod-
     
  15. USAPatriot

    USAPatriot New Member

    Joined:
    Mar 22, 2014
    Messages:
    1,876
    Likes Received:
    1,315
    Last night I also removed the Marshall 12AX7's that I'd put in V1 and V2 and that was definitely the right move. I was a little irritated at how much treble I was getting with the Marshall tubes, so put the stock chinese tubes back in and replaced the aluminum shields. I did put one of the Marshall's in the PI slot, which is not a shared tube. It's a PI and only a PI and the difference was amazing. It's got a hellofa growl to it and nice harmonics, but the OD channel still seems overly noisy at idle. I can't really turn the OD up past 2 without the noise being an irritation. My previous 22H didn't have this severe of an issue. Robert Perales is telling me to roll the other 3 preamp tubes to see if it makes any difference. I also asked him why the factory specs for the bias should be so low...16mV...when the plate voltage is 377 (as of last night). That's measured both at pin 3 and across pins 3 and 7. It's identical. I've asked them for any documentation they might have that might answer some questions -Rod-
     
  16. USAPatriot

    USAPatriot New Member

    Joined:
    Mar 22, 2014
    Messages:
    1,876
    Likes Received:
    1,315
    I spent hours tweaking and rolling tubes. One JJ from 2003 in V3 gave it a really nice tone but the note definition just stunk and made things muddy. Right now the stock tubes are in V1 and V2, I've got Marshalls in V3 and V4 and a Tungsol in the PI slot. That one will probably change tomorrow. Dunno why but I've just not liked Tungsols in the 22H's. In fact, the retrovalves did better IMO. I've got some other china tubes (different from the ones that came stock in this) that I could still try. It was easier to just leave like this while I tinkered with it. -Rod-

    [​IMG]
     
  17. USAPatriot

    USAPatriot New Member

    Joined:
    Mar 22, 2014
    Messages:
    1,876
    Likes Received:
    1,315
    Well, I found an interesting solution to my OD noise problem. I'd rolled every glass tube I had and finally concentrated on the PI, with limited success. I got frustrated and tossed a low gain retrovalve into the PI and there was a near blissful silence, even with the gain up at 5. And I really couldn't tell any negative effects on the tone. I was pleased! For grins and giggles I pulled the clean one out and put in a red (high gain) retrovalve and that was even better! Not as quiet but still far better than any of the glass I'd tried and the only change in tone was it being a little bit throatier, which I liked. After about 20 minutes the amp must have deemed itself properly warmed up as there was a very quick change in character. The OD was less buzzsaw and more small block chevy, which was really cool to experience. The amp still has less than about 3 hours on it so some components and the speaker are still settling in. I'm liking it, but it may take awhile to warm up properly every night. We'll see. -Rod-
     
    solarburnDSL50 and Rocktane like this.

Share This Page