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Carvin PB 300 at 2 ohms crapping out?

Discussion in 'Amps and Cabs [BG]' started by dgce, Oct 23, 2005.


  1. dgce

    dgce

    Jun 17, 2001
    Massachusetts, USA
    I have an old Carvin PB 300 head that I've had going into an old KMD 4x10 8 ohm cab for quite a while with no problems. The amp has been great. The Carvin rates at 150 watts at 8ohms, 200 watts at 4ohms, and the full 300 watts at 2ohms. I recently bought a 2x10 Avatar cab rated at 4ohms. According to Dave at Avatar, I'm getting like 2.7 (or something like this) ohm rating when I run both cabs together which is supposed to be safe for my Carvin amp. So I should be getting close to the full 300 watts with this set up. Eventually I plan to lose the crappy old KMD cab and buy a 2x12 Avatar rated at 4ohms so I can finally get the full 300 watts from my Carvin.

    Problem:

    When I play with both cabs hooked up, the Carvin sometimes shuts down on me in the middle of my gigs! This seems to happen whenever I crank the volume on my bass or when I really dig into the strings (which I do a lot). To fix this I reset the amp by quickly turning off the amp, then turn it back on, then I back off the volume knob on my bass and keep playing. Needless to say, this is not too cool in a live situation.

    What am I doing wrong? I basically have the Avatar going into one speaker jack and the KMD going into the other. It appears this is working the amp too hard and to protect itself, the Carvin shuts down the speakers. Sooooooooo, I thought I'd try daisy chaining the cabs. I could have the Carvin go into my Avatar 2x10 then have the Avatar go into the KMD 4x10. I can't really try this at full volume for another 2 weeks at the next band rehearsal (I don't dare attempt this at my apartment with my landlady living right over me!).

    Do you think daisy chaining will fix the problem? Why the heck am I having problems to begin with? I want to buy another 4ohm cab but I’m nervous that I’ll continue to have this problem. Help! Anybody!!!

    Thanks,

    r
    PS for the record, the Avatar cab is awesome.
     
  2. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA

    That probably won't help. Unless I miss my guess, daisy-chaining through the Avatar will just yield a parallel cab connection, exactly the same as what you have plugging both cabs into the head. And if you really did have one of the cabs rewired to allow a series connection, the total load to your amp would be 8+4, or 12 ohms. Not the best solution there either.

    When this is going on, does the head feel hot to the touch? Does it have adequate ventilation, or is it packed in an overstuffed rack? Do the fan and the vent slats have room to "breathe"? And, even though it's a stopgap solution, do you have an external fan that can be aimed at the head to move more air around it?

    Hate to have to mention this, but there are a lot of threads and reports of Carvin amps shutting down on thermal protection when connected to loads that they should be able to handle.

    Sounds like you might have to abandon the plan of connecting a 2-ohm load, if the head is tempermental at 2.7... or you might find yourself having to swap into another head to pull it off.
     
  3. dgce

    dgce

    Jun 17, 2001
    Massachusetts, USA
    Thanks for the info, Big. I heard from Dave at Avatar this a.m. and in theory, this set up I have with the 2 cabs should be fine. The head is solid state and it has an internal fan. It doesn't seem to be hot from what I can tell through the carpeted casing.

    For now, I'm stuck with my set up and will just have to keep my bass volume low when using both cabs. I can't return the Avatar for an 8ohm cab now as far as I know. For small and medium gigs as well as rehearsal for my 2nd band, the 2x10 alone is fine. But for my classic rock band and most of our gigs, I need both cabs. So what to do? I'm hoping Dave has another suggestion. otherwise, I guess I'll have to lose the Carvin head. I still want to get an Avatar 2x12 cab but now I'm not sure if I should order it as an 8ohm or 4ohm. Maybe Dave can work out a deal with me where I could return the 2x10 4ohm cab and buy a 2x12 and a reduced price 2x10 cab both rated at 8 ohms. I will not get the full 300 watts from my amp but at least the damn thing will work!

    If you or anyone has any other suggestions, do bring it up. I'm getting kinda desperate here.

    Thanks,

    r
     
  4. Luis Fabara

    Luis Fabara

    Aug 13, 2000
    Ecuador (South America)
    Audio Pro - Ecuador
    Ok.

    Lets help

    No. Daisy chain wont help. The cabs will still be electrically in Parallel so the impedance will be the same.

    The amp is overheating, thats why it shuts off. Thats tipical for a Carvin when they are pushed up to its published specs. (I have serviced many, used many, sold many.

    300 watts may be too little for your gig, and thats why you are pushing the head so hard.
    I would stick with the 2x10" at 4ohms and use it with that Head wich I believe they go well together.

    But I higly recommend, always having about 30% More power than your cabs can handle.. at 4 Ohms.
    Never believe the specs when rated at 2 Ohms, most of the time, the amps will run too hot, the headroom is decreased, and the damping factor is not good.

    Btw. Even if you hook up the cabinets in parallel. The cab at 4ohms receives more power than the cab at 8ohms. Thats something you should consider too.

    Also on note, resistance of a speaker isnt linear or absolute. It is nominal. so, while a cab says 4ohms, it really depends on what frequency it is reproducing. Keep the head safe at 4ohms.

    Recomendation: Buy a POWERFUL Head instead of better cabs.
     
  5. dgce

    dgce

    Jun 17, 2001
    Massachusetts, USA

    Thanks. Wow, had I only known this before I ordered the Avatar 2x10 in 4ohm format. Now I'm beyound the 14 day return date to Avatar. I think the 2x10 and 2x12 cabs both rated at 8ohms would be perfect for me. As for the 2x10 4ohm alone; its excellent with my 2nd, quieter band and rehearsals. But for my classic rock band, I want to move more air. This is a real bummer; now I have two cabs I can't use together and when I order a 2x12 cab from Avatar, even rated at 8ohms, I will not be able to use it with this current 2x10 4 ohm cab; not with this head and likely not with any other without running risk of cooking the amp. ugh!!!!
    r
     
  6. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA
    Well, hold on. That's not quite right.

    For openers, you said you have an "old" Carvin head. And the head is acting up when you give it a 2.7 ohm load, which it is supposed to be able to handle.

    Maybe that's not the best head to build your rig around, since it's getting up in years and is starting to exhibit problems.

    My suggestion: Proceed with acquiring your 4 ohm B212. I have one, and I think you'll be quite surprised at how good it can be on it's own, without the B210. It, along with the Carvin head, should suffice for most gigs. Of course, you can use the B210 alone for "quieter" applications, where you don't want to carry the larger cab.

    Then, as time permits, start saving a few dollars and prepare to phase out the Carvin. This thread should help:

    http://www.talkbass.com/forum/showthread.php?t=152454
     
  7. dgce

    dgce

    Jun 17, 2001
    Massachusetts, USA
    Thanks! Actually this is exactly what I planned to do after I found out it was too late to swap the 2x10 4ohm for an 8 ohm cab. Dave at Avatar had mentioned in the past when I wasn't sure if I wanted to order a 2x12 or 1x15 to marry to the 2x10 that the 2x12 is their best sounding stand alone unit. And I figured at 4ohms, that the 2x12 cab alone would do the trick and for smaller gigs and rehearsals, I'll continue to use the 2x10. Being able to use both together would be nice but there you are.

    As for the Carvin head; yes it’s old but it’s in surprisingly excellent condition. In fact up until this recent new cab business, the Carvin has been great. I bought it used maybe 3 years or so ago and it looked like an amp that someone kept in a box in the attic for the past 15 years. Even the old vinyl cover Carvin used to make was in brand new condition! But yr right, I shouldn't base everything on this head. So the short term plan is to purchase an Avatar 2x12 cab at 4ohms and gig with just one or the other cab depending on the size of the gig. But in the future if I keep gigging the way I am now with these two bands (it's been hopping!) I'll invest into a new (or at least newer) and more powerful head that I should be able to run at 2ohms if need be.

    Now I'm going to read this thread you sent over. I appreciate yr help.

    r
     
  8. dgce

    dgce

    Jun 17, 2001
    Massachusetts, USA
    Okay, I just checked out that thread. Very informative, especially the post from the person who has a SWR head with an Avatar 2x12 at 8ohms and an Avatar 1x12 at 4ohms (a mismatch not too far from my current set up). This person said he/she had not had any problems at all. Of course, this is a SWR head that I also presume is a bit younger than my budget Carvin.

    Speaking of Carvin, there is another option. If I bought a more recent biampable Carvin head, I could run each 4ohm cab to each amp (the 2x10 for the high and 2x12 for the low). This set up is supposed to sound awesome from what I've read. As far as I know, running 2 4ohm cabs in a biamp situation shouldn't be a problem, no?

    r
     
  9. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA
    That wouldn't be my choice of head..... I had a R600, and had problems with it...... but from an impedance standpoint, it would work fine.

    As long as you keep the PB300 as a backup..... ;)
     
  10. dgce

    dgce

    Jun 17, 2001
    Massachusetts, USA
    Bummer, that's what I had in mind. What problems did you have with it?

    Say, have you heard anything about Carvin's new B500 head (kid brother to the B1500)? I think Bassplayer had a review of this amp recently and I belive it was quite positive. Its not biamp-able but I dig its more streamline, basic approach compared to Carvin's more complicated Redline not to mention the B500's power.

    r
     
  11. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA
    Cutting out. Sound just disappeared for 2-3 seconds, then came back on again. Made it un-giggable. The PB200-15 I had did the same thing, at just about the same time. And, unfortunately, there are threads 'round here by other owners describing similar problems.

    I do hope the new line is an improvement. I've heard good reviews myself; hopefully the early-failure issues are resolved.

    As long as you keep the PB300 as a backup, ready to run into the B212 only in an emergency, you won't be caught in a jam.

    Another option might be to use the PB300's pre, and drive a separate power amp.
     
  12. dgce

    dgce

    Jun 17, 2001
    Massachusetts, USA
    Oh, I think the PB 300 going into the Avatar 2x12 alone will be fine. My asking about the Carvin Redline and B500 is just me planning for the future (dreaded gearhead disease). I don’t think it’s worth the fuss using the PB 300 for its preamp and getting an additional amp for the power; hell I might as well just flat out buy a new head considering what little money I paid for it. We’ll see down the road.

    Bummer about yr Carvin experiences. For years I was a Peavey man when back in the early 90s I took a chance and ordered the Carvin PB 300 as a combo (1x15 and a tweeter). I have to say that combo was the best sounding amp I'd ever had at that time and it never gave me a problem. Fast forward, I dropped out of the music thing for a while and got rid of a lot of equipment. However, when I started thinking about coming back in, I wanted to be frugal not knowing if I'd even score a gig so I looked into a used Carvin PB 300 combo. Well I found that head and I already had an old funky KMD 4x10 cab in the role of a coffee table. The Carvin was cheap, very clean, and I had experience with it. Like I said, up until this impedance issue with the 2 cabs, the amp has been great; a real gem on the cheap.

    So was I just lucky with these old Carvins or did Carvin redesign great amps with great bang for buck for unreliable new ones with too many whistles and bells?

    r
     
  13. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA
    Agree. Plus, that way, you have 100% backup, important for gigging... if you bought only a power amp, and the pre in your Carvin head goes south, you're screwed.

    As I said earlier, I think a second head, capable of safely driving a 2-ohm load (or biamping with 4's) is the way to go. And keep the Carvin for emergencies.

    Impossible to know. I suppose all manufacturers have their "hits" and their "misses". I own a couple pieces of gear from mfrs. that I swear by, while others revile 'em for problems they've had in the past. A lot of folks dislike my Ampeg SVT-3Pro head; I love it.

    Different strokes for different folks....