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DaveH

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Everything posted by DaveH

  1. wouldn't shorted be NO load, not a huge load? And open is basically infinite resistance, or HUGE load. If I understand it right, Higher loads than designated are more likely to blow transformers, while lower loads are more likely to blow power tubes. Mesa at least says it's ok to try mismatches, but I think they usually mean 1 step, 4 -> 8 or 8->16 or the otherway. Mesa are probably overbuilt enough to take a 2 step change, but I don't know for sure. If it's a multispeaker cab, might be easier to rewire it to lower the resistence if possible. No. A short will draw a HUGE amount of current....that's what blows fuses. An infinite resistance passes no current. Does that make sense? Think of a light switch....when it's off, there's an infinite amount of resistance with respect to ground, and the light does not burn. Turn the switch on, the resistance goes way down (whatever the resistance of the bulb is) and the light is on, flowing current through the circuit and dissipating heat (watts, power, whatever you want to call it). That's extremely simplified, but it's the same basic idea as with the output. Tube amps like to have a load, versus having no load....you NEVER want to fire up an amp out of standby without a cab hooked up, or you will blow the output transformer. I guess you could look at it as a bigger impedance number being a bigger load if you want to, but electrically speaking that is not correct....you're looking at it simply as a higher number being a bigger load. The thing is, a higher secondary impedance is actually going to have less current flowing in the output of a given amp, versus if you were running a lower impedance in that same amp. In other words, Higher Z = less current, and Lower Z = more current (with more current being a bigger load, electrically speaking). I never said that you cannot get away with mismatching *up*, as in the impedance number, I said it's safer to mismatch *down*. Most amps will most likely not be hurt mismatching in either direction, but keep in mind that mismatching *up* will in effect have the voltage chasing the current (which is going to be constant) and it (the voltage) will have to rise higher because of that, than with a lower impedance.....when this voltage gets reflected back through the transformer (and it WILL reflect), it will get stepped up as a multiple of the turns ratio of the output transformer.....if it rises high enough, it can cause arcing inside the transformer windings and/or tubes which can damage or destroy either/both. There are many, many variables involved. The case Arnie brought up involving Joe Walsh....he said the output was less than one ohm. As I said, that's almost a short, which is a huge load. Lots of current, and heat, will result because of that. It's no wonder he was blowing tubes and trannies, he was taking it well past the realm of normal operation. That's the key. You can go too far with it like Joe did, but as long as it is kept reasonable I stand behind what I said about it being safer to go mismatch down rather than up, in impedance. Joe's tone sounded fantastic because his amp was about to blow. The last thing you mentioned about keeping the mismatch within one step in either direction....you *should* be safe doing this with most any production amp.
  2. Well good Lord, with a load of under 1 ohm it was almost a dead short! Of course he was eating tubes! Look at it like this: A 1 ohm load is pulling a lot more current through the output, and the amp will be louder than with a 16 ohm load. With more cuurent there is more power being dissipated, and more heat. So, which is the bigger load, 1 or 16? One ohm is. The fact is, mismatching too much in either direction is a bad thing, but given a choice, I would mismatch in the lower ohm direction (bigger load) before the other direction. You will get less voltage on your tube plates, and less chance of arcing in the tubes or output transformer.
  3. Actually both tube and transistor, it shouldn't really make any difference anyway; the basics are pretty much the same. Dave not trying to really argue and obviously do what you think is best.. the only major failure I ever had was with a P.A running a low speaker load...It was pretty spectaclar.. flame out the back and a lot of smoke Well, it DOES make a difference....the only basics that are the same at this point is that they both amplify a signal. Beyond that, tubes and transistors are totally different in the way they operate. I'm not trying to argue here either, Craig, just stating facts which are based on electronics theory (and which are are proven through Ohm's Law). I stand behind what I said.
  4. Old Fenders are 4 ohms, and Marshalls higher. Wouldn't tha make Marshalls the more fragile of the two? But all in all, it is best to stay with the plan. Exactly my point! And yes, it's best to stay within the parameters.
  5. I don't think so.... I had amp techs/companies tell me to never do that... It's the same concept of chain to many cab in to your P.A. ... look at the back of many amps.. Wattage goes up as the speaker load drops...which results in more heat.... I could be wrong on this but I've never had a amp failure with a higher speaker load... I've had a power burst into flames with a lower power load. The theory I described is Ohm's Law, and you can't change it. Think about it. A lot of old Fenders use a direct-to-ground shorting jack on the output, so that if you play a dumbass for a moment and forget to plug in a speaker cab, you won't blow the OT as long as you realize your mistake in time....this is because you have a HUGE load (direct short). If that jack does NOT short to ground (it remains open - no load), you'll take out that OT in a matter of seconds. That's just the way that it is. Again I refer you to old Marshalls that were notorious for eating outputs, and they were set up at 16 ohms which results in higher voltages being reflected back. With higher resistance, it takes higher voltage to achieve the amount of current present. This is simple Ohm's Law. Something just occurred to me....the techs/Factory you were talking to were most likely talking about TRANSISTOR amps. These are totally different animals than tube amps, in that a direct short like that will most definitely kill the output transistors in the blink of an eye, while an open condition will not bother them in the least. I automatically think in terms of tubes, since that's what I build. They definitely should not be confused.
  6. Actually, that's totally wrong. It's safer to go lower in impedance, ie 8 ohm out into a 4 ohm load, than to go up. Simplified, the power tubes are current sink devices, and they drive current into the output transformer (the OT). The current is stepped up by the turns ratio of the primary and secondary, and driven into the load. The higher the load resistance, the higher the voltage will have to rise to achieve the current that's being driven. It's Ohm's Law, and that never changes. Then, that voltage will be reflected back to the primary, and it will get stepped up accordingly by whatever the turns ratio of the OT is.....you can easily end up with 1000VDC and more on the plates with mismatching. SOme amps can take it, some can't. You ever wonder why so many old Marshalls had blown output transformers, while it was rare with Fenders? The load ratings are not set in stone either, rather they're more of an average. Everything changes depending on frequency, etc. Sometimes you might find that an amp actually sounds better with a mismatch, but keep the above in mind.....it's just safer to stay within the set parameters.
  7. I really should know this, but I don't. Even with thi pitiful lack of info, I know someone here can tell me: It sounds very much like early Rod Stewart, and the chorus lyrics contain something like "it's 7:00, and it's time for a paaartaaay" Or something like that.
  8. That is COOL! You look like you owned that 'stage'.
  9. Wow, that IS a cool story! Cool history for sure. Like cmatthes, I've tried in vain to have one of these built, Hamer just won't cooperate.
  10. Welcome to the board. As for who owns it now, I'll let them speak up. Anyway, are you gonna share the story?
  11. I'm very sorry to hear this, my deepest condolences.
  12. I'm going to have to agree with you there! Yea...what they said! What you said!
  13. What's his friend, the keyboard player, have to say about things?
  14. Yeah, Mark always makes me say "wow" when I hear him. As for the albums, 'Rock City' and 'Fire Down Under' are my faves, with FDU leading. I got RC when it first came out....between that album, and Moxy's 'Ridin' High', my tape player stayed awfully busy. Guy Speranza (Rock City thru Fire Down Under) and Rhett Forrester (Restless Breed and Born In America) are both deceased now. I think Guy died from some form of cancer, and Rhett was murdered in Atlanta IIRC.
  15. Not sure if any of these have been mentioned yet, if so I overlooked them: - Moxy. A great hard rock band from the 70's that *almost* hit it big. - Riot. They sort of died when Guy Speranza left, but Mark Reale is a hell of a guitar player. They came close as well, but always got screwed over somehow....Sammy Hagar, for one, stuck it to them. - The Godz. A no frills biker band from Ohio, they never came real close to making it big AFAIK, but I loved their first two albums. There are others too, but these immediately came to mind.
  16. Chris, if you're serious about an SG and aren't hung up on getting an old one, then spring for a later model '61 Reissue. I have a 1996 '61 RI that kills, and the ones that I've compared to the (later model) Standards and Specials are higher quality wood and construction. The RI's are worth the extra money imo.
  17. Thanks Dave....bastid....hehe Kurt, would you be interested in a Heritage? It has minor play wear, the hardware that is nickel has a nice patina to it, and it had a fret dress by Mark Erlewine shortly before I aquired it. Plays great, and it has Gibson '57 Classics in both positions.
  18. What, you don't like the clean looking ones like this? (Btw, it's NOT for sale, I'm just trying to make your LP jones a little more intense.)
  19. The one in the middle looks great! Is that Korina? Yep, it's korina with an ebony board. Here's a better pic of it. There sure are a lot of beautiful guitars in this thread.
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