I have an amp that is advertised as 150 watts. It even has 150 in the Model of the amp TBX150H. It can be used at 8ohms (100W) or 4ohms (150W). I had my cabinet wired previously at 16 ohms. Sounded thick. Then I rewired it to 4 ohm to get that advertised 150W. Is there a reason that the sound (to my ears anyway) from the amp/speakers sounds better BEFORE wiring the 4ohms? It would seem that if the thing is advertised as 150W..that 4ohms would be the preferred setting. I thought it sounded fuller/thicker when wired at 16 ohm. Or is it just my ears tricking me?
Hi. IME there's two possible explanations. Your amps output section handles the 16Ohm load better than 4Ohm. Very common thing with budget SS amps. Or, one or more of the speakers are out of phase with the other(s). If a regular tube amp sounds audibly different with different OT taps, there's usually something wrong with the circuit or OT. IME anyway. Regards Sam
Tube amps make the same power regardless of load. SS amps output power depends on the load impedance. So a SS amp will put out a lot less power into 16 ohms versus 4 ohms. You are also more prone to clipping the signal to the speakers using a 16 ohm load. This is because your headroom all but goes away. If the four ohm load makes 150W and the eight ohm load only makes 100, what is the 16 ohm making? 50 watt or so? Then if you are cranking this 50 watts, the power section is prone to clipping or at least going into distortion. This will alter the overall tone of the amp.
That's mainly because of the difference in negative feedback between the 16ohm setting and the 4ohm setting, rather than the difference in the impedance itself. The amount of negative feedback changes when you move taps, unless you have moved the NFB lead from whichever tap it is attached to, and attached it to the speaker jack tip instead. Because of the way that these tube marshalls are wired, this will also make a difference as well as the massive difference that it makes with Solid State amps.
I didn't think we had to have a certain price tag amount to ask a question. I'm not some 15 yr old kid with his first head. If you spend some time with the head and an EQ through the effects loop.. and you know what your doing.. this cheap head can sound MEAN! If I want that "Meshuggah tone".. thats the head I'll play. If I want want blues//Classic rock I'll plug into another head. I'm 39 and I have owned a buffet of heads in my days. And I've played through a million more. Mesa's, Marshall's, Ampegs, Randall's, Laney, Peavy's, etc, etc, etc.. That Ibanez sounds way better for metal than my Marshall 8200 ever could regardless of the price tag. And I have the sound clips to prove it. For a thick, deep, hi gain head with Mesuggah tone.. the only thing that I've heard that sounds better is the Rectifer which is 4X as much. If anyone would like to give me a video clip of their amp that sounds better for newer metal, I would love to hear it.
I thought it was the other way around: if the NFB wire is attached to the speaker outputs, the negative feedback changes with the impedance selected, whereas if it's attached to a specific OT tap, the negative feedback remains constant regardless of impedance chosen. Cheers!
I called it a budget amp and that is what it is. It makes sense to point this out, because it really tells a lot about "how the amp is built." Some 150 watt solid state guitar amps have a solid power supply. Some of the cheaper ones are built with substandard components. I wasn't bashing you for owning this amp. You obviously have it dialed in to your sound.
Nope. With it connected directly, the transformer can have NO bearing on it. With it connected to a tap, it is feeding through the transformer, and depending on the setting, through one quarter, one half, or the whole of the secondaries, which affects the level of NFB.
Sorry man.. I didn't catch what you were saying the first time. Yea, I'm fully aware this is a budget head. A $250 price tag basically insures that no experienced guitar player can even try and take this head seriously. For that price..its basically a disposable head. I only bought it for one purpose. As wierd as it sounds... with a BBE Sonic Maximizer through the effects loop, the gain on only 5.5-6.. and a week of fine tuning...this thing isn't too different to the Red Channel on the Rectifer I had. Very Meshuggah like. And thats with bland G12M-70's. For fun I'll post some vids comparing it to my Marshall 8200 once I get the Man O Wars installed.
Hmmm... I don't know, man. Everything I've read says that if it's attached to the speaker output, it's variable, whereas when it's connected to a specific tap, it's constant... Check out this thread over at the MetroAmp forum: MetroAmp.com Forum • View topic - Negative feedback wire connected to speaker output jack? Cheers!
Actually that thread doesn't even go it it, really. The closest is the first reply, mentioning that on the jack the NFB is "on" regardless of the tap, which is pretty much what I've said in less detail. The NFB cannot change with the settings when wired directly to the speaker jack tip.
In the post that has "Marshall 101 From "Clay's" x web site. Negative Feedback Circuit" at the top, it states this: "On some older Marshall’s (like my '69) the negative feedback (purple) wire was connected to the speaker jacks, so the feedback varies depending on which speaker impedance is selected." This jives with most things I've read regarding negative feedback, specifically regarding Marshall circuits and the purple feedback wire connection. Cheers!
The Marshalls that have the selector for impedance, with a speaker jack wired NFB it would HAVE to change. Set the jack for 8 ohms, the NFB would be off the 8 ohm middle tap of the transformer, set it for 16 ohms the NFB would see the full secondary.
An amp with dedicated jacks and no selector like the DSL, yeah it would be the same regardless and wouldnt change, but the selector changes the whole ballgame.
I know exactly what he's saying. In one band that I was in, the other guitarist and I had 2210's with 1960 cab's. His cab was wired for 8 ohm's, while mine was wired for 16. I noticed that his amp had a more up front and in your face sound. It just cut through the mix better. I also had no idea you were supposed to change those glass bottle's that get hot in there either! I really didn't do any investigation, but always thought from then on that it had something to do with the sound.
