using 4ohms or 16ohms is there a difference ?

[Ken]

Call the Mythbusters!!!!

Ken

 

[LowerBeef]

When did Marshall start including 4 ohm taps on their output transformers? The earliest JTM45s had 8 and 16 ohm and 100 volt taps.

And when did they implement the switchable stereo 8 ohms / mono 4 and 16 ohms on the cabs? From what I've found it was the 90's?

 

[Purgasound]

When did Marshall start including 4 ohm taps on their output transformers? The earliest JTM45s had 8 and 16 ohm and 100 volt taps.

Since the late sixties...

 

[Purgasound]

I always answer question like this with this logic. People have been playing Marshall's for a long time. Tube amps in general apply as well.

"If there was a tonal difference that was appreciable between various ohm settings, it would be common knowledge today and everyone would be using it."

You can do all the testing you want, but the fact is all the best guitarist's in the world do not make claims such as, "I only run four ohms...it sounds the best."

There's nothing "magic" to discover. Again, if there was, it would have been discovered back 40's when tube amps were already a mainstay in Americana.

I COMPLETELY agree.

 

[plexi-paul]

I agree with the statement that if it made a big difference, we would have heard about famous guys doing it. Having said that, I ran my JVM410 into my 1960A both ways and I would swear the 4ohm sounded better. Call me crazy but 16ohm had too much high end and 4ohm had a better bottom end with a rounder high end. I also found that my amp ran hotter this way...which scared me a little so i stopped doing it.

Anyhow, to my ears, I heard a difference. Maybe there was something wrong with my amp....don't know. All i can say is try it and let your ears be the judge.

 

[jcmjmp]

I agree with the statement that if it made a big difference, we would have heard about famous guys doing it. Having said that, I ran my JVM410 into my 1960A both ways and I would swear the 4ohm sounded better. Call me crazy but 16ohm had too much high end and 4ohm had a better bottom end with a rounder high end. I also found that my amp ran hotter this way...which scared me a little so i stopped doing it.

Anyhow, to my ears, I heard a difference. Maybe there was something wrong with my amp....don't know. All i can say is try it and let your ears be the judge.

Matched or mismacthed - That's a different story alltogether.

 

[Ken]

Call me crazy but 16ohm had too much high end and 4ohm had a better bottom end with a rounder high end .

Yeah, I "think" my 16 ohm output is brighter too, but then I'm using a different cabinet to compare so that's not really relevent.

Ken

 

[Jonathan Wilder]

As has been said countless times...that switch is NOT a "tone tweak". It is there to match the amp's output impedance to the impedance of the cabinet.

EVERYTHING you do to an amp affects tone. But just because something sounds good doesn't mean it's good for the amp electrically.

Also, the negative feedback loop comes into play here. Most current Marshalls have the negative feedback loop tied to a certain ohms tap on the output transformer. This WILL affect tone and you can alter the tone of the amp by relocating which tap the NFB loop is taken from. However some older Marshalls had it tied to the speaker jack, which made the NFB loop variable based on which tap you were on.

The all too common myth of "It sounds better because you're using all of the windings of the transformer when on the 16 ohm tap" is nothing more than pure bullshit. If the transformer were a 4 ohm only transformer, you would be using the full winding yet it'd be the same as being on the 4 ohm tap of the transformer.

A lot of this tonal difference you hear has a lot to do with where the negative feedback wire is located relative to which tap it's on.

Again, the impedance selector is NOT and was never meant as a "tone tweak". It's there for electrical reasons to match the amp's output impedance to the impedance of the cab config you're running...plain and simple.

One 16 ohm cab = 16 Ohm setting

One 8 ohm cab OR two 16 ohm cabs = 8 Ohm setting

One 4 ohm cab OR two 8 ohm cabs = 4 Ohm setting

 

[LPMarshall hack]

As has been said countless times...that switch is NOT a "tone tweak". It is there to match the amp's output impedance to the impedance of the cabinet.

EVERYTHING you do to an amp affects tone. But just because something sounds good doesn't mean it's good for the amp electrically.

Also, the negative feedback loop comes into play here. Most current Marshalls have the negative feedback loop tied to a certain ohms tap on the output transformer. This WILL affect tone and you can alter the tone of the amp by relocating which tap the NFB loop is taken from. However some older Marshalls had it tied to the speaker jack, which made the NFB loop variable based on which tap you were on.

The all too common myth of "It sounds better because you're using all of the windings of the transformer when on the 16 ohm tap" is nothing more than pure bullshit. If the transformer were a 4 ohm only transformer, you would be using the full winding yet it'd be the same as being on the 4 ohm tap of the transformer.

A lot of this tonal difference you hear has a lot to do with where the negative feedback wire is located relative to which tap it's on.

Again, the impedance selector is NOT and was never meant as a "tone tweak". It's there for electrical reasons to match the amp's output impedance to the impedance of the cab config you're running...plain and simple.

One 16 ohm cab = 16 Ohm setting

One 8 ohm cab OR two 16 ohm cabs = 8 Ohm setting

One 4 ohm cab OR two 8 ohm cabs = 4 Ohm setting

My JCM 900 head has an 8 ohm switch and a 16 ohm switch. Printed next to the 16 ohm switch is (4). I understand the (4) is only if you modify the amp for that. So that said, I could never use a 4 ohm cab with my amp since it is only really capable of 8 or 16 ohms. Am I getting that right?

 

[Jonathan Wilder]

My JCM 900 head has an 8 ohm switch and a 16 ohm switch. Printed next to the 16 ohm switch is (4). I understand the (4) is only if you modify the amp for that. So that said, I could never use a 4 ohm cab with my amp since it is only really capable of 8 or 16 ohms. Am I getting that right?

Correct...not without the mod that swaps the 8 ohm for the 4 ohm tap.

 

[LPMarshall hack]

Correct...not without the mod that swaps the 8 ohm for the 4 ohm tap.

Thanks!

 

[Claret Badger]

Well actually that 4 in paranthesis is originally marked for the COMBO 900 - whilst the 16ohms is applicable for the heads.


HTH

 

[Kunnz]

will more or less windings on the OT alter the sound ?

my Ceriatone JTM45 sounds better when it is switched on 16 Ohm...
the sound is clearer, more dynamic...

Exactly, that's why I went to the trouble to explain some of the science/electronics behind it. There may not be a "correct" or even a "better" way, it all depends on how it sounds.

I agree, my theory is the transformer helps make the characteristic tone of the amp, using as much of the windings as possible increases the tone you get out of it.

hello,

I have a dsl 100 and a single mc412 cab both support 4ohms and 16ohms. i usually use the 4ohm on both setting. Is there any difference with using both amp and cab set to 16ohms ?

Yeah, I "think" my 16 ohm output is brighter too, but then I'm using a different cabinet to compare so that's not really relevent.

Ken

I use a really old old vintage OT. Old copper winding matures and sounds great as the atoms become more aligned with use over time. Like fine wine.

 

[jcmjmp]

I use a really old old vintage OT. Old copper winding matures and sounds great as the atoms become more aligned with use over time. Like fine wine.

not sure if you're serious or not... but atoms don't align themselves over time.

 

[LowerBeef]

As has been said countless times...that switch is NOT a "tone tweak". It is there to match the amp's output impedance to the impedance of the cabinet.

I hope no one misread me as suggesting that you run the amp at a mismatched impedance, I was always referring to configuring the cab as 4 ohm and using the 4 ohm tap vs configuring the cab as 16 ohm and using the 16 ohm tap.

amp 4 ohm = cab 4 ohm

amp 16 ohm = cab 16 ohm

 

[LowerBeef]

A lot of this tonal difference you hear has a lot to do with where the negative feedback wire is located relative to which tap it's on.

I've wondered about this. In the case of the feedback not matching the tap used for the speaker isn't the output side of the transformer acting as an autoformer?

 

[Jonathan Wilder]

I've wondered about this. In the case of the feedback not matching the tap used for the speaker isn't the output side of the transformer acting as an autoformer?

It's kinda interesting really. It forms a sort of variable tuned circuit.

Say for instance your speaker is on the 16 ohm tap while your NFB is on the 8 or 4 ohm tap. That places an inductor (the secondary coil from the 16 to the 8 or 4 ohm tap depending on which one the NFB is connected to) in series with the NFB resistor. There's also an inductor to ground (the other 1/2 of the secondary from the NFB tap to ground). When the switch is set to the same tap where the NFB resistor is, the inductor in series goes away. If the NFB resistor is on the 8 ohm tap, the series inductor is BEFORE the inductor to ground on the 16 ohm setting while it appears AFTER the inductor to ground on the 4 ohm setting.

On amps with the NFB on the speaker jack, there's no inductor in series with the NFB resistor, but you still have the inductor to ground. Its inductance varies with the impedance selector setting.

 

[MartyStrat54]

I use a really old old vintage OT. Old copper winding matures and sounds great as the atoms become more aligned with use over time. Like fine wine.

I really got to know where you heard/read this?

 

[Jonathan Wilder]

I really got to know where you heard/read this?

+1. I heard this only works on 880 volt 3 phase power trannies that are fired on via a solenoid controlled contactor.

 

[MartyStrat54]

You're just jealous that I have an amp that actually uses a key to turn it on.

880V being converted into an awesome power supply. The power filter caps are the size of large coffee cans. Is a two-inch thick resistor a big one? Well this amp uses them. All the P2P connection were mig welded. This is one sick puppy. An icon of amp technology. It is a one-of-a-kind as I don't want anyone cloning this monster.

I'm not even going to describe the Mercury Super-Super Stack. I will tell you that it weighs 52 pounds and the leads are all 4 gauge. It comes with a Teflon coated top so you can cook breakfast on it. Bacon anyone? Might as well put all of that heat to work, right?

The mains fuse is 200 amp Slo-Blo and the HT is 70 amp. It has attachments on the side for jumping car batteries or arc welding. Try that with a Super Lead.

Well, I gotta go. My neighbor's car needs a jump.