#1
Hey everyone, I really appreciate the help. I have a VHT 50/CL that I am plugging into a Marshall 1960AV cab.

My question is, would I be better off going 4 ohm or 16 ohm. They both can be set for either. I just wanted to know if anyone could explain if this will have an effect on volume, tone, tube life, etc...

I searched the forums and really couldn't find any answers. Thanks in advance for any input.
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#3
I think it doesn't have a big difference. Don't quote me on that, tho.
#4
I've heard it's better to use the highest ohm setting when possible, since it uses more winds on the output transformer. Supposedly, this allows the the OT to give you the best sound. Haven't really noticed much of a difference personally, although I don't have a super trained ear either.
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#5
Cool, thanks
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#6
impedance is not equavilent to, nor directly effects, the efficiency of your amp, nor is there any direct correlation between the two. Power = voltage2/impedance so technically an amp with lower impedance has potential for more power, but really with guitar amps running on such a high voltage the effect of a lower impedance is nominal. the time impedace gets to be a big deal is with car amps runing on smaller voltages.

Long story short I dont think you will notice any difference between the two, but im no amp expert, perhaps someone else may be able to offer another opion.
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#7
Since you have a choice, use 16 ohms. Any resistance in the speaker cable will be a smaller percentage of the total load on the amp. That means less power will be wasted heating the speaker cable and more going to the speakers.

Granted, this will be an extremely small loss. But it could make a difference with a poorly made or long cable.
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#8
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That means less power will be wasted heating the speaker cable and more going to the speakers.


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#9
oh i thought this had something to do with 1 or 2 cabs being able to plugged into a head


In a way it does. It's also to be able to match the amp's output to a single or double cabinet setup with different impedances. But if you have two 8 ohm cabinets, it lets you run both wired series for 16 ohms total, or both run parallel for 4 ohm output. Then it also can be run with one cabinet either 4 or 16 ohm. So it works both ways.
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Last edited by Paleo Pete at Nov 4, 2007,
#10
Quote by chris_kedro
Hey everyone, I really appreciate the help. I have a VHT 50/CL that I am plugging into a Marshall 1960AV cab.

My question is, would I be better off going 4 ohm or 16 ohm. They both can be set for either. I just wanted to know if anyone could explain if this will have an effect on volume, tone, tube life, etc...

I searched the forums and really couldn't find any answers. Thanks in advance for any input.


The lower the resistance (ohms), the more volume you will have. I would go with 4 ohms if you need power, but 16 ohms will most likely be more stable. As long as you don't put an incorrect load or no load, your tubes should be fine for either.
#11
Higher ohms ratings filter off high end and boost mids. Part of the vintage fender tone was down to the 2 ohm and 4 ohm cabs they used. The marshall tone comes from their 8 and 16 ohm cabs. That is part of the reason the marshall JTM 45 sounded so different than the 6G6 bassman even though the JTM 45 was meant to be an exact copy of the bassman.

So you have to ask yourself if you want a sharp high end or a stronger midrange.
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#12
Quote by Fingerboy18
The lower the resistance (ohms), the more volume you will have. I would go with 4 ohms if you need power, but 16 ohms will most likely be more stable. As long as you don't put an incorrect load or no load, your tubes should be fine for either.

This is untrue for tube amps. Mismatching in either direction with an impedance matching output transformer results in less power. Using the 4ohm tap with a 4ohm cab, is the same power rating as using the 16ohm tap with a 16ohm cab.
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#13
Quote by CorduroyEW
Higher ohms ratings filter off high end and boost mids. Part of the vintage fender tone was down to the 2 ohm and 4 ohm cabs they used. The marshall tone comes from their 8 and 16 ohm cabs. That is part of the reason the marshall JTM 45 sounded so different than the 6G6 bassman even though the JTM 45 was meant to be an exact copy of the bassman.

So you have to ask yourself if you want a sharp high end or a stronger midrange.

Corduroy, you keep stealing my posts -_-

But yeah, the higher LRC of the higher impedance speaker would peak the mids, and the lower LRC of the lower impedance would peak the treble.
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#15
Quote by Erock503
This is untrue for tube amps. Mismatching in either direction with an impedance matching output transformer results in less power. Using the 4ohm tap with a 4ohm cab, is the same power rating as using the 16ohm tap with a 16ohm cab.


Hmm not what I've learnt but I do believe you. I am an Electrical Engineering student but have not been taught tubes formally. Thank you for restating my suggestion. I am sure that if you have no load it can damage a tube amp though.
#16
yes, no load will damage a tube amp, and running too far a mismatch can also damage it.

haha, since you are a EE major, I can bore you. Gotta love Kirchoff. You are thinking in terms of SS amps that use a transistor circuit to amplify the sound. Normally, lower resistance, more current can flow, therefore more power. There is no output transformer involved.

With a tube amp however, it uses an impedance matching output transformer to match the very large circuit impedance, to the very small load/cab impedance. You now have to take into account an Impedance source, and an Impedance load.

IE. a 100W tube amp rated at 4ohms:

PLoad = current^2 x RLoad
100W = I^2 x 4ohm
I = 5 amps. This is what the output transformer is designed for in this example.

P=I^2 x R, or P = (V/R)^2 x R
Pload = (Vsource^2 x Rload) / (Rsource + Rload)^2 = (Vs^2 x 4) / (4 + 4)^2 = 100W
Vsource = 40V

I = Vsource/(Rsource + Rload) = 40V/(4ohm + 4ohm) = 5 amps using a matching impedance cab/load of 4ohm

PL = load power = 100W with a 4 ohm cab
Vs = voltage source (fixed in the circuit) = 40V
Rs = impedance source (fixed in the circuit - impedance matching output transformer) = 4 ohm

mismatching in either direction now will reduce power because of this relationship. For example, mismatching with a smaller impedance load of 2ohm

2 ohm cab*
I = 40V/(4ohm + 2ohm*)= 6.67 amps. This is more current than the OT was designed for, which can damage it.

The power formula is:
Pload = (Vsource^2 x Rload) / (Rsource + Rload)^2 = (40^2 x 2ohm) / (4 + 2)^2 = 89W
or
Pload = I^2 x Rload = 6.67^2 x 2ohm = 89W

So even though you are using a lower impedance cab, there is less power. You are also pushing more current than the transformer was designed for, so it can be damaged that way too.
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Last edited by Erock503 at Nov 29, 2007,
#17
so, Erock503, in your opinion, am I still best off using 16 ohms? I'll admit, I was too lazy to try playing with both settings, I'll give it a try tonight and see if I can hear the difference.
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#18
I would think you have to try it both ways, and let your ears decide. As long as you are matching the impedance, you won't hurt anything, and it's all down to what sounds best to your ears. I ran mine on 16ohm when I had the choice between 4 and 16ohm, but that's just what sounded good to my ears, it wasn't like a night and day difference though.
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#19
about 12 ohms....


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#20
Quote by Fingerboy18
The lower the resistance (ohms), the more volume you will have. I would go with 4 ohms if you need power, but 16 ohms will most likely be more stable. As long as you don't put an incorrect load or no load, your tubes should be fine for either.
This is not true because the 16 ohm output has a higher voltage then the 4 ohm. You might get more power from putting 4 ohms on the 16 output up until you burn up the xformer. I'm not sure if impedance matching is a consideration with regard to power xfer. But overloading the amp sure is.
#21
Quote by Dave_Mc
about 12 ohms....
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i clicked this link for the purpose of saying that exact same thing
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#22
I'm an idiot and I accidentally clicked the "Remove all subscriptions" button. If it seems like I'm ignoring you, I'm not, I'm just no longer subscribed to the thread. If you quote me or do the @user thing at me, hopefully it'll notify me through my notifications and I'll get back to you.
Quote by K33nbl4d3
I'll have to put the Classic T models on my to-try list. Shame the finish options there are Anachronism Gold, Nuclear Waste and Aged Clown, because in principle the plaintop is right up my alley.

Quote by K33nbl4d3
Presumably because the CCF (Combined Corksniffing Forces) of MLP and Gibson forums would rise up against them, plunging the land into war.

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Et tu, br00tz?