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Tonal variations in output taps???? Can someone explain.

jamisonlps

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May 30, 2005
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I've owned my RV50 since I bought new in 2007. At home I mostly use a single 8 ohm speaker and always use the same tap. At gigs and rehearsal I use my 16 ohm cab (2 x 8 ohms in series). Same speakers....I just discovered that all 3 output taps sound different (RV50 has 2 x 8 ohm taps and 1 x 16 ohm tap).

First off, is this normal?? Can someone technically explain how/why this would be. One 8 ohm tap is somewhat harsh and has more headroom to the sound, I can hear it and feel it - the other 8 ohm tap is a littel sweeter sounding and has more compression, you can dig in a little more. When I checked the 16 ohm tap (briefly at low volume) I noticed it was the warmest and had the most compression, least headroom and was the least harsh.

I have been struggling with my sound at rehearsal. At home it sounds fine but I've noticed when running the 2x12 cab from the 16ohm tap my tone has been darker and not cutting through the mix as well. Yet, I like the compression and "less harsh" tone.

Anyway, is it normal to hear these differences? Different components the signal is traveling through, different windings used on the OT, different combination of the 4 x 6V6 power section??? What would cause this?

Oh, and it's the 8 ohm tap that I use the most (all the time really, I rarely use the other tap) that sounds the brightest/harsh compared to the others.
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roadrunner

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Not sure how to explain what you found, without writing a long diatribe about how transformers are wound.

Suffice to say, most of the old Marshalls I've ever had sounded best on the 4 ohm tap, especially pre '70 100 watts, slightly not as vibey on the 8 ohm tap and the 16 ohm tap is usually the most clean/sterile sounding.
Might just be the impedance mismatch that I like to hear but it's a good way to get an old Marshall to sound good thru just about any 4x12.
 

riscado

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I have a question roadrunner! When you say you prefer the 4ohm tap in old marshalls, are you always using the same speaker impedance on the other side?

Example you have a 4x12" with a total of 4ohms, and you prefer the marshall on the 4ohms setting? Or you have a cab that has a total of 8 ohms and you still prefer the marshall in the 4 ohms setting (despite the mismatch)?

Thanks
 

jamisonlps

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Roadrunner, it's the opposite for me. All else being equal the 16 ohm tap has the least high end and more compression (better feel too). From everything I've read most say that the higher impedance tap will use more windings - so more resistance and capacitance and will have less high end which is what I am hearing.

Going from an 8 ohm to a 16 ohm tap with the correct speaker loading (say a 1x12) isn't exactly a controlled experiment either. An 8 ohm speaker of the same model is said to be brighter (on paper at least) than it's 16 ohm counterpart due to the voicecoil having more windings.

Still none of this explains why both of my 8 ohm taps sound different...they are wired in parallel. I'll try to record clips because there's many who say my ears are just fooling me...
 

jamisonlps

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By looking at the schematic, this makes since Wizard.

http://users.telenet.be/orangefg/OFG_SCHEM/RV50C_sheet3.jpg

The 16 ohm tap uses more windings on the secondary and is the warmest most compressed, the middle 8 ohm tap is the loudest, brightest, least compressed (most headroom) from what I hear and is the first 8 ohm tap, the 8 ohm tap furthest away is not as bright and is piggybacked off of the first. Based on everything I've heard, read and see looking at the schematic - I think I'm comfortable with this concept now.

I guess I am just blessed/cursed with good ears cause I know what I hear and am not just imagining things.
 
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jamisonlps

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Oh and another thought based on what I'm hearing and my biasing experience...forgot the taps, go with whatever speaker/cab configuration you have and run the properly matched outputs, you can dial in your tone with biasing by ear. Last time I biased I ran the mA lower but was using a single 8 ohm speaker off the 8 ohm tap. This gave me less headroom and not so much of a "hi-fi" sound, more compression and a better feel.

Running the 16 ohm cab (2 x 8ohm in series) I had typically biased hotter. So essentially you can balance out your tone based on what tap you are running off of...all of this depending on the effect that tap is having on your output signal.
 

roadrunner

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I have a question roadrunner! When you say you prefer the 4ohm tap in old marshalls, are you always using the same speaker impedance on the other side?

Example you have a 4x12" with a total of 4ohms, and you prefer the marshall on the 4ohms setting? Or you have a cab that has a total of 8 ohms and you still prefer the marshall in the 4 ohms setting (despite the mismatch)?

Thanks

All the 4x12's I have are 16 ohm cabs, at least that's how they're rated... they seldom actually measure exactly 16 ohms.
Depending on the sound I want to hear, I set the amp to 4, 8 or 16 ohms. The mismatch is also good for bringing the volume down a bit, especially with a 100 watt amp.
 
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