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Guitar amp, and PP Tubecad Calculator
Guitar amp, and PP Tubecad Calculator
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Old 29th January 2018, 04:59 PM   #1
john65b is offline john65b  United States
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Default Guitar amp, and PP Tubecad Calculator

Hello all,

Just finished my Guitar amp build based on the Ampeg B15N schematic...a 6L6 PP based output and a pair of 6SL7 input tubes doing the amplification and phase splitting...but I have a question...

Using PP Tubecad on my output I see that the 3rd and 5th Harmonic Distortion numbers quite high on the EL34, a fair bit better 6L6GC, and surprisingly rather low on KT88 - around 1/4th of the EL34...

Now I have listened to all three and have made my choice of what pleases me the most...

But question is the Odd Order harmonics - is it "good" to keep them low on a guitar amp? Is it nothing more than a myth that the high Odd Order Harmonics are what makes the "Marshal" sound and the dominant Even Order Harmonics make the "Fender" sound?

I don't know if it is just a coincidence that the EL34 have the highest Odd Order and the Marshals (I know of) run EL34 output tubes...

Again, it really doesn't matter in the end as I know which one I most like, but just asking in general...

BTW - great sounding amp - I rebuilt this thing at last three times before I realized the secret to removing all the Hum was just elevating the heaters...duh.
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Old 29th January 2018, 05:55 PM   #2
jazbo8 is offline jazbo8
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Guitar amp, and PP Tubecad Calculator
Doesn’t TubeCad PP only model triode output stages? Guitar amps without any third harmonic distorsion would sound quite bad, perhaps Marshall has higher 3rd HD than Fender, but probably not by much.
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Old 29th January 2018, 08:48 PM   #3
john65b is offline john65b  United States
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My TCJ PP Calculator (whoops, not TubeCAD) does all sorts of other tubes - 6L6GC / EL34 / 5881 / 6550 / KT88 / KT100, etc...
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Old 30th January 2018, 04:22 AM   #4
Enzo is offline Enzo  United States
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Rules of thumb do not matter - statistics do not apply to individuals. The one you like best is the best one for you. WHo cares what anyone else thinks about odd harmonics?
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Old 30th January 2018, 05:26 AM   #5
dotneck335 is offline dotneck335  United States
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Quote:
Originally Posted by john65b View Post
Just finished my Guitar amp build based on the Ampeg B15N schematic...a 6L6 PP based output and a pair of 6SL7 input tubes doing the amplification and phase splitting...but I have a question...
Using PP Tubecad on my output I see that the 3rd and 5th Harmonic Distortion numbers quite high on the EL34, a fair bit better 6L6GC, and surprisingly rather low on KT88 - around 1/4th of the EL34...
Now I have listened to all three and have made my choice of what pleases me the most...
So.......which one sounds the best to YOU??
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Old 30th January 2018, 07:19 AM   #6
jazbo8 is offline jazbo8
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Quote:
Originally Posted by john65b View Post
My TCJ PP Calculator (whoops, not TubeCAD) does all sorts of other tubes - 6L6GC / EL34 / 5881 / 6550 / KT88 / KT100, etc...
TCJ = TubeCad Journal, afaik, the PP Calculator only models triodes and triode-connected pentodes/beam tetrodes. So the distortion profiles do not really tell you much when those tubes are used in guitar amps...
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Old 30th January 2018, 12:18 PM   #7
john65b is offline john65b  United States
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Which sounds best? The 6L6 - the GE metal can 6L6...not Sovtek 6L6GC or other 6L6GC I have (yup, I know the dissipation difference between the two)...crazy, but me likes! And they are dirt cheap too...just found a pair in my stash and decided to try them...

But in general, Odd Order Harmonics are to be avoided in design, or is it a myth...
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Old 30th January 2018, 01:10 PM   #8
jazbo8 is offline jazbo8
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Total myth...
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Old 30th January 2018, 03:19 PM   #9
Tubelab_com is offline Tubelab_com  United States
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Quote:
Odd Order Harmonics are to be avoided in design, or is it a myth...
Odd order above the 3rd harmonic are not "musical," IE they don't fall close to a standard note that would be used in the same scale as the fundamental, and tus may sound dissonant in the presence of the fundamental and other notes of the same scale.

This applies to HiFi amps, especially those used to listen to complex music where many notes are sounded simultaneously.

A screaming lead guitar is usually a single note, or a power chord (one chosen such that the IMD products are not terribly dissonant). The "proper" distortion profile is the one that the user likes.

Quote:
Which sounds best? The 6L6 - the GE metal can 6L6
I must have blown up 50 or so metal 6L6's in my high school days. At the time they weren't cheap, they were FREE!!! Several hundred brand new RCA's were donated to our high school electronics class by the local US Air Force base. They did sound awesome as the paint was peeling from the can!

I was given a box full of old metal tubes at a hamfest. There were a pair of metal 6L6's, and EIGHT metal 6V6's along with some other metal tubes suitable for preamp duty......time for an all metal amp?????

The TCJ simulator does only do triode connected tubes, and no simulator on earth can accurately model a guitar amp overdriven by a pedal board set on KILL!
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Old 30th January 2018, 03:42 PM   #10
JMFahey is offline JMFahey  Argentina
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Quote:
Is it nothing more than a myth that the high Odd Order Harmonics are what makes the "Marshal" sound and the dominant Even Order Harmonics make the "Fender" sound?
Myth with absolutely no base.
Unless you compare a push pull 20/50/100W head (Marshall or any other brand, including Fender) to a Fender Champ, which is single anded ... and boasts of puny 5W (closer to 2W RMS)
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