Fender amp question

**Tom Karol** · 08-10-2009, 12:38 PM

TDD -
Once I get the Henriksen, I'll never buy another amp in my entire life. I promise ... really - please tell my wife!

By the way, here's how I think it works:
One 'notch' louder (+3db) requires 2x the power;
'Twice' as loud (+10db) requires 10x the power.

Jazzarian · 08-10-2009, 01:01 PM

Originally Posted by BigDaddyLoveHandles

Heh, I don't think that when people think of doubling the volume, they mean from 100 to 200 decibels

Actually it's 10x|Power Out/Power In| in dB watts, if you want to get technical.

**BigDaddyLoveHandles** · 08-10-2009, 01:48 PM

Hmmm... I'm trying to think of a good non-technical definition of "twice the volume", and the best I can think of is going stereo with two identical amps instead of one. But then you also have the spacial, space filling, effect of spreading the cabinets apart.

**BigDaddyLoveHandles** · 08-10-2009, 02:03 PM

Originally Posted by Jazzarian

Let's get some simple physics out of the way first. To double the perceived volume of a 45 watt amp,you'd need........450 watts.

I guess the 800W Acoustic Image Clarus+ would suffice

(Seriously, how do Acoustic Image amps rate those crazy wattages?)

Jazzarian · 08-10-2009, 02:09 PM

Originally Posted by BigDaddyLoveHandles

I guess the 800W Acoustic Image Clarus+ would suffice

(Seriously, how do Acoustic Image amps rate those crazy wattages?)

450 watts should drown out Dizzy or Billy Cobham.

It's easy to get large power output numbers with transistors than tubes. 500 watts for a bass amp is quite typical these days.

**BigDaddyLoveHandles** · 08-10-2009, 02:26 PM

Originally Posted by Jazzarian

It's easy to get large power output numbers with transistors than tubes

Yes, but do the numbers mean anything, when comparing tube amp loudness with SS amp loudness?

For example, the Fender Twin (say the Blackface, '65 reissue) is rated 85W and the Roland Cube 80x is rated 80W. But noone would claim the Cube is almost as loud. There seems to be separate scales wrt tubes versus SS.

Jazzarian · 08-10-2009, 02:44 PM

Originally Posted by BigDaddyLoveHandles

Yes, but do the numbers mean anything, when comparing tube amp loudness with SS amp loudness?

For example, the Fender Twin (say the Blackface, '65 reissue) is rated 85W and the Roland Cube 80x is rated 80W. But noone would claim the Cube is almost as loud. There seems to be separate scales wrt tubes versus SS.

Nope, watts is watts, current squared times the resistance. Or the voltage squared divided by the resistance.

The difference being, when pushed, humans can tolerate the even harmonics of tube distortion much better than the odd harmonic distortion of transistors. Thus you can tolerate a tube amp on 10 but not a transistor amp.

If both were putting out 50 watts, they're would be no difference in percieved volume.

**rwfthesr** · 08-10-2009, 03:41 PM

Going through amps shows either how long we've been here or how much (extra) money we had laying around. I started playing Funk and Jazz in the late '60 professionally and don't want to think about the guitars and basses that I've gotten rid of! But it's still all about the sound we perceive in out minds that we look for. Regardless of wattage.

**BigDaddyLoveHandles** · 08-10-2009, 11:49 PM

Originally Posted by Jazzarian

Nope, watts is watts, current squared times the resistance. Or the voltage squared divided by the resistance.

The difference being, when pushed, humans can tolerate the even harmonics of tube distortion much better than the odd harmonic distortion of transistors. Thus you can tolerate a tube amp on 10 but not a transistor amp.

If both were putting out 50 watts, they're would be no difference in percieved volume.

I'm sorry, but I still have a hard time buying the logic. By this reasoning, a 100 watt lightbulb is a loud as a Marshall stack!

To take another pair: the Pro Tube Twin Reverb and the diminutive Phil Jones CUB. They're both 100W but I can't believe any metric of "loudness" that takes them to be equal. Even with the 25W switch thrown, the Twin could literally blow that 11lb amp across the stage.

Wattage really measures how the amp consumes electrical current, right? Just as you have to turn to lumens to see how bright a lightbulb is, you have to turn to something else for a measure of how loud an amp is. And since loudness is rather subjective (think of how commercials often seem louder than TV programs), maybe there isn't a good single measure of loudness, but wattage seems an especially weak choice.

**TieDyedDevil** · 08-11-2009, 12:10 AM

Originally Posted by BigDaddyLoveHandles

I'm sorry, but I still have a hard time buying the logic. By this reasoning, a 100 watt lightbulb is a loud as a Marshall stack!

Hold on... I can't hear you. Let me turn down the lights.

To take another pair: the Pro Tube Twin Reverb and the diminutive Phil Jones CUB. They're both 100W but I can't believe any metric of "loudness" that takes them to be equal. Even with the 25W switch thrown, the Twin could literally blow that 11lb amp across the stage.

Absolutely correct.

Wattage is meaningless as an indicator of perceived volume unless all other factors are equal.

If you hold wattage constant, then EQ and speaker efficiency are the two biggest factors that affect perceived volume.

Speaker efficiency is the easiest to understand. It's a measure of how much of the electrical energy gets converted to sound. Speaker efficiency varies widely. As a broad rule of thumb, speakers having an extended frequency response tend to be less efficient.

Also, it takes much more power to reproduce low frequencies than it does to reproduce high frequencies. This is why bass amps need more power.

The ear's sensitivity to sound varies widely by frequency, being most sensitive at around 1,000 Hz. The more energy you concentrate in those midband frequencies, the louder your rig will sound. Take a look at the frequency plot for a guitar speaker: you'll see that the response is about 10 dB higher in the midband than it is at the extremes. A guitar speaker has almost no response at all below 50 Hz or above 5,000 Hz.

Long story short: at least part of the answer for the discrepancy between the Twin and the Cub is that the Twin has more efficient speakers and a narrower frequency response centered in the midband. (Hint: you can make the Cub *seem* louder by rolling off the bass and treble and cranking the mids.)

Jazzarian · 08-11-2009, 12:26 AM

Originally Posted by BigDaddyLoveHandles

I'm sorry, but I still have a hard time buying the logic. By this reasoning, a 100 watt lightbulb is a loud as a Marshall stack!

To take another pair: the Pro Tube Twin Reverb and the diminutive Phil Jones CUB. They're both 100W but I can't believe any metric of "loudness" that takes them to be equal. Even with the 25W switch thrown, the Twin could literally blow that 11lb amp across the stage.

Wattage really measures how the amp consumes electrical current, right? Just as you have to turn to lumens to see how bright a lightbulb is, you have to turn to something else for a measure of how loud an amp is. And since loudness is rather subjective (think of how commercials often seem louder than TV programs), maybe there isn't a good single measure of loudness, but wattage seems an especially weak choice.

Base 10 logarithm scale for power. Same as the Richter Scale. A Magnitude 7 earthquake is 10 times more powerful than a 6.

If you used the same speaker to compare a 50 watt transistor amp to a 50 watt tube amp, both putting out half power and less the .1% total harmonic distortion, you'd hear no difference between tube and transistor.

If you used the same speaker to compare a 50 watt amp to a 500 watt amp, you'd indeed get double the perceived volume, but that's it.

It's not subjective, sound level dB is easily measured.

**BigDaddyLoveHandles** · 08-11-2009, 12:50 AM

Who mentioned having to use the same speaker? I thought we were comparing combo amps, not amp heads!

And I didn't want to get into dB's, because as TDD mentioned, there's more to it than that: one amp could be more midrange focused, which sounds subjectively louder, damn the decibels... (this is my louder commercials observation. I've seen TV segments where they measure the loudness of TV commercials in dB's to prove that are not any louder, but they sound louder because of the way they are compressed.)

**ES350** · 08-12-2009, 07:47 PM

Have a '68 TR here and I subbed 2xKT88 for the stock 4x6L6; nice cleans, big, a lot fatter than the stock setup...without the Fender midrange bump. The PT handles it just fine...

**BigDaddyLoveHandles** · 08-13-2009, 12:06 AM

Originally Posted by ES350

Have a '68 TR here and I subbed 2xKT88 for the stock 4x6L6; nice cleans, big, a lot fatter than the stock setup...without the Fender midrange bump. The PT handles it just fine...

Translation, please

**rwfthesr** · 08-13-2009, 01:51 AM

Substituted 2 KT88 for the 4 stock 6L6s effectively cutting wattage in half for his TR (Twin Reverb) also getting a warmer tone.

**ES350** · 08-13-2009, 07:53 PM

Well, no...the KT88/6550 puts out up to 70-80 watts in a single PP pair. It just lets the amp run cooler and gets a different tone (fatter, better low end) than the typical Fender BF thing. Think of it as a BF Fender preamp with a Sunn/Dynaco power amp...mo' better.

**rwfthesr** · 08-16-2009, 05:28 PM

ES350 am I correct in saying that my 100 amp Twin will have the power cut using the 2 KT88s?

**dh82c** · 08-16-2009, 06:56 PM

Originally Posted by ES350

Have a '68 TR here and I subbed 2xKT88 for the stock 4x6L6; nice cleans, big, a lot fatter than the stock setup...without the Fender midrange bump. The PT handles it just fine...

I thought the 6550 had close to the same output impedance as 6l6s.
You arent worried about an impedence mismatch? PT is ok.. I am more worried about the OT