Tube Amp Myths

northernguitarguy

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I bought a Blues Junior 3 probably 3 years ago, and after a while it just didn't sound quite right. I stopped playing it and instead used an old Marshall solid state amp i have.

I took it into my local guitar shop, and they were about to buy it from me but after extensive testing in store they decided it wasn't right and needed a service. The aged rocker type that worked there gave me a lecture about how tube amps don't like being played at bedroom volumes and they need to be cranked up or they start to play up. So . . is there any truth to that? I took it out once for the one and only time i ever took it to a bar with my guitar teacher and i think it toppled over in my boot . . i would think that's probably the root of the issues. When i turn it on now it has got worse and one of the tubes glows pink and that's about it . . so i know it needs a few new tubes at least.

Was he talking rubbish then?
A good master volume control can do a lot. And while a tube amp doesn't necessarily need to be cranked to sound good, the sound does flourish when it gets turned up.

The Blues Junior might just be the wrong amp for the sound you want.
 

Scott A Novak

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Tube watts are louder than solid state watts.
Effectively they are. Most squalid state amps are singled ended output designs. When they clip they create odd order harmonics that are unpleasant to most people's ears. By contrast, most tube amps (Except for those nasty single ended output practice amps) do NOT have single ended output stages and tend to cancel odd order harmonics and create even order harmonics, which are generally pleasant to the ears. So you can drive a tube amp harder than a solid state amp without the tube amp sounding obnoxious.

That is why I say a tube amp can effectively sound louder than a squalid state amp. But all bets are off if the solid state amp has a balanced configuration.

Scott Novak
 

Scott A Novak

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The aged rocker type that worked there gave me a lecture about how tube amps don't like being played at bedroom volumes and they need to be cranked up or they start to play up. So . . is there any truth to that?
If the amp has a standby switch that turns off the B+ while leaving the filament voltage on, it's possible that it can start to poison the cathode. In that case it may help to reverse the poisoning by driving the tubes hard. A better solution is not to use the standby switch.

It's also true that all electronics go through a break in period, and there will be some small sonic changes after the initial burn in period. However, most people aren't paying enough attention to notice.

Electrolytic capacitors go through some oxide unformation inside the capacitor when the amplifier is off and it takes some run time to reform the oxide layer. So if you haven't turned on your amp for a week, it will sound better after it has been running for an hour. Also, electrolytic capacitors sound better when they are warmer, so your amplifier should sound better after it thermally stabilizes, assuming it was a competent design.

Scott Novak
 
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Scott A Novak

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Two biggest myths are that you need matched sets of power tubes and balanced PI tubes.
It's true that you can use unmatched tubes. Just like you can use mismatched size tires with mismatched tread designs. But the car will handle and brake better with matched treads and sizes on the same axle.

Matched phase inverter tubes do work better, especially if you using differential pairs. This can be proven on the test bench and also by listening tests. Likewise, matched output tubes will sound better and last longer.

It's also true that you can introduce local negative feedback with large value cathode resistors and reduce the effects of mismatched output tubes. But they will still sound better and clip more evenly with matched tubes.

Tube matching becomes even more critical with fixed bias. Using an individual bias control on each output tube DOES NOT CORRECT the problems caused by mismatched output tubes!!!

Scott Novak
 

MechEngVic

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Biggest tube amp myth: A solid state amp can sound as good as a tube amp. Ain't never heard a-one!
 

Scott A Novak

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Yet the Champ 5F1, Princeton 5F2A, GA-5, and Vox AC15 are up there with the 5E3 as some of the most defining tones in classic rock.
As they say "Ignorance is Bliss", "Father, forgive them, for they do not know what they are doing", and "These go to 11".

Scott Novak
 

guitfiddle

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Effectively they are. Most squalid state amps are singled ended output designs. When they clip they create odd order harmonics that are unpleasant to most people's ears. By contrast, most tube amps (Except for those nasty single ended output practice amps) do NOT have single ended output stages and tend to cancel odd order harmonics and create even order harmonics, which are generally pleasant to the ears. So you can drive a tube amp harder than a solid state amp without the tube amp sounding obnoxious.

That is why I say a tube amp can effectively sound louder than a squalid state amp. But all bets are off if the solid state amp has a balanced configuration.

Scott Novak
IIRC ss amps are rated at full power, while tube amps are rated at their max power before distortion. You could find a ss amp rated for 100 watts that only gives you 80 without clipping. You might also find a 50 watt tube amp that gives 80 at max, so they're matched pretty well, and the speakers don't really see any difference. A watt is a watt.

That's not to say one amp can't be voiced to sound "louder", but that's down to circuit rather than wattage.
 

Scott A Novak

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IIRC ss amps are rated at full power, while tube amps are rated at their max power before distortion. You could find a ss amp rated for 100 watts that only gives you 80 without clipping. You might also find a 50 watt tube amp that gives 80 at max, so they're matched pretty well, and the speakers don't really see any difference. A watt is a watt.

That's not to say one amp can't be voiced to sound "louder", but that's down to circuit rather than wattage.
Here is a link to the FTC power specifications for audio amps.:
The amplifier power is to be measured at a maximum of 2% harmonic distortion. There is no differentiation between SS and Vacuum Tube amps.

But I noticed that the power specification is technically incorrect as it contradicts the way power bandwidth is specified.

"(e) Rated power shall be obtainable at all frequencies within the rated power band without exceeding the rated maximum percentage of total harmonic distortion after input signals at said frequencies have been continuously applied at full rated power for not less than five (5) minutes at the amplifier's auxiliary input, or if not provided, at the phono input."

Assume that the rated power band is 20 HZ to 20 KHZ. Rated power bandwidth is specified at the -3dB power points. In other words, at 20 HZ and at 20 KHZ the amplifier is only outputting 1/2 of it's maximum rated power, even though the specification states that the amplifier must produce it's rated power throughout it's power bandwidth. It's a technical impossibility by definition!!!

IDIOTS!

Scott Novak
 

OBX351

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Handwired amps tube are better than PC board amps.
Leo Fender's amp designs were 100% original, actually the original amps he produce were from common radio, PA and phono designs as well as schematics from RCA and Western Electronics.
 

grumphh

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"Even order harmonics come from tubes (and always sound good) and odd order come from SS (and are what make SS sound bad)"


Hey, looking at this last page of posts it seems that we have found ourselves a person dedicated to keep the tube amp myths alive :D
 

OBX351

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I bought a Blues Junior 3 probably 3 years ago, and after a while it just didn't sound quite right. I stopped playing it and instead used an old Marshall solid state amp i have.

I took it into my local guitar shop, and they were about to buy it from me but after extensive testing in store they decided it wasn't right and needed a service. The aged rocker type that worked there gave me a lecture about how tube amps don't like being played at bedroom volumes and they need to be cranked up or they start to play up. So . . is there any truth to that? I took it out once for the one and only time i ever took it to a bar with my guitar teacher and i think it toppled over in my boot . . i would think that's probably the root of the issues. When i turn it on now it has got worse and one of the tubes glows pink and that's about it . . so i know it needs a few new tubes at least.

Was he talking rubbish then?

A good master volume control can do a lot. And while a tube amp doesn't necessarily need to be cranked to sound good, the sound does flourish when it gets turned up.

The Blues Junior might just be the wrong amp for the sound you want.
Very true! If you don't want to mod the Marshall you can get an attenuator. Here's a great video by Dr Z that discusses the difference between an attenuator, Air Brake and a MV.

I use Dr Zs with a few of my amps and an Aracom with my vintage Marshalls. Both work very well.

I have PPIMV on my Marshall clones. I believe a PPIMV doesn't "front end the amp", meaning it doesn't drive the preamp tubes to get distortion and the PPIMV allows you to lower the volume. Again I believe the PPIMV allows you to drive the power tubes like you would at fuller volumes but it allows you to attenuate or lessen the volume via a PPIMV volume knob.
 
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northernguitarguy

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"Even order harmonics come from tubes (and always sound good) and odd order come from SS (and are what make SS sound bad)"


Hey, looking at this last page of posts it seems that we have found ourselves a person dedicated to keep the tube amp myths alive :D
Based om what?
 

northernguitarguy

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Very true! If you don't want to mod the Marshall you can get an attenuator. Here's a great video by Dr Z that discusses the difference between an attenuator, Air Brake and a MV.

I use Dr Zs with a few of my amps and an Aracom with my vintage Marshalls. Both work very well.

I have PPIMV on my Marshall clones. I believe a PPIMV doesn't "front end the amp", meaning driving the preamp tubes to get distortion and allow you to lower the volume. Again I believe the PPIMV allows the power tubes to come into play to create the tone like you would at fuller volumes but allow you to attenuate or lessen the volume via a PPIMV volume knob.
My new Orange has a 'Headroom/Bedroom' feature, that reduces power from 15w down to 1W and lower. It's an excellent feature and makes an attenuator superfluous. However, prior to this, I was using my VOX Night Train through a Bad Cat Unleash. It definitely sounds better attenuated at low volume than using the MV alone.
 

OBX351

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My new Orange has a 'Headroom/Bedroom' feature, that reduces power from 15w down to 1W and lower. It's an excellent feature and makes an attenuator superfluous. However, prior to this, I was using my VOX Night Train through a Bad Cat Unleash. It definitely sounds better attenuated at low volume than using the MV alone.
That's a pretty cool trick amp builders are doing more often. I have a Blackstar Artisan 15 that can go from 15 to 5 watts with a switch. However I hang a Dr Z AB on it and leave it at 15 watts. I like the attenuation better then going to 5 watts. The PPIMVs in my clone Marshall 25 to 50 watt amps also work very well. With either application you do lose tone because you can't drive the speakers as hard but the trade off of being able to play when people are in the house and keeping my bad from getting worse is worth it!
 




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