I understand the great sound of early rock amplifiers came from the way their power amps distorted. I understand how and why this would happen and how that would affect the overall amp response to playing. But how important, power amp distortion is for these modern ultra high gain amps (i.e. mesa dual rec and peavey 5150)? How much power amp contributes to their tone? I know that at low volumes their already sound great, so this led me to assume that most of their sound (at least what i can get from low volumes) comes from their preamp distortion. Unless i am missing something and they also have power amp distortion at low volumes....
Thanks for the help
Thanks for the help
Is there a particular amp you are reffering to as they all sound a little (some more than) different from one another and most (not all) of the differences in sound depend on the type of speaker system or systems that are used.
Just as one tube may sound different than another tube even though they are the same type (or number) and even the same maker in some cases.
The same is possible in soild state systems aswell although less likely. jer
Just as one tube may sound different than another tube even though they are the same type (or number) and even the same maker in some cases.
The same is possible in soild state systems aswell although less likely. jer
These days a lot of metal guys prefer to use pedals to create distortion rather than get if from overdriving their amps.
I play in a band that is not metal, but we recently played in a show that was all metal- except for us. Now I've seen a lot of shows at this particular venue, and I knew that the mic *everything*, but I was surprised to see how small some of the guitar amps were- as little as 25 watts! Without the PA, none of the metal bands would have been all that loud.
I think the quick answer might be that amps with a "master volume" and "gain" controls depend on the preamp for the sound.
The "modern" way to get power-tube distortion. Build a smaller amp. Then you can over drive it without creating sports-stadium level volumes.
If you are after a classic rock or blues kind of sound you can get it with preamp distortion and a rather clean power amp stage. This way your master volume control can be used. It takes more then two 12ax7 gain stages to have the full effect.
I just recently built a tube based "pedal" (the box is way to large and is AC powered to be called a pedal but is is used the same way) using two 12AX7 stages. It has a tube overdrive sound, believe me if you drive a 12AX7 with a 90 volt peak to peak signal it will clip, big time and make a sound not that much unlike a power tube driven to clipping but I think the preamp sounds different because a 12AX7 class-A triode can't cause the power supply inside an amp supply to sag like a pair of push-pull EL34 can.
Hi hpupo,
I am not sure, I can answer your question with regards to a technical perspective.
My Marshall 6100/30th anniversary runs with 4 EL34 in the power amp.
The distortion of the lead channel sounds pretty much like modern/new metall.
This is pretty independent of the volume - you have to get above a certain volume to let the 4x12" speaker "breath" but this is far from running the power amp into saturation. At the same volume setting, even the bass notes in the clean channel are still glass clear and clean (for guitar player ears not Hifi ears).
This would imply that the distortion HAS to be generated in the preamp stages.
The control experiment: Running the same amp on only 2 EL34 in triode mode (possible in this model) can give you nice overdrive sounds in the "crunch" channel. With this setting and at higher volume, the clean channel is not clean any more - obviously the power amp is now starting to clip.
Interestingly, this sounds entirely different. Much more like the old rock n' roll sound - definitely not what you would associate immediately with metal.
In this case, the use of good pedals (distortion or just boosters, like Rangemaster) really makes a difference and a lot of sense.
I realize, this was not a technical answer, but I hope you can read between the lines that this strongly argues for preamp-only distortion in "modern" high gain amps, if one can generalize this at all.
Cheers,
Martin
I am not sure, I can answer your question with regards to a technical perspective.
My Marshall 6100/30th anniversary runs with 4 EL34 in the power amp.
The distortion of the lead channel sounds pretty much like modern/new metall.
This is pretty independent of the volume - you have to get above a certain volume to let the 4x12" speaker "breath" but this is far from running the power amp into saturation. At the same volume setting, even the bass notes in the clean channel are still glass clear and clean (for guitar player ears not Hifi ears).
This would imply that the distortion HAS to be generated in the preamp stages.
The control experiment: Running the same amp on only 2 EL34 in triode mode (possible in this model) can give you nice overdrive sounds in the "crunch" channel. With this setting and at higher volume, the clean channel is not clean any more - obviously the power amp is now starting to clip.
Interestingly, this sounds entirely different. Much more like the old rock n' roll sound - definitely not what you would associate immediately with metal.
In this case, the use of good pedals (distortion or just boosters, like Rangemaster) really makes a difference and a lot of sense.
I realize, this was not a technical answer, but I hope you can read between the lines that this strongly argues for preamp-only distortion in "modern" high gain amps, if one can generalize this at all.
Cheers,
Martin
A lot of the early guitar amps were built "wrong" so that there was a distortion component in the sound. It probably started out as the manufacturer trying to save money and later evolved to deliberate choices as players began exploiting the performance envelope.
You could introduce it at any or all stages, although since you want some consistency in control settings it probably was limited.
Single-ended stages produce harmonically rich distortion. Tube amps tend to have large overload margins, with consistently rising distortion components, so you can run the amp in an area of operation that generates predictable distortion levels.
You can't use as much Negative Feedback in a tube amp (due to the output transformer and it's effect on phase) ... low or no NFB will create higher distortion that is none the less consistent with the amps distortion signature.
Cheap unregulated power supplies would tend to sink and result in higher distortion with sustained signals at the same volume setting. So, you can introduce distortion just by adjusting playing style with the classic amps, or choose pickups or guitars that can exploit that characteristic. Some amps use tube rectification to deliberately sink the supply to get a similar effect where solid state rectification would tend to be more robust and therefore cleaner.
Output transformers can be deliberately chosen (on newer amps) or were simply installed to save money (original classic amps) that were inadequate for low distortion output. Thus higher distortion at rated output.
Circuit design and parts selection in the preamp stage can influence the distortion characteristics of the amplifier. Also, as mentioned earlier, large overload margins can be exploited to overdrive a following stage.
You could introduce it at any or all stages, although since you want some consistency in control settings it probably was limited.
Single-ended stages produce harmonically rich distortion. Tube amps tend to have large overload margins, with consistently rising distortion components, so you can run the amp in an area of operation that generates predictable distortion levels.
You can't use as much Negative Feedback in a tube amp (due to the output transformer and it's effect on phase) ... low or no NFB will create higher distortion that is none the less consistent with the amps distortion signature.
Cheap unregulated power supplies would tend to sink and result in higher distortion with sustained signals at the same volume setting. So, you can introduce distortion just by adjusting playing style with the classic amps, or choose pickups or guitars that can exploit that characteristic. Some amps use tube rectification to deliberately sink the supply to get a similar effect where solid state rectification would tend to be more robust and therefore cleaner.
Output transformers can be deliberately chosen (on newer amps) or were simply installed to save money (original classic amps) that were inadequate for low distortion output. Thus higher distortion at rated output.
Circuit design and parts selection in the preamp stage can influence the distortion characteristics of the amplifier. Also, as mentioned earlier, large overload margins can be exploited to overdrive a following stage.
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Read this: - http://www.peavey.com/support/technotes/hartley/chapter_3.pdf ...white paper by Hartley Peavey which explains how undersized (by hi-fi standards) transformers contribute to the typical sound of a valve guitar amp.
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well, IMHO I feel that the main contributing factors envolved is the preamp and then the speaker.
The marshall 8100 valve state is a perfect example of this.
The poweramp stage is solid state and very clean as it does not add any coloration to the sound.
The first one I had tried out was a combo model that had a green back in it.
And my impression was "MAN THIS IS SH$%" and it was not turned up loud by any means.
So then I started a search for a cabinet and I tried every thing under the sun and found that the 5150 cabinet was to my liking over the marshall 1960a and 1960b.
And all of them were much better than the standard marshall cabinet and especialy the smaller valve state cabinets.
Never the less I didn't get any of them and used it on my sunn 610 and sunn 215 setup.
Later on I due to other reasons the power amp quit working so I was forced to use a seperate power amp.
I used my sunn concert slave mainly as I have two of them
I used my BGW,QCS,SANSUI G9000 stereo and PEAVEY CS series.
Non of those amps changed the way my setup sounded including my AMPEG V4-B as a poweramp ,only a little as it was a very power full tube amp and played very clean.
So then I started running the marshall direct into the mixer so that I could practice all hours of the night (without waking up the neighbor hood and landing me a free ride in collier county's finest) using head phones.
No matter what I did with eq's on the mackie 32-8 mixer, I, just could not get "that sound" in my headphones.
Then one day it dawned on me that my ART POWER PLANT had an AMP CABINET MIC simulator filter circuit built in to it and always gave me a sweet tone when I recorded direct to tape and in my headphones.
So then I set up the power plant to a clean setting and plugged the preamp out of the marshall 8100 into it, and ,"BOOM" there it was, "that sound",right there in my damn headphones.
We went on to record many guitar's and bands that didn't bring thier amps with that configuration.
It sure helped to keep noise level down for the recording enviroment as well.
The art power plant is the only piece that I ever regret losing and I still have yet to find another one .
It did come with the schematic in the manual but now I can't even find that.
Endless searchs on the net turn up nothing, including the ART web site, go figure?
As it used to be listed.
So IMHO the power amp itself is third in my list of what colors the sound as far as musical instruments are concerned. jer
P.S. If anyone has or can get me a copy of the schematic of the art power plant it sure would be much appreciated!
The marshall 8100 valve state is a perfect example of this.
The poweramp stage is solid state and very clean as it does not add any coloration to the sound.
The first one I had tried out was a combo model that had a green back in it.
And my impression was "MAN THIS IS SH$%" and it was not turned up loud by any means.
So then I started a search for a cabinet and I tried every thing under the sun and found that the 5150 cabinet was to my liking over the marshall 1960a and 1960b.
And all of them were much better than the standard marshall cabinet and especialy the smaller valve state cabinets.
Never the less I didn't get any of them and used it on my sunn 610 and sunn 215 setup.
Later on I due to other reasons the power amp quit working so I was forced to use a seperate power amp.
I used my sunn concert slave mainly as I have two of them
I used my BGW,QCS,SANSUI G9000 stereo and PEAVEY CS series.
Non of those amps changed the way my setup sounded including my AMPEG V4-B as a poweramp ,only a little as it was a very power full tube amp and played very clean.
So then I started running the marshall direct into the mixer so that I could practice all hours of the night (without waking up the neighbor hood and landing me a free ride in collier county's finest) using head phones.
No matter what I did with eq's on the mackie 32-8 mixer, I, just could not get "that sound" in my headphones.
Then one day it dawned on me that my ART POWER PLANT had an AMP CABINET MIC simulator filter circuit built in to it and always gave me a sweet tone when I recorded direct to tape and in my headphones.
So then I set up the power plant to a clean setting and plugged the preamp out of the marshall 8100 into it, and ,"BOOM" there it was, "that sound",right there in my damn headphones.
We went on to record many guitar's and bands that didn't bring thier amps with that configuration.
It sure helped to keep noise level down for the recording enviroment as well.
The art power plant is the only piece that I ever regret losing and I still have yet to find another one .
It did come with the schematic in the manual but now I can't even find that.
Endless searchs on the net turn up nothing, including the ART web site, go figure?
As it used to be listed.
So IMHO the power amp itself is third in my list of what colors the sound as far as musical instruments are concerned. jer
P.S. If anyone has or can get me a copy of the schematic of the art power plant it sure would be much appreciated!
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