A two-stage poweramp?

[petejt]

Here's my idea

 

 

Low-wattage amps sound great. Lots of that good poweramp crunch. And they can still be plenty-loud for small gigs & recording.

 

 

But when it comes to live performance, or you just want to blow the neighbours right away, you need to re-amp it through another poweramp. And if you want great stereo effects, you need another stereo poweramp for the re-amping.

 

 

Well, why not combine the two in one amp head?

 

You can have a preamp in it if you like, but,

 

I reckon, it'd be great to have an amp head that has a low wattage poweramp with selectable valves (e.g. EL34, EL84, 6V6, etc. etc.), that you can drive to the mutha{censored}in {censored}house, and then its output load signal gets converted to a line-level signal, that then gets re-amplified by a big-arse clear high wattage poweramp? (KT-88's, KT-77s, 6L6 etc.)

 

I suppose an 'effects loop' can be added too, for stereo effects.

[teemuk]

At that point, I'd go digital. No need to smear the tube distortion from amp #1 with tube distortion from amp #2.

Yet, I don't see how much this really differs from e.g. Vox Valvetronix, except that the "power amp" is a 12AX7 and not a typical power tube. And the Valvetronix amps are by no means the only amps using this very same idea.

See for example,
Teisco: Checkmate 100 (features a transformer-coupled PP pre-amp stage likely used for tremolo modulation)
Guytron: Patented "your" idea
Koch: OTS (Output Tube Saturation)
Magus Innovations: Ultimate Attenuator and Ultimate Tube Amp
PS Systems: EB100S
Songworks: Little Lanilei 3350LT (12AX7 output running to a power soak, amplified by 50W SS)
SWR: TubePath
Fender: Transconductance Amplifier (not entirely the same idea but close)
Vox: Valve Reactor (not entirely the same idea but close)
Warwick: Pro Tube IX hybrid: 12AX7 + EL84 in the preamp

[RoboPimp]

guyatron'd

[petejt]

At that point, I'd go digital. No need to smear the tube distortion from amp #1 with tube distortion from amp #2. Yet, I don't see how much this really differs from e.g. Vox Valvetronix, except that the "power amp" is a 12AX7 and not a typical power tube. And the Valvetronix amps are by no means the only amps using this very same idea. See for example, Teisco: Checkmate 100 (features a transformer-coupled PP pre-amp stage likely used for tremolo modulation) Guytron: Patented "your" idea Koch: OTS (Output Tube Saturation) Magus Innovations: Ultimate Attenuator and Ultimate Tube Amp PS Systems: EB100S Songworks: Little Lanilei 3350LT (12AX7 output running to a power soak, amplified by 50W SS) SWR: TubePath Fender: Transconductance Amplifier (not entirely the same idea but close) Vox: Valve Reactor (not entirely the same idea but close) Warwick: Pro Tube IX hybrid: 12AX7 + EL84 in the preamp

 

 

I'm not being understood.

 

 

 

Take for example, a massive Zachman-style rig with all those processors and a VHT 2150 poweramp full of KT-88s or Mesa/Boogie 395 poweramps etc. yet he runs a cranked Mojave Peacemaker in front of it all.

 

The first amp head is cranked (or not, whatever the situation may be), so there's full poweramp saturation.

 

Now, that's either too loud for one situation, or not loud enough for another situation.

 

Or still, if you want effects after it (which sound better than in the effects loop), the signal needs re-amping anyway to be sent to the speakers, because the signal gets knocked back down to line level for the effects.

 

 

What I am saying is-> instead of using two external poweramps, or running one amp head into another poweramp/amp head,

 

 

why not just have TWO poweramps in the one amp head?

 

 

Where the first is a low-wattage poweramp (whose valves can be changed on the fly for different sounds, e.g. like the Egnater Rebel 20, THD Univalve), that has its own volume control.

 

And the second is either a mono, or even better, a stereo poweramp that also has its own volume controls.

 

That way you really do have a cranked poweramp sound at a low volume (because you can turn the final volume right down and it's below a whisper, without using an attenuator or Power Scaling).

 

Or, a cranked poweramp sound that can drive effects of whatever you like, and then re-amplified by an internal high wattage system that's super clear and undistorted but still has the valve warmth.

 

 

 

 

See? I'm not 'guyatron'ed.

[thinkpad20]

I see whatcha mean... one amp with two separate power amps built in, and you choose which one the signal goes through (it doesn't go through both). Interesting idea; however I imagine that the practicality would be somewhat limited seeing as it would weigh a friggin ton, making it not so desirable as a low-wattage amp... but who knows

[newholland]

i'd think that'd open itself to all sorts of problems because you'd be driving a LOT of power into another amplifier instead of just a line level into a power section.

 

seems like a big resistive element like an attenuator works better for that sort of thing, because it presents a static load to the amp.

 

besidedly, you'd also need not only two output transformers, but probably two power sections... so you'd need to build the thing on casters just to move it! on top of it all... i can imagine all sorts of distortion occurring from the two different amps being run together unless it was some new technology i dunno if they've created yet..

 

it's a cool idea.. but it's kinda reinventing the wheel, and i'd think if they COULD do it, somebody probably would have!

[petejt]

I see whatcha mean... one amp with two separate power amps built in, and you choose which one the signal goes through (it doesn't go through both). Interesting idea; however I imagine that the practicality would be somewhat limited seeing as it would weigh a friggin ton, making it not so desirable as a low-wattage amp... but who knows

Actually, you just expanded on the idea .


The main idea is that it saves having to re-amp an overdriven amp head/poweramp, because the second amp that does the re-amplifying (e.g. usually a big-arse VHT2150) is in the same chassis as the low-wattage poweramp.


And you're right, thinking about it now, it would be heavy because it'll need at least three output transformers, likely four.


Still, it is an idea. It could be made practical.

[.homewrecker.]

Actually, you just expanded on the idea . The main idea is that it saves having to re-amp an overdriven amp head/poweramp, because the second amp that does the re-amplifying (e.g. usually a big-arse VHT2150) is in the same chassis as the low-wattage poweramp. And you're right, thinking about it now, it would be heavy because it'll need at least three output transformers, likely four. Still, it is an idea. It could be made practical.

To the average HCAFer but to most it won't be. And to those it would matter they have road crews to take care of their {censored} for them. Good idea but in practice I don't think it'll have much broad application, especially for the amount of work needed to make it work.

[petejt]

To the average HCAFer but to most it won't be. And to those it would matter they have road crews to take care of their {censored} for them. Good idea but in practice I don't think it'll have much broad application, especially for the amount of work needed to make it work.

 

 

Well, it'd just be the size of a normal amp head, since there'll be no preamp in there. It saves having to carry an extra poweramp.

 

All you need extra is a preamp, so really it's like just having an external rack preamp and an external rack poweramp/amp head sized poweramp.

[.homewrecker.]

Well, it'd just be the size of a normal amp head, since there'll be no preamp in there. It saves having to carry an extra poweramp. All you need extra is a preamp, so really it's like just having an external rack preamp and an external rack poweramp/amp head sized poweramp.

 

 

But you're still going to have 2 power amps in 1 unit, with two HUGE sets of iron, which is going to weigh a lot. Regardless it's an interesting idea.

[petejt]

i'd think that'd open itself to all sorts of problems because you'd be driving a LOT of power into another amplifier instead of just a line level into a power section. seems like a big resistive element like an attenuator works better for that sort of thing, because it presents a static load to the amp. besidedly, you'd also need not only two output transformers, but probably two power sections... so you'd need to build the thing on casters just to move it! on top of it all... i can imagine all sorts of distortion occurring from the two different amps being run together unless it was some new technology i dunno if they've created yet.. it's a cool idea.. but it's kinda reinventing the wheel, and i'd think if they COULD do it, somebody probably would have!

 

 

 

I don't really know how line level converters work. All I know is that they take in a load level signal & convert it to a line level signal. Custom Audio Electronics make one, and it's just a half rack space-sized box, pretty small.

 

There definitely would be a line level converter between the poweramps, so effects can be used between them.

 

My THD Hotplate ain't that big, and it converts the load signal to a line level signal, as well as providing attenuated speaker outputs.

 

 

 

About the "two power sections"- that's the whole idea. Having two different poweramp sections in the one chassis. One is low wattage, the other is high wattage so the final listening volume can be controlled without affecting the poweramp distortion.

 

 

Of course, it doesn't include how the speakers interact with distortion, but hey I can't fit that into the box.

[yabba]

I don't see how it's really any more 'practical' than just having two separate amps

[petejt]

I tell you what inspired the idea.

 

 

At the moment, at home I'm jamming with my Engl Fireball into the Hotplate, whose line level output signal goes to the effect returns of my solid state Roland Jazz Chorus 120 combo amp.

 

The sound is actually quite good. I love how the Jazz Chorus spreads the sound with its, ahem, chorusing...and also provides reverb. It also provides the option of running effect units AFTER the Fireball, rather than use the effects loop.

 

It's actually a handy little setup, because I can use just the Fireball head & the Jazz Chorus combo for small gigs/rehearsals etc. rather than drag two 4x12 cabs, or even one.

 

 

I'm doing this because, my lazy arse STILL hasn't bought the bolts to screw in the new speakers in my Marshall 4x12 cab that I cut up to half-convert into a Leslie rotating speaker cabinet..........

 

 

Anyway, although I like the Jazz Chorus, it would be nice to re-amplify with a valve poweramp, than solid state.

 

So I thought it'd be an idea to have two poweramps in the one chassis, where the first is low wattage for more crunch, effects can be inserted via line level signal, and the second is clean & clear to control the volume.

[Elric]

This may sound crazy but I have an amp idea that is an extension of this, that I think would really take it to the next level.... If someone could pull this off it'd be totally awesome: You could not only double the power amp sections into high-power/low-power but also do separate preamp sections each voiced appropriately for one type of use: low volume practice/high power gigging. You could even take it a step beyond that and put each system in it's own "container"... (let's call it a "head" for the sake of discussion) and then leave one set up where it belongs (in your bedroom) and the other where it goes (rehearsal space). Man, that would be amazing and probably even more practical than carrying two amps in a single box that has a bunch of goofy design compromises that cause it to not be stellar in either application.

 

I'm sure that {censored} would sell like hotcakes, I'm going to do a patent search right now.

[newholland]

I don't really know how line level converters work. All I know is that they take in a load level signal & convert it to a line level signal. Custom Audio Electronics make one, and it's just a half rack space-sized box, pretty small. There definitely would be a line level converter between the poweramps, so effects can be used between them. My THD Hotplate ain't that big, and it converts the load signal to a line level signal, as well as providing attenuated speaker outputs. About the "two power sections"- that's the whole idea. Having two different poweramp sections in the one chassis. One is low wattage, the other is high wattage so the final listening volume can be controlled without affecting the poweramp distortion. Of course, it doesn't include how the speakers interact with distortion, but hey I can't fit that into the box.

 

 

no-- i gotcha there-- take a look into the THD univalve-- you can use that in this context-- only half of what you're talking about though-- it obviously doesn't have the secondary power amp. but it IS geared to put a line level signal out. mebbe a schematic'd give you the skinny on how they do it. hell-- if you use a single ended front end with a minimal preamp into a beastly power amp... could be a solid idea- but i'm not certain as to how well accepted it's been, as the univalve's been around a while, and i don't know of anybody using it that way. could just be the THD's implementation doesn't sound that great... dunno!

[petejt]

no-- i gotcha there-- take a look into the THD univalve-- you can use that in this context-- only half of what you're talking about though-- it obviously doesn't have the secondary power amp. but it IS geared to put a line level signal out. mebbe a schematic'd give you the skinny on how they do it. hell-- if you use a single ended front end with a minimal preamp into a beastly power amp... could be a solid idea- but i'm not certain as to how well accepted it's been, as the univalve's been around a while, and i don't know of anybody using it that way. could just be the THD's implementation doesn't sound that great... dunno!

 

 

I didn't know that the Univalve had a line out.

 

But I did know that it can change the poweramp valve to whatever you want, which was part of my inspiration for the first poweramp in the chassis.

[Pankot]

You might find this interesting too:

http://www.londonpower.com/sscaling.htm

 

It takes the output of a low power tube amp directly (no line level pad) and "scales it up" to a higher power level.

[newholland]

 

there she is-- but i'm not sure it goes THROUGH the OT.

[petejt]

^^ thanks

[knucklefux]

i think you're trying to combine two things that don't necessarily go together very well.

 

as a general rule, the lower powered amps are intended to be cranked so that the power section breaks down and distorts, where the higher powered amps are designed so that the power section stays clean.

 

i don't really see a benefit in having a preamp married to both kinds of power sections:idk:

[petejt]

i think you're trying to combine two things that don't necessarily go together very well. as a general rule, the lower powered amps are intended to be cranked so that the power section breaks down and distorts, where the higher powered amps are designed so that the power section stays clean. i don't really see a benefit in having a preamp married to both kinds of power sections:idk:

 

 

 

 

You're forgetting the fact that this allows people to run their low wattage cranked poweramp into (via line out) EFFECTS, which then gets re-amplified by the high wattage poweramp WITHOUT USING ANOTHER SEPARATE POWERAMP.

 

 

You get the SOUND of cranked poweramp valves cooking from the first poweramp, then that gets converted to a line level signal so it can run a string of effects, and then that gets sent BACK to the chassis into (stereo) inputs of the high wattage poweramp for the CLEAN POWER, and then to the speakers.

[knucklefux]

solemmegetthisstraight....

 

you think that it would sound good to run a signal through an output transformer then back into a tube input stage, a power stage, and another output transformer?

 

not only will it NOT work, it CAN'T work. at least, not the way you think.

[potaetoes]

and what if the low-wattage power amp used a 12AX7 like a pair of power triodes pumping out like one watt... oh wait, that's basically what a phase inverter is. amps already have those.

 

and in any amp with a post-PI master volume, it's mission already accomplished.

[petejt]

solemmegetthisstraight.... you think that it would sound good to run a signal through an output transformer then back into a tube input stage, a power stage, and another output transformer? not only will it NOT work, it CAN'T work. at least, not the way you think.

 

 

I never said that.

 

 

 

 

 

 

The amp consists of a chassis (just a box) that has two individual POWERAMPS in it.

 

Between the poweramps, is a line level converter.

 

 

 

There is an input for the first poweramp. The signal goes in, gets cranked by the master volume, through the output transformer, and to the line level converter.

 

The converter sends a stereo line level signal, to two outputs, where effect units can be patched in.

 

The effect units (such as a reverb, delay box, a pedal that can handle +4dB, the fancy Eventides etc.) process the signal, then send the signal to the stereo INPUTS of the second, high wattage stereo poweramp that is inside that chassis. Two master volumes control the, master volumes.

 

That poweramp then sends the final load output, to whatever speakers are connected. Say two 8ohm cabs, two 16 ohm cabs, 4ohm, whatever.

[petejt]

and what if the low-wattage power amp used a 12AX7 like a pair of power triodes pumping out like one watt... oh wait, that's basically what a phase inverter is. amps already have those. and in any amp with a post-PI master volume, it's mission already accomplished.

Not really though. It's not the same as cranking two EL84 valves, or even two EL34 valves, and then turning it into a line level signal that can drive effect units POST POWERAMP, which is then re-amplifiied by a high wattage stereo poweramp, that is physically inside the SAME BOX as the first poweramp.


The preamp, is external to everything. It would just weigh the box down too much since there's gonna be two output transformers & a power transformer in there already.