Ok, I am trying to understand what I am hearing, and how to replicate it, adjust it, enhance it, play with it etc. When I crank up a large tube guitar amp i.e Marshall, Fender etc, something is happening in the power amp side that I love the sound of but cannot seem to achive by any other method. Is it rectifier sag? Is there some weird electromagnetic interaction between the transformer and the tubes? Does anyone one know what I am talking about? It is a large dark sound, very smooth but not the creamy heavy compressed sound of cranked pre-amp tubes. It just has a body and depth and a rich thick spanky kinda quality. No it is not speaker cone break up, that I understand ! Those lil amps that use pre-amp tubes don't have it, EL84's seem unable to produce it. 5881's seem prone to it as do some 6550's. Is it the large beam in some tubes? Anyway what I want to know is.....How do I get it at low volumes? No I dont want to use a power soak or thd hot plate or even a marshall power brake, cause all of them seem to reduce this strange thing I hear and love so much ! Can't I just build something that would be rich in that sound? What is "that" sound ?
Anyone ?
Anyone ?
I think you'll need to provide more info- is the amp Class A or AB? What power valves? (They all sound different when overdriven). EL84's will do it, they simple have a different quality of distortion to the octals.
The phenomenon of power valve distortion versus the fuzzy pre-valve distortion is discussed all over the web- even a cursory Google should turn up lots of info. Here's what wikipedia offers for example: http://en.wikipedia.org/wiki/Valve_sound
The phenomenon of power valve distortion versus the fuzzy pre-valve distortion is discussed all over the web- even a cursory Google should turn up lots of info. Here's what wikipedia offers for example: http://en.wikipedia.org/wiki/Valve_sound
wow you have good hearing, must be the clear Dakota air. Interesting you find 'that sound' from 5881 and 6550 and not EL84. Perhaps because the former has higher plate resistance so forms a more ideal filter together with the output tranny? Or do higher impedance types compress in a manner to make the transition from clean to crunch better sounding? Or is it the higher power that makes the acoustics in the air compress in a manner to make 'that sound'. Perhaps a power soak doesn't do it for you because the sound waves need a certain energy to make that feeling?
Anyways, I'm sure there are tons of theories, but most amps that have 'that sound' simply have them by chance. I dont think they were designed to have 'that sound' but just have a lucky combination to make it. If I knew I'd be making them....
Then there's the fact that some guitarist prefer one sound over the other and perhaps dont hear 'that sound' in the same amps you do, and some again simply dont care, they just play...
Anyways, I'm sure there are tons of theories, but most amps that have 'that sound' simply have them by chance. I dont think they were designed to have 'that sound' but just have a lucky combination to make it. If I knew I'd be making them....
Then there's the fact that some guitarist prefer one sound over the other and perhaps dont hear 'that sound' in the same amps you do, and some again simply dont care, they just play...
Well thanks for the input but.......so far I'm still lost (but makin real good time) ! Let me try this. I have not as yet heard "that sound" from many amps. So the idea that it just sorta happens is a possibility. But..... My SovteK mig 60 does it, as do a couple of my Marshalls, my 100watt superlead (a 1972 )I think? But my marshall EL84 20/20 does not, but my Marshall 9005 50/50 only kinda does it, and it really seems not to matter much if it is on full or 1/2 power setting. I got some "darker" EL84 from the tubedepot and set biasing "just so" according to their suggestion and it did make my 20/20 a lil darker but........"that sound" still isnt there at all. I certainly understand the subjective nature of this, but my buddy's fender twin will do it (a blackface) if it is turned up all the way with both channels patched together (I run the SLP with the inputs patched) I had a univox that did it, and a way old relic heathkit from way back that did it, (it was a unit for mono hi-fi and I wish I still had it) and have heard it in some other units too. It's driving me crazy! I have been searching and searching the web, listening to amps all over for years and still do not know WHAT "that sound" is ! That is my major issue these days (and I have more issues than a magazine rack) so I am still seeking the answer to this epic quest what causes "that sound" ? Any other thoughts, ideas, leads, websites, builders, experiences ?
I would second the notion that it has to do with the the speakers just compressing a massive amount of air. Maybe your ears distorting too. My Fender Twin does what you describe - at least to my ears. The closest I can get at lower power is my SF Princeton (pp 6v6) which packs a JBL E110. The magnet is about the size of my head. It is still pretty loud, and probably still much louder than what you are looking for.
If you record that sound, is it preserved on the recording? Freddy King lugged Twins and Quads to get his sound, but I know a guy who can nail the CD sound on a Champ. When he plays it in person on a Twin, it is like something you have never heard before.
Sometimes it just doesn't scale down. The ax84 project has been working on that for years. Kinda sorta successful. The closest I came is with a borrowed P1 into the speakers on my Twin. Close, but no cigar, and still pretty loud.
Will a tele into a dimed Twin, you really are not getting much distortion from the circuit per-se. A Bassman is a basic Fender circuit with a transformer designed to give you another octave or so lower. A Marshall was just a Bassman with EL34s. They are all very similar. Designed to my eyes as PAs.
And remember that your guitar is interacting with the amp output too. Without volume, that goes away.
If you record that sound, is it preserved on the recording? Freddy King lugged Twins and Quads to get his sound, but I know a guy who can nail the CD sound on a Champ. When he plays it in person on a Twin, it is like something you have never heard before.
Sometimes it just doesn't scale down. The ax84 project has been working on that for years. Kinda sorta successful. The closest I came is with a borrowed P1 into the speakers on my Twin. Close, but no cigar, and still pretty loud.
Will a tele into a dimed Twin, you really are not getting much distortion from the circuit per-se. A Bassman is a basic Fender circuit with a transformer designed to give you another octave or so lower. A Marshall was just a Bassman with EL34s. They are all very similar. Designed to my eyes as PAs.
And remember that your guitar is interacting with the amp output too. Without volume, that goes away.
Hi Dakotadave,
I'd bet you'll get many opinions on this.
Most agree that three things happen-
(a) The Power Supply Sags
(b) The Tubes themselves distort (how depends how they've been wired)
(c) Transformer Saturation
(d) The tubes have a high output impedence, which leads to a high damping factor (in most of these guitar amps anyway)
(e) The speaker cone itself breaking up
If you're talking about the spanky tone, I would suggest that the transformer saturates (or comes close) for the initial attack, and releases its energy gradually, prolonging the note's tone.
Transformer cores saturate more quickly with lower frequency, which would explain some of the fatness lent to the note.
I think in reality all of the factors are what creates the sound. A guitar amp's output is an extremely complicated non-linear system. Just look at all the well researched, unsuccessful attempts by commercial companies to get the sound without using the real deal.
Most don't sound even similar, some sound close, but none do the job as well- which is why we still use the same stuff these days
I'd bet you'll get many opinions on this.
Most agree that three things happen-(a) The Power Supply Sags
(b) The Tubes themselves distort (how depends how they've been wired)
(c) Transformer Saturation
(d) The tubes have a high output impedence, which leads to a high damping factor (in most of these guitar amps anyway)
(e) The speaker cone itself breaking up
If you're talking about the spanky tone, I would suggest that the transformer saturates (or comes close) for the initial attack, and releases its energy gradually, prolonging the note's tone.
Transformer cores saturate more quickly with lower frequency, which would explain some of the fatness lent to the note.
I think in reality all of the factors are what creates the sound. A guitar amp's output is an extremely complicated non-linear system. Just look at all the well researched, unsuccessful attempts by commercial companies to get the sound without using the real deal.
Most don't sound even similar, some sound close, but none do the job as well- which is why we still use the same stuff these days
Alrighty then, how do I "play" with transformer saturation levels? Can anyone tell me how to build something that will allow me to adust the above mentioned variables on some sort of test unit ? I will buy a variac or build an adjustable tube rectifier (with some of you good peoples help of course!) How do I twist all three of these at the same time to discover the magic ?
1) Power supply sag -Ok maybe I will just buy a variac
2) Transformer saturation-clueless here <----
3) Power tube distortion -perhaps just overdrive the input ?
Sounds like a great project huh? Oh and although some have resonable sound and all---- NONE of those lil pre-amp tube for power amps have ever made "that sound" in my world!
I am getting more and more inclined to think it is a tranny thing? Combined with the sag in the power supply ? Ill order the variac just as soon as someone can tell me how to adjust tranny saturation levels ? Yes ? No ? Get a life Dave ? Oh and yes it can be recorded, and from my super low tech listening experiments "that sound" can be enhanced or softened with speakers but........it is not produced by the speakers themselves
that much I do know and understand !
1) Power supply sag -Ok maybe I will just buy a variac
2) Transformer saturation-clueless here <----
3) Power tube distortion -perhaps just overdrive the input ?
Sounds like a great project huh? Oh and although some have resonable sound and all---- NONE of those lil pre-amp tube for power amps have ever made "that sound" in my world!
I am getting more and more inclined to think it is a tranny thing? Combined with the sag in the power supply ? Ill order the variac just as soon as someone can tell me how to adjust tranny saturation levels ? Yes ? No ? Get a life Dave ? Oh and yes it can be recorded, and from my super low tech listening experiments "that sound" can be enhanced or softened with speakers but........it is not produced by the speakers themselves
that much I do know and understand !
Get a life Dave!
Got to PA a gig for my daughters band next week (20th May), will be using a Behringer BX1200 (120W transistor bass combo), a Fender KXR-60 60W transistor keyboard combo (fed via a DI box from a guitar), and a Behringer 400W+400W mixer/amp - not a valve in sight, and don't want any!.
Got to PA a gig for my daughters band next week (20th May), will be using a Behringer BX1200 (120W transistor bass combo), a Fender KXR-60 60W transistor keyboard combo (fed via a DI box from a guitar), and a Behringer 400W+400W mixer/amp - not a valve in sight, and don't want any!.
One thing that hasn't been mentioned is the fact that the power section has negative feedback wrapped around it. That MUST affect the overdriven sound as that's when the NFB is failing to do its 'intended' job. When clipping it adds a slew of harmonics instead of reducing them.
The other (obvious) thing is the choice of tube. I'll agree that the 6V6 does what you talk about well, maybe the best of all, assuming I know what it is you're hearing. If you want to get it at low levels you might look for a small beam tube in the 6x6 family. The 6F6 is actually a really nice tube, though not a whole lot less power than a 6V6. With 300V on plate & screen it'll put out about 5W. There are also a bunch of small signal beamers and pentodes, probably way to many to choose from!
A variac is an absolute necessity when experimenting, but it won't do a thing to contribute to so-called sag. For that you need a loose supply; in my experience too much capacitance in a guitar amp kills the tone. 20uF on plate and 10 or 15 on the screen and earlier stages is a good place to start. You can try adding more to taste.
When playing with the variac, don't be surprised if higher voltage gives you a brown sound you're looking for. It's counter intuitive....
As for transformer saturation, I think most people grossly over estimate its influence. The flux level in the core is inversely proportional to frequency. In other words the OT is sized for the output power and the lowest frequency that needs to be amplified. (Low E on a guitar is about 80Hz; 4x the 20Hz that most hi-fi amps are designed for. That's the real reason guitar amps have smaller output transformer, not because the (vintage) manufacturers were cheapskates or designing for distortion.) Anyway, you might get some saturation when playing power cords way down low, but when playing leads higher up you're NOT going to be working the core hard.
Having said that, I do believe that the OT has a lot to do with the overall sound, but not because it's saturating. Unfortunately, that power amp sound you're looking for might require some iron even if you're not trying to drive a speaker.
Good luck. Your quest is an old one that has been attempted by many, many people before you. But that doesn't mean you can't find success. Worst case you'll learn a ton.
-- Dave
The other (obvious) thing is the choice of tube. I'll agree that the 6V6 does what you talk about well, maybe the best of all, assuming I know what it is you're hearing.
If you want to get it at low levels you might look for a small beam tube in the 6x6 family. The 6F6 is actually a really nice tube, though not a whole lot less power than a 6V6. With 300V on plate & screen it'll put out about 5W. There are also a bunch of small signal beamers and pentodes, probably way to many to choose from!A variac is an absolute necessity when experimenting, but it won't do a thing to contribute to so-called sag. For that you need a loose supply; in my experience too much capacitance in a guitar amp kills the tone. 20uF on plate and 10 or 15 on the screen and earlier stages is a good place to start. You can try adding more to taste.
When playing with the variac, don't be surprised if higher voltage gives you a brown sound you're looking for. It's counter intuitive....
As for transformer saturation, I think most people grossly over estimate its influence. The flux level in the core is inversely proportional to frequency. In other words the OT is sized for the output power and the lowest frequency that needs to be amplified. (Low E on a guitar is about 80Hz; 4x the 20Hz that most hi-fi amps are designed for. That's the real reason guitar amps have smaller output transformer, not because the (vintage) manufacturers were cheapskates or designing for distortion.) Anyway, you might get some saturation when playing power cords way down low, but when playing leads higher up you're NOT going to be working the core hard.
Having said that, I do believe that the OT has a lot to do with the overall sound, but not because it's saturating. Unfortunately, that power amp sound you're looking for might require some iron even if you're not trying to drive a speaker.
Good luck. Your quest is an old one that has been attempted by many, many people before you. But that doesn't mean you can't find success. Worst case you'll learn a ton.
-- Dave
Ok now we are getting some where I think maybe perhaps sorta kinda a lil bit? Ok so lets say I drop a ton of cash on some magnaquests find the lowest ouput biggest beam type tube ever made then what ? Put a "knob" on the nfb circuit? Start with what where? What do you folks think of trying something like this? In your experience folks what would this "sound" like ?
http://www.lh-electric.4t.com/projects/tiny3w.htm
http://www.lh-electric.4t.com/projects/tiny3w.htm
dakotadave said:
That, kinda sorta, is a Gibson Skylark GA-5. At least some used 6BM8, or so I read - mine is 6v6. Buy one for under $100 off Fleabay. It will be spankless. If an El84 doesn't have what you are looking for, a 6BM8 single ended certainly won't either.
If you really want a good starting point, I think www.ax84.com is a good place to go. Build a Lowatt or an October. Or if you really want to kickstart things, buy their P1 kit for $200. You could be building next weekend. It is nice for what it is, and you will have a much better understanding of where to go next.
-e
This here is a Gibson GA1-rt Maestro, 6BM8 single ended. 8 glorious watts.
http://www.schematicheaven.com/gibsonamps/ga1rt.pdf
-e
http://www.schematicheaven.com/gibsonamps/ga1rt.pdf
-e
Hope you figure this one out, interesting quest! Perhaps the preamp never gets 'that sound' because the preamp tubes are always run real easy, such as 1mA or even less idle. While the output tubes are run hard, close to max. It would be interesting to build a preamp that runs the tubes near their limits so when they are overdriven they actually put out some steam. Maybe they would produce more mojo like the output tubes do. Such a preamp would also give more strain on the power supply and perhaps give some sag without the master volume turned all the way up.
Ok back to the issue "that sound" tranny and sag? yes ? How do I make that happen ? Beam tube uhuh yes !?! Seems like that is a major point of "that sound" So since I have never built one (but that dosent scare me at all )somebody lay it on me! A diagram schematic whatever . I'll even buy some of your old junk if you think it has "that sound" errr maybe anyway ! Lowest power big beam type tube is a ? I have a bunch of trannies here old hammond stuff from organ amps mostly a few carilion some misc other stuff blah blah > Also good venders for new hammond stuff .Have wholesale status with some of them there folks ! Sorry still cannot convince me on the ax84 stuff, to many non "that sound" units out there songworks, torres, thd etc etc. I would really like to play with tranny saturation and the sag factor but dunno how or where to begin ?
Oh and cant I just push the input hard to get the power tube(s) to "soft clip" ? Anyone ever build an adjustable NFB circuit ?
Whoa slow down there.....
ok here it is a lil less ocd'ed
1) lowest wattage output BIG BEAM type tube is ________?
2) I can make the tranny saturate by______________?
3) Power supply sag will best be achived by___________?
4) Neg Feed Back circuit should ___________-?
And I can bread board this to play around with it by__________?
Oh and cant I just push the input hard to get the power tube(s) to "soft clip" ? Anyone ever build an adjustable NFB circuit ?
Whoa slow down there.....
ok here it is a lil less ocd'ed
1) lowest wattage output BIG BEAM type tube is ________?
2) I can make the tranny saturate by______________?
3) Power supply sag will best be achived by___________?
4) Neg Feed Back circuit should ___________-?
And I can bread board this to play around with it by__________?
dakotadave said:
1) Do a paramter find in Duncan Monroes tdsl pe. 6HU8 is pretty down there. A pentode, not a beamer, wimpy and two in one bottle.
2) Read RDH4. Google rdh4 and geek zone.
3) a wimpy power supply.
4) Read Morgan Jones, RDH4, some of the books at pmillett.com
5) You get a piece of wood and screw things into it. Use relay sockets for your octal tubes. Tag strips & nails for the rest. Lethal, but convenient.
Your questions are not going to get you much closer to an answer. It seems to me you looking for the shortcut which does not exist for you.
I think the 6BM8 will sound more like an EL84 than anything else you might be familiar with.
Have you heard/tried a Fender Champ? It might be the sound you're looking for. Still not sure how much power you want. At first I was thinking that you wanted something that would be built into a larger amp ... One thing I always wanted to try is loading a black/silver face Champ with a 4 ohm power resistor, then putting a volume pot across the resistor. Feed that to the input of your favorite 'big' amp for the ultimate stomp box. The entire output stage (including driver tube, output tube, and transformer all with its own NFB loop) could easily be built into a larger amp. That would be the ultimate master volume control, I suppose.
Anyway, if you haven't tried a Champ then look around some of the shops nearby that sell used and vintage gear. It's worth a listen if only to get an idea what's already been done well. Note: Fender has made a few amps with 'Champ' in the name. I'm talking about the little ones with an 8" speaker, 3 tubes, 3 knobs (volume, bass, treble) and very little else.
Schematics are available in the web somewhere, I'm sure. Output and power transformers are available from lots of places.
-- Dave
Have you heard/tried a Fender Champ? It might be the sound you're looking for. Still not sure how much power you want. At first I was thinking that you wanted something that would be built into a larger amp ... One thing I always wanted to try is loading a black/silver face Champ with a 4 ohm power resistor, then putting a volume pot across the resistor. Feed that to the input of your favorite 'big' amp for the ultimate stomp box. The entire output stage (including driver tube, output tube, and transformer all with its own NFB loop) could easily be built into a larger amp. That would be the ultimate master volume control, I suppose.
Anyway, if you haven't tried a Champ then look around some of the shops nearby that sell used and vintage gear. It's worth a listen if only to get an idea what's already been done well. Note: Fender has made a few amps with 'Champ' in the name. I'm talking about the little ones with an 8" speaker, 3 tubes, 3 knobs (volume, bass, treble) and very little else.
Schematics are available in the web somewhere, I'm sure. Output and power transformers are available from lots of places.
-- Dave
It all depends what kind of sound you want.
There are many variables involved, the most important being your taste. There is very little consensus in this area, bar people sticking to a couple of designs that work well for a number of situations.
There is a big difference between a HiFi amp and a guitar amp. In all respects. And most manufacturers are cheapskates, even if sometimes it pans out for the better. It's just business.
There are many variables involved, the most important being your taste. There is very little consensus in this area, bar people sticking to a couple of designs that work well for a number of situations.
There is a big difference between a HiFi amp and a guitar amp. In all respects. And most manufacturers are cheapskates, even if sometimes it pans out for the better. It's just business.
Ok then how about this - Help me build a tube rectified power supply with adustable sag. Schematics? Web sites ? Let me start with this and go from there. And I guess I will still need to have all y'alls thoughts on what low watt beam type tube to use, OH and hey I just was thinking (yeah I do that) that every amp I ever heard with "that sound" had more than one beam type tube does that maybe do something I haven't been considering ?
I've been looking at Mullards book and at the reprint of the British GE book and Brue Rozenblints beginner's guide lots of web sites and here too. May I say I believe :
Ignorance is cure-able Only stupid is forever !
But I have not found much about my quest in these books but I have found lots of information, like I have in this forum . So let me see if I can qualify my situation here !
I dont need to re-invent the wheel, the internal combustion engine, or the vaccum tube. But I do need to cure my ignorance and if the internet and its resources are the easy way well.......
I've been looking at Mullards book and at the reprint of the British GE book and Brue Rozenblints beginner's guide lots of web sites and here too. May I say I believe :
Ignorance is cure-able Only stupid is forever !
But I have not found much about my quest in these books but I have found lots of information, like I have in this forum . So let me see if I can qualify my situation here !
I dont need to re-invent the wheel, the internal combustion engine, or the vaccum tube. But I do need to cure my ignorance and if the internet and its resources are the easy way well.......
This is a very complex situation .....
There is a number of things to keep in mind...
There are standing waves occuring...since the speakers are jumping pretty hard and overhoot...this cone movement is generating a back EMF..this translated back through the output transformer and is steped up in voltage across the primary winding...some of these signals are harmonically destructive while others sum...
The OPT is really not far into saturation in most of the Marshall and Fender amps....
The other ting to keep in mind is that the output valves are acting like TRIODES with low plate resistance when the amp is cranked..
Look at the output waveform when cranked...you see a SQAURE WAVE.....well the top flat section of the waveform is where the plate load is swinging into the TRIODE region of the plate curves...
Since the flat section takes up 98% of the waveform, this means the tube swing spend vertually no time in Saturation region..so the average plate resistance with respect to time is low like 800 ohms.....this will now change the frequency response of the outputstage dramatically, since the inductance, leakages, winding capacitance take on a new transfer function at this point with respect to the new effective plate resistance...
The speakers play a major role, since they are usually in saturaton during this situation and they take on new non-linear characteristics as well.....
You will have blocking distortion at the grids of the output stage....due to the typical high impedance drivers of the phase inverter... The phase inverter decoupling cap will overcharge from the feedback loop durring overload and the time constant for the feedback loop to recover becomes very long, say goodbye to high frequency response...
This is just the tip of the iceburg... there are MANY other variables going on....you need to look at the plate load, since this is critical, the voltage sag with recovery time....the screen supply with it's LC filter usually rings and can oscillate above the plate voltage..ect..ect...
Chris
There is a number of things to keep in mind...
There are standing waves occuring...since the speakers are jumping pretty hard and overhoot...this cone movement is generating a back EMF..this translated back through the output transformer and is steped up in voltage across the primary winding...some of these signals are harmonically destructive while others sum...
The OPT is really not far into saturation in most of the Marshall and Fender amps....
The other ting to keep in mind is that the output valves are acting like TRIODES with low plate resistance when the amp is cranked..
Look at the output waveform when cranked...you see a SQAURE WAVE.....well the top flat section of the waveform is where the plate load is swinging into the TRIODE region of the plate curves...
Since the flat section takes up 98% of the waveform, this means the tube swing spend vertually no time in Saturation region..so the average plate resistance with respect to time is low like 800 ohms.....this will now change the frequency response of the outputstage dramatically, since the inductance, leakages, winding capacitance take on a new transfer function at this point with respect to the new effective plate resistance...
The speakers play a major role, since they are usually in saturaton during this situation and they take on new non-linear characteristics as well.....
You will have blocking distortion at the grids of the output stage....due to the typical high impedance drivers of the phase inverter... The phase inverter decoupling cap will overcharge from the feedback loop durring overload and the time constant for the feedback loop to recover becomes very long, say goodbye to high frequency response...
This is just the tip of the iceburg... there are MANY other variables going on....you need to look at the plate load, since this is critical, the voltage sag with recovery time....the screen supply with it's LC filter usually rings and can oscillate above the plate voltage..ect..ect...
Chris
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