Class A
Question:
> Can someone please tell me what the Class A thing means? what is a Class A > tube amp? what’s a Class AB?
Technical Definition: A class A amp runs its output tubes under conditions that cause each tube to reproduce the entire waveform input: Class AB amps run the output tubes under conditions where they cutoff, so that one tube forms one part of the waveform and the other tube in the push pull pair forms the other. All single ended amps are class A, few push pull amps are class A. No single ended amps are class AB. Practical Definition: Class AB puts out more power for a given tube complement and amount of power consumed. It also has a different sound. Really you don’t care. Just listen to amps. Buy, build use the ones you like. ROn
Response:
Can someone please tell me what the Class A thing means? what is a Class A tube amp? what’s a Class AB? thanks Jonathan
Response:
My .02 toward a simplified explanation: Class A: The entire guitar signal (think sine wave) is reproduced/amplified by one tube (two or more tubes might be doing this simultaneously). All tubes in the power amp reproduce/amplify the full signal. An amp with only one power tube *must* be Class A. Class B: Half the waveform is reproduced/amplified by one tube. When the waveform crosses over the horizontal axis (think x-axis or zero-line) the tube shuts itself off while another tube turns itself on to continue amplifying the rest of the signal. As you might guess such an abrupt change-over isn’t handled by the two tubes (or pairs of tubes, etc.) very well. The point where the signal crosses over is prone to distortion… crossover distortion. Class AB: In order to reduce crossover distortion some overlap is designed into the amplifier. Tubes work for more than 50% but less than 100% of the signal. Qualities: Class A… Runs hot (shorter tube life), more taxing on power and output transformers. Less efficient (less power than if the same tubes were redesigned to run Class AB) . Distortion emphasizes ‘even-order harmonics’ (think octave, perfect fourths and other musical tones) – that’s the BIG plus of Class A. Class AB… More efficient (more watts per tube). More ‘odd-order harmonics’ (think of 2nds or augmented 5ths – dissonant combinations) added to the signal when distortion sets in. My explanation shouldn’t have centered on ‘tube’ because the same principles apply when using solid-state components. Hope this helps some, STRINGBEND
Response:
>My .02 toward a simplified explanation: >Class A: >The entire guitar signal (think sine wave) is reproduced/amplified by one tube >(two or more tubes might be doing this simultaneously). All tubes in the power >amp reproduce/amplify the full signal. An amp with only one power tube *must* >be Class A.
That’s basically true for amps which are trying to be linear; however, a single tube amp can be used in other power classes, such as C. But it won’t sound good in an audio application. Just being a little nit-picky 
/RF rfries at pacbell dot net
Response:
<Snip terse and clear explanation of differences between A A/B and B amps> Besides the Vox AC-30 and the older Fender Bassman, what other common amps are Class A? Charles Thomas Guitarist, Singer, Songwriter…. not an amp tech I don’t play anyone on the Internet except myself
Response:
> <Snip terse and clear explanation of differences between A A/B and B amps> > Besides the Vox AC-30 and the older Fender Bassman, what other common amps are > Class A?
Bassmans are class AB. Best known class A amp after Vox is the Fender Champ. The Boogie SimulClass amps could be operated class A or class AB. Any amp with a single power tube is class A, that includes almost all small tube practice amps in the Champ’s class (plus innumerable tube powered table radios and phonographs). — Brian Rost 3Com Corp. 978-264-1550 Playing the bass is like dancing the limbo: how low can you go?
Response:
> > <Snip terse and clear explanation of differences between A A/B and B amps> > Besides the Vox AC-30 and the older Fender Bassman, what other common amps are > Class A? > Bassmans are class AB.
It was my understanding that the older Bassmans (blond? brown?) back when they had tube rectifiers and presence controls were class A. I guess I was misinformed. Apologies. CT
Response:
> Besides the Vox AC-30 and the older Fender Bassman, what other common amps are > Class A?
Just a few off the top of my head: Matchless amps (not sure if *all* are, but most are) some Mesas (Maverick, Blue Angel, Mark IV) Trace Elliott Velocette Carvin Vintage 33 VHT Pitbull (class A or AB) Crate Vintage amps Mark — Mark J. Rosen "Underfoot the ground is patched with http://www.grok.org manzanita stark and shining in the breeze"
Response:
>Besides the Vox AC-30 and the older Fender Bassman, what other common amps >are >Class A?
Well I’m no expert but I believe many of the tweed Fenders (not just the Bassman) were Class A bias. Of course a Champ or a tweed Princeton would be Class A. (Any *guitar or audio* amp with a single power tube is going to be Class A). I also think several of the old Gibsons, Supros, etc. were Class A. If you’ve got a book of schematics you can look for 220 ohm +/- resistors on the cathode. This doesn’t indicate Class A – it indicates Cathode Bias, but very often where you find one you find the other. In the past few years ‘Class A’ seems to be almost trendy. I’m sure the Matchless DC-30 and all the other Vox clones are Class A. Plus everybody from Mesa to Crate advertise Class A amps as if they’re the holy grail of tone. I’m sure I’d enjoy owning a Vox (or a Trainwreck, etc.), but I’m partial to the Blackface Fenders (Class AB) with reverb for now. <g>
Response:
> <Snip terse and clear explanation of differences between A A/B and B amps> > Besides the Vox AC-30 and the older Fender Bassman, what other common amps are > Class A?
All the little amps with one output tube, like the champ and it’s brethren. Otherwise a pretty small pack of push pull class a amps. Most push pull amps are designed with advertisible power rating in mind. ROn
Response:
Check out the dual el-84 Trace Eliot Velocette…if you can find one. Class A and amazing.
Response:
I’m pretty sure both the smallest Carvin tweed amp (Nomad?) and the Peavey Classic 20 and Classic 30 are class A amps, as well. Tim Armstrong Chief Zymurgist – Atlanta BeerGarten, Newport News, Virginia
Response:
I modified a Bassman back in 66 . . . sure it was class AB… – checking my mind for holes – – Hide quoted text — Show quoted text ->Besides the Vox AC-30 and the older Fender Bassman, what other common amps >are >Class A? >Well I’m no expert but I believe many of the tweed Fenders (not just the >Bassman) were Class A bias.
Response:
>Well I’m no expert but I believe many of the tweed Fenders (not just the >Bassman) were Class A bias. Of course a Champ or a tweed Princeton would be >Class A. >(Any *guitar or audio* amp with a single power tube is going to be Class A). >I also think several of the old Gibsons, Supros, etc. were Class A. >If you’ve got a book of schematics you can look for 220 ohm +/- resistors on >the cathode. This doesn’t indicate Class A – it indicates Cathode Bias, but >very often where you find one you find the other.
Cathode bias amplifiers are almost always Class A, or very close to it (yeah, the old RCA book shows a cathode-biased "AB1" amplifier, but there’s only a 6 ma per tube diff between zero signal & max current. Pretty awful close to Class A). That includes a majority of amps built in the 1950’s. Class AB1 really didn’t start to take off in consumer tube amps until people started wanting more power and cheap bias rectifiers became available. Prior to ca. 1955, most fixed bias amps had an extra tube for bias rectification, this was generally only seen in high powered industrial/commercial/movie theater stuff. Ned Carlson Triode Electronics "where da tubes are!" 2225 W Roscoe Chicago, IL, 60618 USA ph 773-871-7459 fax 773-871-7938 12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun http://www.triodeel.com Your Start Page for Tube and Tube Amp info on the net… http://www.triodeel.com/tlinks.htm
Response:
all bassmans are class AB. the original Ampeg Jets are class A Jim Eppard e&e audio Boom’s Farm Productions Applehead Recording
Response:
>> Besides the Vox AC-30 and the older Fender Bassman, what other common amps are > Class A? >All the little amps with one output tube, like the champ and it’s >brethren. Otherwise a pretty small pack of push pull class a amps. Most >push pull amps are designed with advertisible power rating in mind. >ROn
I don’t think there are any "push pull" amps that are class "A". A push pull amp by it’s nature is a class "AB" amp. Some Class AB amps use a method of removing the center tap on the output transformer and rewiring the output tubes to convert to a class A amp. This is what Mesa’s Simuclass is all about. It is a very simple conversion on most amps and I would be glad to post general info on how to do it if anyone is interested. Mike
Response:
> I don’t think there are any "push pull" amps that are class "A".
Wrong answer TechnoPoseur! Go to a Matchless dealer and you’ll see tangible evidence to the contrary. Hell, Come on over and look at my Blue Angel – pure push-pull class A. > A push pull amp by it’s nature is a class "AB" amp.
Yeah, well maybe in your little fantasy world this is true, but thankfully it’s not true here in the real world. Note the title of chapter 13, section 6 of the "Radiotron Designer’s Handbook" (4th Edition): "Push-Pull Pentodes and Beam Power Amplifiers, Class A, AB1" Of course, I’m sure you’re much smarter than old F. Langford-Smith ever was (you *do* know who he is, don’t you). > Some Class AB amps use a method of removing the center tap on > the output transformer and rewiring the output tubes to convert > to a class A amp. This is what Mesa’s Simuclass is all about. > It is a very simple conversion on most amps and I would be glad > to post general info on how to do it if anyone is interested.
Given the fact that you don’t even exhibit a marginal understanding of one of the most basic principles of tube circuit design I think I’ll take a pass on any "help" from you. Sheesh, – Punkerdubh
Response:
Duncan Convertible (dual class)
Response:
>My – arn’t you being a bit hard on the guy? Anyway, if push-pull can >be A or AB – what about push-push? Must be pure class B – or have you >not heard about that one. It is kind of a rare term.
Uh….Uh-huh-huh….he said "hard-on"…Uh….how about "pull-pull", Beavis? Na, na, nanatna, nanana nanana nanatna! (Iron Man air riff) 8^)
Response:
>So you haven’t heard of it – try an old Lafayette catalog! >push push in the bush
YEAH! Only we used to say, "Push (pause) Push (pause) Push in-to the bush"! And, I DO have an old Lafayette catalog, AND an old Allied (pre-Radio Shack) catalog with Dynaco Stereo 70’s and all of the cool stuff that we all want NOW. My father was only partly cool, when I was in high school (1965), he bought a Knight receiver (20 watts real SS power), a Garrard Lab 80 turntable with Empire cartridge (ooooh!), and the Knight speakers with a 15" Jensen woof, a 4 x 10 mid horn, and a dome tweet. This was actually counter to his thinking as we built model cars as kids while listening to one of his "Silver Marshall" monster-sized tube floor radios that he bought and repaired. Oh, well, I guess solid state fooled a lot of people for a while! The speakers were damaged when the sump pump failed (common Midwest disaster), but they still worked and we sold them at the estate auction for what they went for new and they were 22 years old! I must be getting old.
Response:
> My father was only partly cool, when I was in high school (1965), he > bought a Knight receiver (20 watts real SS power), a Garrard Lab 80 > turntable with Empire cartridge (ooooh!), and the Knight speakers with a 15" > Jensen woof, a 4 x 10 mid horn, and a dome tweet.
Woohoo! I have a Knight. It was the amp for the sound system at my Church when it was built and when they cleaned out the closets they found it and gave it to me. It is 32 watts of tube power and it really kicks! I use it with a box I built using 2 Celestion Greenbacks (25w) and to piezo horns. It sounds great and works great for a keyboard amp too! Aaron. — http://www.avweb.net -=- you know you want to
Response:
My – arn’t you being a bit hard on the guy? Anyway, if push-pull can be A or AB – what about push-push? Must be pure class B – or have you not heard about that one. It is kind of a rare term. – Hide quoted text — Show quoted text -> I don’t think there are any "push pull" amps that are class "A". >Wrong answer TechnoPoseur! Go to a Matchless dealer and you’ll >see tangible evidence to the contrary. Hell, Come on over and >look at my Blue Angel – pure push-pull class A. > A push pull amp by it’s nature is a class "AB" amp. >Yeah, well maybe in your little fantasy world this is true, but >thankfully it’s not true here in the real world. Note the title >of chapter 13, section 6 of the "Radiotron Designer’s Handbook" >(4th Edition): "Push-Pull Pentodes and Beam Power Amplifiers, >Class A, AB1" Of course, I’m sure you’re much smarter than old >F. Langford-Smith ever was (you *do* know who he is, don’t you). > Some Class AB amps use a method of removing the center tap on > the output transformer and rewiring the output tubes to convert > to a class A amp. This is what Mesa’s Simuclass is all about. > It is a very simple conversion on most amps and I would be glad > to post general info on how to do it if anyone is interested. >Given the fact that you don’t even exhibit a marginal understanding >of one of the most basic principles of tube circuit design I think >I’ll take a pass on any "help" from you. >Sheesh, >- Punkerdubh
Response:
So you haven’t heard of it – try an old Lafayette catalog! push push in the bush – Hide quoted text — Show quoted text ->My – arn’t you being a bit hard on the guy? Anyway, if push-pull can >be A or AB – what about push-push? Must be pure class B – or have you >not heard about that one. It is kind of a rare term. >Uh….Uh-huh-huh….he said "hard-on"…Uh….how about "pull-pull", Beavis? >Na, na, nanatna, nanana nanana nanatna! >(Iron Man air riff) >8^)
Response:
>My – arn’t you being a bit hard on the guy? Anyway, if push-pull can >be A or AB – what about push-push? Must be pure class B – or have you >not heard about that one. It is kind of a rare term.
As far as I’m concerned, if anyone spouts patently wrong information and claims that it’s fact, then they’re fair game for a flame. Unless, of course, they have their tongue planted in their cheek. BTW, why limit yourself to binary thinking? I’m working on a class WD40 push-push-pull-push-pull-pull-pull amp – it uses hexadecodes (a tube with fourteen grids). – Punkerdubh
Response:
>all bassmans are class AB.
I think a few *really* old ones were Class A, at least my book shows a couple of diagrams of ones with cathode resistors. One has a 125 ohm cathode resistor..sounds like them 6L6’s ran awful hot, or at real low voltage. >he original Ampeg Jets are class A
Yup. Ned Carlson Triode Electronics "where da tubes are!" 2225 W Roscoe Chicago, IL, 60618 USA ph 773-871-7459 fax 773-871-7938 12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun http://www.triodeel.com Your Start Page for Tube and Tube Amp info on the net… http://www.triodeel.com/tlinks.htm
Response:
Are single power tube amps the only true class A amps ?
Response:
>Are single power tube amps the only true class A amps ?
Oh no!!! Another Class A thread! No. And not all single ended amps are Class A. Pete — And all that was left was to test it. –Dr. Jekyll
Response:
> Are single power tube amps the only true class A amps ?
Trying to ‘type" that fingering your lips sound, like bbl bbl bbl bbl.
Response:
> Are single power tube amps the only true class A amps ?
not at all, paralell SE can have pretty much as many power tubes as you want and still be class A. adam
Response:
>> Are single power tube amps the only true class A amps ? > Oh no!!! Another Class A thread! > No. And not all single ended amps are Class A.
Sure they are Pete -at least guitar and audio amps are. Lloyd – Hide quoted text — Show quoted text -> Pete > — > And all that was left > was to test it. –Dr. Jekyll
Response:
> Are single power tube amps the only true class A amps ?
No Single power tube audio amps are definitely Class A as are parallel configurations. Push pull amps CAN be Class A; but it’s quite common to see cathode biased push pull amps advertised as being Class A when in fact they are Class A/B. But the most important fact is that it really doesn’t matter. Tone only matters. Weather an amp is Class X or Class Y doesn’t mean the amp sounds good or not. As always use your ears to decide… Lloyd
Response:
What I was getting around to is for instance if you were using EL34 power tubes and perhaps a 5U4 as a rectifier with a couple of 12AX7’s for preamp how many EL34’s would it take to come up with 30 or 40 watts of power.I know that class A isnt as efficient as AB and that over 4 power tubes 6 max starts leading into other troubles.
– Hide quoted text — Show quoted text -> Are single power tube amps the only true class A amps ?
Response:
> What I was getting around to is for instance if you were using EL34 power > tubes and perhaps a 5U4 as a rectifier with a couple of 12AX7’s for preamp > how many EL34’s would it take to come up with 30 or 40 watts of power.I know > that class A isnt as efficient as AB and that over 4 power tubes 6 max > starts leading into other troubles. > Are single power tube amps the only true class A amps
Circa 11 watts per tube (EL34 Class A) into 30 or 40 means that you could do it with a quad of EL34s. I don’t know off hand if a single 5U4 would be able to handle the current needed -anyone? Lloyd
Response:
>>Are single power tube amps the only true class A amps ? > Trying to ‘type" that fingering your lips sound, like bbl bbl bbl bbl.
It’s called "lip strummin". dw
Response:
With tubes, push-pull class A & parallel-tube class A are also common. However, any single-power-amp-tube or parallel-power-tube *audio* amp *must* be class A – it cannot be anything else or it would not be linear (i.e., unuseable for audio). The reason for this is simple: the tube must conduct for 360 degrees of the signal (no cutoff) or some of it will be missing. Similarly, any push-pull *tube* *audio* amp *must* be class A, AB1, AB2 or B – it cannot be C which is likewise nonlinear. Solid state power amps can & often do run higher classes of operation than tubes can. There is gear around today with MOSFETS running class H. This is of little concern to a guitar player, except that some of the finest SS amps operate at other classes. You question is interesting because practically speaking, a single-tube class A power amp stage is still typically rather high distortion/low power/inefficient/heavy per watt. P-P design cancels out much harmonic distortion and permits operation at more reasonable efficiency. Parallel-tube class A power stages have been of interest & experimentation for many years, but usually with the primary goal of achieving a low enough output impedance to eliminate the output transformer for audiophile purposes – not of making a guitar amp perform better. Almost all of the other tube stages in your amp are class A, too – but they are voltage amplifiers, not power amplifiers. I, for one, have never understood the point of pursuing a class A guitar amp (beyond single-tube), when AB1 typically makes a lot more power with about the same distortion behavior (depending upon specific design). Most people who post to & read this NG are only concerned with tube amps and with harmonic distortion – an awfully narrow view relevant largely only to one style of playing ("classic" rock or crank/blues). However, intermod distortion is a major deal to those playing clean styles (like jazz, funk, surf or techno). Tubes are also far outclassed tone-wise by SS for many other modern styles of playing. So I’m wondering why most people here seem so ignorant of and disinterested in modern guitar amps (or even some of the better vintage SS ones), and instead ponder things like "amp class." A lot of the best music is played clean – and it takes a lot more power than most tube amps can produce in a reasonably-sized package to get out from a stage playing clean; maybe 10x as much (twice the volume/dynamic capacity). If I could make a single-power-tube class A guitar amp play clean, I’d build one with an 813 for real balls. Don’t ask me where I’d find the output iron, how I’d make the 2.5kv supply safe for a portable device, or who’d carry the fkr. :-) The truth is that an 8-lb SS amp would kick the shit out of it tonewise at equal power, and that tube amp technology is very limited tone-wise, guitar-wise & power-wise, though good at some things. I look forward to the day when the NG catches up at least to the mid-’60’s, amp-wise & knowledge-wise. – Hide quoted text — Show quoted text – > Are single power tube amps the only true class A amps ?
Response:
– Hide quoted text — Show quoted text -> With tubes, push-pull class A & parallel-tube class A are also common. > However, any single-power-amp-tube or parallel-power-tube *audio* amp > *must* be class A – it cannot be anything else or it would not be > linear (i.e., unuseable for audio). The reason for this is simple: > the tube must conduct for 360 degrees of the signal (no cutoff) or > some of it will be missing. Similarly, any push-pull *tube* *audio* > amp *must* be class A, AB1, AB2 or B – it cannot be C which is > likewise nonlinear. Solid state power amps can & often do run higher > classes of operation than tubes can. There is gear around today with > MOSFETS running class H. This is of little concern to a guitar > player, except that some of the finest SS amps operate at other > classes. > You question is interesting because practically speaking, a > single-tube class A power amp stage is still typically rather high > distortion/low power/inefficient/heavy per watt. P-P design cancels > out much harmonic distortion and permits operation at more reasonable > efficiency. Parallel-tube class A power stages have been of interest > & experimentation for many years, but usually with the primary goal of > achieving a low enough output impedance to eliminate the output > transformer for audiophile purposes – not of making a guitar amp > perform better. > Almost all of the other tube stages in your amp are class A, too – but > they are voltage amplifiers, not power amplifiers. > I, for one, have never understood the point of pursuing a class A > guitar amp (beyond single-tube), when AB1 typically makes a lot more > power with about the same distortion behavior (depending upon specific > design). > Most people who post to & read this NG are only concerned with tube > amps and with harmonic distortion – an awfully narrow view relevant > largely only to one style of playing ("classic" rock or crank/blues). > However, intermod distortion is a major deal to those playing clean > styles (like jazz, funk, surf or techno). Tubes are also far > outclassed tone-wise by SS for many other modern styles of playing. > So I’m wondering why most people here seem so ignorant of and > disinterested in modern guitar amps (or even some of the better > vintage SS ones), and instead ponder things like "amp class." A lot > of the best music is played clean – and it takes a lot more power than > most tube amps can produce in a reasonably-sized package to get out > from a stage playing clean; maybe 10x as much (twice the > volume/dynamic capacity). > If I could make a single-power-tube class A guitar amp play clean, I’d > build one with an 813 for real balls. Don’t ask me where I’d find the > output iron, how I’d make the 2.5kv supply safe for a portable device, > or who’d carry the fkr. :-) The truth is that an 8-lb SS amp would > kick the shit out of it tonewise at equal power, and that tube amp > technology is very limited tone-wise, guitar-wise & power-wise, though > good at some things. I look forward to the day when the NG catches up > at least to the mid-’60’s, amp-wise & knowledge-wise.
You make it sound like tube amps can’t do clean? I can tell you that my Guytron has just killer cleans[1] and it’s nothin but tubes… Lloyd [1] 100 watts from EL34s. – Hide quoted text — Show quoted text -> Are single power tube amps the only true class A amps ?
Response:
- Hide quoted text — Show quoted text ->With tubes, push-pull class A & parallel-tube class A are also common. >However, any single-power-amp-tube or parallel-power-tube *audio* amp >*must* be class A – it cannot be anything else or it would not be >linear (i.e., unuseable for audio). The reason for this is simple: >the tube must conduct for 360 degrees of the signal (no cutoff) or >some of it will be missing. Similarly, any push-pull *tube* *audio* >amp *must* be class A, AB1, AB2 or B – it cannot be C which is >likewise nonlinear. Solid state power amps can & often do run higher >classes of operation than tubes can. There is gear around today with >MOSFETS running class H. This is of little concern to a guitar >player, except that some of the finest SS amps operate at other >classes. >You question is interesting because practically speaking, a >single-tube class A power amp stage is still typically rather high >distortion/low power/inefficient/heavy per watt. P-P design cancels >out much harmonic distortion and permits operation at more reasonable >efficiency. Parallel-tube class A power stages have been of interest >& experimentation for many years, but usually with the primary goal of >achieving a low enough output impedance to eliminate the output >transformer for audiophile purposes – not of making a guitar amp >perform better. >Almost all of the other tube stages in your amp are class A, too – but >they are voltage amplifiers, not power amplifiers. >I, for one, have never understood the point of pursuing a class A >guitar amp (beyond single-tube), when AB1 typically makes a lot more >power with about the same distortion behavior (depending upon specific >design). >Most people who post to & read this NG are only concerned with tube >amps and with harmonic distortion – an awfully narrow view relevant >largely only to one style of playing ("classic" rock or crank/blues). >However, intermod distortion is a major deal to those playing clean >styles (like jazz, funk, surf or techno). Tubes are also far >outclassed tone-wise by SS for many other modern styles of playing. >So I’m wondering why most people here seem so ignorant of and >disinterested in modern guitar amps (or even some of the better >vintage SS ones), and instead ponder things like "amp class." A lot >of the best music is played clean – and it takes a lot more power than >most tube amps can produce in a reasonably-sized package to get out >from a stage playing clean; maybe 10x as much (twice the >volume/dynamic capacity). >If I could make a single-power-tube class A guitar amp play clean, I’d >build one with an 813 for real balls. Don’t ask me where I’d find the >output iron, how I’d make the 2.5kv supply safe for a portable device, >or who’d carry the fkr. :-) The truth is that an 8-lb SS amp would >kick the shit out of it tonewise at equal power, and that tube amp >technology is very limited tone-wise, guitar-wise & power-wise, though >good at some things. I look forward to the day when the NG catches up >at least to the mid-’60’s, amp-wise & knowledge-wise. > You make it sound like tube amps can’t do clean? > I can tell you that my Guytron has just killer cleans[1] and it’s nothin but > tubes… > Lloyd > [1] 100 watts from EL34s.
Hi, I’ll say. Still audiophiles are crazy about tube amps as well as guitar players. Tony – Hide quoted text — Show quoted text ->>Are single power tube amps the only true class A amps ?
Response:
- Hide quoted text — Show quoted text -> What I was getting around to is for instance if you were using EL34 power > tubes and perhaps a 5U4 as a rectifier with a couple of 12AX7’s for preamp > how many EL34’s would it take to come up with 30 or 40 watts of power.I know > that class A isnt as efficient as AB and that over 4 power tubes 6 max > starts leading into other troubles. > Circa 11 watts per tube (EL34 Class A) into 30 or 40 means that you could do > it with a quad of EL34s. > I don’t know off hand if a single 5U4 would be able to handle the current > needed -anyone?
(Pssst …. Lloyd, I think you’re speaking of EL84s, a quad of which will do around 30 – 40 watts. If Keith wants the same output from EL34s, he’ll only need a pair, which can actually give him up to around 50 watts.) Monte
Response:
Thank you everyone.Once again you’ve helped immensely.
Response:
– Hide quoted text — Show quoted text ->> What I was getting around to is for instance if you were using EL34 > power >> tubes and perhaps a 5U4 as a rectifier with a couple of 12AX7’s for > preamp >> how many EL34’s would it take to come up with 30 or 40 watts of power.I > know >> that class A isnt as efficient as AB and that over 4 power tubes 6 max >> starts leading into other troubles. > Circa 11 watts per tube (EL34 Class A) into 30 or 40 means that you could > do > it with a quad of EL34s. > I don’t know off hand if a single 5U4 would be able to handle the current > needed -anyone? > (Pssst …. Lloyd, I think you’re speaking of EL84s, a quad of which will > do around 30 – 40 watts. If Keith wants the same output from EL34s, he’ll > only need a pair, which can actually give him up to around 50 watts.)
(….No Monte, the EL34 is (according to the tube manuals) only capable of 11 watts of output in a CLASS A configuration. Don’t believe all the manufactures hype about their cathode biased amps being "Class A".) – Hide quoted text — Show quoted text -> Monte
Response:
Big difference between "Class A", and "Classy".LOL
Response:
> You make it sound like tube amps can’t do clean? > I can tell you that my Guytron has just killer cleans[1] and it’s nothin but > tubes…
Not meant to imply going that far – of course some do great clean. It just seems counterproductive for modern clean situations (or even pedal/effects situations?) to deal with all the weight & bulk for equivalent pwr. Consider what it takes to do 250w of clean (or even 400+ as some agressive clean players are doing in ordinary clubs). Sand has come a long way from sterility, too. BTW my small fkp: a single tube may indeed run other than A if it’s a dual-section tube working PP.
Response:
One may question whether operating class has any practical relevance to real-world classy playing, or if anyone should care, beyond pwr delivery. But you might want to be careful that your joke doesn’t start a "Class E" myth next<g>. – Hide quoted text — Show quoted text – > Big difference between "Class A", and "Classy".LOL
Response:
> > (Pssst …. Lloyd, I think you’re speaking of EL84s, a quad of which will > do around 30 – 40 watts. If Keith wants the same output from EL34s, he’ll > only need a pair, which can actually give him up to around 50 watts.) > Monte > (….No Monte, the EL34 is (according to the tube manuals) only capable of > 11 watts of output in a CLASS A configuration. Don’t believe all the > manufactures hype about their cathode biased amps being "Class A".)
Hmm … no manufacturer’s hype …. I was looking at the RC-27 and mistakenly quoted the EL34’s Max Plate Dissipation instead of Max Signal Power Output. My bad. Monte
Response:
Related Posts