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Thread: Denis Cornell.

  1. #1
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Denis Cornell.

    I've decided to resume my relationship with electricity.

    Here's one you don't see every day...the last time I played one of these was 16 years ago.

    A 15 watt, twin channel, Class A, valve rectified Cornell Rambler. Not that well known outside of the Motherland, but easily sits alongside other modern small production amps makers - think Matchless, Bad Cat et al.

    Tipping plenty of its head to Vox, this little beauty is right up my street. Lovely chimey cleans, but with an added muscularity...it reminds me of the Matchless tone of a Chieftain that I had. The foot switchable second channel puts plenty of crunch on the table, and using the filter control one can make that as raspy or as creamy as one wants. Perfect for someone like me that hates tap dancing with effects pedal gizmotronics...

    Once I've mortgaged the house to get some decent Blackburn & Brimar glass into it, it's going to sound even better than it does now.

    Thanks to my forum Pal who put this my way and made it happen. My neighbours would like a word.....



    For those of you interested in finding out a little more about Cornell amps, this Tone Quest report is a good read...

    http://www.cornellamps.com/wp-conten...eport-2003.pdf

    Shakespeare walks into a pub, the Landlord says "get out, you're Bard"

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    Re: Denis Cornell.

    I knew it was just a matter of time, and with class.
    So, what new guitar are you not telling us and wife about?


  3. #3
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Quote Originally Posted by jhmp View Post
    I knew it was just a matter of time, and with class.
    So, what new guitar are you not telling us and wife about?

    Thanks Pal.

    A vintage 57 Special and a 2003 R4 Brazilian Oxblood on loan from a Forum Brother, and Gentleman.

    I'm sure you'll understand that discretion dictates there being no pictures of the guitars.

    Shakespeare walks into a pub, the Landlord says "get out, you're Bard"

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    Re: Denis Cornell.

    Wraptails dominate my heart, I'm sure they excel with that amp!

    I always wanted to try one of the Beck models with a humbucker...

  5. #5
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Quote Originally Posted by jhmp View Post
    Wraptails dominate my heart, I'm sure they excel with that amp!

    I always wanted to try one of the Beck models with a humbucker...
    The p90's sound so juicy as to be ridiculous. This guitar is just magnificent...I absolutely get it.

    The Oxblood is a Battleship...lovely big neck, and a voice that you're going to pay attention to. I think it's got Burstbuckers 1 & 2 in it...there's not a thing wrong with them to my ears. I can see why these R4's are so popular...superb instrument.

    Shakespeare walks into a pub, the Landlord says "get out, you're Bard"

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    Re: Denis Cornell.

    Congratulations! Denis makes some lovely amps, and with that Special in it you'll struggle to get a bad sound.

  7. #7
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Quote Originally Posted by springhead View Post
    Congratulations! Denis makes some lovely amps, and with that Special in it you'll struggle to get a bad sound.
    I'll bring it to the meet Jules...where I'll demonstrate my penchant for getting bad sounds out of brilliant kit...
    Shakespeare walks into a pub, the Landlord says "get out, you're Bard"

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    Re: Denis Cornell.

    Cornell make some great amps but I do wish they wouldn't incorrectly describe it as a class A amplifier. Any amplifier using 2 x EL84 output valves that is rated at more than 12 watts cannot possibly be operating as a true class A amp, it is class AB. The same applies to Vox AC 15's and AC 30's that are often incorrectly described as class A. It doesn't make it any less of an amp, it's just not class A! (Rant over )

  9. #9
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Quote Originally Posted by PaulD View Post
    Cornell make some great amps but I do wish they wouldn't incorrectly describe it as a class A amplifier. Any amplifier using 2 x EL84 output valves that is rated at more than 12 watts cannot possibly be operating as a true class A amp, it is class AB. The same applies to Vox AC 15's and AC 30's that are often incorrectly described as class A. It doesn't make it any less of an amp, it's just not class A! (Rant over )
    The bastid...dyer think I'll be able to get a B side partial refund??

    It's all gobbldeygook to me to be honest, but Denis specifically refers to this amp as having a Class A output design, page 4...perhaps he's quite cleverly avoided saying it's "true" Class A...maybe it's Class A 'ish...

    Shakespeare walks into a pub, the Landlord says "get out, you're Bard"

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    Re: Denis Cornell.

    Self-biasing the push-pull output using cathode resistors is not Class A.

    A true Class A amplifier has the tube (valve for you Olde World guys) "on" 100% of the cycle. Current use is much higher than AB, but actual audio output is lower. The extra power usage is given off as heat. Output transformer for Class A must be designed properly to compensate for both current and heat. Class A output transformers are usually much larger are more expensive than Class AB of comparable audio output. The benefit of running Class A is elimination of cross-over distortion. I see the benefit of this if you're listening to pre-recorded music, but not so much in a guitar amplifier function where the goal is introduction of distortion (and harmonics).
    2007 CR8
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    Re: Denis Cornell.

    Not sure about claiming a refund - you could try but you're on your own with that one! At the end of the day it's just marketing hype as there seems to be some mythical status attached to class A and a perception that it is somehow better. In actual fact the vast majority of the classic amps that we all know and love are probably class AB to a greater or lesser extent. Probably the only ones that can categorically be said to be true class A are the small single ended amps with only one output valve such as the Fender Champ. And yes you are right when you say it is class A 'ish as it will be biased closer to pure class A than to pure class B.

    Randall Aiken has some good articles on the subject for the technically minded here:

    http://www.aikenamps.com/index.php/the-last-word-on-class-a

    http://www.aikenamps.com/is-the-vox-...really-class-a

  12. #12
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Thanks fella's, particularly for those links; which,even for this technological buffoon, is proving to be fascinating stuff.

    I'm going to school, I may be gone some time...

    Shakespeare walks into a pub, the Landlord says "get out, you're Bard"

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    Re: Denis Cornell.

    Quote Originally Posted by thejaf View Post
    Self-biasing the push-pull output using cathode resistors is not Class A.

    A true Class A amplifier has the tube (valve for you Olde World guys) "on" 100% of the cycle. Current use is much higher than AB, but actual audio output is lower. The extra power usage is given off as heat. Output transformer for Class A must be designed properly to compensate for both current and heat. Class A output transformers are usually much larger are more expensive than Class AB of comparable audio output. The benefit of running Class A is elimination of cross-over distortion. I see the benefit of this if you're listening to pre-recorded music, but not so much in a guitar amplifier function where the goal is introduction of distortion (and harmonics).
    You are partially correct in what you say, it is correct that in a class A amplifier the output valve (or valves) are conducting 100% of the cycle but a push-pull output stage can be biased to be either pure class A, class AB or pure class B regardless of wether it is cathode biased or fixed biased. (99.99% of push-pull guitar amps will be biased as class AB)

    As for the output transformer there is no such thing as a class A transformer but the transformer for a single ended amplifier will be larger than an equivalent rated push-pull transformer because it requires an air gapped core in order to prevent core saturation.

    To summarise a single ended amplifier (one output valve) will always be class A, a push-pull amplifier (2 or more output valves) can be either class A, class AB or class B

  14. #14
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Quote Originally Posted by PaulD View Post
    You are partially correct in what you say, it is correct that in a class A amplifier the output valve (or valves) are conducting 100% of the cycle but a push-pull output stage can be biased to be either pure class A, class AB or pure class B regardless of wether it is cathode biased or fixed biased. (99.99% of push-pull guitar amps will be biased as class AB)

    As for the output transformer there is no such thing as a class A transformer but the transformer for a single ended amplifier will be larger than an equivalent rated push-pull transformer because it requires an air gapped core in order to prevent core saturation.

    To summarise a single ended amplifier (one output valve) will always be class A, a push-pull amplifier (2 or more output valves) can be either class A, class AB or class B
    So Paul how would you describe the class of this Cornell...biased to pure Class A perhaps?
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    Les Paul Forum Member DrRobert's Avatar
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    Re: Denis Cornell.

    There are a few, not many, true class A guitar amplifiers, including some by Alessandro. Worth mentioning that, it is hard to get a lot of power out of true class A-the 4 EL84 amps I have from Alessandro that operates in class A is 20w vs a loud 30 from the AC30 in "high" class AB.

    It's also worth mentioning that even tube gurus like Randall Aiken get tied up in knots with how you describe what happens to a class A amp when you reach cutoff-when the negative swing of the input sine wave reaches the point where it's no longer conducting. Technically, at that point you're operating in class AB. But any guitar amp, pushed hard, is going to reach that point. If it's pure class A right up until then, is it still class A? Who knows...

    I think the marketing advantage of "class A" is that it's attaching itself to the Vox heritage-cathode biased EL84s with little to no negative feedback=Vox=class A (even though it isn't).

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    Re: Denis Cornell.

    Quote Originally Posted by ourmaninthenorth View Post
    So Paul how would you describe the class of this Cornell...biased to pure Class A perhaps?
    It would be technically possible to bias the Cornell in such a way that was operating in pure class A (I've not got any first hand experience of the Cornell circuit but it would probably involve changing some component values and reducing the voltage that the valves are operating at in order to accomplish this) but the maximum output when biased that way would be 12 watts or less and it almost certainly would not sound as good as it does now.

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    Re: Denis Cornell.

    Quote Originally Posted by DrRobert View Post
    There are a few, not many, true class A guitar amplifiers, including some by Alessandro. Worth mentioning that, it is hard to get a lot of power out of true class A-the 4 EL84 amps I have from Alessandro that operates in class A is 20w vs a loud 30 from the AC30 in "high" class AB.

    It's also worth mentioning that even tube gurus like Randall Aiken get tied up in knots with how you describe what happens to a class A amp when you reach cutoff-when the negative swing of the input sine wave reaches the point where it's no longer conducting. Technically, at that point you're operating in class AB. But any guitar amp, pushed hard, is going to reach that point. If it's pure class A right up until then, is it still class A? Who knows...

    I think the marketing advantage of "class A" is that it's attaching itself to the Vox heritage-cathode biased EL84s with little to no negative feedback=Vox=class A (even though it isn't).
    My understanding is that to be defined as pure class A both sides of the output stage have to be conducting at the point just before the output sine wave, as viewed on an oscilloscope, starts to clip (the same point as we measure RMS output). If pushed beyond this point one side may well go into cut-off but it is still defined as a class A. Of course where do we more often than not operate our amps? Well beyond the clipping point 'cus that's where they sound best! So as you say it's a bit of a moot point really! I guess the only amps that we can say with 100% certainty are operating in pure class A all of the time are single ended amps.

  18. #18
    Les Paul Forum Member latestarter's Avatar
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    Re: Denis Cornell.

    Lovely looking amp. Three volumes...just in case!
    Otherwise known as Grant.

  19. #19
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    Re: Denis Cornell.

    Quote Originally Posted by latestarter View Post
    Lovely looking amp. Three volumes...just in case!
    I know Grant, bloody hilarious isn't it? In case of civil unrest break out the third volume...

    This is how it works.....

    Channel one volume balanced with master.

    Foot switchable Channel two - with same overall master setting, gain to suit, and channel two volume button to balance 1/2 channel volumes

    So you have lovely full bodied chimey clean, switched to snarly, crunchy, slightly compressed overdrive, all at the same output volume (obviously adjustable upwards overall, or independantly) For home players like me, it's perfect. Think of a Pete Cornish SS3 into the Matchless clean and you're there...





    Terrific piece of kit.
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    Re: Denis Cornell.

    It sounds perfect!
    Otherwise known as Grant.

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    Re: Denis Cornell.

    The "Our Class A design has less-cross over distortion". Surely if it were Class A it wouldn't have any!

    No doubt a fine amp though and looking forward to hearing it if you can bring it along in January Paul. The only other Cornell I've heard in the flesh is Wilko Johnsons, from a position of ten feet in front of it with a silly grin on my face!

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    Re: Denis Cornell.

    Quote Originally Posted by springhead View Post
    "Our Class A design has less-cross over distortion". Surely if it were Class A it wouldn't have any!
    Ha Ha good point, I didn't notice that! It seems someone wasn't thinking when they wrote their advertising hype!

  23. #23
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Quote Originally Posted by springhead View Post
    The "Our Class A design has less-cross over distortion". Surely if it were Class A it wouldn't have any!

    No doubt a fine amp though and looking forward to hearing it if you can bring it along in January Paul. The only other Cornell I've heard in the flesh is Wilko Johnsons, from a position of ten feet in front of it with a silly grin on my face!
    The double bastid....

    The last Cornell I played through I had Greeny in me hands, now that made me smile...

    I'm having the chassis out later, so we can have a mooch around the engine room....stand by...to the tools was the cry...this should do it..Class A? I'll give you bloody Class A..

    Shakespeare walks into a pub, the Landlord says "get out, you're Bard"

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    Re: Denis Cornell.

    Yeah that'll open it. And maybe a wrecking bar to gently lever it out, mind you don't scratch the paint.

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    Re: Denis Cornell.

    Quote Originally Posted by ourmaninthenorth View Post
    The double bastid....

    The last Cornell I played through I had Greeny in me hands, now that made me smile...

    I'm having the chassis out later, so we can have a mooch around the engine room....stand by...to the tools was the cry...this should do it..Class A? I'll give you bloody Class A..


    Damn! All those years of experience building and repairing amplifiers and I thought my soldering iron was my most useful tool.... I need one of those!!

  26. #26
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Here you go Lads...

    I've dropped a right bollock here, the Wife's just come home from work..seen the tools out and issued forth the kiss of death..."while you've got those out, can you just...??"





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    Re: Denis Cornell.

    PaulD wrote: "To summarise a single ended amplifier (one output valve) will always be class A, a push-pull amplifier (2 or more output valves) can be either class A, class AB or class B"

    Fwiw and fyi, there are single-ended, Class A amplifiers with more than one power tube.
    Ex: http://schematicheaven.net/gibsonamps/gibsonette.pdf

    there are others..
    "As soon as man does not take his existence for granted, but beholds it as something unfathomably mysterious, thought begins." Albert Schweitzer

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    Re: Denis Cornell.

    Quote Originally Posted by Wally View Post
    PaulD wrote: "To summarise a single ended amplifier (one output valve) will always be class A, a push-pull amplifier (2 or more output valves) can be either class A, class AB or class B"

    Fwiw and fyi, there are single-ended, Class A amplifiers with more than one power tube.
    Ex: http://schematicheaven.net/gibsonamps/gibsonette.pdf

    there are others..
    That Gibson is Parallel Single Ended, PSE. Both output valves are doing the same thing at the same time, i.e. Class A. More power out than one valve but not as efficient as push-pull. I've never understood the attraction of PSE. You save on a phase inverter but have to use a larger, heavier more expensive output transformer than a push-pull amp using the same pair of power bottles.

    Paul - that's some busy innards, very nice. Quite a labour intensive build. I'll have to dock him some safety points for taking the live from the IEC socket to the side connector of the fuse holder - should be on the far end. Please be careful if you change/check the fuse - pull the mains plug out first or it could bite you.

    And get those shelves put up for her...

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    Re: Denis Cornell.

    Quote Originally Posted by springhead View Post
    That Gibson is Parallel Single Ended, PSE. Both output valves are doing the same thing at the same time, i.e. Class A. More power out than one valve but not as efficient as push-pull. I've never understood the attraction of PSE. You save on a phase inverter but have to use a larger, heavier more expensive output transformer than a push-pull amp using the same pair of power bottles.

    Paul - that's some busy innards, very nice. Quite a labour intensive build. I'll have to dock him some safety points for taking the live from the IEC socket to the side connector of the fuse holder - should be on the far end. Please be careful if you change/check the fuse - pull the mains plug out first or it could bite you.

    And get those shelves put up for her...
    +1 on that fusing situation, Spring. good eye.

    As for the parallel single-ended....maybe they were interested in what true Class A does compared to Class AB??? I cannot bring to mind the more modern amps that do PSE...but iirc one design has 3 tubes in parallel and one or even two can be pulled out of the circuit for lower output levels.
    "As soon as man does not take his existence for granted, but beholds it as something unfathomably mysterious, thought begins." Albert Schweitzer

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    Re: Denis Cornell.

    Quote Originally Posted by Wally View Post
    PaulD wrote: "To summarise a single ended amplifier (one output valve) will always be class A, a push-pull amplifier (2 or more output valves) can be either class A, class AB or class B"

    Fwiw and fyi, there are single-ended, Class A amplifiers with more than one power tube.
    Ex: http://schematicheaven.net/gibsonamps/gibsonette.pdf

    there are others..
    Yes, I left out parallel single ended just to keep things simple as they are not very common.

  31. #31
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Quote Originally Posted by springhead View Post
    That Gibson is Parallel Single Ended, PSE. Both output valves are doing the same thing at the same time, i.e. Class A. More power out than one valve but not as efficient as push-pull. I've never understood the attraction of PSE. You save on a phase inverter but have to use a larger, heavier more expensive output transformer than a push-pull amp using the same pair of power bottles.

    Paul - that's some busy innards, very nice. Quite a labour intensive build. I'll have to dock him some safety points for taking the live from the IEC socket to the side connector of the fuse holder - should be on the far end. Please be careful if you change/check the fuse - pull the mains plug out first or it could bite you.

    And get those shelves put up for her...
    The treble bastid..now the bugger's trying to kill me....
    Shakespeare walks into a pub, the Landlord says "get out, you're Bard"

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    Re: Denis Cornell.

    Quote Originally Posted by ourmaninthenorth View Post
    The treble bastid..now the bugger's trying to kill me....
    It's a cunning plan to make sure you don't sue him for claiming it to be class A!

  33. #33
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Quote Originally Posted by PaulD View Post
    It's a cunning plan to make sure you don't sue him for claiming it to be class A!
    Shakespeare walks into a pub, the Landlord says "get out, you're Bard"

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    Re: Denis Cornell.

    Quote Originally Posted by springhead View Post
    I'll have to dock him some safety points for taking the live from the IEC socket to the side connector of the fuse holder - should be on the far end. Please be careful if you change/check the fuse - pull the mains plug out first or it could bite you.
    It may well be that it is this type of fuse holder:-

    http://uk.rs-online.com/web/p/panel-...lders/0563784/

    In which case neither contact is accessible when the fuse is removed so it would be perfectly acceptable to wire it that way.

  35. #35
    Les Paul Forum Member ourmaninthenorth's Avatar
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    Re: Denis Cornell.

    Quote Originally Posted by PaulD View Post
    It may well be that it is this type of fuse holder:-

    http://uk.rs-online.com/web/p/panel-...lders/0563784/

    In which case neither contact is accessible when the fuse is removed so it would be perfectly acceptable to wire it that way.
    Yeah, it's like that one...only with two side contacts rather than the one of the RS.

    Is he back down to double bastid then...??
    Shakespeare walks into a pub, the Landlord says "get out, you're Bard"

  36. #36
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    Re: Denis Cornell.

    Quote Originally Posted by ourmaninthenorth View Post
    Yeah, it's like that one...only with two side contacts rather than the one of the RS.

    Is he back down to double bastid then...??
    Yeah, he's probably not going to electrocute you so double bastid should do it!

  37. #37
    Les Paul Forum Member Pat Boyack's Avatar
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    Re: Denis Cornell.

    Congrats and welcome to the family!! Class A, Class AB.........I prefer CLASS ACT!! Love my Cornell and I'm looking to sell enough of my blood to get the 48/50 Plexi for the big stages.

    My amp guy says my Cornell is the best build he has ever seen. You can't beat the quality Denis provides.

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