My head amp

Anything to do with the things that make the music we listen to.
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The Stratmangler
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#46

Post by The Stratmangler »

What speaker you hanging off the back end?
Chris :happy3:
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Paul Barker
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#47

Post by Paul Barker »

The output stage should have power of 5.7 watts THD 10%. Interesting, enough gain in the ef86 to overdrive the output stage and enough distortion in the output stage to make it an instrument.
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Nick
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#48

Post by Nick »

Paul Barker wrote:Ah I missed the pickup noise comment as my tele isn't yet built I have yet to find out.

SO the tremelo worth trying?
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Paul Barker
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#49

Post by Paul Barker »

Yes nice guitar sound.
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Paul Barker
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#50

Post by Paul Barker »

Looking at output pentodes for single ended.

Image

Thinking el84 a little under powered. But I found 6550 overpowered for my situation.

In the photo the EL37 of which I have some looks interesting.
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Dave the bass
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#51

Post by Dave the bass »

I might be out of my depth here but... that 1st stage pentode EF86 is high gain yes, so, if a fella comes along with a badly screened single coil guitar pick up like a cheap (or even expensive) tele or a strat knock-off isn't that 1st stage going to be prone to being knocked into oscilation without a grid stopper by the extra injection of stray RF being conducted into the amp here at the 1st stage.?

I think it'd be saved if his mate comes along also with an electric guitar and plugs in the 2nd i/p as the Z is halved yeah so that'll help.

Just saying like... :-)

DTB
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Paul Barker
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#52

Post by Paul Barker »

Yes I think a ferrite bead and a grid stopper would be necessary.

Normally I am sure you know I wouldn't put a pentode up front. But when the amp is an instrument and venerable companies like Vox have achieved a great sound things just have to be tried.

But I am considering going octal for ease. I can breadboard more easily with relay bases and try different things without having to organise a way to hold the amp upside down and check voltages. This is why I only looked at octals in the above screen shot. I am just not sure where I will find octal pentodes in my piles of valves, I have always shoved them aside with disdain in the past.
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Mike H
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#53

Post by Mike H »

Not an EF86, they're usually so well behaved I doubt it'll happen. :D They're specifically designed for audio band only, problee starting to roll off from 11 - 12k at a guess.
 
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Mike H
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#54

Post by Mike H »

PS: octal version would be EF36/37.

I think the main issue however might be whether or not you like the sound of EF86/36/37 pentode, actually....

PPS: you might find an octal IF pentode to try, but not sure if there is one that doesn't include variable mu...

And it could be temperamental at HF/RF....
 
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Paul Barker
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#55

Post by Paul Barker »

I am going to try a 6sj7 I found that I have just one. Otherwise I could make up an adapter to fit ef86 into octal relay base.
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Mike H
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#56

Post by Mike H »

Ah right that might be interesting.

Mind you it's sharp cut-off pentode so might get lop-sided waveforms (?)

Not actually used one meself....
 
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Paul Barker
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#57

Post by Paul Barker »

We'll see. Sounds like it may just pay to adapt an ef86 socket.

The following clip inforrms me just how much the amp is part of the instrument. Chuck Berry is geting cross because someone touched his amp. HE also gives Keith Richards a lesson in tone, but Keith on his strat and whatever amp just can't do the tone Chuck demonstrates on his Gibson and whatever amp set to his personal settings. Chuck puts down a sound which makes Keiths sound dull and mechanical. Chuck is playing music without making it sound mechanical and lifeless, aged 60!

Liaten to the better instument in Chuck's hands at 5min 06 secs makes KEith sound like he's playing a lump of dull plastic.

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The Stratmangler
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#58

Post by The Stratmangler »

I had to giggle at the band all looking skywards at both Chuck and Keef's prima donna shenanigans.
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Paul Barker
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#59

Post by Paul Barker »

Mike H wrote:Ah right that might be interesting.

Mind you it's sharp cut-off pentode so might get lop-sided waveforms (?)

Not actually used one meself....
Yes I have been doing mental gymnastics trying to predict keeping it out of cut off. Just depends on the input signal amplitude. Really I need more HT to satisfy this valve!

Have managed to find a 70ma tansformer which should be weak enough and have substituted ez80 with 6x5 which should retain in combo with weak transformer the necessary power supply sag at power peaks, all important to the design. The first output valve to try will be a metal 6l6, which is not much more powerful than the el84. I should get an instrument out of it anyway.
Last edited by Paul Barker on Sun Mar 18, 2012 12:42 pm, edited 1 time in total.
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Paul Barker
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#60

Post by Paul Barker »

The Stratmangler wrote:I had to giggle at the band all looking skywards at both Chuck and Keef's prima donna shenanigans.
Yes, I think Chuck tolerate the generation that copied him begrudgingly, the sound he gets compared to the sound Keith gets speaks for him. He needn't have been so snappy, should have let his skill his guitar and his amp combination do the talking.

That is what I picked out of the Buddy Guy BBking chat. Buddy was using thinly veiled disdain in his non vebal and verbal communications, King was being much more charitable.

At the end of the day the consumer voted for change and went with the new breed's in both genres. rightly or wrongly, things change.
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