My head amp

Anything to do with the things that make the music we listen to.
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Paul Barker
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Post by Paul Barker » Fri Apr 06, 2012 3:59 pm

Can't argue with that.

Replace the ECC82 with a 5687 and you're done. :D :D :D

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ed
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Post by ed » Fri Apr 06, 2012 4:01 pm

woohooo!!!

you will likely remember when I mentioned that firstwatt thang lots of people wanted to drown me in the pond.......

digital sound shaping, what ever next!

snigger

btw you are duty bound to report on it's abilities, I had been tempted, it's only funding that has saved me thus far......
There's nowhere you can be that isn't where you're meant to be

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Paul Barker
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Post by Paul Barker » Fri Apr 06, 2012 8:55 pm

Just quickly refering to this again:
Image
I found gain was no problem, and as you know I don't like bypassing cathode bias resistor if I don't have to.

But I was very surprised when I just did the math.

The output needs 12v peak efficiency of Cf is .93 so I need 12.9. the 6sj7 provides a gain of 37 as drawn so sensitivity is 348mV peak 246mV RMS.

But I am not used to dealing with Pentodes so I didn't do the maths I just knew it would do. Yes it does do. But since then I just did the maths.

Unbypassed is effective cathode resistance of 1/gm + 2k = 2,606 ohm.

But if I bypassed it then it is 606 ohm, but the gain becomes 161.

If you used this circuit in stereo with a shared cathode resistor at 1k gain is a very healthy 61.

It is a very useful little VA stage. Obviously for hifi you would proper clean up the Screen supply and the plate supply. In this guitar amp it is deliberately not linearised.

What a lot of gain? Handy if you were to use global feedback.

For audio you might use a 52k anode load for more linear operating point and scrifice gain. Bypassed stage gain 81 unbypassed but shared resistor 31.

Of course a big factor is that it is driving a CF which we used a figure of 1meg ohm for input resistance and with no miller factor HF is very good.

If you were RC coupling you would also lose gain with anything less than 1 meg grid resistor but it is not influenced too much. The gain of 31 example comes down to 21 with a 100k grid resistor.

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IslandPink
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Post by IslandPink » Fri Apr 20, 2012 3:30 pm

Hey Guys -
Big news !
Paul's going to have a guitar to play through his amp , by this evening !
White flags of winter chimneys waving truce against the moon ( Mitchell )

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pre65
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Post by pre65 » Fri Apr 20, 2012 3:45 pm

IslandPink wrote:Hey Guys -
Big news !
Paul's going to have a guitar to play through his amp , by this evening !
What time is the first performance ? :lol:
Life is what happens to you while you're busy making other plans. John Lennon

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Post by chris661 » Fri Apr 20, 2012 6:34 pm

IslandPink wrote:Hey Guys -
Big news !
Paul's going to have a guitar to play through his amp , by this evening !
Pictures!!

Is this going to be a musical Owston?

Chris

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Paul Barker
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Post by Paul Barker » Fri Apr 20, 2012 9:14 pm

Thank you Mark for arranging that. your sister told me she rang you because she had forgoten all about it.

Doesn't sound as bad as I expected from a cheap Chinease copy.

the head amp is too quiet , guitar amps obviously need more gain than what we are used to.

Also there is a nasty hum with it. May actually be the guitar because the amp is fine playing from the SII.

I would be embarrased to bring it to Owston, not good enough.

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Post by Paul Barker » Sat Apr 21, 2012 8:19 am

I will just say that the electric guitar neck and string positions are so much easier to play, I am looking forward to learning some electric guitar. Such things as puting your first finger across all strings while moving up one finger (bringing 4 into play) starting with E and moving up the neck, I found torturous for my left hand on classic neck on this tele neck it is comparatively achievable against huge wall of difficulty hurdle on classic neck. At the bridge end the strings seem wider apart too which makes life easier for picking the individual strings without smudging the adjecents.

Not that I can play or anything. Just the tasks set for learning are more quickly achievable.

Obviously the finger pads are now saw as this is first metal string instrument I have tried. It is chease wire isn't it? Fingers being the cheese.

The sound from the bridge pickup is the one I like best with bright tone on the guitar tone control.

I think adding feedback to the amp was a mistake it needs to be bright sounding. I can now see why it is that there are so many bright forming -3db high pass filters in guitar amp designs, you really have to work at the brightness on a number of levels.

Not sure about the sound of both pickups, think I prefer the bridge alone to bridge with neck.

Neck alone is more dull at the moment. That may be just my amp.Also this is just the cheap Chinease pickups that came with. Need to try the Seamore Duncan Alnico really. But that means taking the strings off, which surprisingly were in tune and stay in tune. Classic strings need tuning every time you pick it up and then half way through.. the ones I have are called Jack Daniels (recommended by local shop as actually coming off same production line as some fancy make, so inference very strong that is actually what they are) . But I find them very soft (the classic ones) although the tone they make on the yamaha is beautiful they get marked where you press them onto the frets and I think this is the reason for my fret buzz on the classical. My teacher gets the same fret buzz. he thinks it is more the strings than the neck. though the classic neck is a pile of pooh compared to other classic guitars I have tried, he maintains it is playable. he is very much against spending money on guitars or any instruments.

I think what it is is what Ed was warning against. Lots of people pick up the guitar buy all expensive stuff and then it collects dust. Fair point Ed!

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The Stratmangler
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Post by The Stratmangler » Sat Apr 21, 2012 9:47 am

Paul Barker wrote:I will just say that the electric guitar neck and string positions are so much easier to play, I am looking forward to learning some electric guitar. Such things as puting your first finger across all strings while moving up one finger (bringing 4 into play) starting with E and moving up the neck, I found torturous for my left hand on classic neck on this tele neck it is comparatively achievable against huge wall of difficulty hurdle on classic neck. At the bridge end the strings seem wider apart too which makes life easier for picking the individual strings without smudging the adjecents.

Not that I can play or anything. Just the tasks set for learning are more quickly achievable.

Obviously the finger pads are now saw as this is first metal string instrument I have tried. It is chease wire isn't it? Fingers being the cheese.

The sound from the bridge pickup is the one I like best with bright tone on the guitar tone control.

I think adding feedback to the amp was a mistake it needs to be bright sounding. I can now see why it is that there are so many bright forming -3db high pass filters in guitar amp designs, you really have to work at the brightness on a number of levels.

Not sure about the sound of both pickups, think I prefer the bridge alone to bridge with neck.

Neck alone is more dull at the moment. That may be just my amp.Also this is just the cheap Chinease pickups that came with. Need to try the Seamore Duncan Alnico really. But that means taking the strings off, which surprisingly were in tune and stay in tune. Classic strings need tuning every time you pick it up and then half way through.. the ones I have are called Jack Daniels (recommended by local shop as actually coming off same production line as some fancy make, so inference very strong that is actually what they are) . But I find them very soft (the classic ones) although the tone they make on the yamaha is beautiful they get marked where you press them onto the frets and I think this is the reason for my fret buzz on the classical. My teacher gets the same fret buzz. he thinks it is more the strings than the neck. though the classic neck is a pile of pooh compared to other classic guitars I have tried, he maintains it is playable. he is very much against spending money on guitars or any instruments.

I think what it is is what Ed was warning against. Lots of people pick up the guitar buy all expensive stuff and then it collects dust. Fair point Ed!
To quote Bryan Adams....
I got my first real six-string
Bought it at the five-and-dime
Played it till my fingers bled
Was the summer of '69
This is normal :wink:

Ed is definitely right about buying expensive stuff - there are plenty of really really good guitars out there that don't cost a fortune.

I'm firmly of the belief that a good guitarist can get a decent sound out of almost any guitar.
How do you get to be good?
The little quote sums it all up.

Once you get to be a fairly decent player that's the time to spend money on a really good guitar !!!
Chris :happy3:

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Nick
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Post by Nick » Sat Apr 21, 2012 10:32 am

Sounds good Paul, I guess you see how much of the HiFi stuff doen't help with this, flat responses are neither here or there.

I you want to build up good hard fingers practice the bends in this solo (and have some spare strings) :-)

Last edited by Nick on Sat Apr 21, 2012 10:39 am, edited 1 time in total.
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The Stratmangler
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Post by The Stratmangler » Sat Apr 21, 2012 10:35 am

Nick wrote:Sounds good Paul, I guess you see how much of the HiFi stuff doen't help with this, flat responses are neither here or there.

I you want to build up good hard fingers practice the bends in this solo (and have some spare strings) :-)
Sadist :lol:
Chris :happy3:

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Nick
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Post by Nick » Sat Apr 21, 2012 10:39 am

There is that :-)
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Post by Cressy Snr » Sat Apr 21, 2012 11:02 am

Wish I could play guitar but I have never succeeded in getting a clean chord out of one. My finger ends are all at least the diameter of 1p pieces. Cant get a finger onto a string anywhere on the neck without touching the adjacent ones :lol:

My fingers are too fat to play guitar, too short to play piano. I was given a euphonium at school and I'm a dab hand on the treble recorder with Irish jigs. I would be brilliant barping away on the baritone sax in a soul brass section, only two notes to learn; bard-up, bard-up, bard-up :lol: :lol:
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Post by Dave the bass » Sat Apr 21, 2012 11:27 am

The Stratmangler wrote:
Nick wrote:Sounds good Paul, I guess you see how much of the HiFi stuff doen't help with this, flat responses are neither here or there.

I you want to build up good hard fingers practice the bends in this solo (and have some spare strings) :-)
Sadist :lol:
Why are you lot giving Paul any easy time?........... :-)

In for the kill!




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Paul Barker
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Post by Paul Barker » Sat Apr 21, 2012 11:59 am

I can get that tone but not anywhere near that ability. No ability at all yet.

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