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Old 21st April 2009, 08:14 AM   #21
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Originally posted by revintage

This may be true for hifiamps, but for guitar it is all about tone. Here it is usually easier to get it right with PP.

PP, pentode, Class-A and cathode-bias is a sure way of getting it right.

The tone was exactly what I meant. However, class A is the way, but f^a^r^t^i^n^g sound (the real term of electric guitar players) may be produced by them as well (grid currents charge caps shifting bias).
The Devil is not so terrible as his math model is!
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Old 21st April 2009, 08:21 AM   #22
AuroraB is offline AuroraB  Norway
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Location: Norway, -north of the moral circle..
I don't remember if Jack Darr's "Guitar Amplifier Handbook" is in PMillett's collection. If not do a google...
There's plenty of info on the net, - spend some search time..

This one is also worth reading - although with a twist..
While the Lie leapt from Bagdad to Constantinopel, the Truth was still looking for it's sandals!
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Old 21st April 2009, 08:26 AM   #23
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Originally posted by AuroraB
This site has a LOT of info, including fully spec'd instructions, layout etc. for several of the mythical (?) Dumble and Trainwreck amps..

Aye...I'm old enough to have been presented with mysterious black boxes with an impressive fiddled front label spec sheet, the guts only had with a couple of back to back diodes with markings removed...such reputation cost a few Quid (), claiming fantastic harmonic performers and other mystery injection boxes.Still there is a hi fi amp on the market which looks shiny with an ECC83 lit up on the front panel to 7V and doesn't have one iota of electrical signal flowing through it. And yes it claims class A "tube sound".

Can we all be the wiser and be gaged.....keep ears pricked. Some of us MI'ers have been through this gag.

If you keep to advice through this forum, you'll get something worth running.

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Old 21st April 2009, 09:14 AM   #24
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This class AB output stage sounds nice with a guitar. No output transformers needed.

Not recommended for mass production, but fine for DIY (selecting of resistors is needed).
The Devil is not so terrible as his math model is!
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Old 21st April 2009, 11:42 PM   #25
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I have all of Kevin O'Connor's books.
"Principals of Power" (POP) is mostly about Power Amplifier Design with some examples of Musical Instrument and Hi Fi Power Amps.

"The Ultimate Tone" (TUT) is the series which is more relevant to guitar amplifiers. It currently runs to 6 Books TUT1 through TUT6.

Of these the following are probably most relevant to you:
TUT3 "Generations of Tone" - Contains complete designs for cloning the "Icons" of Guitar Amplifier tone from Fender Princeton and Bassman, Vox AC30, Marshall Plexi to Ampeg SVT etc.
TUT5 "Tone Capture" also contains complete designs and build instructions for amplifiers including the London Power "Standard" Amplifier which runs that 2 Channel footswitched LPSP preamp I mentioned, has a full tube buffered effects loop, a superior reverb using a 12AT7 push pull driver and a power scaled power amplifier. I built one of these for a friend. It is probably not an easy project for a first time builder and it has a heap more "bells and whistles" than you would ever use. My own amplifier uses a modified version of this preamp, no reverb or effects and a simplified Power Amplifier without the Power Scaling.

I would recommend TUT3 as the book to buy in the first instance.
TUT5 is good if you want to "cut and paste" bits of designs together for your own "flavour" but requires a higher level of knowledge/understanding.

TUT1 and TUT2 cover basic level stuff on power supplies, power amps, and preamps and are good for the beginner. It also covers the most common sorts of modifications done to amplifiers.

TUT4 and TUT6 are the "high brow" books covering Power Scaling and advanced techniques such a GMX (gm multiplication) using a tubes to produce the sound you want and then MOSFETs to scale up that sound. They are for the more advanced guitar amp "tinker".

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Old 22nd April 2009, 12:14 AM   #26
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I have built 5 guitar amps. Some of them SE, others PP.
For clean to crunch tones SE is good. But for rock/metal type tones I do prefer PP. PP does job better - tighter, cleaner, punchier, better bass, you have more of that rrrrrrr in your sound - harder sounding.

Also power supply is very important. Guitar amps uses much much less filtering than hifi amp, wanna know why? Because it sounds better with guitar. I have tried lots of things just to discover how it sounds.

For good guitar amplifier I recommend:
* definately very good OT - with low quality OT, it will always sound bad.
* go for push-pull - suits all playing styles
* use cheap MKT coupling caps - MKP or other suited for hifi doesnt sound good for guitar
* use ceramic caps instead of silver micas
* fixed/cathode bias suites well different styles, fixed for metal definately

There is no magic in guitar amps. Very good sounding amps are just very good tweaked amps by ear.

I just love mine push pull 2x6V6, fixed bias, SLO preamp, OT is Marshall 18W.
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Old 22nd April 2009, 12:19 AM   #27
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Define for your self, what style do you play or what you need. Then look for amplifiers schematics which does that very good. Study them, look for similarities. I recommend build a clone, then possibly tweak it to your liking.
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Old 22nd April 2009, 07:25 AM   #28
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Of Kevins books, I suggest you start with TUT3.
I would recommend TUT3 as the book to buy in the first instance.
So now you have got the same advice from both Gingertube and me. BUY !
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Old 22nd April 2009, 11:15 AM   #29
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Thank you very much, I will try to find where I can get that here in Europe.
I also have found "Valve Amplifiers" third Edition by Morgan Jones (as PDF form, if you know what I mean ).
Very well written theory, but almost 700 pages, so I think I'll buy that book to.

BTW It is funny, I e-mailed by coincidence with I guy that deals and trades with second hand amplifiers. To make the long e-mail short, he also told of a push-pull configuration (n the Laney Chrome O Zone) that's not driven symmetrical. (the COZ has 4 EL84 in PP, right for 30W). He told me that this is mostly done to get some more bluesy sound of it.
It's about those techniques that you help with the total sound (you like).
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Old 22nd April 2009, 11:41 AM   #30
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Very good responses in this thread, and they reflect the great diversity in taste when it comes to guitar amps/sound. About 1 1/2 years ago I decided to launch into understanding the subject and started with Kevin O'Connor's books. They are well written, not too obscure, but contain a wealth of information. I would suggest that there is also some value in building one of the clones as a first cut. I'ts habbit forming.
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