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Old 8th July 2004, 03:19 PM   #1
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Default guitar preamp

i would like to built a very simple guitar preamp using one tube like 12ax7 with a tone stack. Does anyone have a idea or schematic ? Thanks
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Old 8th July 2004, 09:41 PM   #2
alk is offline alk  Europe
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Here's one, not sure if it has a tone stack but it's pretty simple:

http://www.dogstar.dantimax.dk/tubestuf/mctube.htm
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Old 9th July 2004, 08:04 AM   #3
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There are many different guitar pre-amps and power amp circuits hereAX84 site



Also have a look at this site for info. and a simulator for the different types of tone stacks. Duncan amplifiers

ciao

James
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Old 10th July 2004, 05:45 PM   #4
benny is offline benny  Australia
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hi,

what do you want from this preamp? do you need distortion, or just clean? what kind of distortion, or what kind of clean? do you want a crunch tone, hi-gain (if you want hi gain you will want more than one 12AX7 tube), fuzz, jazz clean, etc.

the one alk gave is designed for distoriton, and there is no tone stack, but a tone stack is a simple thing to add into any design, as long as you remember that the tone stack, if using a traditional FMV tonestack will determine the overall voicing of the amp, and if adding one into a design, you may need to play around with component values a little to find a voicing that suits you. a much more versatile tone stack that can be used is the baxandall tone stack, and despite only having two tone controls as oposed to three, actually gives a much wider range of tonal control. however, while it will make the preamp more versatile, it won't give you anything like a specific marshal or fender or whatever type voicing you may want as with the traditionally used FMV tone stack as these are designed with a specific voicing in mind, and despite three controls, these controls don't actually alow you to stray from the overall voicing.

also, what will you be driving with this preamp?

my personal preferance for designing a 1x12AX7 pre amp, especially if intending to use a tone stack, would be to design it for clean tones. if you want distortion, i recomend you budget for two tubes, or use a simple solid state stage as your first stage.

cheers
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Old 10th July 2004, 11:44 PM   #5
alk is offline alk  Europe
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Hi Benny,

I was in the process of making a Mc tube for myself- see the link.
You said for distortion you would choose 2 valves.
Well i had my doubts before attempting this distorsion preamp, cause in the guitar world it is often used a silicon based preamp, the tube screamer, which uses a dual op amp. Since i know that all guitar players prefer vaves over transistors i find odd that this little pedal is so popular. I have the circuit and may try it someday but what i do want to ask you is: doesn't valves always sound better? Isn't valve distortion warmer? Well my input would be a pcl86 se monoblock which i use for cd music and sometimes electric guitar; sounds good but too clean and no real gain.
Do you have any idea of what kind of distortion should i expect from this preamp?
Any schematic for a 2 valve distortion preamp? and, why do you think this is better?

Best regards:

Alk
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Old 13th July 2004, 01:56 PM   #6
benny is offline benny  Australia
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hi,

Quote:
I was in the process of making a Mc tube for myself- see the link.
i like the creative layout.

Quote:
You said for distortion you would choose 2 valves.
this is to take full advantage of the unique clipping of tubes. i will come back to this later, although one valve is fine for light crunch and the likes, and good for even moe distortion if you use a solid state first stage such as the Marshall AVT series does.


Quote:
Well i had my doubts before attempting this distorsion preamp, cause in the guitar world it is often used a silicon based preamp, the tube screamer, which uses a dual op amp. Since i know that all guitar players prefer vaves over transistors i find odd that this little pedal is so popular.
this pedal is so popular for two reasons. firstly, because it is considered one of the better sounding silicon based distortion pedals, seccondly, silicon pedals are much more reliable and practicle for a musician. they are much more rugged for a start which is something the performing musician needs. silicon style pedals are so rugged infact that they are almost completly indestructable. The oly pedal i have ever bought was a boss DS1 pedal, and i have put that pedal through hell (i once dropped it from our seccond story balcony in a drunken moment of uncoordination onto hard concrete for just one example), and it still works as good as day one. If i did this to a tube pedal, no matter how well you protected the tube, just the impact from falling would have pretty much destroyed the inside of the tube, at the very least would have made it pretty microphonic. you also have the heat factor of a tube... and the size... and weight... and power suply (silicon pedals you can run straight from a single 9V battery, a tube pedal will need mains power with a bulky transformer to suply filament and plate suplies)... etc.... see where i'm going... silicon pedals are much more reliable and practical as far as a muso is concerned... and, they cost less, so even if you do break it, it's not as big a loss.




Quote:
I have the circuit and may try it someday but what i do want to ask you is: doesn't valves always sound better? Isn't valve distortion warmer?
yes. this is because of the unique way in which valves clip. firstly, there is the asymetrical clipping. This results in more 2nd order harmonics, which are much more pleasant to the human ear... this is why they sound warmer.

they also have a unique way of clipping which is why their distortion is less 'buzzy' than transistor distortion. In a transistor, as soon as the maximum peak level is reached, they cut straight in with clipping. as soon as your signal exceeds the max alowable peak before clipping, it is flattened right out. In a tube, there is a small area where the signal will start to compress instead of clip just below the clipping point. It is only a very small area, but it is enough to allow a smoother, more seamless transition into clipping.

Quote:
Well my input would be a pcl86 se monoblock which i use for cd music and sometimes electric guitar; sounds good but too clean and no real gain.
Do you have any idea of what kind of distortion should i expect from this preamp?
i would not use it for distortion. if you want to use it, use it as the first stage of your preamp. i will come back to this point soon as well.

Quote:
Any schematic for a 2 valve distortion preamp?
nope, no schematic... though i will 'help' you design one if you want.


Quote:
and, why do you think this is better?
this is better if you want a hi-gain preamp... one tube is fine for just a bit of crunch, but once you want more gain than this you will want more stage to avoid the distortion becoming buzzy... the harder you clip your signal at one stage, the more transistor like the clipping because of what i was describing about how a tube compresses slightly before clipping, and the more you clip at once the less this 'roll' into cliping is noticeable... if you clip each stage lightly, you will get less buzz and more crunch in your distortion.... this is why hi gain amps will use up to six stages in one channel of their preamp....
sorry if that's not a very good explanation i don't think, but it will do for now.

keep asking questions if you want and i will answer when i can.

cheers
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Old 13th July 2004, 02:42 PM   #7
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Default Fender Tube AMP

Most of the older Fender amps use the same preamp so look for a schematic for say a Fender Super Reverb amp as and example. The circuits are not that complicated and they sound good. There all over the Net.

If you can't find one then let me know.
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Old 13th July 2004, 10:29 PM   #8
alk is offline alk  Europe
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Hi,


Quote:
will want more stage to avoid the distortion becoming buzzy...
yep...i try the mctube and was impressed but only in crunch territory, if i wanted real distortion (more gain) then a very unpleasant noise came along and well....that level of hum irritates me. So now it's in the work bench, see if i can get rid of the hum. Maybe a seperate power supply.

Good to know about gain stages, thanks for the info. And no, not really high gain for me. I play in my room mostly so...besides i don't have a band so no problems with drum players.

Some day i will make myself a proper guitar amp. But for now the pedal is fun and i'm going to build an mosfet booster to check the difference.

Quote:
once dropped it from our seccond story balcony in a drunken moment of uncoordination onto hard concrete for just one example),
Boss effects are famous for their long lifespan and, yes they will survive a life on the road but they also get used in the studio so it's got to be something else.

I would like to make you some more question but i 'm going on holidays for quite some time so...anyway thanks for your help.

Cheers,

Alk
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Old 29th February 2012, 07:05 AM   #10
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Hi all!
Is be a schematic or project of a guitar hybrid preamp with tube/valve ECC83 or PCC88 in combination with MOSFETs.
Schematic that has bass, middle, treble, and the presence or a similar effect?
Something like this schematic:
http://tremolo.elektroda.net/Przedwz...***_preamp.gif
Thanks and cheers!

Last edited by formula 22; 29th February 2012 at 07:09 AM.
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