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Stormbringer Preamp - A beginners project log/diary

Started by stormbringer, September 27, 2012, 12:18:28 PM

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stormbringer

Hello, i have decided to create a thread where i will post the progress of the designing and building of this.

Hopefully other beginners will find this interesting, and that it will also give me the chance to get some help along the way with some of the mistakes i will probably make. :P

Now this is quite an ambitious project, probably bigger than recommended for someone with my limited experience and knowledge, nevertheless i'm going for it. There will be quite alot of experiments along the way. The project status right now is in the preparation for design stage.

So what's the Stormbringer Preamp supposed to become?

I'm playing in a Rock/Metal-band with female vocals, we get compared alot to Evanescense, nightwish, within temptation (mostly due to the female vocals), although i would say we got our own style, but that's really not important when it comes to this.

I use a quite limited array of sounds right now:
1. Clean with or without slight delay
2. Heavy driven distorsion for rhytm part
3. Distorsion with slight delay for leads/solos.

What i lack in my current setup, is a reliable volume boost with lifted mid for solos, currently using an analog pedal, i want this built in, inside the preamp itself, also, instead of the standard reverb, i would rather use a delay module, as it is way more useful to me when we're playing live, as i cant really use reverb directly on the amp when the rig is miked anyway.

Features:
Channel 1: clean channel with gain, bass, mid, treble and Level
Channel 2: Distorsion channel with gain, bass, mid, treble, presence and level, also switchable in to boost mode which has a Tone control + Level control, more or less a solo function.
Channel 3: Same as channel 2, but will try to color the sound a little differently between them.
Master volume, and delay, i haven't really figured out how many control knobs i'm giving it yet. Initially i was thinking about a single "blend"-control only, and lock it to 300 ms or so. But think that maybe a repeat+length control may be required anyway. Gonna have to get back to that later.

The footswitch and buttons:


  • Channel 1
  • Channel 2
  • Channel 3
  • Ch2 Boost
  • Ch3 Boost
  • Delay

I know that the amount of buttons could be lowered by making the first button toggle between 1 and 2/3 while a second button switch 2/3, and a single boost. But there's just too much stomping. on my randall RH100 this drives me nuts sometimes and makes me wanna take a riverdance class just to not get stressed when switching.

So that means i will use momentary buttons for channel 1/2/3 in the footswitch, the other could be latching.

Outputs:
Preamp Out, this goes to power amp input, i want to include a switch on the back that switches between 0.75, 1.0 and 1.25 v in order to match different input sensitivity in various power amps.
Line out with level control. A balanced line is always nice to have. Will build some rudimentary cab sim circuit here to avoid the satanic chainsaw-sound when connecting a very distorted guitar to a line.

I did some mockups on the front + back panel to get a better view of what i'm doing here. See attachments.

Power supply
i don't know yet how high voltages i need, this will require some more designing and experimenting. Will start at 12 and increase when needed.

Switching
Been looking at LDR, Relays and JFET, feeling that JFet seems to suit me best,

The Guts
JFET gain stages, i like the sound from the various j201 pedals i have built, but will try out some different JFets aswell.
the amount of stages is not yet defined, will also take some more designing.

Hopefully i got most of the information listed here, I will post whenever i got something interesting (well, that's subjective, isn't it? ;))

If you read all the way here, then thank you for your interest! :)

el nino

my guitar want's to kill your father

polo16mi

Sounds like very ambitious plan, keep going. Interesting to see and follow it.

I thinking that the more time you spend on design stage and planning, the more time you save after, when mounting.

Roly

Quote from: polo16mi on September 27, 2012, 02:57:37 PM
Sounds like very ambitious plan, keep going. Interesting to see and follow it.

I thinking that the more time you spend on design stage and planning, the more time you save after, when mounting.

"Long think - short do".

Single output at 1.25V, three sockets and fixed attenuator for 1.25, 1.0 and 0.75V.

Balanced and unbalanced is always nice to have.

I'd start with a higher supply than 12V, at least 18V, perhaps even 24v depending on the devices in view.

We await developments with interest.   :tu:
If you say theory and practice don't agree you haven't applied enough theory.

J M Fahey

Or, like a friend's Father said: "do it right at once, whatever time it takes .... if you do it quick and wrong .... you'll have to repeat it anyway"

polo16mi

Quote from: J M Fahey on September 28, 2012, 10:36:13 AM
Or, like a friend's Father said: "do it right at once, whatever time it takes .... if you do it quick and wrong .... you'll have to repeat it anyway"

I have kind of same said:  "There is two way to do a job: Well done..or..again"

stormbringer

Thanks for the tips Roly. :)

I do have a 12-0-12 transformer scrapping around. Maybe i should use that one then. :)

Got some new parts delivered today. A bunch of useful stuff. JFets, tons of capacitors, resistors, pots etc. Stocking up for the coming experiments.

I also took a piece of scrap aluminum sheet i had and built a small box, in which i mounted 6 pots (Gain, bass, mid, treble, presence (with a switch to disable), and volume + a 1/4 jack. this will be my lab detachable tonestack while experimenting and designing. ^^  Also a marshall type cab-sim integrated inside, with a 3pdt-switch to bypass the sim and put eq directly to the jack. Easy to just hook this up to the breadboard without having pots all over the desk worrying about shorting them while playing around.

Working on the board layout right now, will put sockets for the capacitors and resistors in the tone stack for quick and easy change. Might upload a couple of pics when it's running. :)

polo16mi

#7
Maybe useful for your project, add to you "test bank" a Ruby/Little Gem as amp (LM386-1W).

Only need to put your preamp choice, and play it on.

When you have your desired preamp design, just change amp stage to you need.

joecool85

Quote from: polo16mi on September 28, 2012, 03:02:31 PM
Maybe useful for your project, add to you "test bank" a Ruby/Little Gem as amp (LM386-1W).

Only need to put your preamp choice, and play it on.

Good idea, could make your prototyping go faster.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

stormbringer

Haven't had that much time this weekend to work on the project, but managed to finish the Tonestack + cabsim box, gonna connect this to the breadboard while building to get an idea of what it will actually sound like. The little gem amp might be a good thing too. Thanx for the tip. :)

Attaching pictures of the tonestack box. Not the most beautiful build in town, but it works, and that's the important thing (who needs pretty lab stuff anyway? ^^), no access to a metal brake, so made a temporary one from angle iron, hinges and an old table.

Currently drawing up my USB JFET measuring device and working on firmware. Also working on the design of my power supply, will take Roly's advice and go for 24V, although this cabsim runs on 9, that's not the one i will use in the actual amp later. :)

Also decided to add Send/return to the back plate.

Note, images are quite bad. Phone camera.

phatt

Hi Storm bringer,,
The input Z of IC3 (Cabsim) is so low your tone pots will be rendered almost useless.
Not that it will matter because R7 (10k) will have already killed the input anyway.
Hi Z tone circuits need to be looking into a very hi Z other wise you just waste pots.

I'd be investing into some breadboard setup and maybe getting some simulation software and while you are getting used to using that read lots of stuff. 8|

Phil.

stormbringer

Oh. I took the tone stack from a project i found and built which i liked the sound from, it had that 10k resistor too, but with a JFET Follower in front of it, and 5 gain stages so high enough level to work? i see the point though. i will remove it entirely.

The Cab sim is a schematic i also have already built earlier and it did work, then again i have only been running it after buffered circuits.
found it here, i just adapted it for a TL074 instead of 2 TL072:

http://www.diystompboxes.com/pedals/schems/msim.jpg

Thanx for pointing out these mistakes. :)

Roly

Google download for LTSpice - it's at the best possible price.  ;)  There is a Yahoo users group that is chocka with component models.

Also grab Duncan's Tone Stack Calculator if you don't already have it.
If you say theory and practice don't agree you haven't applied enough theory.

stormbringer

Yeah. Already got both. :)

Guess i was a bit naive with these circuits. I'll scrap that board and rebuild just a standard tonestack for now.

stormbringer

Went over the circuits and changed some things. removed the 3PDT switch, and added another output jack instead. So the first jack is just post tonestack out, and the other with the cabsim on. Also added a follower/buffer before the tonestack, Feeling ready to start designing and testing now. Doing it quite slow though. reading ALOT about the subject right now.

Will check back when i got something useful done. :)

As mentioned earlier, this tonestack-box is built entirely for experimenting purposes, so that i can instantly hook up the circuit under experiment and try it out, getting a bit more feel to the final result.