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 supplyi 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.
SwitchingBeen looking at LDR, Relays and JFET, feeling that JFet seems to suit me best,
The GutsJFET 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! :)
hey stormbringer
it's interesting plan
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.
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:
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"
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"
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. :)
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.
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.
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.
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.
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 (http://www.diystompboxes.com/pedals/schems/msim.jpg)
Thanx for pointing out these mistakes. :)
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.
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.
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.
Pictures (and circuits) or it didn't happen. :cheesy:
Well, here's a sound clip. Nothing special. just hooked up my homebuilt OD808 Clone before the tonestack and recorded some random riff through the sound card. first without cab sim, then with cab sim.
http://soundcloud.com/gmprog/cabsimtest-1 (http://soundcloud.com/gmprog/cabsimtest-1)
The cab sim schematic
(http://www.diystompboxes.com/pedals/schems/msim.jpg)
Attached the tone stack aswell, it does have an added presence knob through a switch to turn it on/off + volume knob.
Using this in front of the tone stack.
Simple Jfet Buffer (http://www.muzique.com/schem/eagle.htm)
:dbtu: Cool sound, dude!
What´s your axe? Pickup that she load?
It's an ESP LTD FX260SM with passive EMG's :)
(http://medias.audiofanzine.com/images/normal/ltd-fx-series-fx-260sm-natural-satin-356198.jpg)
Looking at various power supply solutions, and decided to do some experiments. got this AC brick that i dont use for anything. 12v, 1A AC output. More than enough current for my preamp, and i dont have to dabble with mains either until i feel more comfortable with it. Got transformer, fuses/holders and all in stock, but there's something about 230v that gives me chills down my spine, even though i have actually installed mains outlets and stuff (under the supervision of my uncle though, a certified electrician). I rather wait for that until it's time to install the entire thing in a case.
Now, according to Rod Elliot's page http://sound.westhost.com/project05.htm (http://sound.westhost.com/project05.htm), a 16v AC should be able to give +/-15v using a full wave voltage doubler. and 12 VAC +/-12.
Quite interested i decided to try this out in both ltspice and Proteus. but both sims gives me around +/-11.2 VDC. Guess i will breadboard this next and see what the results are. i'm just curious to why i get these results. :)
Another question that i have been unable to find the answer to, is how i calculate maximum current with this type of circuit? It can't be as simple as just halving the AC adaptor's avaliable current?
Edit: regarding the current i found out through ltspice simulation that the capacitor values are linked to the current/ripple. so that answers my question partially, but i'm still curious about how the current draw is defined from the adaptor/transformer itself. :)
Attaching the ltspice circuit below
There must be something wrong.
Those caps will charge to the peak of 12VAC, in practice you'll have +/-16Vdc or a little more unloaded (because real world transformers are slightly overwound) or with the small consumption of any preamp.
Now if you pull 1/2A from each rail, yes, a cheap transformer will have losses, although going down to less than 12V seems too much.
I'm talking about raw voltages, of course.
Rodd Elliott refers to regulated rails, and regulators will , of course, give you the exact value indicated by they name, but need *at least* 3 or 4 V above it for themselves.
Quote from: stormbringer
there's something about 230v that gives me chills down my spine
And so it damn well should! I'm retired now but part of my gig included industrial installations and repairs, and sometimes live board work, variable speed drives up to 100HP. Shaking hands with beef is only part of it; the domestic supply can deliver an awesome amount of power into a short for a few hundred milliseconds before the protection pops, sending a spray of white hot metal in all directions. When you get casual about dealing with the power mains it's time to quit while you are still alive. I like your plan and would do the same myself.
{I'm in Australia, 240V 50Hz, where are you?}
Yeah, there's something wrong there. 12VAC is root(2) more peak, and unloaded the caps should both charge to the +ve and -ve peak values (less diode drops);
12 * 1.414 = 16.968 or +/-17 volts, but as JM says a real tranny is "soggier" and will start out higher no load and may end up lower at full load current.
Quote from: LTSpice Help
the output voltage is given by
Voffset+Vamp*sin(p*Phi/180)
that is (ignoring Voffset = 0);
e = E
max * Sin(Theta)
i.e. "Vamp" = E
max = the maximum or peak voltage, not V
rms, so E
max (i.e V
amp) has to be multiplied by root(2) = 1.4142 to be the same as "12 volts"(rms).
12 * 1.4142 = 16.9704, call it 17 volts.
Just a couple of things to remember if you are going to follow this up with 7812/7912 three pin regulators; a) the pin order is different between the +ve and -ve regs (and the -ve tab has to be insulated), and b) stick small caps
right on the reg pins, input to ground and output to ground (0.01-0.1uF) to prevent any instability.
Thanx for the replies guys.
I will make a test circuit for this and try it out. Oh, and i'm planning lm317/lm337 regulators. I really like those.
i'm in sweden 230v/50hz. Yeah, i got alot of respect for high currents and voltages. i always take precautions when working with electricity, even if it's not in the lethal range ie down at 5v and low current, but gaining that extra few seconds from not discharging capacitors etc just isnt worth it. Only shock i have ever had was an electric fence for horses, it was terrible. i can only imagine what (actually i dont even want to) the mains outlet would feel like.
A janitor at work got his shoulder against a rail in the roof that shouldnt even have current that caused his muscles to contract enough to break both his shoulders. No, i'm staying careful. :)
Well, unless I'm mistaken, Scandinavian Countries (including Sweden) don't even have grounded outlets because high resistance soil can't be trusted for grounding purposes, go figure.
That's why their Electrical Safety rules are the toughest in the World.
Worst boot I can remember getting was in a factory working on a press guard installation, standing on a plastic milk crate I somehow managed to get each hand between two phases, 415V - worst case you could imagine with the current path through my chest cavity. Felt like I had been kicked in the chest by a horse for a few days afterward (and a hell of a lot more careful forever thereafter). :P
When probing live valve/tube amps I keep my wrist resting on the grounded chassis, and the other hand in my back pocket - an old trick that is a leading cause of old technicians. Or as a boss of mine was fond of saying, "there are careless techs, and old techs". :dbtu:
Yeah, outlets in kitchens and bathrooms are always grounded. And if you install new outlets anywhere nowadays they have to be, but for example in older apartments (like mine), there are no grounded outlets in the other rooms. so i usually ground myself to the radiator (they are water heated in my apartment) before handling semiconductors. Maybe it's not needed, but i havent broken anything due to ESD so far. :)
Hi stormbringer,
Some of my schematics might interest you? Give you ideas to ponder :tu:
http://www.ssguitar.com/index.php?topic=2013.0.
In my experience you still may need post cab sim tweaking.
Give me a week or 2 and I'll be posting my latest adventures,, which has many more tricks.
Phil.
Thanx Phatt, will keep an eye out. :)
Right now i'll just go with the cabsim + tone stack i built while working on the gain stages and experimenting, later on however i will explore those parts a little deeper, right now i just needed something that worked while working on the basic parts of the preamp.
Project update:
Built a voltage doubler and hooked up a dual gang Pot to let me tune voltage between 1.5-12v from some scrap parts (well, the pot + capacitors atleast). Waiting for a LM337 to arrive so that i can complete and test it, Also found yet another AC-AC adaptor (15 VA) while searching my electronic recycling plant (Or as my girlfriend calls it, the basement, good backup in the case my 12 VA adaptor doesnt pull it off. Unless i get the awaited LM337 tomorrow i'll probably make a small voltage monitor using a pic + lcd display for the circuit. Easier tuning in voltage in a visual way than using a manual voltmeter.
Quote from: stormbringer on October 05, 2012, 06:30:53 PM
Another question that i have been unable to find the answer to, is how i calculate maximum current with this type of circuit? It can't be as simple as just halving the AC adaptor's avaliable current?
Yep that one messed with my brain some years back.
The current rating of the rectified secondary voltage is dependant on what type of rectification is used.
This little gem helped me get my head around it.
Take note of the *IDC over IAC*
Phil.
That's great Phatt! Thanks!
I've been laying a bit low the past week, literally actually. Lumbago..
Waiting for a bunch of 4700uF capacitors now in order to complete my supply. :)
"electronic recycling plant" You wanna see my whole house mate! I'll just mention seven console organs and about 30(?) computers; the synths, guitars, amps and cabs you will just have to imagine - then there's my electronics stuff... bush heaven. ;)
"Lumbago" Bugger. Had a back injury when I was a teen, quickly learned to "lift from the knees". I got arthritis in my hands so badly I switched from guitar back to keys - cured! So play more, but get a good strap, wide. Take care. :tu:
That sounds like a great collection. i pick up most stuff that's going to the scrapheap at work, mostly printers, computers and such, but there are always parts to scavenge, or fix. gotten some quite nice heat sinks from laser printer power supplies, and using the casing from an ATX supply for my lab supply. a colleague plugged it in a 230V outlet without checking the 115/230 switch in the back. :P it went boom, quite a few scorched components. but the case and heat sinks are fine.
My back is getting alot better, i can get out of bed instantly when i wake up. A few days ago i had to crawl out of bed. I definately need to stay away from heavy lifting for a while, fortunately we are finishing up our album at the moment, a couple of months left to release party, tour etc.
Almost done with my lab supply design now. Been plowing through electrical safety rules for a couple of days to make sure it's as safe as possible, i want to go through every possible measure.
Will fine tune, simulate and code some more and then post schematics.
i'm mostly basing the supply itself on Rod Elliots +/- 25 lab supply, http://sound.westhost.com/project44.htm (http://sound.westhost.com/project44.htm), but with a 12-0-12 1 A transformer instead.
The addition i've made is digital monitoring and current control.
There's a TIP122 darlington on each rail driven by Bc547/557's with led indicators that light up when current is limited and the transistors choke the regulator inputs. the limits are set by pots connected to the Adc of a pic16F690, there's also an overload LED that lights when the total current gets above what the transformer can safely deliver, will set this value in software. it's easy enough to change if i make a bigger supply with the same control logic.
On the output side there's a 0.1 ohm shunt resistor on each rail. each side of the resistor goes through a 1:10 voltage divider, buffered (positive side)/inverted (negative side) by 2 lm358 opamps, and differential amplified by a gain of 100 by another lm358. the outputs on the diff amps goes to pic Adc, so does the voltages from the buffer after the shunt resistors for voltage indication.
Now, i'm aware that i will lose some precision with this.
1. the lm358 is not rail to rail, and will have an offset voltage. i will have to adjust for that in software
2. the voltage dividers will lower my precision some.
I'm setting the PIC's Vref at 2.5 volts, the Adc should never go above 1.2 volts in though. but this gives me about 2.44 mV resolution, which i feel is sufficient for my needs.
i know i'm a bit off the original project, but i feel that proper tools will improve the testing and design, so i rather spend more time getting to the finish line. :)
A PIC! "Software"? Egad, I stop when the smoke gets too thick!
This is very good to hear. Back when I was a teenager it was a matter of build my test gear or go without, even my first multimeter, a habit that has stuck. As I'm sure you are aware, building test equipment is rather more demanding than just amps &c; your results are only as good as your test gear, and to deliver results you can depend on it has to be an order of magnitude better than the amps (or whatever) under test, and this can be very demanding. Oscillators in particular can be quite an adventure.
A long while ago I bought a kit for a Noise and Distortion meter after a constructional article in a reputable electronics magazine. Well! First thing, if you ever want to build any sort of instrument with aspirations to precision, start with a metal case.
It took a deal of redesign and much added shielding to get it a) stable, and b) satisfactory. It now resolves down to -85dB, but in it's original incarnation was lucky to make -40dB and very prone to simply taking off under its own steam. I never saw a letter of complaint and have to think that all the hapless kit builders thought it must be all their fault.
I hope you intend to fully document your build and put it up on the net. If so I'd be happy to give it space on ozvalveamps.org (http://ozvalveamps.org). :dbtu:
Tried a different approach writing the firmware. Tried out FlowCode, microcontroller programming without actual programming. Really fun to work with, but terribly optmized code. My program got 250 words too big at first. managed to optimize by hand down to 3 words+, but realized this is a no-go as i need to add offset voltage compensation and so on.
So i guess i will make a rewrite from scratch in C, I do work as a programmer, so it's my cup of tea. But for anyone wanting to experiment with MCU's, and dont care about using a bigger chip with the benefit of no coding, i highly recommend flowcode. :)
Assembler Roolz! :dbtu: :lmao:
Well, assembler is a great way to gain maximum control, but so inconvenient to work with. So much simpler to reuse my old LCD functions i wrote ages ago in C. :) Going for dual displays, one for each rail, as i noticed i didnt have any bigger displays than 16*2 with backlight. all my 20*2 and 20*4 are without.
so it kinda looks like this right now:
| Rail - xxxxmA | Rail + xxxxmA |
| -xx.xxV [xxxxmA] | xx-xxV [xxxxmA] |
top line shows actual current, bottom line shows set voltage and current limit.
1 pot for each rail voltage, and another for setting the current limit. Those are actually analog, which might be odd when there's an MCU involved, but i decided to go analog for the PSU itself and Digital for the monitoring and limiting.
I got the firmware done in C now with 60 % of the code space used instead of the flowcode variant that hit the ceiling, and am working on the PCB layout for the supply. So hopefully it will be done in a couple of days, decided to order a bigger transformer too, if this works out the way i hope i might upgrade it to a 2A 12-0-12 instead of the 500mA one i'm using later on if i want to begin looking at power amps too. (although i will need an even bigger one if i wanna do a 100W amp, there's still a long way there. Preamp is next.
I'm reminded of the saying that "it's hard to remember you came to drain the swamp when you are up to your arse in alligators". :cheesy:
(http://static.ddmcdn.com/gif/alligator-feeding-frenzy.jpg)
In very slightly related news; I bought a bunch of coloured screw terminals a couple of weeks ago intending to fit them to a computer power supply for bench use. Well I had to buy some more yesterday because the first lot slipped through the same wormhole in space that pens and socks use to go to a parallel (or perhaps divergent) universe. I've turned my workshop upside down three times last week, discovering many long forgotten things along the way, but of terminals, not a trace. :grr
Waiting for my goldsmith Girlfriend to make the front panel for the PSU as she offered to. :) Will be a brass plate.
Before i start soldering the boards i did some measurements while moving around the guts of the supply to make sure my board wont get too big. I also put in a small DC fan, not sure if i will need to use it, but, hey. when did you last hear of a power supply running too cool? ^^ Also got my 2000mA transformer, so i figure the 150 mA used by the fan (well actually i think i'll just pwm it and get it down some more) wont be a problem. Now the fancy way to do this would be to let the pic read a temp sensor and adjust the fan accordingly, but that means i will have to redesign a little, and pick a bigger Pic, no spare pins atm. I think i'll probably just run this one of a potted 555 if at all.
Also looking at fabricating a small enclosure that will seal the input jack + switch. i dont want any mains points touchable at all, especially with the small hole array at the back panel of the ATX case. inserting a guitar string or wire by mistake would be bad. So i will make some sort of bracket to make sure it cant get nasty.
Attached pictures of the "mockup" placement and the LCD, Terminals + knobs, still in bags.
Oh, and the plate which the transformer secondary wires are resting at on the picture will be the front. Gonna cut it into a frame for attaching the front panel when i get it.
Exciting project. So since you are doing this with a PIC, will you share your code?
Yeah, i plan to upload both pic code and schematics when done. :)
Going a bit slower than i anticipated, but getting forward. Installed the transformer, did all the wiring up to the bridge rectifier and figured out where on the heatsink i want to mount it later on,a used LOTS of heatshrink tube. Love that stuff. Now i'm going away over the weekend, so probably wont get much done. But i need some mounting materials anyway, so might aswell go away while waiting for the delivery.
By the way, Roly. what's up with electronics and Australia? Is everyone a pro engineer over there? :D
Stumbled across this guy (Dave Jones) a few days ago.
http://www.eevblog.com/episodes/ (http://www.eevblog.com/episodes/)
That stuff is excellent! i've learnt so much just watching those teardowns and of course his PSU design project, and on top of that, you also got Rod Elliot, and you seem to know quite alot yourself. :)
Murphy's Law of projects - everything takes twice as long and costs twice as much as expected (except when it takes longer or costs more ::) ).
Fan control;
http://www.ssguitar.com/index.php?topic=2591.0 (http://www.ssguitar.com/index.php?topic=2591.0)
Heatshrinking all the mains stuff helps to prevent "errant guitar string" moments.
Quote from: stormbringer
By the way, Roly. what's up with electronics and Australia? Is everyone a pro engineer over there? :D
:lmao:
I've only seen a bit of Dave's stuff but he sure likes to rip into things. Rod is very good value and sets a cracking standard on his website that we try to live up to. I'm (supposedly) retired after a long and varied career in electronics including consumer, industrial, bio-med, programmer and of course theater/music/soundie, and been a musician, keys and guitar, since I was a kid (but not a very good one which is why my career was in electronics and not show business 8| ).
That fan control looks Nice! will try it out if i can fit the board in the case. Space is getting tight! :S Note to self: next psu i build will be atleast twice the width of an ATX psu Case.
Was soldering my prototype board, but i really need to start over, i dont like having the 4700uF caps that close to the heatsink. So will either have to try and move them some, or raise the regulator board a little so that they wont get more heat than they have to. Completed the LCD Daughter board and shot a photo with them in the front panel my GF is working on, It will be polished and engraved though, only rough cut so far. And i need way smaller knobs. :P
Very steampunk. :dbtu:
I've found that I can bolt up to three gutted 'puter PSU cases together for valve amp chassis'. I'm nothing if not cheap. ;)
Smaller knobs? Bigger panel!
Hello Stormbringer,
I am currently building my amp too. recently finished power amp module and cabinet speaker assembly. Stuck on preamp. My requirement is quite same as yours. can you please elaborate your plans on adding several components. since you have already completed tonestack+cabsim. is it common for all the channels(tone stack).? Or each individual channel will have a separate but same tone stack? what is your plan on different channel. Mr Fahey recommends 1.Elliot project 27/27b 2. Marshall Lead 12 preamp.
dont know but curious: why dont you use higher voltages like +-15v for opamp biasing which is very common in commercial amps?
you can check my thread recently started:
http://www.ssguitar.com/index.php?topic=2759.0
thanks
Hey. :)
Currently working on som high priority stuff for the band, so going a little slow with the amp project. I had to make a better backing track solution than our current mp3 variant, the new backing tracks from our producer really need to be stereo (or preferrably 4-8 channels), so i've made a small pic-controlled remote control with a display and buttons that controls a computer through the serial port running a minimalist microcore linux (6 mb iso) to play multichannel Flac-files.
The reason i did not go with +-15 for the opamp in the cab sim is that the one i found, and liked was made for single supply. The tone stack will be tweaked later on. The cab sim + tonestack i posted here is something that i use as a "plugin module" to test the actual preamp circuit while designing and experimenting without having to make a huge breadboard circuit just to test a couple of gain stages etc. There will be +-12 for the jfets though in the preamp itself. I've been looking quite alot at the Rod elliot project, but i really like the sound i get from jfet circuits i've been building and want to do a PROPER design with those. No trimpots, doing correct biasing etc. :)
ok! Best of Luck!