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The objective here is to build a portable guitar preamp that I can carry around and gig with different people. It can also replace the preamp section of my guitar amp, which is a Peavey, and borrow the sounds of Fender/ Marshall/ Vox from its tonestack.

Step 1: Schematics

I did not design the schematics myself. Since my objective is to make this preamp portable, I searched for the simplest preamp design and found this from www.redcircuits.com . This is called a "Solid-state Fender Blackface Preamp", which is a transistor version of the original valve circuit from the "Fender Blackface".

http://www.redcircuits.com/Page120.htm

I then borrow the tonestack from the Tonemender that is found at www.runoffgroove.com . The Tonemender is a booster with a very flexible tonestack, which can re-create the Fender, Marshall and Vox responses.

http://www.runoffgroove.com/tonemender.html

Details of these schematics can be found at the links above, which explain clearly what these circuits do and how they work.

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hi man <br>I'm a bit confused about the parts so can you add a parts list too.<br>Thank you
<p>This is a great instruction. Can you do one for a tube? I have a 12Fs.Q8 and several 12AV6 that I would like to put to use. Also, one extra 6J1 and two 6N3. Any info would be nice. Have a great day.</p>
<p>Im a newbie in electronics, is this possible guitar&gt;audio interface&gt;computer line? should I use a power supply to power this before using or can I just plug the interface directly to the computer?</p>
<p>There should be an easier way to do it. Meaning, a better lay-out sketch/drawing. More detailed. One problem with smd's is insufficient mounting options. The industry needs to try harder. You are messing with guitar player's that want to play more and fidget less. Things like Tl072's, 4558's, TDA2030a's. Need plugs. Even if they must adapt a tube base to do it, or use an octopus harness and screw lugs. I prefer fiberboards and eyelets over phenolics and pcb's I realize a lot of work went into what you've done so far. It is a device I truly want to explore. I need it simple because I believe once I understand something I can make it simpler for the next person. I was raised on 60's chevy's and they had become so simple it was going to bankrupt them. Tv's, phones, and laptops can be built to support the landfills but not your guitar amps. Even the solid states in your pre-amps should be formatted for handwiring and long lasting serviceability. I just replaced a crumbling and spongy flakewood baffle board on a 70's Vibrolux. When I want to hook an iphone to an amp on stage and pray I do not lose the phone signal ( or whatever)- well, I will see if my cash flow will allow me to keep some throw-a-way landfill bound PCB and flake board expendable ( collateral damage) short-life expectancy throw-a-way guitar amp around. So, until this pre-amp can be laid out and assembly made simpler, I must request that you make them and offer them for sale. I realize the great potential of a solid state pre-amp through a tube power amp. As did Music Man. I would rather prefer the solid state pre-amp be independent from the rest of the amp. I respect what you've done - make it available to buy !</p>
<p>There should be an easier way to do it. Meaning, a better lay-out sketch/drawing. More detailed. One problem with smd's is insufficient mounting options. The industry needs to try harder. You are messing with guitar player's that want to play more and fidget less. Things like Tl072's, 4558's, TDA2030a's. Need plugs. Even if they must adapt a tube base to do it, or use an octopus harness and screw lugs. I prefer fiberboards and eyelets over phenolics and pcb's I realize a lot of work went into what you've done so far. It is a device I truly want to explore. I need it simple because I believe once I understand something I can make it simpler for the next person. I was raised on 60's chevy's and they had become so simple it was going to bankrupt them. Tv's, phones, and laptops can be built to support the landfills but not your guitar amps. Even the solid states in your pre-amps should be formatted for handwiring and long lasting serviceability. I just replaced a crumbling and spongy flakewood baffle board on a 70's Vibrolux. When I want to hook an iphone to an amp on stage and pray I do not lose the phone signal ( or whatever)- well, I will see if my cash flow will allow me to keep some throw-a-way landfill bound PCB and flake board expendable ( collateral damage) short-life expectancy throw-a-way guitar amp around. So, until this pre-amp can be laid out and assembly made simpler, I must request that you make them and offer them for sale. I realize the great potential of a solid state pre-amp through a tube power amp. As did Music Man. I would rather prefer the solid state pre-amp be independent from the rest of the amp. I respect what you've done - make it available to buy !</p>
<p>Can I replace 2N3819 with BF245A or any other transistor?</p>
can i hav the circuit diagram of your merged layout
It is kind of like this.
<p>Everyone else seems to understand what you have done, because they have not asked any questions.</p><p>I am presuming that you have taken the tone circuit from the middle of the tone circuit on the FET circuit and swapped it with the tone circuit on the op-amp circuit.</p><p>Do you know how different it would sound if you used the op-amps in the final cicuit? Maybe with a few mods?</p>
<p>can this be AC powered? if not, can u make a revision of this in AC mode.. TIA :)</p>
I tried to build this project using vero board but it didn't work. Do you know if anyone has done this using veroboard ? Thanks
I have some questions <br>1 I will be using a larger enclosure so that I can fit a mains transformer with 24 volt secondary and a filtered power supply with a 7824 regulator that I have. Can you foresee any problems ? <br> <br>2 Is there any need to have all the offboard shielded? <br> <br>3 I am confused with 2 input wiring. Obviously the jack sockets are switched but I am not sure how to wire them <br>I think this is a very good circuit and is just what I need
Hi, <br> <br>1. I am not experienced with power supply. One reason I do not want to get into it is because of the high voltage. Second reason is that I did built some power supplies in some other projects and found that many unforeseeable issues may happen. For instance, shielding of the transformer is important or the magnetic field may interfere with the signal. You may want to put it as far from the circuit and wiring as possible. <br> <br>2. It is always better to have them shielded. <br> <br>3. You need mono jacks with switch. http://www.guitar-parts.com/catalog/jack-14-inch-female-choose-style-1. the middle one in the image of this link. Once you get the jack, check its connectivity with a multimeter by inserting a jack. You need to figure out which pin is the switch (one that will be disconnected from the tip when the jack is inserted). Once you figured out how this switch works (it is easy when you can and play around with it physically), you should be able to connect according to the circuit. <br> <br>Good luck!
Ooops .... Will this work as a headphone amp?
When I tested this unit I use a headphone, so I would like it would work as a headphone amp. However, you will need a stereo jack for the output. Otherwise, you only get the sound from one side. Thanks.
With this work as a headphone amp?
Hi, very cool, what software did you use <br>to design your circuit board? THAMKS!!!
you may try something like &quot;diy layout creator&quot; for simple layouts. Cheers!
try attenuator <br>
Is there a way to use a power source instead of using batteries????? thanks
Hi, <br> <br>It was already routed to accept a DC power adapter. However, from experience, unless you have a very clean power source, batteries sound better. <br> <br>Actual wiring depends on the DC jack you buy. You can use a multimeter to check for the connection. <br> <br>You can refer to the wiring diagram for any guitar effects. They are all the same for the DC jack/ battery part. <br> <br>http://www.generalguitargadgets.com/pdf/ggg_sgo_lo_wiring.pdf
It will be awesome if you'll upload the layout in a higher resolution so we all can see the values of resistors and capacitors.
could you have a parts list of the merged circuit.<br>and better labels of what the component are(Like value of resistors and cap.)
i got a couple of questions more ,<br>where do the transistors go ?<br>
transistors are those little circles (3 in a row, aligned vertically). There are 4 in pairs, and 1 next to the 4u7 before the output. The pinout follows the one shown on the right.
what's those white holes for ?
hmm, if you're still wondering, if you mean the ones near the jacks, they're the spots that off board components connect to the board, with wire.
Okay ! thank you . xx
i am planning to build an amp.. now i have found this one.. if i was to build an amp what are other circuits i need to create?? that circuit is where the guitar gets plugged in right?? and if i was to implement it on diy amp, how many watts could i get out from that circuit??
this is the circut where the guitar gets plugged in, but you would have your regular input and then for the output have the leads go to speakers. other circuts would be optional (like distortion or FX)
i have built a preamp now i need is a power amp for the speakers, i was wondering if you have an idea on how to build a power amp that is about 50 watts?.. <br>thanks for the input..
check esp, they have free amp circuits... there's also an open design amp somewhere, i forget, ax... something...
Hey how could I add a distortion option to this?
If you made this battery powered could you use it a headphone amp?
The way you are making 18V+ is not so good, if one battery goes out of juice, it will rapidly drain the other and back and forth, this can lead to leaking. <br><br>Why not up the voltage from a single cell? Or run at 9v?
Hey jthank, nice build! When you inserted in the original cicuit the tonestack from the Tonemender, you use -18v as Vref? It's possible that you post your adaptation of both circuits?
Thanks Patodana. I used only the tonestack from the Tonemender, to replace that in the Blackface's original circuit.<br> <br> The tonestack is the section I highlighted in red in the new photo. This is the part that shape the sound.<br> <br> If you look at the Blackface's circuit, coming out of the 1st set of transistors, the signal goes into the tonestack, then the signal goes to the vol (P4) with or without the C6 (bright switch) to enter the 2nd set of transistors.<br> <br> So instead of going into the original tonestack, in my version, the signal comes out of the 1st set of transistors to the Tonemender tonestack (the red part), then to vol (P4) and the 2nd set of transistors.<br> <br> If you look at the Tonemender circuit again, the signal comes out of the 1st opamp, then into the tonestack, then into the 2nd opamp.<br> <br> So if you look closely, both circuits are actually doing very similar things.<br> <br> The tonestack is totally passive and it does not use any power. Vref in the Tonemender = Earth = 0V. Hope it helps!
Thanks for your reply! I asked, just to be sure, since Tonemender's Vref it's around 4.5v and Blackface uses double rail voltage, so... I was a little confused (shame on me LOL)<br> In a couple of days I'll start to work on it. I'm interested on make a bass version, so I need to tweek the voicing in the tone section and some caps here and there, you know.<br> Thanks again for your kindly response!<br> I let you know as soon as I get positive results.<br> Cheers!<br>
http://www.guitar-parts.com/pictures/918c/Jack-1-4-inch-female-Choose-Style.jpg<br> The guy at the store gave me the stereo plug , how do i wire it for mono ?
go back and buy a mono :|
Okay okay . xx
you can just use the tip and the sleeve, and do not connect the other pins. check with a jack and multimeter if you are unsure.
Where do the inputs go in from ? sorry , i'm a beginner , ( learnt quite a bit . )
the inputs are at the bottom left corner. The drawing shows where the tip and the sleeve should go. hope it helps.
Hey , i can't see what to label , i'm lost , mind to explain ?
Hi, I thought about doing the same 'ible, but with a TL072 instead of 4 transistors, it is also a small preamp, and it si also portable, but needs only 5 volts to work.<br>Ill post the link to m 'ible as soon as it's up.<br><br>P.D: Cool project, could you upload some videos or sound to have a listen on it???
I also had come across some opamp circuits, which surely would work the same way. One other reason for my choice of this circuit is I think the transistors would give a more tube-like sound than opamps.<br><br>Looking forward to your instructable!<br><br>P.S.: I will try to get some sound clips when I've got the time.
nice project !<br><br>for the big amount of gain you can remove the C8 cap and put the Jfet buffer like on the red circuit page,<br><br>just replace the output r&eacute;sistor by a 100k log pot and you get a master volume.
Thanks for your comment. I actually had put the buffer, so adding another pot (possibly a trim pot) to replace the output resistor would be the solution for me!
Awesome project. Could you wire an XLR connector in somehow and use this as a Direct box?

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