Building a 2 channel guitar head

[unpluggedman]

I'm planning to build my first guitar amp and I would really use some help getting my schematics etc. right because I'm a beginner in electronics. So, basic idea is to have 2 switchable channels: clean and distortion (2 different preamp circuits) both with versatile tone controls. The power amp could be somewhat transparent so that it would not affect too much to the tone and sound itself, I'm trying to leave that for the preamp section. This amp is going to be sort of a practise amp so it doesn't need to push out tons of watts, say 10..50W would be ok for driving my 1x12" cabinet loaded with 8 ohm Celestion Vintage 30 speaker.

So far I've thought to use gaussmarkov's Dr. Boogey as a distortion channel. I really like those soundclips found on youtube about this pedal. And what comes to the clean channel I'd like it to be as clean as it can but slight overdrive is not bad at all when cranking up the volume as long as there is enough headroom for clean sound. One option might be MXR micro amp clone + some tone stack attached to it.
For example Marshall style tone stack would be nice:
http://www.beavisaudio.com/techpages/blocksfragments/Marshall_Guvnor_Tone_Stack.gif

I looked into ROG's Tonemender but it didn't somehow convince me. I'm using EMG 81 and 60 active pickups and mostly 60 for cleans so the clean channel should be quite clear and a bit tight, no loose bottom end although the V30 is fairly bright itself.

Do you guys have any suggestions for the clean channel? And of course for the power amp which I have no idea at the moment.

[phatt]

Hi chum,
            Your hunch about Tonemender is correct as it's a potential noise maker.
(no disrespect to rog as some of their ideas are well worth building but that one I have tested and it's no match for my home made *PhAbbTone* circuit posted on here)
My PhAbbtone will deliver pure *CLEAN TONE* with no clipping artifacts added.

The poweramp??  Try an LM3886 power chip as that will make life easy for you.

As to OD sounds well I'll leave that till you get the basics sorted. 8|
The OD is a complex issue and it is really more dependent on what you consider a good OD sound should sound like.
Some want lots of hi freq content (More modern metal) while others want the (more subdued)  60/70's blues OD sound.

Really comes down to what music you wish to play.
A BB King blues sound will disappoint the metal slayers xP
If you catch my drift?

You will find some of my circuits here;
http://www.ssguitar.com/index.php?topic=2013.0
Have fun,,,Phil.

[unpluggedman]

Thanks for your post Phil!

Those soundclips of your PhAbbtone and DDC are great! That's something I've been looking for.
And yes, I mostly play metal but that's why I'm going to build the Dr. Boogey preamp for my distortion channel 

I wonder does the PhAbbtone work as a "stand-alone" preamp or do I need to put some clean booster circuit after it (in case I want no distortion and don't want to use the DDC)? What I'm trying to tell is:

guitar > PhAbbtone > clean booster?? > power amp   OR JUST   guitar > PhAbbtone > power amp

I was thinking if  it's possible to put a bypass switch between PhAbbtone and DDC so I could have CLEAN sound and switchable distortion sound in same channel?

[phatt]

Hi unpluggedman,

~ ? tricky one to answer?  xP
Having just pondered your request,,
I've realised that I Goofed up a little as you wish to build the whole thing including powerstage.

You would probably need some extra circuitry before a LM3886 chip.
Depends on what sensitivity is built into the powerAmp you wish to build.

the PhAbbtone was built as an add on *Before any common guitar Amp* so as said it's only giving you
a one times gain and a bit more (via the trim pot) if needed.

Even so it would still deliver a fair bit of signal to a bare power amp but most would want more
to produce the full output of the poweramp.

The whole point of my tone circuit is to insert the TONE controlling device **Before** any OD/distortion units as 9 out of ten OD circuits have some form of tone control which is nearly Always after dist.

The difference is nothing short of stunning.

Bear in mind the sound you heard was mostly a $150 cheap strat (no brandname PU's)
and the output was via a Graphic EQ and Keyboard Amp.

You would only need one extra opamp stage to do what you ask,, heck the preamp in the Laney linebacker  is about as basic as it can get and is only a 40 Watt poweramp and I'm never past half way and often told I'm too friggin loud,,
even with a 2 drummers and a big bass amp.

If you wish to cover the heavy metal stuff then just insert a graphic EQ before your signal goes to poweramp.

Yes you can certainly insert a bypass switch to turn off the distortion,  just like any stomp box setup.

Have fun,, Phil.

[unpluggedman]

Hey, I came up with this block diagram showing features I want from this amp.
I think master volume would be really usefull for controlling the overall volume,
unless the power chip circuitry has it's own volume controll.

[J M Fahey]

Yes, looks fine.
Build it.

[Alexius II]

I would personally put the tone stack after MXR, but otherwise it looks cool 

[unpluggedman]

Maybe I'm going to use some sort of input/output connectors for PCBs so I can easily swap the tonestack before or
after the microamp and see which works (sounds) best.

Now about my power supply. I need +/- 18V for the power amp, 12V for channel switching relays and 9V for preamps.
Would it be ok to use this schematic: http://www.generalguitargadgets.com/pdf/ggg_bipolar_ps.pdf
and add 12V regulator between the 18V and 0V rails and also 9V regulator between 12V and 0V?

Something like this:

[J M Fahey]

Even simpler:
* use +/- 18V for the power amp.
* add a series resistor to each relay coil, 1/2 the value of its coil resistance, so you turn them into "18V relays".
Example: if the coil has 600 ohms DC resistance, add 300 ohms 1/4W in series with each.
* you'll easily lower those 18V into 9V for the preamp, using a 470 ohm 1/4W resistor and a 9V zener.
Put a 100 to 470uFx16V in parallel with he Zener.

[unpluggedman]

Should that Zener be other way round or is this the right direction?
Btw, what difference would it make to use 100uF instead of 470uF in parallel with the Zener?

[phatt]

Try this instead.
with psu caps bigger is often better but don't go stupid.
470uF if you have one if not 220uF.
min would be 100uF
Phil.