Hi Scrappy
I cant help you build this,but I am curious...
You say you play MEtal type music.
Why did you chose this amp?
It uses the "flexwave" clipping,which I own several Crates and I dont much like the Flexwave clipping for metal.
I REALLY like the MOSFET clipping of my GX series amps it is much "heavier" than the flexwave type. Look at a SHAKA pedal or ZEN drive for other examples of Mosfet clipping.

I did notice they use several stages of the flexwave clipping in this amp so I would suppose it sounds much better than mine which only has one opamp stage doing flexwave duty.
Have you used this amp? Is it the favorite of all the ones you have tried?

I would suggest buying a used one and paying a tech to modify it.
It would be alot cheaper that way.I would guess half the cost after paying someone to
recap and modify the ciruit,VS building one from scratch.
Or try and figure out why you like this amp and find someone to build you something similiar.

There are alot of good builders that use these forums- JM Fahey comes to mind as someone who could do what you want.
Also try DIYstompboxes there are alot of professional FX and amp builders there.

OF course the BEST would be to buy that amp and then read up on electronics
and modify it yourself.You could start by downloading Teemuks book and paying a visit to GEO (RGs site)

Thats awesome Donald,I would love to hear some sound clips if you can.
Did you bend the pins on the 3886 to fit the spacing of the perf?
Or do you have the back row of pins not going through the perf?

How does your heat sink run?
Does it even get warm?

I did some A/B tests with my ears so I know that doesnt hold water for anyone else .
But I know what I like.

Hey Strick I was looking at your schematic and noticed its not a chip amp.
What transistors are they using ? TIP31 type set-up?
Sorry its off topic just curious...

Hey Strick -Nice work,you figured that out rather nicely.
Maybe this will help.
I bought a 42VCT 80VA toriodal transformer from APEX JR for 10$
I think that would be just what your looking for,hope this helps and let us know what happens.
http://www.apexjr.com/index.html
click on the picture of the transformer.

Quote from: marmora on September 25, 2009, 10:01:36 AM
Where can I find the Nichicon UKW line?

Try Mouser http://www.mouser.com/Search/Refine.aspx?Keyword=nichicon+ukw
Or if you want the best caps (they wont fit in alot of PCBs) try the UKZ line
http://products.nichicon.co.jp/en/pdf/XJA043/e-kz.pdf
But be warned they are HUGE I have both UKW and UKZ series in my bins the UKZ are 2-4x as big as UKW line.
The UKZ uses the "Muse" logo and an even better dielectric than the UKWs for improved sound.
Hope that helps.

Thats IF used a TL071 if he used a more common DUAL opamp the pin out is different.

Why not try a 12V version of your fav tube amp?
Maybe 12V F2B or SLO100 at 12V could be interesting.
even a scaled down 5e3 would be an easy start.

Also I would suggest telling us what IC you are using- the original Rat uses LM308N an IC that has a different pinout than most dual op-amps.
With that chip your v-ref is on pin 3 via the 1M resistor btween the input cap and the 1k resistor that connects to pin 3.Your V+ is on pin 7.And pin 4 is ground.
This all changes if you used a different chip.

Thats actually a great idea.
thanx for that.

Hey Phatt check this out
http://www.bonavolta.ch/hobby/en/audio/2sk135se.htm

And this It uses a transformer with a set of MOSFETs
http://www.turneraudio.com.au/solidstateamps4-50w-mono-mosfet.htm

I found them in this thread http://www.diystompboxes.com/smfforum/index.php?topic=79034.0

That Turner guy has alot of neat designs and ideas look at his rebuild of that old JBL into an instrument amp.
And check out his pre-amp designs really cool.
I hope this helps.

Oh thats quite a coincidence.
I just picked up those RS trannies today.I was gonna try em with my lm3886 but...
Any chance I could get one?

OK I agree with JM 100%
I too see a break on the same trace he mentioned.
And also that the switching is a seperate issue from the "solder job"
The voltages you talked about with the pedal are used to switch channels.
The Voltage that "SHOCKED" you several times greatly concerns me
DO you have a DMM?
Can you check that the large filter caps are bled(at 0 volts) before proceeding?
If you have a DMM you can check the traces for continuity AFTER you make sure you dont have voltage left in the circuit.
Then with the schematic you can repair the traces,and hope you dont have a bad IC that you need to de-solder to fix the channel issue.
PLEASE BE CAREFUL
Also from the pic of the top of the PCB if you look under the diodes it looks like the trace was indeed an X before he soldered it.Unless thats just the solder I see,but it looks like copper in that pic.
Not saying thats a good solder job,cause it does lack but he may of actually used the right path.
Get your schematic,read up on draining or discharging capacitors and some other safety tips.
Wait till the missus is shopping and have at it again.

I was eyeing them at RS this afternoon.
Thats really sweet idea you had using two of them at 10$ each hard to beat that price.

I am dying to hear what this amp sounds like.

I am no master,but FWIW(not alot)
I think the input impedence is a little low.
I would change the 100n to 200n(input cap) and lower the 1st stages bypass to something around 4.7uf or lower(like680n) and lower the bias resistor to around 820R.
I like a warmer biased triode.
The way it is- its biased clean and should sound good.

It looks like a decent pre-amp.
The huge filter cap and voltage regulator on the DC heaters is something not usually seen on guitar amps,more a HIFi 300B type setup,all its missing is the choke.
Again that will help the sound removing heater noise from the circuit.

OK I looked at it some more that attack set-up looks pretty cool.
In that it should make some fairly high gain sounds.
And with the cathode follower at the end the impedence will be low for use with an SS PA.