My Crunch Box Version

[Goodrat]

I think I would make one this way. Verified on experimenters board.
http://www.rickviola.com/images/CrunchRV.jpg

[Goodrat]

I think that 2.2uF on pin 7 could be a 1.0uF.

[J0K3RX]

I think I would make one this way. Verified on experimenters board.
http://www.rickviola.com/images/CrunchRV.jpg

Hey Rick,

A lot of different values from the original crunch box..? Also, I tried many dual op-amps and seemed that the LM833 sounded the best to me anyway. No presence trim? You have any sound demos?

BTW - Nice antenna stuff man!

~Jim

[Goodrat]

I made some changes since yesterday. A few errors. I replaced the file with the 4/16 version so all good now.
For better noise, I changed the second feedback resistor from 1M to 100K and changed the 2nd input cap and resistor accordingly to give the same gain and response. I did not like where the power supply 100uf was on the schematics floating around and there is less hum where I put it. The bias resistors I think are better at 100K for less battery draw and a smaller cap can be used there. The bias feed to the first stage should be quieter at 100K rather that 1M.
I don't really get the presence thing so I put a nice functional treble control.
I use the TLO82 because I have some. I will plug in others and compare, including an OPA one.
I just drew up a layout for a Radio Shack IC experiment board 276-159 that can be purchased real cheap. I will post that after I double check it.
Maybe I will but a Joyo version and do a compare and film that.
BTW, If you come across my "Scooch Box" I have many changes to that design (less switches) to get around to also.

[mremic01]

This is interesting. The Crunch Box is one of my favorite distortions. Do you have any particular goal in mind with this version?

[Goodrat]

Well I spent a year or so playing with my "Scooch Box" and I still have improvements I want to do with it.
I heard some demo's on the Crunch box and I liked it. I bought a Joyo Clasic Overdrive today because I wanted a nice basic Tube Screamer sound. I figured the circuit was simple enough on the Crunch box, so I built it on one of those press on experimenters boards. I want just a basic treble control with the Crunch so I put in a "Stupidly wonderful tone control" in place of the tone/presence and that was fine. Now I'm thinking that the drive control sounds useless on the lower end of the control, so I compromised and put a 20K there. Normally this is shorted to the wiper but in the Crunch box it is open and the response is a little weird and gets muddy. Then I just did a few things I learned with all my experimenting.
It is simple enough to solder on one of those Radio Shack 276-159 boards so maybe for about $20 for a box, jacks, switch etc. I can have a nice fuzz box.
Although, with these Joyo pedals on the market, for only slightly more I can skip all the trouble and modify that if I want.
But what fun would that be?
Maybe I should make my version and lend it to someone who has an original to compare.

Update: OK, I ordered a Joyo crunch box which should sound just like the MI version (most say). I will compare and tweak if I need to.

I'll know in a few days if my tweaks are any good.

Update 2:
After looking more carefully at the second stage and drive pot, I put some values back to original. I realized that the drive pot would behave worse if the second stage feedback resistor was 100K instead of 1M, because the right side of the pot adds to the series input R of the second stage when turned CCW. In combination with the cap in series is why the bass roll off gets lower and the second stage gain is drastically cut. (muddy).
I will experiment with a cap on the right side of the pot to wiper, as this will become in series with the other cap and roll off lows at a higher frequency when the drive is CCW, or at least put some resistance there to lower what is on that side of the pot for less gain cut. Anyway, my current thoughts are in the updated diagram (Dated 4-17-12).
I will have the clone tomorrow and have a better opinion.

[Goodrat]

Is there a particular LED preferred for clipping? I noticed the 3mm's I have light up more than a 5mm, but the 5mm sound better.
I have no specs on either. (at least I think those are the dimensions). All I know is the 3mm's I have when used as a power on indicator, I can get away with a 10K resistor and still plenty bright.

[J0K3RX]

Is there a particular LED preferred for clipping? I noticed the 3mm's I have light up more than a 5mm, but the 5mm sound better.
I have no specs on either. (at least I think those are the dimensions). All I know is the 3mm's I have when used as a power on indicator, I can get away with a 10K resistor and still plenty bright.

I use the 5mm red... I think they sound the best on the CB.

[Goodrat]

I got the Crunch box clone today (Joyo). Good news... Success! It sounds and behaves the same as my prototype.
I had to make sure I used a linear pot in the tone. I increased the 9V filter cap from 100uF to 470uF.
It should even be a 1000uf but it has to fit in the box.
I have to check if there is any weird pop at turn on since I actually turn power on and off with the switch.
I like the 250K lin pot/50K resistor combo at the volume control. It should be better than a cheap log pot (so they say).
I need to swap IC's to see how a better one will hiss less when the volume is at max.
The Joyo is slightly less hiss. I'm not sure what is in there yet, but I am using a TLO82 at the moment in my proto.
The drawing link is updated on this thread and I have a layout I am verifying and tweaking.

[Goodrat]

The Joyo has an 833 op amp and all parts I read match the schematics.
The trim should be on the other side of the board, I would think.
http://www.rickviola.com/images/Joyo1.JPG
http://www.rickviola.com/images/Joyo2.JPG

[J0K3RX]

Yup, that's a Crunch Box and you got it for a fraction of the price... The CBv2 is like $139.00! I have to say the Joyo looks really well built... I like to use a 16mm B20K pot for the presence control mounted with the vol, tone and gain rather than the 20k on-board trimmer... I have also tried different combinations of LED's and other diodes and some sound really good. One combination that sounds pretty good is 4 - 1n34a's.  There are a lot of possibilities with the Crunch Box and I am surprised that there has not been more interest in the forums!? MI Audio has a new Super Crunch, I don't know if it's for sale yet but I got a pic of it... Looks like they did some pretty cool updates/mods..

[Ronan]

There are a lot of possibilities with the Crunch Box and I am surprised that there has not been more interest in the forums!?

I agree, its my "standard" against which I compare other dirt creations. The Joyo is the same circuit (I own both). The Joyo is not built that well when you are close up, but its good enough. You don't want to start substituting parts on a Joyo, the PCB breaks up pretty easy, you get a couple of goes and thats it. The MI crunch box uses medium brightness LED's, 9 to 10mA @ 2.0V, 19 to 22mA @ 2.2V, and the lenses are milky red, not clear red. The circuit is so close to a Marshall Guvnor its not funny, but MI really nailed the tone control (and pres control), the tone control is very versatile and the slightly metallic midrange of the marshall tone seems to be there.

[Goodrat]

Nice mods!
Yes, I do NOT intend to mod the Joyo. Although I may put the trim pot on the other side of the PCB.
I wanted to keep a golden unit around to compare what I build.
I'm need to compare the tone control more closely. So far, what I hooked up in my proto has the same range.
I don't know why they keep using lower values in the bias resistors.
The 47 ohm I put on the 9V input and a higher cap also reduces hum more.
I need to order an 833 chip. I'm using a TL072 at the moment.
I also bought the Joyo Classic overdrive. Nice. I'm all set. Too bad I never play live, but I'll be ready.

This is how I intend to build one for the fun of it:

http://www.rickviola.com/images/CrunchLayoutRV.jpg

[Goodrat]

Small pots:
http://www.diystompboxes.com/smfforum/index.php?topic=97114.0

[Goodrat]

A/B test today, I am pleased. The tone control works just as well, gain, all fine.
Max volume is slightly less with the 250K pot linear with 50K on lower leg to make it log, but just slightly and who needs max output volume?
I could always put a 100K log.
The 47 ohm on the 9V input with a larger cap will clean up any hum from a wall wart much better.
The 100K's with 1uF rather than 22K with 10uF on the bias should make less hiss and hum , but I have to get an 833 to be sure.
The tone control is an easier build and has a full range and the volume will not drop off when at min.
It seems this is a nice quick and easy Crunch box.

Update: after playing for a while, I notice a slight difference. It's hard to explain. I will wire up the presence pot to see what that does.
If I still notice it, maybe it is the chip.

[Goodrat]

[Goodrat]

OK, I give up. I'm putting the presence control back in.
Schematic:
http://www.rickviola.com/images/Crunch2RV.jpg
Layout:
http://www.rickviola.com/images/CrunchLayout2RV.jpg

Why mess with it.
So basically, the only thing I am doing is changing the 9V input with cap and resistor  and the bias resistors and cap.
If I didn't get the Log/Lin notes right, someone let me know. It matches my Joyo now. All seem to be linear except the tone is anti-log (CW to wiper increases from zero slowly).
I also noticed they set my presence trimmer full CCW.
That threw me off because it was bright and I could not recreate with my proto half way up.
Hmmm, maybe we don't need no stinken presence control.

[deadastronaut]

soundclips?....comparison?....just curious. 

[Goodrat]

I'll try a video tonight. I wanted to make sure all the drawings were correct. They are now.
So if anyone saved a drawing I linked on this thread (any version), save a new one dated at least today (4-23-12).

[Goodrat]

Here is a quickie. The right pot on the proto in the simple tone control from my first link with no presence. The left pot is gain.
The Joyo Crunch box has the presence full so it is basically not in the circuit anyway.
Sorry, I never know what to play in these vids. I'll do a better one when I have an 833 chip which may be brighter. This has a TL072.
http://youtu.be/1VU04ZxYTN4
http://rickviola.com/images/CrunchRV.jpg