Ok so this will be my first......

[chuckusa]

Your schematic calls for a jrc4558 ( btw often the prefix can be different, lm4558. Same thing just different manufacturers.)
This is a dual op amp in a dip8 package.

I googled the pinout for you
http://www.elektropage.com/default.asp?tid=618

Your lm308 is a sIngle op amp in a dip8 package
Notice the pinout is different. So this won't be a drop in replacement part

The pinout and is on page 2 here

http://www.analog.com/media/en/technical-documentation/data-sheets/lt0108.pdf

It's always a good idea to google such things or ask here for opinions.

However having said congratulations on securing the parts for a future build.

The rat is an absolute classic.

Rich

Oh cool thanks for the help I will probably get me a Rat 2 to fiddle with next payday. Yea I figured at least I could have some parts for the future if they didn't drop into my ole beater rocktek lol.

[thermionix]

if memory serves, its the same as the arion 4 knob distortion

If memory can count, I'm thinking there's at least one difference. 

[chuckusa]

So I got it today. It actually works! From what I can count there are 6 clipping diodes. Them I think are what I am going to hook up to my little breadboard first to do some experimenting.

[thermionix]

Schematic shows two clipping diodes, D5 and D6.  The others are for non-audio purposes, mostly bypass switching.  What's your impression of the sound?

[chuckusa]

I feel like most reviews on youtube said. The pedal pots have very little change on the sound. It sounds real cheap, and its not real dynamic. The distortion is thin and plain... Exactly what I thought it would sound like. I guess I am going to start farting around with them two clipping diodes. See what changes I can get with my breadboard.

[chuckusa]

Im taking baby steps lol. Can someone kinda walk me through how I am suppose to wire my hot and ground to the diode locations? I know physically how to do it, but I mean like which side of the pair do I attach the hot and cold wires to run to my breadboard and I am to take out the pair of diodes right? Im such a noob.

[patrick398]

Im taking baby steps lol. Can someone kinda walk me through how I am suppose to wire my hot and ground to the diode locations? I know physically how to do it, but I mean like which side of the pair do I attach the hot and cold wires to run to my breadboard and I am to take out the pair of diodes right? Im such a noob.

If you're wanting to experiment with different diodes you can carefully remove them by desoldering. Do you have a desolder pump or desolder braid? The board looks single sided so shouldn't be to tricky to remove. Once they're out and the holes are clear of any solder i'd recommend putting some sockets in so you can easily swap in and out different diodes and see which combination you like. Look into symmetrical and asymmetrical clipping arrangements.

I usually keep a few strips of this handy, so you can make in-line sockets of any size you need. Just score it with a scalpel and gently snap a piece off.
https://www.taydaelectronics.com/30-pin-dip-sip-ic-sockets-adaptor-solder-type.html

As for what diodes to try; someone will be able to give you some exact details here, but different diodes will change the clipping characteristics. Germanium diodes have a lower clipping threshold so will distort 'softer' in theory. Silicon will likely sound a little harsher.  You can also try using LEDs as they have a sound all of their own.

Other things you may want to experiment with that will be easily to try are input and output caps. If you think it sounds a little thin try increase the size of these, or play around with different values for C9 to change the frequency response of the tone pot (someone correct me if i'm wrong here)

Take everything i say with a pinch of salt, i'm only about a page ahead of you in the 'electronics 101' book.

[thermionix]

Im taking baby steps lol. Can someone kinda walk me through how I am suppose to wire my hot and ground to the diode locations? I know physically how to do it, but I mean like which side of the pair do I attach the hot and cold wires to run to my breadboard and I am to take out the pair of diodes right? Im such a noob.

Either way, doesn't matter in the case of these clipping diodes.  There's one pointing each direction, so together as a pair there's no polarity.

[chuckusa]

Alright I will get my hands dirty soon lol. Thanks for the support!

[chuckusa]

So I found a my first sweet spot. I tried pairs of Germanium 1n34a, 1n4001, and bat41 diodes.

I found that two ger 1n34a and one bat 41 arranged like this picture I liked. Make it sound like a whole new pedal.
Also I found that if I jumped where one of the two diodes go on the pedal board, and used two leads from one other diode spot, that I could tap into the signal. I had trouble with resoldering the area and had to scratch into the board to get a good connection. But it did work for me this way.

[chuckusa]

My next question is what can I do to change the power to the signal I guess you would call it? Like over drive how it already sounds, maybe make it thicker and sizzling solo bends pulls ect? With out too many overtones or scratch? I guess what I want to do is learn how to slowly but surely change the flavor, I got the crunch down for now. But changing resistors, caps and jfets, doesnt that also change the chewyness of the tone? Where should I start?

[pollyshero]

...That pdf would be cool, if you can find it...
[/quote]

Sorry I dropped out for a few days - been a bit busy.  Anyway, I discovered I didn't have the .pdf after all BUT here's a link to download: https://www.ibiblio.org/kuphaldt/electricCircuits/DC/DC.pdf

Enjoy.

BTW - nice work so far.  Congrats!

[chuckusa]

...That pdf would be cool, if you can find it...

Sorry I dropped out for a few days - been a bit busy.  Anyway, I discovered I didn't have the .pdf after all BUT here's a link to download: https://www.ibiblio.org/kuphaldt/electricCircuits/DC/DC.pdf

Enjoy.

BTW - nice work so far.  Congrats!
[/quote]


Thanks a lot!

[chuckusa]

Also can you guys recommend an alternate IC chip I can use and what sound change can I expect from each that you name please?

I read from another forum about a OPA2134 ic chip. Supose to give a marshal sound. Same chip used in the guv'nor?

Also what range capacitor and resistor value packs from ebay should I invest in so I can be ready to bring up and down values?

[thermionix]

Also can you guys recommend an alternate IC chip I can use and what sound change can I expect from each that you name please?

I read from another forum about a OPA2134 ic chip. Supose to give a marshal sound. Same chip used in the guv'nor?

Also what range capacitor and resistor value packs from ebay should I invest in so I can be ready to bring up and down values?

In most cases, the differences between different compatible dual opamps is VERY subtle, sometimes not even audible.  You will get much more change by swapping cap and resistor values.  I think the Guv'nor used a TL072.  You could build one with the OPA chip and it would probably sound about the same.

I don't know what value packs are sold on Ebay, but for the long haul stock up on all the common values, resistors from maybe 10 ohms to 4.7M, caps from 10pF to 220uF or so.  Look over several popular schematics and see what numbers are most common.  Tayda is a good place to stock up on cheap caps and resistors.  And there's a currently 15% discount code (15VOLTS) in effect until 6pm NYC time (Sunday).

[chuckusa]

Also can you guys recommend an alternate IC chip I can use and what sound change can I expect from each that you name please?

I read from another forum about a OPA2134 ic chip. Supose to give a marshal sound. Same chip used in the guv'nor?

Also what range capacitor and resistor value packs from ebay should I invest in so I can be ready to bring up and down values?

In most cases, the differences between different compatible dual opamps is VERY subtle, sometimes not even audible.  You will get much more change by swapping cap and resistor values.  I think the Guv'nor used a TL072.  You could build one with the OPA chip and it would probably sound about the same.

I don't know what value packs are sold on Ebay, but for the long haul stock up on all the common values, resistors from maybe 10 ohms to 4.7M, caps from 10pF to 220uF or so.  Look over several popular schematics and see what numbers are most common.  Tayda is a good place to stock up on cheap caps and resistors.  And there's a currently 15% discount code (15VOLTS) in effect until 6pm NYC time (Sunday).

Thanks a lot for the help. I will search for these values and when im ready I will start looking about which value does what.

[chuckusa]

Ok guys I have a decent assortment of 1/4 watt resistors. Where can I start changing them out to reshape my sound and flavor? I need kinda like a little hint lol...





I replaced the R26 3.3k with a 100 ohm 1/4 watt resistor. It brought down the cheap overtoney tin fuzz sound that the pedal used to have. Not too much but it is becoming less cheap sounding with each mod I do.


The Marshall Guvnor, it uses a TL072 duel stage IC chip right? Will this chip drop into this Rocktek board? And will I notice a difference in sound if it does?

[thermionix]

The TL072 will drop in and work.  I wouldn't expect much of a sound change from it.  IMO not worth the trouble, the 4558 is used in many fine-sounding dirt pedals.  Look at what can be changed around the opamps.  The feedback loops are probably good places to try some mods.  Look at other circuits for ideas.

[Kipper4]

I hear you with the op amp swapping thing. Might be my ears aren't hi fi enough.

Try swapping some caps maybe C20 try bigger and smaller.
C5  C9.

Heres a neat trick. Put some other value caps in parallel with the existing values.
Crock clip leads. Then when you find the sound you like.

Google parallel cap maths. Do your sums.
Always good to practice.
Replace the nearest new value in circuit.
Bosh.

[chuckusa]

Great tips guys. Thanks a lot for the advice. I will read up on some of this stuff.