Tube Screamer Clipping

[Mgt280y]

Been messing with this on an off and finally got enclosure and everything sorted to complete
asked the question in an earlier post on how to add additional clipping as the schematic from tayda was not available and the toggle below was suggested
bit i cant get right is the combination of silicon diodes and germanium diodes on the up and down possition of the switch

Original was as per the picture
Issues

1 - i have i cant remember what diodes i used  as i made no notes before un boxing it

led stage good
1 other good (cant remember is si or ge)
1 very low output volume (guessing low clipping voltage?)

Question is leaving the 2 Yellow 3mm Led in as below what combination of symetrical or asmetrical Ge and Si diodes can i use to give me 3 noticabley different sounds with similar output levels within reason

i am planning on building a rig with a rotary switch at some point for my work bench with loads of different stages so i can test them on curcits before commiting in the future but want to get this on done first.

any help and advise much appreciated

[Mgt280y]

Anybody 

[GibsonGM]

Question is leaving the 2 Yellow 3mm Led in as below what combination of symetrical or asmetrical Ge and Si diodes can i use to give me 3 noticabley different sounds with similar output levels within reason

Hi bud,

There aren't many combinations that will get you a similar volume level but 3 noticeably different sounds! I think that is why nobody has replied.

If you check the particular diode's Vf, forward voltage...you will see that Si diodes conduct at about .5V, and Ge at about .3V.      So naturally, your clipped signal will be lower, depending on what you choose.

You can put them in series to raise that clip threshold...you could use 3 Si in one direction, and an LED in the other, for one example, that would come close to 'equal'.   You would want to measure the Vf's, if you want to match them in some way or predict their relative loudness.

So, rather than being able to tell you what to do, this is a matter of your having to experiment on breadboard and find what works well for what you want to do.   There are other parameters at work, also.   You may find that different types of diodes emphasize different frequencies a bit, so the volume level may seem different....you'll have to make them work to your own sense of 'good tone'!   

[EBK]

If you want 3 that sound different, and you can deal with different volume levels (you aren't planning to switch this mid-song, right?), here's a suggestion for a starting point (literally drawn on the back of a napkin):

For more ideas, take a look at aion's tube screamer project docs (gives you a chance to see some of the most beautiful PCBs on the planet too).  I'll just link to the main project page, but the StratusCirrus is what you'll want to look at: https://aionelectronics.com/diy-pcb-projects/

[Mgt280y]

thank you both,
so is it right that if i look at the forward voltages of the components and use multiples to get all 3 similar ish to the led stage the loudness should be ish similar, and the clipping charatristics of ge si will give me the tone, you are right not going to be changing mid song but the one that was quite was a big sweep on the vol to get it anywhere near,

Putting them in series does that just add the vf together?

thinking i might run the jumpers to a small perf (have room in the enclosure) rather soldier straight to switch and use sockets to allow different combinations

[GibsonGM]

Yes; series will add the Vf together.  Eric's showing you the way it is usually done, but that results in different volumes...it's very hard to get them close!


Think about what you are doing....Ge will clip early, giving you a fuzzy, 'hard' distortion.  Si will clip later (larger signal).  Now - if you used 2 Si, and 4 Ge, say...to make volumes close....you may find they don't still have that big difference!

I say try a bunch of combinations, like Eric laid out.  They will sound different, but the volumes will be different.   

If you wanted to be VERY adventurous, you could find a couple of combinations you like, and using a switch with enough poles, you could switch in or out a volume compensating resistor, pot or some other element at the same time you select the appropriate diodes!   

[Mgt280y]

i did look at using a 2 pole 6 way rotary and having 6 clipping stages with 6 resistors/cap/something to compensate but couldnt work out what section of the circuit the resistor ect would have to connect into thats all a bit complicated for me lol

[GibsonGM]

I don't think they sound ALL that much different, just my opinion!  A little.  But to me, once you've done symmetric vs. asymmetric, the rest is level.   I like LED clipping, so I use them most.  Other opinions may vary...

Ge, Si, LED...if you got creative, maybe using trimmers, you could set a level for each set!  And use your rotary switch 

[Mgt280y]

Got a load of different diodes so going to have a play can I use a DMM to measure vf somehow or do I have to find data sheets

And Jfet and mosfet can they be used if so how do I wire as they have 3 legs

[GibsonGM]

You sure can use a DMM to find Vf...if you don't have a diode function on your meter, or the diodes don't fit its range (mine will do Vf up to like .7v only, LEDs would be higher)...just make a circuit with your diode and a resistor to limit current (oh, 1k or so).  Measure the voltage drop across the resistor, that's Vf 

I think you'll find that doing it by ear might be faster.

Mosfet etc.  read this:
http://www.muzique.com/lab/zenmos.htm

[antonis]

I quit to compete fast as hell guys like Sir Mike...!!! 

[GibsonGM]

I quit to compete fast as hell guys like Sir Mike...!!! 

LOL I woke up early, my cat would not stop meowing!!  So I am in here like a hawk. You beat me on the other post, positive ground, though, so I had to modify mine!   

[anotherjim]

Measure the voltage drop across the resistor, that's Vf 

Not enough coffee, Mike?

[ashcat_lt]

thank you both,
so is it right that if i look at the forward voltages of the components and use multiples to get all 3 similar ish to the led stage the loudness should be ish similar, and the clipping charatristics of ge si will give me the tone

No.  I think I'm agreeing with GibsonFM here.  Two silicon diodes in series will not sound enough different from an LED to be worth it.  Two GE/Shottkey in series will be about exactly the same as one Si.  Symmetry matters, how far past the (total) Vf your signal tries to go matters, diode type doesn't make enough difference to warrant a switch.

To get the effect of changing diodes (with different Vf) without changing the output level, all you have to do is change the input level.  Unfortunately in a TS, the gain structure affects the filter action, so gain (or attenuation) before the actual clipping section is what you really need.

[GibsonGM]

Measure the voltage drop across the resistor, that's Vf 

Not enough coffee, Mike?

There is NEVER enough coffee, Antonis..... 

Mgt - just play with some diodes, and you will see what we're trying to show you    They are not dissimilar enough to need a 'large stock' of them, or to have many on a switch....I believe your idea of 3 types/configurations is probably the upper limit....

[aron]

I like the difference in dynamics with more or less diodes. It makes a difference in the "feel".

[ElectricDruid]

I like the way your design uses the lower Vf of the diodes to "replace" the yellow LED, even though it's still in circuit. Very neat.

If you tweak things so the levels are more similar, you'll have to think about what you're going to do about that. That trick won't work if you have other diode combinations that have a larger Vf than the LED.

Tom

[Mgt280y]

Yeah I did think of that the led stage would always have to be the highest but hopeful I can get the sounds I'm after without it being a problem

[antonis]

Measure the voltage drop across the resistor, that's Vf 

Not enough coffee, Mike?

There is NEVER enough coffee, Antonis..... 

It definately isn't, Sir ...

I can claim it using the fact that you answer to me quoting Jim's post....!!! 

[duck_arse]

.....  GibsonFM here.  ......

(tee-hee) carry on, chaps.