GGG ITS8 help

[Phoenix60]

This is my first build,  a tube Screamer clone from General Guitar Gadgets.  I got some help earlier in a different thread, but now I have a different question so I hope its ok to start a new thread.  I've gone with the diode lift option, so i have an on off on switch that is supposed to switch between the silicon clipping and led clipping,  and provide a "clean" boost in the off position.   I believe I'm getting clipping in the silicone diodes, they sound clipped, and lower in volume than the other switch positions.   However, I don't hear any difference between the off position and what I think is the  led clipping position.

My question is, is  this normal?  If not, how should I proceed?   From what I've read, I know
I shouldn't expect a clean signal in the boost position.   

Not sure if this is related, but when I turn the tone pot all the way down I also lose all volume.

Thanks for your help.

[EBK]

Since I'm in the middle of rebuilding one of these, I'll try to help.  The output corresponding to the center switch position (open loop) should be much louder than the LED clipping. If they are the same loudness, then your LEDs may not be working.  Could you post some pics of your build?

It is also possible, that you aren't driving the LED clipping hard enough, which could mean you have an incorrect resistor somewhere.

Edit: I see your pics in the other thread.

[Phoenix60]

Thanks.   One of the on positions sounds well clipped, and at a lower volume.  I thought that was the led.  The off position and other on position sound exactly the same to me., and both louder than the led.  Shouldn't there be a difference in sound between the silicone diode clipping and no clipping?

Thanks

[EBK]

The silicon clipping should be the quietest setting.

I have a couple resistors that are different from yours, but that might be explained by the mods I chose (I went with the Landgraff "boutique" version).  I'll look more closely when I have time.

[Phoenix60]

Ok thanks, is there a way to test the leds in circuit?

[antonis]

What colour is your particular LEDs ..??

[Phoenix60]

They're red

[antonis]

Considering Red LEDs forward voltage drop of 2V, you should have clipped signal for IC1 output greated than 2V..

Is it posible to have wrong R6 (4k7) resistor value (bigger..)..??

[EBK]

....

I'm copying your pics to here so I don't have to go look for them later.   

[Rob Strand]

Turn off the lights, crank the gain,  play the notes hard.  You might be able to see the LEDs light very faintly.

[willienillie]

For no real reason, my 1590B build with the same PCB.



Straight 808 clone (but true bypass obviously).  1979 Malaysia TI RC4558P, 1S1588 clippers, aluminum and tantalum electros, carbon film resistors, Switchcraft jacks.

The board is double-sided taped to the backs of the pots.

Green for original tone!

[Govmnt_Lacky]

Straight 808 clone (but true bypass obviously).  1979 Malaysia TI RC4558P, 1S1588 clippers, aluminum and tantalum electros, carbon film resistors, Switchcraft jacks.

Got an entire bag of these things in the parts locker. Was wondering what to do with them 

[willienillie]

I've liked them as clippers in everything I've tried (TS, Rat, OD-1, BMP?).  Sure they're just small signal silicon diodes.  There are slight differences though.  Check 'em out.  If you don't like them, I'll be happy to dispose of them for you!  I think I bought 60 or 80 from Paul P. down in Melbourne, and he doesn't offer them anymore.  They are not easy to find in the US.

[Govmnt_Lacky]

I've liked them as clippers in everything I've tried (TS, Rat, OD-1, BMP?).  Sure they're just small signal silicon diodes.  There are slight differences though.  Check 'em out.  If you don't like them, I'll be happy to dispose of them for you!  I think I bought 60 or 80 from Paul P. down in Melbourne, and he doesn't offer them anymore.  They are not easy to find in the US.

Pretty sure the Fv on these are higher than standard silicon diodes. Around 1V if I remember correctly. As opposed to the standard 0.6V on a 4148 or 914.

EDIT: Sorry about the de-rail 

[EBK]

While we are sharing, here is the current state of my rebuild:

It's still on the wrong side of the enclosure waiting for me to complete the wiring (I'm waiting for a toggle from Smallbear).  I did first build this in a green enclosure ("for original tone"  ), but I'm hoping to etch the new enclosure.

And here is where mine should be different, based on the mods doc:

[willienillie]

Pretty sure the Fv on these are higher than standard silicon diodes. Around 1V if I remember correctly. As opposed to the standard 0.6V on a 4148 or 914.

Not per my meter.  I've heard that said about MA-150s, another of the original TS clipping diode types.  I have a pair of those, they read about 0.7 Vf on my meter, so just a little higher than most Si diodes, at whatever current my meter tests with.  But they sound WAY cleaner to me, too clean actually, in the 808 at least.  The 1588s seem normal, but they have an interesting "color" to them.  Must be that blue stripe.

Another one I like is the 1S2473, famously used in some earlier Boss pedals, but they sound good in a TS too.  I like those paired with the JRC chip, and the 1588s with the TI.  I could just be insane though.

[duck_arse]

those posted photos don't seem to show any clipping switch. can we see how you have it wired, please?

[EBK]

Not sure if this is related, but when I turn the tone pot all the way down I also lose all volume.

Are you gradually losing volume as you adjust the tone, or is it just suddenly gone at the end of the pot's travel?

[Phoenix60]

Thanks for all the replies.

Thanks EBK for posting my pics.  Fun fact: EBK are my initials too!

I will get a pic up of how I wired the switch shortly

Bad news.  When I plugged in to check the tone pot all I'm getting is a rapidly decaying signal on all 3 switch positions.  The pedal has not been doing that for the last 5 days   The tone pot was acting like a volume control, gradual decline.

Here's the pic, switch is wired from left to right as you're looking down C3, C2, C1

Sorry about the rats nest, first build

[Phoenix60]

Considering Red LEDs forward voltage drop of 2V, you should have clipped signal for IC1 output greated than 2V..

Is it posible to have wrong R6 (4k7) resistor value (bigger..)..??

I double checked with my meter and it reads 47k