Eternity “tone” pot

[DJPsychic]

Just built an eternity via http://tagboardeffects.blogspot.com/2012/02/lovepedal-eternity.html

Everything works except the tone pot.  At "0" it's barely darker than bypass signal. Treble does increase when pot is turned up.

Everything is wired correctly. I've seen a couple others with similar issue but have yet
To find culprit. Any insight always appreciated. Thanks!

[Mark Hammer]

The cap to ground after the clipping stage should be 150nf (was 220nf on a TS-9).  The resistor to ground from the Tone pot wiper should be 330R (220R in a TS-9).  If either of those was wrong, you could still get a treble boost with the Tone control, but less treble rolloff.

[DJPsychic]

Thanks Mark always appreciate your input.

Everything seems to be the correct value. I did find a resistor that needed a little more solder, but unfortunately did not fix the issue.

[DJPsychic]

So I've gone over the build again and again still can't find any mistakes. Looking at the tagboard layout, is the tone pot wired correctly via the schematic?

[ElectricDruid]

So I've gone over the build again and again still can't find any mistakes. Looking at the tagboard layout, is the tone pot wired correctly via the schematic?

Seems to be. Did you do that cut under the 150n? Without that, it'll be pretty off.

[DJPsychic]

Yep it appears so Druid.

Here's a pic of board.  In the words of Missy Elliot I flipped it and reversed it, to match the layout




(A bit of mess now that I see it photographed  )

[DJPsychic]

For anyone interested, I was  able to test an original Eternity Burst.  Not the exact same as the original E, but close enough and uses the same B5k.

The "tone" pot (or "glass") as they call it, functions in the same way. So that's that. I think it's meant to add "glass"  vs acting as a treble pot.

I'm going dig into it and explore some more mods.

Would it be easy enough to make the "glass" pot more functional as a true tone pot?

[ElectricDruid]

Yep it appears so Druid.

Pity, that would have been an easy fix!

(A bit of mess now that I see it photographed  )

I think that looks pretty nice. Some of those joints look slightly underheated to me - a little bit blobby and not flowed completely - but the copper is clean and the solder is shiny, so it's all good. Certainly nothing that'd make me worry about the functioning. You could try wiggling things on the component side while looking at the solder side. That sometimes shows up a bad joint somewhere.

[DJPsychic]

Not sure if you saw my other post on this thread, but I compared my build to an original Eternity today it sounds the same. So I guess that's how it's supposed to sound!

Would really like to make it into a proper treble pot. Maybe using a big muff treble?

[fowl]

Not sure if you saw my other post on this thread, but I compared my build to an original Eternity today it sounds the same. So I guess that's how it's supposed to sound!

Would really like to make it into a proper treble pot. Maybe using a big muff treble?

As it is, it's a tube screamer tone control with different pot/cap/resistor values.  If you change those values to TS specs, or similar, it might work more like you expect.

[DJPsychic]

Not sure if you saw my other post on this thread, but I compared my build to an original Eternity today it sounds the same. So I guess that's how it's supposed to sound!

Would really like to make it into a proper treble pot. Maybe using a big muff treble?

As it is, it's a tube screamer tone control with different pot/cap/resistor values.  If you change those values to TS specs, or similar, it might work more like you expect.

So looking at the TS vs the Eternity..

"Tone 2" Eternity: 150n/470r

TS: 220r/220n

"Tone 1" Eternity: 150n
TS: 220n

Those seem to be the major differences. Still kind of noob so most likely
Completely wrong 

[ElectricDruid]

Decent analysis here of the TS tone circuit, showing you how the bits work and what they're equivalent to at the extreme ends of the pot. Makes a non-obvious circuit a lot clearer, for me anyway:

https://www.electrosmash.com/tube-screamer-analysis#tone-stage

This should give you a good guide for value-tweaking.

[Mark Hammer]

I wrote a long response yesterday, as promised, and I don't know where it went.  Must have clicked on the wrong thing.

But the short version here....

1) Less "gain".  The circuit shown on the tagboard site uses a 1k/220nf ground leg in the clipping stage. That provides for a max gain of 500+, and a bass rolloff similar to a TS-9.  Change that to 3k3/100nf and that will drop the max gain to 150-ish and lower the bass rolloff down to 480hz, for a "meatier" tone.  That will make the Gain control less "twitchy" for you.

2) The schematic I have (provenance unknown) shows a 2+2 diode complement, not 2+1.  A 2+2 combo will clip a litle less obviously and provide more output.

3)  The 1k/150nf pair on the output of the clipping stage provides less treble cut than on a TS-9.  There is also no feedback cap in the clipping stage which assists in treble cut in the TS-9 as gain is increased.  Consider putting a 68pf cap in the feedback loop of the clipping stage.

Wish me luck, I'm hitting "post".

[ElectricDruid]

In the "references" for that Electrosmash article, there's a AMZ link which has some really good ideas for changes to the standard TS tone circuit. Definitely worth a look:

http://www.muzique.com/lab/tstone.htm

[DJPsychic]

I wrote a long response yesterday, as promised, and I don't know where it went.  Must have clicked on the wrong thing.

But the short version here....

1) Less "gain".  The circuit shown on the tagboard site uses a 1k/220nf ground leg in the clipping stage. That provides for a max gain of 500+, and a bass rolloff similar to a TS-9.  Change that to 3k3/100nf and that will drop the max gain to 150-ish and lower the bass rolloff down to 480hz, for a "meatier" tone.  That will make the Gain control less "twitchy" for you.

2) The schematic I have (provenance unknown) shows a 2+2 diode complement, not 2+1.  A 2+2 combo will clip a litle less obviously and provide more output.

3)  The 1k/150nf pair on the output of the clipping stage provides less treble cut than on a TS-9.  There is also no feedback cap in the clipping stage which assists in treble cut in the TS-9 as gain is increased.  Consider putting a 68pf cap in the feedback loop of the clipping stage.

Wish me luck, I'm hitting "post".

Thank you Mark,

Yes I think you've answered me twice so I have plenty of info needed. Great explanation, Thank you, (again!)

[DJPsychic]

In the "references" for that Electrosmash article, there's a AMZ link which has some really good ideas for changes to the standard TS tone circuit. Definitely worth a look:

http://www.muzique.com/lab/tstone.htm

Thanks Druid. I've been digging into the info. I shall return with the greatest od pedal ever created 

[ElectricDruid]

I shall return with the greatest od pedal ever created 

Oooh, do, do!!

[Mark Hammer]

I wrote a long response yesterday, as promised, and I don't know where it went.  Must have clicked on the wrong thing.

But the short version here....

1) Less "gain".  The circuit shown on the tagboard site uses a 1k/220nf ground leg in the clipping stage. That provides for a max gain of 500+, and a bass rolloff similar to a TS-9.  Change that to 3k3/100nf and that will drop the max gain to 150-ish and lower the bass rolloff down to 480hz, for a "meatier" tone.  That will make the Gain control less "twitchy" for you.

2) The schematic I have (provenance unknown) shows a 2+2 diode complement, not 2+1.  A 2+2 combo will clip a litle less obviously and provide more output.

3)  The 1k/150nf pair on the output of the clipping stage provides less treble cut than on a TS-9.  There is also no feedback cap in the clipping stage which assists in treble cut in the TS-9 as gain is increased.  Consider putting a 68pf cap in the feedback loop of the clipping stage.

Wish me luck, I'm hitting "post".

Thank you Mark,

Yes I think you've answered me twice so I have plenty of info needed. Great explanation, Thank you, (again!)

So THAT's why it looked like the post never made it.  I was looking in the wrong thread! 

[DJPsychic]

Haha yep, that's on me for starting two threads in one day!