Caesar cuts high end

[DAJE]

IMPORTANT - READ FIRST:
I have very carefully triple-checked ALL of the resistors and ALL of the capacitors, and they are definitely all correct. I test all of them before soldering so I know that they're all within spec.

The 3102 and the 3207 have been tested in my other chorus pedal where they function correctly and with plenty of top end.

I also know that the pots are the correct values and in the right places. I might not have tested them before installation so I can't be certain they're within spec.

I have tested all 5 transistors and swapped the positions around. They're all 2N5088s and they're all in spec, as far as I can tell, with a gain between 350 and 450.

I did the mod where you replace D1 and D2 with 2.2uF MLCCs. Neither affects high-end content.

I have adjusted the trimmer very carefully and while it seems to have a slight effect on the high end, there's no point where the highs aren't cut.

The high cut is the same whether or not the PCB is boxed.

It isn't a subtle effect; the pedal is unusably muffled and it sounds like I've zeroed the tone on my guitar and my amp, while my other choruses - one bought, one home made - have plenty of high end.

 

[DAJE]

D101 = 1N5239B, which is indeed a Zener diode, 1/2W, 9.1V.

 

[Locrian99]

I realize you said you checked all caps. The one time I experienced this I had used a 100n ceramic disc capacitor instead of a 100p ceramic disc capacitor in the feedback loop of the tl072 on a deep blue delay vero build. It sounded like a big muff tone knob turned all the way to the bass side to me. Maybe double check that you didn't make a similar mistake on c19 that mlcc on the bottom right, or maybe even c5. Those would be my first two places to check based on my experience with the DBD build.

 

[DAJE]

I realize you said you checked all caps. The one time I experienced this I had used a 100n ceramic disc capacitor instead of a 100p ceramic disc capacitor in the feedback loop of the tl072 on a deep blue delay vero build. It sounded like a big muff tone knob turned all the way to the bass side to me. Maybe double check that you didn't make a similar mistake on c19 that mlcc on the bottom right, or maybe even c5. Those would be my first two places to check based on my experience with the DBD build.

I promise I really have thoroughly checked them all, and they really are what they're supposed to be. I even visually checked the MLCCs against others I have to make sure they look the same and that the markings are the same.

 

[swyse]

With the blend control can you rule out any parts of the circuit, or is it all muffled regardless? If it is always muffled then you can rule out a lot of the circuit and your problem must be somewhere around the input or output sections I would imagine. I don't think it can be pot related because the only pot touching the signal is the blend pot and I don't think you'd see a big difference in tone EQ wise, just a difference in the two mixes.

 

[DAJE]

Voltages:

TL022:
1 - varies
2 - 4.3
3 - varies
4 - 0
5 - 0
6 - 3.3
7 - varies
8 - 8.7
The variable ones are all sweeping between about 3 and 5.5v

4558
1 - 6.18
2 - 6.47
3 - 6
4 - 0
5 - 6.1
6 - 6.17
7 - 6.18
8 - 9

 

[DAJE]

With the blend control can you rule out any parts of the circuit, or is it all muffled regardless? If it is always muffled then you can rule out a lot of the circuit and your problem must be somewhere around the input or output sections I would imagine. I don't think it can be pot related because the only pot touching the signal is the blend pot and I don't think you'd see a big difference in tone EQ wise, just a difference in the two mixes.

I'll check that later, food time now. I don't think any pot affects the treble content, though.

LATER: I tried zeroing the blend and the depth controls; no difference to the high cut.

 

[DAJE]

I've swapped the red LEDs back in just to confirm that there's no difference. Doesn't seem to be, but it's late here now so I can only play at low volume.

 

[HamishR]

Probably not helpful but two things I would check - the 4K7 in the lower right of the board looks slightly dodgy with the solder, and whenever I socket caps or transistors I am always highly suspicious of the socket making decent contact. Have you wiggled them vigorously while playing through the pedal?

Good luck!

 

[DAJE]

Probably not helpful but two things I would check - the 4K7 in the lower right of the board looks slightly dodgy with the solder, and whenever I socket caps or transistors I am always highly suspicious of the socket making decent contact. Have you wiggled them vigorously while playing through the pedal?

Good luck!

I will try both suggestions, at this point I'll try anything.

EDIT: I reflowed all the solder joints in that area. No effect. I also trimmed the transistor legs so they sit in the sockets a bit more securely, also no effect. Tried jiggling them while the pedal is on, no change.

 

[Locrian99]

Voltages:

TL022:
1 - varies
2 - 4.3
3 - varies
4 - 0
5 - 0
6 - 3.3
7 - varies
8 - 8.7
The variable ones are all sweeping between about 3 and 5.5v

4558
1 - 6.18
2 - 6.47
3 - 6
4 - 0
5 - 6.1
6 - 6.17
7 - 6.18
8 - 9

It seems kind of odd that pin 5 of the tl022 is at 0v I’d have to open mine but looking at the schematic it should be the same as pin 2 shouldn’t it coming from vref b just as pin 2 is? I’m just throwing something out there at this point.

 

[music6000]

I will try both suggestions, at this point I'll try anything.

I don't know if I missed something but why do you have Capacitors where the 2 LED's are suppose to be on the top right corner D1 & D2 ???

Can you remove Capacitor C19 to see what happens to the Sound! or Can you tell me what is written on the Capacitor?
C5 is also the same value?

 

[DAJE]

I don't know if I missed something but why do you have Capacitors where the 2 LED's are suppose to be on the top right corner D1 & D2 ???

I did the mod where you replace D1 and D2 with 2.2uF MLCCs. Neither affects high-end content.

I've put LEDs back in those sockets now, as I also mentioned. Still muddy with either.

Can you remove Capacitor C19 to see what happens to the Sound! or Can you tell me what is written on the Capacitor?
C5 is also the same value?

BC
101

C5 is definitely the same, and they're both identical to the others in the 100pf bag from Tayda.

You can see that I cut one leg - does not have an obvious effect on the sound. Still muffled. Maybe a little less, maybe that's my imagination.

 

[Locrian99]

I opened mine up and pin 5 of my tl022 matches pin 2 kinda jumps from. 4.32-4.4

 

[DAJE]

It seems kind of odd that pin 5 of the tl022 is at 0v I’d have to open mine but looking at the schematic it should be the same as pin 2 shouldn’t it coming from vref b just as pin 2 is? I’m just throwing something out there at this point.

Re-checked, 5 = 4.5 V. Must have got confused. The rest of the readings are approximately accurate.

 

[KR Sound]

Can you post a recording or video of what it sounds like?

 

[music6000]

I don't know if I missed something but why do you have Capacitors where the 2 LED's are suppose to be on the top right corner D1 & D2 ???

Can you remove Capacitor C19 to see what happens to the Sound! or Can you tell me what is written on the Capacitor?
C5 is also the same value?

Can you tell me what value you have at C10 & C16 - 470pF?
I haven't seen a Green cap in that value!?

 

[DAJE]

Can you tell me what value you have at C10 & C16 - 470pF?
I haven't seen a Green cap in that value!?

I have a collection of green caps in pF values, from 220 to 680 or thereabouts. They're tested, they work, I've used them in quite a few pedals without any problems. As I said in the OP, I test all capacitors and resistors before using them to make sure they're in spec.

I could take another pic but the "471" marking would probably be hard to capture, so just take my word for it that it's there.

 

[DAJE]

Can you post a recording or video of what it sounds like?

It's late here now, so not tonight. It's obvious when I compare it to my other choruses, it's pretty similar to zeroing the tone control on my guitar. And yes, it's the same with all the instruments I've tried it on, including bass. Like zeroing the tone control. Crude high cut.

 

[music6000]

It's late here now, so not tonight. It's obvious when I compare it to my other choruses, it's pretty similar to zeroing the tone control on my guitar. And yes, it's the same with all the instruments I've tried it on, including bass. Like zeroing the tone control. Crude high cut.

Did you try adjusting the internal Trimmer to get the sound any better.
Resistors & Capacitors are the only thing that will effect tone!?
You could try lifting a leg on the 4 I have mentioned.