Skeptical Buffer

E

Endosidney

New member
Sooooo….. while browsing for something unique saw glowing reviews and put it together. Sounds great. Then, I saw all of the discussions! I had no idea of the history. Very entertaining

I did not build using the BOM just silk screen values so tantalums are now electrolytic. Would it be worth replacing? Thoughts on OPA2134 instead of TL072?
 
Endosidney said:
Sooooo….. while browsing for something unique saw glowing reviews and put it together. Sounds great. Then, I saw all of the discussions! I had no idea of the history. Very entertaining

I did not build using the BOM just silk screen values so tantalums are now electrolytic. Would it be worth replacing? Thoughts on OPA2134 instead of TL072?
Click to expand...
You won’t hear the difference between Tanya and electros. If you’re giggling for money, I’d change the opamp. Otherwise, as a deaf musician, I couldn’t tell you I hear a difference.
 
Though none of us are qualified to speak technically of this feat of engineering, /s
If you play high gain or use a lot of compression, changing out the 072 for something quieter may be of some perceivable benefit.
A OPA2141 would also be a good choice(lower noise than a 2134). Even a 5532 is quieter the an 072, on paper at least.
It won't likely be a game changer but since it's likely the first pedal in chain and likely always on, any noise reduction is a plus.
 
It might be worth your time to order a second board and build a second pedal with tants and with the OPA chip and see if you can hear a difference between the two.

I used elecs in mine bc I play a strat with vintage single coils that hum like crazy anyway so wgaf
 
Now I’ve noticed the hum!! Before boxing it up I played around with it and it sounded fine on its own and I figured it was good to go. What’s strange is how loud it is with a blues breaker circuit. Literally unusable. Sounds dead quiet with Greer light speed. Klon circuit it’s mildly noticeable. Harmonics on definitely worsens the effect. The strangest thing is how the light speed cuts out the hum entirely. I’d would love to know why this is. I’m both fascinated and slightly annoyed.
 
JohnnyCreepy said:
Did you try different power supplies or 9V battery?
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Didn’t do the 9v, but I’ve got a fender engine 12 and 5…didn’t matter what was powering it or if anything else was in the chain or not or what instrument I tried. I saw some other posts talking about it possibly being the TL072’s
 
I tried a bunch of stuff in the last thread I posted in, the lowtide would cut the hum the way you describe the Lightspeed...some sort of buffer maybe?
Tried 9v battery and my Isobrick, op Amps, different charge pumps, nothing. Binned the enclosure so I'd stop getting angry looking at it.
(Still angry)
 
jwin615 said:
Though none of us are qualified to speak technically of this feat of engineering, /s
If you play high gain or use a lot of compression, changing out the 072 for something quieter may be of some perceivable benefit.
A OPA2141 would also be a good choice(lower noise than a 2134). Even a 5532 is quieter the an 072, on paper at least.
It won't likely be a game changer but since it's likely the first pedal in chain and likely always on, any noise reduction is a plus.
Click to expand...
The data sheet for the TL072 and OPA2134 state maximum power supply at +/- 18V, whereas +/- 15V for the NE5532.
Thus the later is somewhat boarderline here.
 
dot matrix madness said:
The data sheet for the TL072 and OPA2134 state maximum power supply at +/- 18V, whereas +/- 15V for the NE5532.
Thus the later is somewhat boarderline here.
Click to expand...
True, but not an issue. Well within the bounds of its designed operational point. The recommended operating range for a 5532 is +-15 but the max is +-22.
So, we wouldn't even be hitting the recommended operating voltage.
 
I wonder if the noises would go away without the charge pump. Unfortunately, it’s not as simple as just pulling the chip out, it would require some effort to mod.

PPCB does have the eunuch buffer (same as skeptical but sans charge pump). I would think 0~9V would be fine for a buffer.
 
phi1 said:
I wonder if the noises would go away without the charge pump.
Click to expand...

I'm curious as well if this is charge pump noise or if an external noise is being amplified when the EQ is changed.

Does the noise go away if you unplug the cable from the input jack? (or even better, ground the input jack tip)

I agree the charge pump circuit is probably unnecessary / overkill...
 
I've made 3 of these and none of them hum, but I always played them with a clean signal. Imo there's not much of a point with an overdrive pedal as different overdrives will add their own EQ to the mix, so I never experimented with dirt pedals

The Blues Breaker boosts the high freqs, and I could see playing thru this along with the harmonics toggle of the skeptical buffer increasing noise in that sonic region

If it's making noise on its own, it could be the TL072, if they are from amazon.
 
phi1 said:
PPCB does have the eunuch buffer (same as skeptical but sans charge pump). I would think 0~9V would be fine for a buffer.
Click to expand...
I’m not finding any info on the Eunuch variant (truly great name)—was this a pcb or a mod for the Skeptical?
 
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